2 Morphology of the Permanent Incisors

Topics covered within the six sections of this chapter include the following: © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE I. General OR DISTRIBUTIONdescription of incisors NOT IV.FOR Type SALE traits thatOR differentiate DISTRIBUTION maxillary central A. Location of incisors in the mouth from lateral incisors (from all views) B. Functions of incisors A. Type traits of maxillary incisors from the labial view C. Studying tooth morphology B. Type traits of maxillary incisors from the lingual II. Class traits that apply to most incisors view © Jones & Bartlett Learning, LLCC. Type traits of maxillary incisors© Jones from & the Bartlett proximal Learning, LLC A. Class traits of most incisors from the facial view NOT FOR SALE OR DISTRIBUTIONviews NOT FOR SALE OR DISTRIBUTION B. Class traits of most incisors from the lingual view D. Type traits of maxillary incisors from the incisal C. Class traits of most incisors from the proximal view views D. Class traits of most incisors from the incisal view V. Type traits that differentiate mandibular central from lateral incisors (from all views) III.© Arch Jones traits & that Bartlett differentiate Learning, mandibular LLC from © Jones & Bartlett Learning, LLC NOTmaxillary FOR incisors SALE OR DISTRIBUTION A. TypeNOT traits of FOR mandibular SALE incisors OR DISTRIBUTIONfrom the labial view A. Mandibular incisors are smaller and look more B. Type traits of mandibular incisors from the lingual alike view B. Contacts positioned more incisally on mandibular C. Type traits of mandibular incisors from the proximal incisors views © Jones & BartlettC. Mandibular Learning, incisor LLCcrowns are wider faciolingually© Jones & Bartlett Learning, LLC D. Type traits of Mandibular incisors from the incisal D. Maxillary incisors have prominent lingual anatomy NOT FOR SALE OR DISTRIBUTION NOT FOR viewSALE OR DISTRIBUTION E. Mandibular incisor roots are relatively longer F. Mandibular incisal ridges are more lingual VI. Interesting variations and ethnic differences in G. Incisal edge wears labially on mandibular incisors incisors © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Chapter 2 focuses on classNOT traits FOR and type SALE traits OR of permanent DISTRIBUTION As you read this chapter, theNOT word FOR “Appendix” SALE followed OR DISTRIBUTION incisors. The authors recommend that you copy Appendix by a number and letter (e.g., Appendix 1a) is used to denote pages 1 and 2 (front and back pages) located at the end of this the appendix page (page 1) and trait being referenced (trait a). book, or print out these pages from the online source Notice that the trait being summarized after each let- provided© Jones for this &book, Bartlett to facilitate Learning, study and minimizeLLC page ter on an appendix© Jones page & Bartlettis summarized Learning, on the backLLC of turnsNOT as you FOR read thisSALE chapter. OR On DISTRIBUTION page 1 of the Appendix, that AppendixNOT page. FOR As you SALE study ORthe traits DISTRIBUTION of each type of the maxillary right lateral incisor is used as a representative human tooth, be aware that these traits can vary considerably example for all incisors when listing incisor class traits, but from mouth to mouth just as facial features vary consider- be aware that there may be exceptions to the common incisor ably from one person to another. One study of a collection traits presented here, and these are emphasized with capital of 100 maxillary central incisors showed considerable dif- letters (“EXCEPT”). Appendix page 2 includes arch and type ference in such characteristics as size, relative proportions, © Jones & Bartlett Learning, LLC © Jones & Bartlett1 Learning, LLC NOT FORtraits SALE that ORdifferentiate DISTRIBUTION all four types of incisors. NOTand FOR color. SALE OR DISTRIBUTION

9781284218251_CH02_049_077.indd 49 25/03/20 4:23 PM 50 PART 1 ■ Comparative Tooth Anatomy

© Jones & BartlettIt would Learning,be ideal if you LLC could learn the similarities© Jonesdown. &In thisBartlett manner, Learning, the teeth will LLC be oriented as they were NOT FORand SALE differences OR DISTRIBUTION of all incisors while comparing models NOTor in FOR the mouth. SALE OR DISTRIBUTION extracted specimens of all four types of incisors from the Finally, the statistics from Dr. Woelfel’s original research views indicated. Remember when studying the maxillary that were used to draw conclusions throughout this chapter incisors to hold them with their crowns down and roots up. are referenced with superscript letters like this (dataA,B, etc.) For mandibular incisors, hold the crowns up and the roots and refer to data presented at the end of this chapter. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION SECTION I GENERAL DESCRIPTION OF INCISORS

These sections are designed to prepare the learner to perform the following: • Describe the location of incisors in the mouth. • From a selection of all teeth, select and separate out the incisors (using class traits). © Jones & •Bartlett Describe Learning, the functions LLCof incisors. © Jones & Bartlett Learning, LLC • Divide a selection of all incisors into maxillary and NOT FOR SALE• List classOR traitsDISTRIBUTION common to all incisors. NOT FOR SALE OR DISTRIBUTION • List arch traits that can be used to distinguish maxillary mandibular (using arch traits). from mandibular incisors.

is to (d) help guide the mandible posteriorly during the final A. LOCATION OF© INCISORS Jones & BartlettIN THE MOUTH Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONphase of closing just before theNOT posterior FOR teeth SALE contact. OR DISTRIBUTION Refer to Figure 2-1 or, better yet, to a model of the complete set of permanent teeth while becoming familiar with the location and Universal number of each incisor. There are four LEARNING EXERCISE maxillary incisors: two central incisors (Universal numbers 8 and© 9) Jones and two & lateral Bartlett incisors Learning, (7 and 10). ThereLLC are four Begin with© your Jones front teeth & Bartletttouching together Learning, edge to edge,LLC mandibularNOT FOR incisors: SALE two central OR DISTRIBUTION incisors (teeth 24 and 25) and then beginNOT to FORclose your SALE back teeth OR together. DISTRIBUTION If you have and two lateral incisors (23 and 26). ideal occlusion, when you move posteriorly, you should feel Central incisors are located on either side of their your upper incisors touching (and guiding) your mandibular respective arch (maxillary or mandibular) with their mesial incisors as your mandible moves posteriorly and your teeth surfaces next to one another at the midline, normally in con- close together. © Jones &tact. Bartlett Their distal Learning, surfaces contactLLC the mesial surfaces of the© Jones & Bartlett Learning, LLC NOT FORadjacent SALE lateralOR DISTRIBUTION incisors. Lateral incisors are therefore justNOT FOR SALE OR DISTRIBUTION distal to central incisors, with their mesial surfaces in contact C. STUDYING TOOTH MORPHOLOGY with the distal surfaces of the adjacent central incisors. Their distal surfaces contact the mesial surfaces of the adjacent The morphology or anatomy of incisors can best be stud- canines. Incisors in the mouth are identified with Universal ied by considering the unique shape and specific contours numbers in Figure 2-2.© Jones & Bartlett Learning, LLCof each type of incisor. When ©discussing Jones traits, & Bartlett the external Learning, LLC NOT FOR SALE OR DISTRIBUTIONmorphology of an incisor is usuallyNOT describedFOR SALE from eachOR ofDISTRIBUTION B. FUNCTIONS OF INCISORS five views: (a) facial (or labial), (b) lingual (tongue side), (c) mesial, (d) distal, and (e) incisal. Due to similarities between Mandibular incisors function with the maxillary incisors to the mesial and distal, these surfaces will be discussed (a) cut food (mandibular incisors are moving blades against together in this text under the heading of proximal surfaces. the maxillary© Jones incisors), & Bartlett (b) enable Learning, articulate LLC speech (con- The shape© (outline) Jones and& Bartlett commonly Learning, occurring contoursLLC siderNOT the enunciation FOR SALE of a ORtoothless DISTRIBUTION person), and (c) help (ridges, grooves,NOT convexities, FOR SALE and concavities) OR DISTRIBUTION on each tooth to support the lip and maintain an esthetic appearance. By surface should be memorized so you can describe and iden- current standards, a person lacking one or more incisors has tify teeth by arch, class, type, and side of the mouth; repro- an undesirable appearance (Fig. 2-3). (Did you ever hear the duce tooth contours when constructing crowns, bridges, and song “All I want for Christmas are my two front teeth”?) Their fillings; skillfully remove deposits (tartar and calculus) from © Jones &fourth Bartlett function, Learning, by fitting the LLC incisal edges of the mandibular© Jonesall contours & Bartlett of crowns Learning, and roots; or LLCfinish and polish existing NOT FORincisors SALE against OR DISTRIBUTION the lingual surfaces of the maxillary incisors,NOT restorations. FOR SALE OR DISTRIBUTION

9781284218251_CH02_049_077.indd 50 25/03/20 4:23 PM CHAPTER 2 ■ Morphology of the Permanent Incisors 51

Incisors

© Jones & Bartlett Learning, LLCCanine ©Canine Jones & Bartlett Learning, LLC 8 9 NOT FOR SALE OR DISTRIBUTION 7 10 NOT FOR SALE OR DISTRIBUTION C e rs ntr iso al inc Lateral incisors P Premolars Premolars o s h t t Canines e e r i e o t r r 1st Premolars t o e i e r

t e

s o

NOT FOR SALE OR DISTRIBUTIONP NOT1st FOR Molars SALE OR DISTRIBUTION

Molars Molars

2nd Molars

3rd Molars © Jones & Bartlett Learning, LLC RIGHT © Jones & Bartlett Learning, LLC LEFT NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR3rd Molars DISTRIBUTION

2nd Molars Molars Molars

1st Molars

P o 2nd Premolars s © Jones & Bartlett Learning,t LLC © Jones & Bartlett Learning, LLC e

r 1st Premolars h i t o NOT FOR SALE OR DISTRIBUTIONr NOT FOR SALE eOR DISTRIBUTION e t Canines t e e Lateral r t io h incisors r Premolars te Premolars s o P

26 25 24 23 Canine Cent isors © Jones & Bartlett Learning, LLC © Jonesral inc & BartlettCanine Learning, LLC NOT FOR SALE OR DISTRIBUTION NOTIncisors FOR SALE OR DISTRIBUTION

FIGURE 2-1. Adult dentition with Anterior teeth Universal numbers on the incisors highlighted in red. MANDIBULAR © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

26 25 2324

FIGURE 2-3. Missing anterior teeth greatly affect an esthetic smile. FIGURE 2-2. Relative size and shape of incisors in the mouth show that maxillary central incisors are the widest, followed by maxillary laterals, then mandibular laterals, and, finally, the © Jones &narrowest Bartlett teeth Learning, in the mouth, the LLC mandibular central incisors. © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

9781284218251_CH02_049_077.indd 51 25/03/20 4:23 PM 52 PART 1 ■ Comparative Tooth Anatomy

First, consider the class traits of incisors, that is, traits that distoincisal angles EXCEPT on the symmetrical mandib- apply to most incisors. ular central incisors, where the angles are not noticeably Developmental lobes© Jones: Recall from& Bartlett Chapter Learning,1 that the LLCdifferent (Appendix 1d). Incisor© Jones crown contact & Bartlett areas at Learning, the LLC facial surface of all anteriorNOT FORteeth forms SALE from OR three DISTRIBUTION labial greatest proximal heights of contourNOT FOR on mesial SALE surfaces OR are DISTRIBUTION lobes: the mesial, middle, and distal lobes. The facial surface located in the incisal third. On the distal surfaces, the con- of incisors often has two shallow, vertical developmental tact areas are more cervical than the mesial EXCEPT on the depressions separating the crown into three portions that distal of the mandibular central, which is at the same level formed from three facial lobes (Fig. 2-4A). The three lobes as the mesial due to its symmetry (Appendix 1e). Before also ©contribute Jones to & three Bartlett rounded Learning, elevations onLLC the incisal wear, the incisal© Jones edges of& incisorsBartlett slope Learning, cervically towardLLC edge NOTcalled mamelonsFOR SALE, located OR on DISTRIBUTION the incisal edges of newly the distal EXCEPTNOT FOR on the SALE symmetrical OR DISTRIBUTION mandibular cen- erupted incisor teeth (Fig. 2-4B). Finally, remember that a tral (Appendix 1s). Finally, the cervical line curves toward fourth (lingual) lobe forms the lingual bulge called a cingu- the apex in the middle of the facial (and lingual) surfaces lum. See Table 2-1 for a summary of the number of lobes (Appendix 1l). forming each type of incisor. Incisor roots, when viewed from the facial, taper © Jones & Bartlett Learning, LLC © Jones(become & Bartlettmore narrow) Learning, from the cervicalLLC line to the apex NOT FOR SALEA. CLASS OR TRAITSDISTRIBUTION OF MOST INCISORS FROMNOT (Appendix FOR SALE 1f). TheyOR DISTRIBUTIONare wider faciolingually than mesiodistally EXCEPT on maxillary central incisors, where the THE FACIAL VIEW mesiodistal width is approximately the same as the facio- Refer to page 1 of the Appendix while studying the class lingual thickness (observe this difference in root widths by traits (similarities) of most incisors. Note that there may be comparing the facial and mesial root views in Appendix 1g). exceptions to the common© Jones incisor traits& Bartlett presented Learning, here, and LLCIncisor roots may bend in the© apical Jones one third& Bartlett EXCEPT Learning,on LLC these are emphasized withNOT capital FOR letters SALE (“EXCEPT”). OR DISTRIBUTIONmaxillary central incisor roots,NOT which FOR are notSALE as likely OR toDISTRIBUTION All incisor crowns, when viewed from the facial, have a bend. This root bend varies, but is more often toward the relatively straight or slightly curved incisal edge (vs. all other distal (Appendix 1h). All incisor roots are longer than the types of teeth that have one or more pointed cusp tips). Their crowns (Appendix 1i). crowns are relatively rectangular and longer incisogingivally than© wide Jones mesiodistally & Bartlett (Appendix Learning, 1a). They LLCtaper from the © Jones & Bartlett Learning, LLC B. CLASS TRAITS OF MOST INCISORS FROM widestNOT mesiodistal FOR SALEareas at theOR proximal DISTRIBUTION contacts, becoming THE LINGUALNOT FOR VIEW SALE OR DISTRIBUTION narrower toward the cervical line (Appendix 1b). Incisor crown outlines are more convex on the dis- Incisor crowns, when viewed from the lingual, have less tal than on the mesial surfaces EXCEPT on mandibular bulk in the lingual half because the mesial and distal surfaces central incisors, which are symmetrical (Appendix 1c). converge lingually (best appreciated from the incisal view, © Jones &Incisor Bartlett mesioincisal Learning, angles LLC are more acute (sharper) than© JonesAppendix & Bartlett 1j). The mesialLearning, and distal LLCmarginal ridges converge NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

FIGURE 2-4. A. A maxillary central © Jones & Bartlett Learning, LLC © Jones & Bartlettincisor crown Learning, shows two facial LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALEdepressions OR separating DISTRIBUTION three facial portions formed by three lobes. B. This crown of a left maxillary central incisor, lingual view, shows three rounded protuberances on © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning,its incisal LLC edge called mamelons (arrows). Also, notice the very deep NOT FORA SALE OR DISTRIBUTION B NOT FOR SALE OR DISTRIBUTIONlingual pit next to the cingulum.

9781284218251_CH02_049_077.indd 52 25/03/20 4:24 PM CHAPTER 2 ■ Morphology of the Permanent Incisors 53

© Jones & BartlettTABLE 2-1 Learning, Guideline LLC for Determining the Number© Jonesof Lobes &for BartlettIncisors Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION TOOTH NAME FACIAL LOBES CINGULUM FROM ONE LINGUAL LOBE? TOTAL NO. OF LOBES

Maxillary central incisor 3 Yes 3 + 1 = 4 Maxillary lateral incisor© Jones 3& Bartlett Learning,Yes LLC © Jones3 + 1 =& 4 Bartlett Learning, LLC Mandibular central incisorNOT FOR 3 SALE OR DISTRIBUTIONYes NOT3 FOR+ 1 = 4SALE OR DISTRIBUTION Mandibular lateral incisor 3 Yes 3 + 1 = 4

General rule for incisors: Number of lobes = 3 facial lobes + 1 lobe for the cingulum.

toward© theJones lingual & cingulum Bartlett (Appendix Learning, 1k). ALLC lingual fossa important to© develop Jones proper & Bartlett lingual contours Learning, that are LLCin har- is locatedNOT between FOR theSALE marginal OR ridges DISTRIBUTION and just incisal to the mony with theNOT occlusion. FOR SALE OR DISTRIBUTION cingulum and is more prominent on maxillary incisors. The cervical line on the proximal surfaces curves toward the incisal edge. The resultant curve is greater on the mesial C. CLASS TRAITS OF MOST INCISORS surface than on the distal (compare the mesial and distal views in Appendix 1o). FROM THE PROXIMAL VIEWS © Jones & Bartlett Learning, LLC © JonesThe & incisor Bartlett roots Learning,, when viewed LLC from the proximal, are NOT FORIncisor SALE crowns OR DISTRIBUTION, when viewed from the proximal (mesial orNOT widest FOR in SALE the cervical OR thirdDISTRIBUTION and gradually taper to a rounded distal), are wedge shaped or triangular (Appendix 1m). They apex (Appendix 1f). have a facial outline that is more convex cervically than incisally, and the facial crest of curvature is in the cervical third, D. CLASS TRAITS OF MOST INCISORS just incisal to the cervical line (Appendix 1n). The lingual FROM THE INCISAL VIEW crest of curvature is also© convexJones and & locatedBartlett in the Learning, cervical LLC © Jones & Bartlett Learning, LLC third on the cingulum,NOT but the FOR contours SALE of theOR incisal DISTRIBUTION two Incisor crowns, when viewed fromNOT the FOR incisal, SALE have a ORlingual DISTRIBUTION thirds of the lingual surface and the marginal ridges are con- fossa that is concave just incisal to the cingulum and between cave from the cingulum area to the incisal edge. Therefore, the mesial and distal marginal ridges (Appendix 1t). They the lingual outline is S shaped, being convex over the cingu- have an incisal ridge that terminates mesiodistally at the wid- lum and concave or nearly flat from the cingulum to the inci- est portion of the crown (Appendix 1q). The labial outline is sal edge© Jones (Appendix & Bartlett1p). The concave Learning, portion LLC of the lingual convex but less© Jones curved than & Bartlett the more convexLearning, lingual outlineLLC surfaceNOT on aFOR maxillary SALE anterior OR tooth DISTRIBUTION is an important guid- (Appendix 1r).NOT Marginal FOR ridges SALE converge OR DISTRIBUTIONfrom the mesial and ing factor in the closing movements of the lower jaw because distal incisal angles toward the cingulum (Appendix 1k), and the mandibular incisors glide along this concavity as the the crown outline tapers from proximal contact area toward mandibular teeth move into maximum closure. Therefore, the cingulum (Appendix 1j) resulting in a narrower lingual when restoring lingual contours of maxillary incisors, it is than labial surface. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

ARCH TRAITS THAT DIFFERENTIATE MANDIBULAR FROM SECTION III MAXILLARY INCISORS © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Refer to page 2 of the NOTAppendix FOR while SALE reading OR about DISTRIBUTION these maxillary central and lateralNOT incisors FOR (best SALE seen ORin the DISTRIBUTION arch traits that can be used to differentiate mandibular from mouth in Fig. 2-2). maxillary incisors. B. CONTACTS POSITIONED MORE A. ©MANDIB Jones ULAR& Bartlett INCISORS Learning, ARE SMALLERLLC INCISALLY© Jones ON &MANDIBULAR Bartlett Learning, INCISORS LLC NOTAND FORLOOK SALE MORE OR ALIKE DISTRIBUTION NOT FOR SALE OR DISTRIBUTION From the facial view, the mesial and distal outlines are Both types of mandibular incisors are generally smaller flatter on mandibular incisor crowns than on maxillary than either of the maxillary incisors (Appendix 2p). incisor crowns (compare maxillary to mandibular incisors Mandibular central and lateral incisors look more alike in Appendix 2q) and have contact areas located closer to © Jones &and Bartlett are more Learning,nearly the same LLC size in the same mouth, com©- Jonesthe incisal & Bartlett ridge than Learning, on maxillary LLC incisors (Appendix 2i NOT FORpared SALE to theOR larger DISTRIBUTION sizes and greater differences betweenNOT and FOR 2r). SALE OR DISTRIBUTION

9781284218251_CH02_049_077.indd 53 25/03/20 4:24 PM 54 PART 1 ■ Comparative Tooth Anatomy

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC C. MANDIBULAR INCISOR CROWNS ARE NOT FOR SALEWIDER OR FACIOLINGUALLYDISTRIBUTION NOT FOR SALE OR DISTRIBUTION From the incisal view, mandibular incisor crowns are relatively wider faciolingually than mesiodistally compared to maxillary central incisors, which are wider mesiodistallyO (compare incisal views© in JonesAppendix & 2-h Bartlett to 2-s). Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION D. MAXILLARY INCISORS HAVE PROMINENT LINGUAL ANATOMY Mandibular incisor crowns have smoother lingual surfaces with ©less Jones prominent & Bartlett anatomy Learning,than do maxillary LLC crowns, © Jones & Bartlett Learning, LLC whichNOT have FORdeeper SALE fossae andOR more DISTRIBUTION pronounced marginal NOT FOR SALE OR DISTRIBUTION ridges (Appendix 2m and Fig. 2-5A and B). AB E. MANDIBULAR INCISOR ROOTS ARE FIGURE 2-6. A. Proximal view of the ideal relationship between © Jones & BartlettRELATIVELY Learning, LONGER LLC © Jonesmaxillary & and Bartlett mandibular Learning, incisors when LLCposterior teeth are biting NOT FOR SALE OR DISTRIBUTION NOTtightly FOR together. SALE B. TheOR arrow DISTRIBUTION indicates the direction of movement Mandibular incisor roots are longer in proportion to their of mandibular incisors when the mandible moves forward crowns than are maxillary incisor roots, so mandibular inci- (protrudes) with the incisors touching until they align edge to sors have larger root-to-crown ratios. edge. The resultant wear pattern or facets on the incisal edges of maxillary incisors occur more on the lingual surface on the incisal © Jones & Bartlett Learning, LLCedge, whereas wear occurs more ©on theJones facial surface & Bartlett of the incisal Learning, LLC F. MANDIBULAR INCISAL RIDGES ARE edge on mandibular incisors. MORE LINGUALNOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION From the proximal view, incisal ridges of mandibular inci- G. INCISAL EDGE WEARS LABIALLY ON sors are usually positioned lingual to the midroot axis line, MANDIBULAR INCISORS whereas the incisal ridges of maxillary incisors are more often© onJones or labial & toBartlett the root Learning,axis line (best LLC seen from the Tooth wear ©(attrition) Jones on & theBartlett incisal ridges Learning, of incisors LLC that proximalNOT views FOR on SALEAppendix OR 2o). DISTRIBUTION occurs whenNOT shearing FOR or incisingSALE food OR results DISTRIBUTION in tooth wear that is in a different location on maxillary incisors compared to mandibular incisors (Fig. 2-6). This wear occurs when the labial part of the incisal edges of mandibular incisors slides forward and downward while contacting the lingual surface © Jones & Bartlett Learning, LLC © Jonesand part & ofBartlett the incisal Learning, edge of opposing LLC maxillary incisors. NOT FOR SALE OR DISTRIBUTION NOTThe FOR wear SALE results OR in a DISTRIBUTIONshiny, flat, polished surface of enamel on the incisal edge called a facet [FAS it]. Assuming a nor- mal tooth relationship, wear facets on mandibular incisors form on the labial surface next to the incisal edge. In contrast, wear facets on maxillary incisors form on the lingual © Jones & Bartlett Learning, LLCsurface next to the incisal edge,© possibly Jones extending & Bartlett to the linLearning,- LLC gual marginal ridges. MDNOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

LEARNING EXERCISE AB © Jones & Bartlett Learning, LLC Refer to Table© Jones 2-2 for &a summaryBartlett of Learning,the noticeable LLCarch FIGURENOT 2-5. FOR A. The SALE lingual anatomy OR DISTRIBUTION of a right maxillary central traits that distinguishNOT FOR maxillary SALE from ORmandibular DISTRIBUTION incisors, and incisor is typical for maxillary incisors, with prominent marginal see how many of them can be used to differentiate the rows ridges and cingulum, and a deep fossa. B. The lingual anatomy of this of maxillary and mandibular incisors from various views in mandibular central incisor is typical of mandibular incisors since it Figures 2-7, 2-9, 2-13, 2-17, 2-19, 2-22, 2-24, and 2-26. has very faint marginal ridges and cingulum and a shallow fossa. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

9781284218251_CH02_049_077.indd 54 25/03/20 4:24 PM CHAPTER 2 ■ Morphology of the Permanent Incisors 55

© Jones & BartlettTABLE 2-2 Learning, Major LLC Arch Traits That Distinguish Maxillary© Jones from &Mandibular Bartlett Incisors Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION MAXILLARY INCISORS MANDIBULAR INCISORS

Wider crowns mesiodistally Narrower crowns mesiodistally Less symmetrical crown More symmetrical crowns More rounded© Jones mesial and & distalBartlett incisal anglesLearning, LLC More square mesial© and Jones distal incisal & Bartlett angles Learning, LLC VIEW LABIAL Contact areasNOT more FOR cervical SALE OR DISTRIBUTION Contact areas very incisalNOT FOR SALE OR DISTRIBUTION Lingual anatomy more distinct: Lingual surface smoother: Pronounced marginal ridges Almost no marginal ridges Deeper lingual fossa Shallower lingual fossa

VIEW Sometimes lingual pits No pits ©LINGUAL Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Larger cingulum Smaller cingulum NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Incisal edge on or labial to midroot axis line Incisal edge on or lingual to midroot axis line

VIEWS Facets on lingual slope of incisal edge Facets on labial slope of incisal edge © Jones & Bartlett PROXIMAL Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE ORCrowns DISTRIBUTION wider mesiodistally than faciolingually NOT FOR SALECrowns OR wider DISTRIBUTION faciolingually than mesiodistally Plus traits seen from lingual view can also be seen from the incisal view. VIEW INCISAL

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION TYPE TRAITS THAT DIFFERENTIATE MAXILLARY CENTRAL SECTION IV FROM LATERAL INCISORS (FROM ALL VIEWS) © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION OBJECTIVES FOR SECTION IV

This section is designed to prepare the learner to perform the following: • Describe the type traits that can be used to If possible, repeat this on a model with one or more © Jones & Bartlettdistinguish Learning, the permanent LLC maxillary central from © Jonesmaxillary & Bartlett incisors missing.Learning, LLC NOT FOR SALElateral OR incisor. DISTRIBUTION NOT• FORSelect SALE and separate OR DISTRIBUTIONmaxillary incisors from a selection • Describe and identify the labial, lingual, mesial, distal, of all teeth on a bench top. and incisal surfaces for all maxillary incisors. • Holding a maxillary incisor, determine whether it is • Assign a Universal number to maxillary incisors present a central or a lateral and right or left. Then assign a in a mouth (or on© a model)Jones with & completeBartlett dentition. Learning, LLCUniversal number to it. © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Within this section, type traits are presented that distin- these teeth root up and crown down, as they are positioned guish maxillary central from lateral incisors. Other traits will in the mouth. Also, refer to Appendix page 2 and refer to be helpful when distinguishing right maxillary incisors from Figure 2-7 as you study the labial traits of incisors. left ©maxillary Jones incisors. & Bartlett These Learning, traits are presented LLC for each © Jones & Bartlett Learning, LLC viewNOT of the FORtooth: SALEfacial, lingual, OR DISTRIBUTION proximal (includes mesial NOT FOR SALE OR DISTRIBUTION 1. Crown Shape of Maxillary Incisors (Labial View) and distal traits), and incisal. Based on Woelfel’s studies, the crown of the maxillary central A. TYPE TRAITS OF MAXILLARY INCISORS incisor is the longest of all human tooth crowns (although at FROM THE LABIAL VIEW least two other authors describe the mandibular canine crown © Jones & Bartlett Learning, LLC © Jonesas the longest& Bartlett crown overallLearning,2,3). The LLCmaxillary central also has NOT FORIdeally, SALE examine OR DISTRIBUTION several extracted maxillary central and latNOT- the FOR widest SALE crown OR of all DISTRIBUTION incisors. The crown is usually longer eral incisors or tooth models as you read the following. Hold (incisogingivally) than wide (mesiodistally)A (Appendix 2a).

9781284218251_CH02_049_077.indd 55 25/03/20 4:24 PM 56 PART 1 ■ Comparative Tooth Anatomy

© Jones & FIGURE Bartlett 2-7. MaxillaryLearning, central LLCand lateral incisors, labial views, with© Jones type traits & that Bartlett distinguish Learning,maxillary central LLC from lateral incisors and traits that distinguish right and left sides. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

NOT FOR SALE OR DISTRIBUTION D NOT FORM SALE OR DISTRIBUTION D M

Lateral (Right) Central (Right) © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION MAXILLARY INCISORS:NOT FOR LABIAL SALE VIEWS OR DISTRIBUTION Central (Right) Central (Left)

NOT FOR SALE OR DISTRIBUTIONMesial NOT FOR SALE OR DISTRIBUTION

8 9

© Jones & BartlettLateral Learning, (Right) LLC © JonesLateral & (Left) Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Distal Distal © Jones & Bartlett Learning, LLC © JonesMesial & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION 7 NOT FOR10 SALE OR DISTRIBUTION

TRAITS TO DISTINGUISH© Jones MAXILLARY & Bartlett CENTRAL Learning, FROM LLC LATERAL INCISOR: LABIAL© Jones VIEW & Bartlett Learning, LLC CENTRAL INCISOR NOT FOR SALE OR DISTRIBUTIONLATERAL INCISOR NOT FOR SALE OR DISTRIBUTION Larger crown, wider cervically Smaller crown, narrower cervically Mesial incisal angle is nearly a right angle Mesial incisal angle is rounder Distal contact at junction incisal/middle thirds Distal contact is near middle third Less likely root tip bend to distal Root tip often bends to distal Incisal© Jones edge closer & Bartlettto horizontal Learning, LLC Incisal edge ©slopes Jones cervically & Bartletttoward distal Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION TRAITS TO DIFFERENT MAXILLARY RIGHT FROM LEFT INCISOR: LABIAL VIEW

CENTRAL INCISOR AND LATERAL INCISOR Mesial crown outline flatter, distal more rounded © Jones & Bartlett Learning, LLC Distoincisal angle more rounded© Jones than mesioincisal& Bartlett angle Learning, LLC NOT FOR SALE OR DISTRIBUTION Distal contact more cervicalNOT thanFOR mesial SALE contact OR DISTRIBUTION Incisal edge slopes shorter toward the distal

9781284218251_CH02_049_077.indd 56 25/03/20 4:24 PM CHAPTER 2 ■ Morphology of the Permanent Incisors 57

© Jones & BartlettThe crown Learning, of the maxillary LLC lateral incisor is also longer© Jones & Bartlett Learning, LLC NOT FORincisocervically, SALE OR DISTRIBUTION but it is considerably narrower mesiodistallyNOT FOR SALE OR DISTRIBUTION than the crown of the maxillary central incisor. Since its root is longer, the entire lateral has a longer, more slender lookB (Appendix 2a). The crown outline is less symmetrical than on the central incisor. Normally, the contour of the labial surface of the maxillary© lateral Jones incisor & isBartlett more convex Learning, mesio- LLC © Jones & Bartlett Learning, LLC distally compared to theNOT maxillary FOR central. SALE This OR may DISTRIBUTION be best NOT FOR SALE OR DISTRIBUTION appreciated from the incisal view. Mamelons, and particu- larly labial depressions, are less prominent and less common on the maxillary lateral incisor than on the central incisor.

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC 2. Proximoincisal Line Angles of the Maxillary D NOTIncisor FOR (Labial SALE View) OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION On the outline of maxillary central incisors, the angle formed by the mesial and incisal surfaces (called the mesio- M incisal angle) is close to a right angle. The distoincisal angle © Jones &is Bartlettmore rounded, Learning, and the angle LLC is slightly obtuse or greater© Jones & Bartlett Learning, LLC NOT FORthan SALE a right OR angle DISTRIBUTION (Appendix 2b). NOT FOR SALE OR DISTRIBUTION On maxillary lateral incisors, both the mesioincisal and distoincisal angles are more rounded than on the central incisor (Appendix 2b). The mesioincisal angle is more acute FIGURE 2-8. Location of proximal contacts: Typical of (sharper) than the distoincisal angle, accentuated by the inci- maxillary lateral incisors, the mesial proximal contact area is located sal edge sloping cervically© Jones toward the & distal,Bartlett more Learning,so than on LLCin the incisal third while the distal ©contact Jones is in the & middle Bartlett third. Learning, LLC the maxillary central incisorNOT (Appendix FOR SALE 2c). OR DISTRIBUTIONAlso typical of maxillary lateral incisorsNOT is a FORdeep lingual SALE fossa OR with aDISTRIBUTION caries-prone pit next to the cingulum. 3. Proximal Contact Most Cervical on Distal of Laterals (Labial View) central incisor root is the only maxillary tooth that is as thick at the cervix mesiodistally as faciolingually. Compare the root The m©esial Jones contacts & Bartlettof both the Learning,maxillary central LLC and lateral width seen on© theJones mesial & view Bartlett to the root Learning, width seen LLCon the incisorsNOT are FOR in the SALEincisal third,OR DISTRIBUTIONvery near the incisal edge labial view inNOT Appendix FOR 2n. SALE All other OR types DISTRIBUTION of maxillary teeth for the central and slightly more cervical on the lateral. The have roots that are thicker faciolingually than mesiodistally.D distal contacts of both incisors are more cervical than the Because of its shortness (a small root-to-crown ration) and mesial. For a maxillary central incisor, the distal contact is conical shape, the maxillary central incisor root may be a near the junction of the incisal and the middle thirds; for the poor choice to support a replacement tooth as part of a den- © Jones &maxillary Bartlett lateral Learning, incisor, it is LLC even more cervical, often in the© Jonestal bridge, & Bartlett that is, a replacement Learning, tooth LLC crown attached to, and NOT FORmiddle SALE third OR (making DISTRIBUTION this distal contact the most cervical forNOT supported FOR SALE by, two OR adjacent DISTRIBUTION teeth. any incisor, seen clearly on a lingual view in Fig. 2-8). The root of a maxillary lateral incisor is wider faciolingually than mesiodistally. It tapers evenly toward the rounded 4. Maxillary Central Incisors Have Relatively Shorter apex, and the apical end is commonly bent distally (seen in Roots (Labial View) 12 of the 14 maxillary lateral incisors in Fig. 2-7, lower row). © Jones & Bartlett Learning, LLCThis potential for distal (or mesial)© Jones bend on& Bartlettmost roots Learning,must LLC On a maxillary centralNOT incisor FOR, the root SALE is only OR slightly DISTRIBUTION lon- be confirmed on radiographs NOTand considered FOR SALE when ORextract DISTRIBUTION- ger than the crown resulting in a root-to-crown ratio that ing an incisor. is the smallest of any permanent tooth (Appendix 2d). The maxillary lateral incisor root is longer than on the central.C B. TYPE TRAITS OF MAXILLARY INCISORS This results in a root that appears longer in proportion to the FROM THE LINGUAL VIEW crown© thanJones on the & maxillary Bartlett central Learning, incisor. LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION Refer to FigureNOT 2-9 FORwhile studying SALE theOR lingual DISTRIBUTION traits of maxil- 5. Root Thinner and Longer on Lateral Incisors lary incisors. (Labial View Compared with the Proximal View) 1. Lingual Fossae Deeper on Maxillary Lateral The root of the maxillary central incisor is thick in the cer- Incisors (Lingual View) © Jones &vical Bartlett third and Learning, narrows through LLC the middle to a blunt apex.© Jones & Bartlett Learning, LLC NOT FORIts SALE outline OR and shapeDISTRIBUTION is similar to an ice cream cone. An apiNOT- O FORn maxillary SALE incisors, OR DISTRIBUTIONlarge lingual fossae are located imme- cal bend is not common in the maxillary central incisor. The diately incisal to the cingulum and bounded by two marginal

9781284218251_CH02_049_077.indd 57 25/03/20 4:25 PM FIGURE 2-9. Maxillary central and lateral incisors, lingual views, with type traits that distinguish maxillary central from lateral incisors and traits that distinguish right and left sides. Several circles highlight the more distally placed cingulum on many maxillary central incisors compared to maxillary lateral incisors. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

M D M D © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Central (Right) Lateral (Right)

MAXILLARY INCISORS: LINGUAL VIEWS

9 8

10 7

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC TRAITS TO DISTINGUISH MAXILLARY CENTRAL FROM LATERAL INCISOR: LINGUAL VIEW NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION CENTRAL INCISOR LATERAL INCISOR Larger shallow lingual fossa Deep but small fossa Cingulum distally positioned Cingulum centered Less frequent lingual pit More common lingual pit © Jones & Bartlett PlusLearning, outline characteristics LLC seen from facial apply© to Joneslingual outline & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION TRAITS TO DIFFERENTIATE MAXILLARY RIGHT FROM LEFT INCISOR: LINGUAL VIEW

CENTRAL INCISOR LATERAL INCISOR Cingulum toward distal Longer and straighter mesial marginal ridge © Jones & BartlettDistal marginal Learning, ridge more curvedLLC than mesial © Jones & Bartlett Learning, LLC Both have longer mesial marginal ridge NOT FOR SALE OR DISTRIBUTIONPlus outline characteristics fromNOT facial FORalso apply SALE for lingual OR outline DISTRIBUTION

9781284218251_CH02_049_077.indd 58 25/03/20 4:25 PM CHAPTER 2 ■ Morphology of the Permanent Incisors 59

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION FIGURE 2-10. A. A maxillary lateral incisor has a lingual pit with beginning decay (arrow). B. An unusual lingual root groove crosses the cingulum and extends on to the root and contributed to A B periodontal disease. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION ridges. The lingual fossa of the maxillary lateral incisor, although smaller in area, is often even more pronounced than on the central incisor, and it is more likely to have a pit in the deep fossa that is prone to decay (Fig. 2-10A). Note the deeper© Jones lingual & Bartlettfossae on manyLearning, maxillary LLC lateral inci- © Jones & Bartlett Learning, LLC sors NOTcompared FOR to centralSALE incisors OR DISTRIBUTION in Figure 2-9. Although NOT FOR SALE OR DISTRIBUTION not common, accessory grooves may extend from the lingual fossa around the cingulum and onto the root surface resulting in an increased risk of decay and gingival disease (Fig. 2-10B). © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR 2.SALE Cingulum OR DISTRIBUTION of Maxillary Incisors (Lingual View) NOT FOR SALE OR DISTRIBUTION The cingulum on the maxillary central incisor is usually well developed and is located off-center, distal to the root axis line that bisects the root longitudinally. (This can also be seen from the incisal view.) The© Jones cingulum & onBartlett the maxill aryLearning, lateral LLC © Jones & Bartlett Learning, LLC incisor is narrower thanNOT on the FOR central, SALE and it ORis almost DISTRIBUTION cen- NOT FOR SALE OR DISTRIBUTION DM tered on the root axis line. This difference in location of the cingula, more distal on the central and more centered over the root on the lateral, is best seen incisally in Appendix 2e and is highlighted on many teeth in Figure 2-9. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 3. Marginal Ridges of Maxillary Incisors (Lingual View) FIGURE 2-11. The crown of this left maxillary lateral incisor has such prominent marginal ridges that it may be called “shovel The mesial and distal marginal ridges vary in prominence shaped.” The straighter mesial marginal ridge is longer than the on all maxillary incisors from one person to another. They © Jones & Bartlett Learning, LLC © Jonescurved &distal Bartlett marginal ridge, Learning, which is typical LLC of most incisors may be prominent or inconspicuous, possibly worn smooth EXCEPT mandibular centrals. Hint: Think of the length of a marginal NOT FORfrom SALE attrition. OR OneDISTRIBUTION type of maxillary incisor with a deep linNOT- ridge FOR on anSALE anterior OR tooth DISTRIBUTION as the distance from where the ridge gual fossa and prominent mesial and distal marginal ridges is meets the cingulum to where it disappears (between the proximal called “shovel-shaped incisors”E (Fig. 2-11).4–8 contact and the incisal edge).

9781284218251_CH02_049_077.indd 59 25/03/20 4:25 PM 60 PART 1 ■ Comparative Tooth Anatomy

© Jones & BartlettOn the both Learning, types of maxillaryLLC incisors, mesial mar©- Jones & Bartlett Learning, LLC C. TYPE TRAITS OF MAXILLARY INCISORS NOT FORginal SALE ridges OR (from DISTRIBUTION the incisal edge to the cingulum) are lonNOT- FOR SALE OR DISTRIBUTION ger than the distal marginal ridges due in part to the taper FROM THE PROXIMAL VIEWS of the incisal edge from mesial to distal (Appendix 2f and Refer to Figure 2-13 while studying the proximal traits of Fig. 2-11). This is also accentuated on the maxillary central maxillary incisors. incisor because its cingulum is off center toward the distal. Further, the shorter distal© Jones marginal & ridges Bartlett are more Learning, curved LLC © Jones & Bartlett Learning, LLC 1. Incisal Edges Labial to Root Axis: Maxillary compared to the mesialNOT marginal FOR ridges SALE that OR are straighterDISTRIBUTION NOT FOR SALE OR DISTRIBUTION incisocervically (seen in Fig. 2-11 and on most incisors in Central Has Slight Distolingual Twist (Proximal Fig. 2-9). Views) On both maxillary incisors, the incisal edge is commonly 4. Pits on Maxillary Incisors (Lingual View) just labial to the root axis line or may be on the root axis © Jones & Bartlett Learning, LLC line (Appendix© Jones2o). From & the Bartlett mesial side, Learning, the slight distolin- LLC On bNOToth types FOR of maxillary SALE ORincisors, DISTRIBUTION but more frequently in gual twist ofNOT the incisal FOR ridge SALE of the ORmaxillary DISTRIBUTION central incisor lateral incisors, a lingual pit may be detectable at the incisal places the distal portion at the ridge even somewhat more border of the cingulum where the mesial and distal marginal lingual than on the mesial (best appreciated from the incisal ridges converge. This pit may need to be restored or sealed view in Appendix 2g and Fig. 2-14). in order to prevent or arrest decay. (Notice the deep lingual © Jones &pits Bartlett in Fig. 2-10A Learning, and on several LLC maxillary lateral incisors in© Jones & Bartlett Learning, LLC Fig. 2-9.) 2. Cervical Line of Maxillary Incisors (Proximal NOT FOR SALE OR DISTRIBUTION NOT FORViews) SALE OR DISTRIBUTION

5. Accessory Ridges and Grooves on Maxillary As on all anterior teeth, the cervical line of both types of Incisors (Lingual View) maxillary incisors curves incisally on the mesial and distal tooth surfaces, and this curvature is greater on the mesial Small, narrow accessory© lingualJones ridges & Bartlett separated Learning, by subtle LLCsurface than on the distal surface,© Jones as can be & seen Bartlett on the linLearning,- LLC grooves may extend verticallyNOT FOR from SALE the cingulum OR DISTRIBUTION toward gual surface of a central incisorNOT in Figure FOR 2-15 SALE. To confirm OR DISTRIBUTION the center of the lingual fossa in both types of maxillary inci- this difference in curvature, it is often necessary to turn the sors (fewer in maxillary laterals). There could be from one tooth slightly to view the amount of curvature on the mesial to four accessory ridges. Tooth 9 in Figure 2-12 shows these and then turn it the other way to confirm the amount of cur- accessory ridges most clearly. Tiny grooves separate these vature on the distal. This difference is most pronounced on F,G ridges.© Jones & Bartlett Learning, LLC anterior teeth.© JonesThe amount & Bartlett of curvature Learning, of the cervical LLC line NOT FOR SALE OR DISTRIBUTION on the mesialNOT of the FOR maxillary SALE central OR incisor DISTRIBUTION is larger than 6. Root Contour of Maxillary Incisors (Lingual View) for any other tooth, extending incisally one fourth or more of the crown length (Fig. 2-16), whereas the distal cervical line The ootr contour of all maxillary incisors, like all anterior curves less. The curvature of the mesial cervical line of the teeth, is convex and tapers, becoming narrower toward the maxillary lateral incisor is also considerable but slightly less © Jones &lingual Bartlett surface Learning, so that some LLCof the proximal surfaces are vis©- Jonesthan on & the Bartlett central.H Learning, LLC NOT FORible SALE from theOR lingual DISTRIBUTION view (Fig. 2-9). NOT FOR SALE OR DISTRIBUTION 3. Root Shape and Root Depressions of Maxillary Incisors (Proximal Views) The ootr of the maxillary central incisor is wide faciolin- © Jones & Bartlett Learning, LLCgually at the cervix and tapers to© aJones rounded & apex. Bartlett The lingual Learning, LLC 9 8NOT FOR SALE OR DISTRIBUTIONroot outline is nearly straight NOTin the cervicalFOR SALE third and OR then DISTRIBUTION curves labially toward the tip in the middle and apical thirds. 10 The entire labial root outline is even straighter. From the 7 proximal view, this flatter facial root outline and more convex lingual root outline are evident in many central incisors © Jones & Bartlett Learning, LLC in Figure 2-13.© Jones In contrast, & Bartlettthe root of Learning,the maxillary LLClateral NOT FOR SALE OR DISTRIBUTION incisor tapersNOT more FOR evenly SALE throughout OR DISTRIBUTIONthe root toward the blunt apex. Themesial root surfaces of both types of maxillary incisors FIGURE 2-12. The light reflecting on the lingual surfaces of these maxillary incisors reveals accessory ridges, especially on tooth 9 could have a slight depression in the middle third cervicoapi- (at the arrow). cally, slightly lingual to the center faciolingually, but the distal © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

9781284218251_CH02_049_077.indd 60 25/03/20 4:25 PM CHAPTER 2 ■ Morphology of the Permanent Incisors 61

© Jones & FIGURE Bartlett 2-13. Learning, Maxillary central LLC and lateral incisors, proximal views© ,Jones with type &traits Bartlett that distinguish Learning, maxillary central LLC from lateral incisors and traits that distinguish right and left sides. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

FLFL

Central (Right) Lateral (Right) Mesial View Mesial View © Jones & Bartlett Learning, LLC MAXILLARY INCISORS:© Jones PROXIMAL & Bartlett VIEWS Learning, LLC NOT FOR SALE OR DISTRIBUTIONLeft Central (Mesial) NOT FOR SALE RightOR Central DISTRIBUTION (Distal)

NOT FOR SALE OR DISTRIBUTION NOT FOR SALEFacial OR DISTRIBUTION Lingual 9 8

10 7

TRAITS TO DISTINGUISH© Jones MAXILLARY & Bartlett CENTRAL Learning, FROM LLC LATERAL INCISOR: PROXIMAL© Jones VIEWS & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION CENTRAL INCISOR LATERAL INCISOR More concave lingual crown outline Less concave lingual crown outline Root outline more convex on lingual than facial More even root taper facially and lingually

TRAITS© Jones TO DIFFERENTIATE & Bartlett Learning, MAXILLARY LLC RIGHT FROM LEFT INCISOR:© Jones COMPARING & Bartlett PROXIMAL Learning, VIEWS LLC NOT FOR SALE OR DISTRIBUTIONCENTRAL INCISOR AND LATERAL INCISORNOT FOR SALE OR DISTRIBUTION Cervical line curvature more pronounced on mesial than distal Flatter mesial root surface contour than distal contour

9781284218251_CH02_049_077.indd 61 25/03/20 4:26 PM 62 PART 1 ■ Comparative Tooth Anatomy

MDNOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

CEJ curvature

Crown © Jones & Bartlett Learning, LLC length © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

© Jones & Bartlett Learning, LLC © Jones FIGURE & 2-16. Bartlett Mesial viewLearning, of this maxillary LLC central incisor NOT FOR FIGURESALE 2-14. OR ThisDISTRIBUTION left maxillary central incisor shows a subtle NOTshows FOR the SALE greatest ORamount DISTRIBUTION of curvature of the cementoenamel distolingual twist of the incisal edge, which is more lingual on junction (CEJ) on any tooth: the amount of curvature is one fourth the distal half than on the mesial half. or more of the crown length.

© Jones & Bartlett Learning, LLCroot surfaces are likely to be convex.© Jones A slight mesial& Bartlett root depres Learning,- LLC NOT FOR SALE OR DISTRIBUTIONsion is discernible in the shadedNOT line drawings FOR SALEin Figure OR 2-13. DISTRIBUTION

D. TYPE TRAITS OF MAXILLARY INCISORS FROM THE INCISAL VIEW © Jones & Bartlett Learning, LLC Refer to Figure© Jones2-17 when & studying Bartlett the incisalLearning, view. To LLC follow NOT FOR SALE OR DISTRIBUTION this description,NOT a maxillaryFOR SALE incisor OR should DISTRIBUTION be held in such a position that the incisal edge is toward you, the labial surface is at the top, and you are looking exactly along the root axis line. You should see slightly more lingual surface than labial surface if the incisal ridge is located somewhat labial to the © Jones & Bartlett Learning, LLC © Jonesroot axis & lineBartlett (as in many Learning, teeth, especially LLC the lateral incisors, NOT FOR SALE OR DISTRIBUTION NOTin FOR Fig. 2-17). SALE OR DISTRIBUTION

1. Crown Proportion Faciolingually versus Mesiodistally for Maxillary Incisors (Incisal View) © Jones & Bartlett Learning, LLCThe incisal outline of themaxillary © Jones central & incisor Bartlett is notice Learning,- LLC NOT FOR SALE OR DISTRIBUTIONably wider mesiodistally than NOTfaciolingually FOR SALE(Appendix OR 2h). DISTRIBUTION The mesiodistal measurement of the lateral incisor crown is also most often greater than the labiolingual measurement I M D but less so than on the central incisor. On some lateral incisors, the two dimensions of the crown are almost the same © Jones & Bartlett Learning, LLC size faciolingually© Jones as mesiodistally. & Bartlett Notice Learning, this difference LLC in NOT FOR SALE OR DISTRIBUTION the proportionNOT of maxillaryFOR SALE central OR incisors DISTRIBUTION (relatively wider mesiodistally) compared to lateral incisors in Figure 2-17.

FIGURE 2-15. On the lingual of this right maxillary central incisor, 2. Crown Outline Shape and Cingulum Location of you can just see that the curve of the cementoenamel junction Maxillary Incisors (Incisal View) © Jones &or Bartlettcervical line (markedLearning, with red LLC pencil) is greater (extends more © Jones & Bartlett Learning, LLC NOT FORincisally) SALE on OR the mesialDISTRIBUTION than on the distal, a trait for most teeth in NOTThe FOR incisal SALE outline OR of theDISTRIBUTION maxillary central incisor is some- the mouth. what triangular. The labial outline is broadly curved (on some

9781284218251_CH02_049_077.indd 62 25/03/20 4:27 PM CHAPTER 2 ■ Morphology of the Permanent Incisors 63

© Jones & FIGURE Bartlett 2-17. Learning, Maxillary central LLC and lateral incisors, incisal views©, with Jones type traits & thatBartlett distinguish Learning, maxillary central LLC from lateral incisors and traits that distinguish right and left sides. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

F F

M D © Jones &D Bartlett Learning,M LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION L L

Lateral (Right) Central (Right) © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONMAXILLARY INCISORS: INCISAL VIEWSNOT FOR SALE OR DISTRIBUTION Central (Right) Central (Left)

8 9 Distal Distal Mesial © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Lateral (Right) Lateral (Left)

7 10 Distal Distal © Jones & Bartlett Learning,Mesial LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION TRAITS TO DISTINGUISH MAXILLARY CENTRAL FROM LATERAL INCISOR: INCISAL VIEW

CENTRAL INCISOR LATERAL INCISOR Crown noticeably wider mesiodistally than faciolingually Crown minimally wider mesiodistally than faciolingually Crown© Jones outline roughly& Bartlett triangular Learning, LLC Crown outline more© Jones round or & oval Bartlett Learning, LLC CingulumNOT FORoff center SALE to distal OR DISTRIBUTION Cingulum centeredNOT FOR SALE OR DISTRIBUTION Incisal edge curves mesiodistally Incisal edge straighter mesiodistally

TRAITS TO DIFFERENTIATE MAXILLARY RIGHT FROM LEFT INCISOR: INCISAL VIEW

CENTRAL INCISOR LATERAL INCISOR © Jones & BartlettCingulum more Learning, distal LLC © JonesBest to use & otherBartlett views Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

teeth, the middle third may be nearly flat) forming the base of the triangle, and the other two sides of the triangle converge toward the cingulum (Fig.© Jones2-18). As was& Bartlett seen from theLearning, lingual LLC © Jones & Bartlett Learning, LLC view, the cingulum of theNOT maxillary FOR central SALE incisor OR isDISTRIBUTION slightly NOT FOR SALE OR DISTRIBUTION off-center to the distal, resulting in the mesial marginal ridge measuring longer than the distal marginal ridge (seen best from the lingual view in Appendix 2f). The crown of the lateral incisor resembles the central incisor© Jonesfrom this &aspect, Bartlett but its Learning,outline is more LLC round or oval © Jones & Bartlett Learning, LLC thanNOT triangular FOR since SALE the labialOR DISTRIBUTIONoutline is noticeably more NOT FORINCISAL SALE VIEWS OR DISTRIBUTION convex than on the central incisor. The cingulum of the lat- Right maxillary Right maxillary eral incisor is nearly centered mesiodistally. Compare the lateral incisor central incisor triangular shape of the maxillary central incisor to the more FIGURE 2-18. The outline of the maxillary lateral incisor (on the round or slightly oval shape of the maxillary lateral incisor left) is almost round or slightly oval, whereas the outline of the © Jones &in BartlettFigure 2-18. Learning, These differences LLC in outline shapes are also© Jonesmaxillary & central Bartlett incisor Learning,is somewhat triangular LLC in shape due to its NOT FORevident SALE in OR all teeth DISTRIBUTION in Figure 2-17. NOTflatter FOR labial SALE surface. OR DISTRIBUTION

9781284218251_CH02_049_077.indd 63 25/03/20 4:27 PM 64 PART 1 ■ Comparative Tooth Anatomy

© Jones &3. Bartlett Maxillary Learning, Central Incisor LLC May Have a Very Slight © Jones & Bartlett Learning, LLC NOT FOR SALEDistolingual OR DISTRIBUTION Twist (Incisal View) NOT FOR SALELEARNING OR DISTRIBUTION EXERCISE

The incisal ridge or edge of the maxillary central incisor is In determining a right from a left maxillary central incisor thick faciolingually (1.5 to 2 mm) and is slightly curved from when it is not in the mouth (such as on the operatory table mesial to distal, the convexity being on the labial side. It termi- with other incisors after multiple extractions), you need to nates mesially and distally© Jones at the widest & Bartlett portion of Learning, the crown LLCdistinguish the mesial from the© distal Jones surface. & IfBartlett you look atLearning, LLC (Appendix 1q). The positionNOT FORof the distoincisalSALE OR angle DISTRIBUTION may be the facial surface of a tooth NOTwith its FORroot aligned SALE correctly OR DISTRIBUTION slightly more lingual than the position of the mesioincisal for the correct arch and are able to identify the mesial or angle, which then gives the incisal edge its slight distolingual distal surface, you can place the tooth in its correct quadrant twist as though someone took the distal half of the incisal edge (right or left) and assign its Universal number. Evaluate the and twisted it to the lingual (Appendix 2g and Fig. 2-14). Be rows of maxillary incisors in the figures in this chapter, and, using the chart in each figure, see how many “right from aware that for maxillary central incisors, the two traits just © Jones & Bartlett Learning, LLC left” traits can© Jonesbe used to& differentiateBartlett theLearning, mesial from LLC the discussed (the cingulum displaced to the distal and the dis- NOT FOR SALE OR DISTRIBUTION distal surfacesNOT and FOR therefore SALE right OR from DISTRIBUTION left incisors. For tolingual twist of the incisal edge) are dependent on how the example, in Figure 2-7, look at the labial surfaces for the tooth is held. When viewed from the incisal, the distolingual shape of the incisal angles (more rounded on distal) and twist of the incisal edge is more obvious when the cingulum the position of the contact areas (more cervical on distal), is aligned vertically (Appendix 2g), whereas the displacement or look at the proximal surfaces in Figure 2-13 for the © Jones &of Bartlettthe cingulum Learning, to the distal LLCis more obvious when the incisal© Jonesamount & Bartlettof cervical lineLearning, curvature on LLC the mesial and distal NOT FORedge SALE is aligned OR DISTRIBUTIONhorizontally (Appendix 2e). This is why theseNOT FORsides (more SALE curved OR on DISTRIBUTION mesial). From the lingual view, look two traits are shown on page 2 of the Appendix, showing two at Figure 2-9 for the length of the marginal ridges (mesial is views of the same tooth, each having a slightly different align- longer), and from the incisal view on the maxillary central ment to accentuate the trait being discussed. (Fig. 2-17), look for the distal location of the cingulum on many maxillary central incisors. The incisal ridges on lateral incisors are straighter mesiodistally than on the© Jonescentral incisors. & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

TYPE TRAITS THAT DISTINGUISH MANDIBULAR CENTRAL SECTION V © Jones & BartlettFROM Learning, LATERAL LLC INCISORS (FROM© Jones ALL &VIEWS) Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

OBJECTIVES

This section is designed to prepare the learner to perform the following: © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE• Describe OR theDISTRIBUTION type traits that can be used to NOT FORdentition. SALE If possible, OR DISTRIBUTION repeat this on a model with one differentiate the permanent mandibular central from or more mandibular incisors missing. the lateral incisor. • Select and separate mandibular incisors from a • Describe and identify the labial, lingual, mesial, distal, selection of all teeth on a bench top. and incisal surfaces for mandibular lateral incisors • Holding a mandibular incisor, determine whether it is and the labial, lingual,© Jones and incisal & surfacesBartlett for Learning,the LLCa central or a lateral and right© orJones left. Then, & assignBartlett a Learning, LLC symmetrical mandibularNOT centralFOR incisorSALE (where OR DISTRIBUTIONthe Universal number to it (whichNOT may FORnot be SALEpossible ORfor DISTRIBUTION mesial may be difficult to distinguish from the distal). the symmetrical mandibular central incisor, which you • Assign a Universal number to mandibular incisors could identify as tooth 24 or 25). present in a mouth (or on a model) with complete © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Within this section, type traits are presented that distinguish mandibular central incisors from lateral incisors. A. TYPE TRAITS OF MANDIBULAR INCISORS Other traits will be helpful when distinguishing right from FROM THE LABIAL VIEW left mandibular incisors. These traits are presented for each © Jones & Bartlett Learning, LLC © JonesExamine & severalBartlett extracted Learning, teeth and/or LLC models as you read. view of the tooth: facial, lingual, proximal (including mesial Also, refer to page 2 of the Appendix and Figure 2-19 while NOT FORand SALE distal), OR and DISTRIBUTION incisal. NOTyou FOR study SALE the labial OR surfaceDISTRIBUTION of mandibular incisors. Hold

9781284218251_CH02_049_077.indd 64 25/03/20 4:27 PM CHAPTER 2 ■ Morphology of the Permanent Incisors 65

© Jones & FIGURE Bartlett 2-19. Learning, Mandibular central LLC and lateral incisors, labial views©, Joneswith type traits& Bartlett that distinguish Learning, mandibular centralLLC from lateral incisors and traits that distinguish right and left sides. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

DM DM

Lateral (Right) Central (Right)

MANDIBULAR INCISORS: LABIAL VIEWS © Jones & Bartlett Learning, LLCCentral (Right) © Jones & Bartlett CentralLearning, (Left) LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 25 24 Distal Distal © Jones & Bartlett Learning,Mesial LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Lateral (Right) Lateral (Left) © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION26 23 NOT FOR SALE OR DISTRIBUTION Distal Distal Mesial © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

TRAITS TO DISTINGUISH MANDIBULAR CENTRAL FROM LATERAL INCISOR: LABIAL VIEW

CENTRAL INCISOR © Jones & Bartlett Learning, LLCLATERAL INCISOR © Jones & Bartlett Learning, LLC More symmetrical crownNOT FOR SALE OR DISTRIBUTIONLess symmetrical crown NOT FOR SALE OR DISTRIBUTION Minimal distal and mesial bulge of crown Obvious distal bulge on crown, crown appears to tilt distally Proximal contacts on same level mesial and distal Mesial proximal contact more incisal Smaller than lateral in the same mouth Larger than central in the same mouth

TRAITS© Jones TO DIFFERENTIATE & Bartlett Learning, MANDIBULAR LLC RIGHT FROM LEFT INCISOR:© Jones LABIAL & Bartlett VIEW Learning, LLC

CENTRALNOT FORINCISOR SALE OR DISTRIBUTION LATERAL INCISORNOT FOR SALE OR DISTRIBUTION Very symmetrical: cannot easily tell right from left Distal crown outline bulges more than mesial Distal proximal contact more cervical Distal incisal line angle more rounded © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

9781284218251_CH02_049_077.indd 65 25/03/20 4:27 PM 66 PART 1 ■ Comparative Tooth Anatomy

© Jones &mandibular Bartlett teeth Learning, with the LLCroot down and crown up, the© Jones & Bartlett Learning, LLC NOT FORposition SALE of OR the teethDISTRIBUTION in the mouth. NOT FOR SALE OR DISTRIBUTION

1. Crown Shape of Mandibular Incisors (Labial View) Three mamelons are often© Jones present & on Bartlett newly emerged Learning, man- LLC © Jones & Bartlett Learning, LLC dibular incisors and reflectNOT the FOR formation SALE of the OR facial DISTRIBUTION surface NOT FOR SALE OR DISTRIBUTION from three labial lobes (Fig. 2-20). In most persons, they are soon worn off by functional contacts against the maxillary incisors (a process called attrition). All mandibular incisor crowns are quite narrow relative to their© Jones crown length, & Bartlett but the Learning,mandibular centralLLC incisor © Jones & Bartlett Learning, LLC crownNOT is the FOR narrowest SALE crown OR in DISTRIBUTION the mouth and is consid- NOT FOR SALE OR DISTRIBUTION erably narrower than the maxillary central incisor.J Unlike maxillary incisor crowns in the same mouth where the cen- FIGURE 2-21. When considering the relative size of each type tral is larger than the lateral, the mandibular lateral incisor of incisor, it becomes obvious on this model that the maxillary crown is a little larger in all dimensions than the mandibular central incisors are widest and largest, followed by the maxillary © Jones ¢ral Bartlett incisor Learning, in the same LLCmouth, as seen in Figure 2-21©. Joneslaterals, & then Bartlett the mandibular Learning, laterals, and LLC finally the smallest and NOT FORFurther, SALE the OR mandibular DISTRIBUTION central incisor is so symmetricalNOT narrowest FOR SALE mandibular OR central DISTRIBUTION incisors. that it is difficult to tell lefts from rights unless in place in the mouth or on full arch models. About the only notable difference to be found is the greater mesial than distal curvature sors in Figure 2-19, and notice the lack of symmetry of of the cervical line, but this is not a trait that can be seen in the outline of most mandibular lateral incisors compared the mouth. © Jones & Bartlett Learning, LLCto the symmetry of the central© incisors.Jones When& Bartlett comparing Learning, LLC The crown of the mandibularNOT FOR lateral SALE incisor OR resembles DISTRIBUTION these teeth, be aware that theNOT incisal FOR edges SALEmay have OR worn DISTRIBUTION that of the mandibular central incisor, but it is slightly wider unevenly. and is not as bilaterally symmetrical. Its crown appears The labial surfaces ofboth types of mandibular incisors to tilt slightly distally on its root, giving the impression are most often smooth, but could have two shallow devel- that the tooth has been bent at the cervix (Appendix 2l). opmental depressions in the incisal third if you examine the This© tilt, Jones plus the & sloping Bartlett of the Learning, incisal edge LLCshorter on the surface closely.© KJones & Bartlett Learning, LLC distalNOT (Appendix FOR 1s), SALE makes OR the curvedDISTRIBUTION distal outline of the NOT FOR SALE OR DISTRIBUTION crown from proximal contact area to cervical line shorter than the straighter mesial crown outline. Look at the inci- 2. Incisal Proximal Angles of Mandibular Incisors (Labial View) The crown of the mandibular central incisor is nearly bilat- © Jones & Bartlett Learning, LLC © Joneserally symmetrical,& Bartlett so Learning, the mesioincisal LLC and distoincisal angles NOT FOR SALE OR DISTRIBUTION NOTare FOR very SALEsimilar, formingOR DISTRIBUTION nearly right angles (Appendix 2j). The distoincisal angle may barely be more rounded than the mesioincisal angle. The distoincisal angle of the mandibular lateral incisor, however, is noticeably more rounded than the mesioincisal angle (Appendix 2j). This helps to distin- © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC 26 guish right mandibular lateral incisors from lefts prior to NOT FOR SALE OR DISTRIBUTIONincisal tooth wear. NOT FOR SALE OR DISTRIBUTION 25 24 23 3. Proximal Contact Areas of Mandibular Incisors (Labial View) © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION The esialm NOTand distal FOR contact SALE areas OR ofDISTRIBUTION the mandibular FIGURE 2-20. These mandibular incisors have remnants of central incisor are at the same level: in the incisal third three mamelons that reflect the formation of the labial surface of (Appendix 2i) almost level with the incisal edge. The mesial incisors from three labial lobes (plus one lingual lobe forms the and distal contact areas of the lateral incisor are not at cingulum). These mamelons are partially worn away due to these the same level (Appendix 2i). Although both the mesial © Jones &teeth Bartlett biting against Learning, maxillary incisors. LLC © Jonesand distal & Bartlett contacts areLearning, in the incisal LLC third fairly close to NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

9781284218251_CH02_049_077.indd 66 25/03/20 4:28 PM CHAPTER 2 ■ Morphology of the Permanent Incisors 67

© Jones & BartlettTABLE 2-3 Learning, Location LLC of Proximal Contacts (Proximal© Jones Height of& Contour) Bartlett on Learning,Incisors (Best LLCSeen from Facial View) NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION MESIAL SURFACE DISTAL SURFACE (WHICH THIRD OR JUNCTION?) (WHICH THIRD OR JUNCTION?)

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Central incisorNOT FORIncisal SALE third (nearOR DISTRIBUTIONincisal edge) Incisal/middle junctionNOT FOR SALE OR DISTRIBUTION Lateral incisor Incisal third Middle third (most cervical of incisor contacts) CROWNS MAXILLARY

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Central incisor Incisal third (near incisal edge) Incisal third (near incisal edge; same as mesial) Lateral incisor Incisal third (near incisal edge) Incisal third (but more cervical) CROWNS MANDIBULAR

© Jones &General Bartlett learning guidelinesLearning, for incisors: LLC © Jones & Bartlett Learning, LLC NOT FOR1. SALE On the same OR incisor, DISTRIBUTION the distal proximal contact is more cervical than theNOT mesial contact FOR EXCEPT SALE on mandibular OR DISTRIBUTION central incisors, where the mesial and distal contacts are at the same height. 2. All contacts for both types of mandibular incisors are in the incisal third, as are the mesial contacts on maxillary incisors. Distal contacts of maxillary central incisors are near the incisal/middle junction, and the distal contacts on maxillary lateral incisors are most cervical: in the middle third.

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC the incisal edge, the distalNOT contact FOR isSALE noticeably OR more DISTRIBUTION cer- 1. Cingulum of MandibularNOT Incisors FOR (Lingual SALE View) OR DISTRIBUTION vical than the mesial contact on lateral incisors. Refer to Table 2-3 for a summary of the location of proximal con- As seen from the lingual view (or from the incisal view in tacts for all incisors. Appendix 2k), the cingulum of the mandibular central incisor is convex, small, and centered on the axis line of the root. © Jones & Bartlett Learning, LLC The cingulum© Jonesof thelateral & Bartlett incisor lies Learning, slightly distal LLC to the 4. NOTRoot-To- FORCrown SALE Proportions OR DISTRIBUTION of Mandibular axis line of theNOT root FOR (similar SALE to the maxillaryOR DISTRIBUTION central incisor). Incisors (Labial View) This distal location of the cingula on mandibular lateral incisors is highlighted in Figure 2-22. Mandibular incisor roots are long incisocervically and appear proportionally longer compared to their crown length than on the maxillary incisors. Therefore, the root-to-crown ratio 2. Lingual Anatomy (Marginal Ridges and Fossae) © Jones &is largerBartlett for both Learning, mandibular LLC incisors compared to maxillary© Jonesof & Mandibular Bartlett Learning,Incisors (Lingual LLC View) NOT FOR SALE OR DISTRIBUTIONL NOT FOR SALE OR DISTRIBUTION central and lateral incisors. The lingual fossae of both types of mandibular incisors are barely visible, smooth (without grooves, accessory ridges, or pits), and shallow, just slightly concave in the middle and 5. Root Shape of Mandibular Incisors (Labial View) incisal thirds (Appendix 2m). The marginal ridges of man- The ootsr of both types© of Jones mandibular & Bartlett incisors appear Learning, very LLCdibular incisors are often scarcely© Jones discernible, & Bartlett unlike Learning, on LLC narrow mesiodistally butNOT wide FOR faciolingually SALE OR (ribbon-like) DISTRIBUTION maxillary incisors, where theyNOT are more FOR likely SALE to be OR quite DISTRIBUTION (compare proximal to labial surfaces in Appendix 2n) and prominent (Fig. 2-23). Since the length of the incisal edge taper uniformly on both sides from the cervical line to the slopes cervically toward the distal on mandibular lateral apex. The apical end may curve slightly to the distal (seen in incisors, and the cingulum is located toward the distal, the some incisors in Fig. 2-19). mesial marginal ridge on these teeth appears longer than the © Jones & Bartlett Learning, LLC distal marginal© Jones ridge (Appendix & Bartlett 2k). Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION B. TYPE TRAITS OF MANDIBULAR INCISORS 3. Root Contours of Mandibular Incisors FROM THE LINGUAL VIEW (Lingual View) Refer to Figure 2-22 while studying the lingual surface of As with other incisor roots, the lingual root surfaces of both © Jones &mandibular Bartlett incisors. Learning, LLC © Jonestypes of& mandibular Bartlett incisorsLearning, are mostly LLC convex, and slightly NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

9781284218251_CH02_049_077.indd 67 25/03/20 4:28 PM 68 PART 1 ■ Comparative Tooth Anatomy

© Jones & FIGURE Bartlett 2-22. Learning, Mandibular central LLC and lateral incisors, lingual views© Jones, with type &traits Bartlett that distinguish Learning, mandibular LLC central from lateral incisors and traits that distinguish right and left sides. Circles highlight the distal placement of most cingula on these mandibular NOT FOR SALE ORlateral DISTRIBUTION incisors. NOT FOR SALE OR DISTRIBUTION

MDD MDM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Central (Right) Lateral (Right) © Jones & Bartlett Learning, LLC MANDIBULAR INCISORS:© Jones LINGUAL & Bartlett VIEWS Learning, LLC NOT FOR SALE OR DISTRIBUTIONCentral (Left) NOT FOR SALE OR CentralDISTRIBUTION (Right)

24 25

© Jones & BartlettLateral Learning, (Left) LLC © JonesLateral & Bartlett (Right) Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 23 26 Distal Distal © Jones & Bartlett Learning, LLC © JonesMesial & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

TRAITS TO DISTINGUISH© Jones MANDIBULAR & Bartlett Learning, CENTRAL FROM LLC LATERAL INCISOR: ©LINGUAL Jones VIEW& Bartlett Learning, LLC CENTRAL INCISOR NOT FOR SALE OR DISTRIBUTIONLATERAL INCISOR NOT FOR SALE OR DISTRIBUTION Cingulum centered Cingulum distal to center Same length mesial and distal marginal ridges Longer mesial marginal ridge

TRAITS TO DIFFERENTIATE MANDIBULAR RIGHT FROM LEFT INCISOR: LINGUAL VIEW © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC CENTRALNOT FORINCISOR SALE OR DISTRIBUTION LATERAL INCISORNOT FOR SALE OR DISTRIBUTION Very symmetrical: cannot tell right from left Cingulum distal to center Shorter distal marginal ridge

9781284218251_CH02_049_077.indd 68 25/03/20 4:28 PM CHAPTER 2 ■ Morphology of the Permanent Incisors 69

© Jones & Bartlett Learning, LLC © Jonesof the incisal& Bartlett edge, but Learning, it is much less LLC obvious than on most NOT FOR SALE OR DISTRIBUTION NOTmandibular FOR SALE laterals. OR DISTRIBUTION

2. Cervical Line on Mandibular Incisors (Proximal Views) © Jones & Bartlett Learning, LLCThe cervical line on the mesial© ofJones both types & Bartlett of mandibu Learning,- LLC NOT FOR SALE OR DISTRIBUTIONlar incisors normally has a relativelyNOT FORpronounced SALE curvature OR DISTRIBUTION that extends incisally almost one fourth of the crown length. As on all other anterior teeth, the curvature on the distal is less.M

© Jones & Bartlett Learning, LLC 3. Crest of© CurvatureJones & of Bartlett Mandibular Learning, Incisors LLC NOT FOR SALE OR DISTRIBUTION (ProximalNOT Views) FOR SALE OR DISTRIBUTION As on the labial outline of maxillary incisors, the labial crests of curvature (heights of contour) on both types of mandibular incisors are in the cervical third, just incisal © Jones & Bartlett Learning, LLC © Jonesto the &cervical Bartlett line. Learning,The labial outline LLC becomes nearly flat NOT FOR SALE OR DISTRIBUTION NOTin FOR the incisal SALE third. OR The DISTRIBUTION lingual outlines are “S” shaped, and the heights of contour are also in the cervical third, on the cingulum.

© Jones & Bartlett Learning, LLC4. Root Shape and Depressions© Jones of Mandibular & Bartlett Learning, LLC FIGURE 2-23. You can see the mesial root depression of this Incisors (Proximal Views) mandibular central incisorNOT even from FOR the lingualSALE view. OR Notice DISTRIBUTION that NOT FOR SALE OR DISTRIBUTION the lingual surface of the crown is smooth with little evidence The elativelyr wide faciolingual dimension of the roots at the of marginal ridges or lingual fossa: typical of most mandibular cervix on both types of mandibular incisors is very apparent incisors. from the proximal view. The facial and lingual outlines of the roots of all mandibular incisors are nearly straight from © Jones & Bartlett Learning, LLC the cervical© line Jones to the &middle Bartlett third; Learning,then, the root LLC tapers narrowerNOT on FOR the lingual SALE side OR than DISTRIBUTION on the labial side. You may with its apexNOT on the FOR midroot SALE axis ORline (seenDISTRIBUTION in most roots see evidence of mesial and distal longitudinal root depres- in Fig. 2-24). Recall that the cervical portion of the roots sions from this view (Fig. 2-23). of mandibular incisors is considerably wider faciolingually than mesiodistally (ribbon-like).N There is usually a slight longitudinal depression on the © Jones &C. Bartlett TYPE TR Learning,AITS OF MANDIBULARLLC INCISORS© Jonesmiddle & third Bartlett of the mesialLearning, and distal LLC root surfaces of both NOT FOR SALEFROM OR THE DISTRIBUTION PROXIMAL VIEWS NOTtypes FOR of SALE mandibular OR DISTRIBUTIONincisors. The distal depressions are somewhat more distinct. See Table 2-4 for a summary of Refer to Figure 2-24 while studying the proximal surfaces of incisor root depressions. See Figure 2-25 for a slight mesial mandibular incisors. surface depression on the root of a mandibular lateral incisor. 1. Incisal Edge on Mandibular© Jones &Incisors Bartlett Learning, LLC © Jones & Bartlett Learning, LLC (Proximal Views)NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION D. TYPE TRAITS OF MANDIBULAR INCISORS The incisal edges of both types of mandibular incisors FROM THE INCISAL VIEW are normally located on or lingual to the midroot axis (Appendix 2o). From the mesial side, the distolingual twist To follow this description, the tooth should be held in such of the© incisalJones ridge & ofBartlett the mandibular Learning, lateral LLCincisor places a position that© Jones the incisal & edgeBartlett is toward Learning, the observer, LLC the the distalNOT portion FOR atSALE the ridge OR even DISTRIBUTION somewhat more lingual labial surfaceNOT is up, FOR and the SALE observer OR is looking DISTRIBUTION exactly along than on the mesial (seen clearly in Fig. 2-25), unlike the man- the root axis line as in Figure 2-26. You will see slightly more dibular central that has no twist. Recall that the maxillary of the labial than the lingual surface if the incisal ridge is just central incisor might also exhibit a slight distolingual twist lingual to the root axis line.

9781284218251_CH02_049_077.indd 69 25/03/20 4:28 PM 70 PART 1 ■ Comparative Tooth Anatomy

© Jones & FIGURE Bartlett 2-24. Learning, Mandibular central LLC and lateral incisors, proximal views© Jones, with type & traitsBartlett that distinguish Learning, mandibular LLC central from lateral incisors and traits that distinguish right and left sides. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

MANDIBULAR INCISORS: PROXIMAL VIEWS Left Central (Distal) Right Central (Mesial) © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION 24 NOT FOR25 SALE OR DISTRIBUTION Facial © Jones & Bartlett Learning, LLC © Jones & BartlettLingual Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Left Lateral (Distal) Right Lateral (Mesial) © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION23 26 NOT FOR SALE OR DISTRIBUTION Facial © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Lingual NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

TRAITS TO DISTINGUISH MANDIBULAR CENTRAL FROM LATERAL INCISOR: PROXIMAL VIEWS © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC CENTRAL INCISOR LATERAL INCISOR NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION No distolingual twist Distal of incisal ridge may be more lingual

TRAITS TO DIFFERENTIATE MANDIBULAR RIGHT FROM LEFT INCISOR: COMPARING PROXIMAL VIEWS

CENTRAL INCISOR LATERAL INCISOR © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Distal of incisal ridge even with mesial of incisal ridge Distal of incisal ridge may be more lingual NOT FOR SALEMesial OR cervical DISTRIBUTION line curve greater than distal on both centralNOT and FOR lateral SALE incisors OR DISTRIBUTION

9781284218251_CH02_049_077.indd 70 25/03/20 4:28 PM CHAPTER 2 ■ Morphology of the Permanent Incisors 71

© Jones & Bartlett Learning, LLC © Jonescentered, & Bartlettand the lingual Learning, crest of curvature LLC is centered on the NOT FOR SALE OR DISTRIBUTION NOTsmooth, FOR SALEnarrow cingulum.OR DISTRIBUTION The thick (2 mm) incisal ridge of this symmetrical incisor runs in a straight line mesiodistally toward both contact areas and is at right angles to the labiolingual root axis plane. The mandibular lateral incisor is not bilaterally sym- © Jones & Bartlett Learning, LLCmetrical. If you align the incisal© Jones edge of the& Bartlettlateral incisor Learning, LLC NOT FOR SALE OR DISTRIBUTIONexactly horizontal, the cingulumNOT of FORthe mandibular SALE ORlateral DISTRIBUTION incisor is located distal to the mesiodistal midline (Appendix 2k). Recall that this was also seen on the maxillary central incisor. Looked at another way, if you were to align a mandibular lateral incisor with its lingual cingulum directed © Jones & Bartlett Learning, LLC exactly downward© Jones or vertically& Bartlett (represented Learning, roughly LLC by NOT FOR SALE OR DISTRIBUTION the dotted verticalNOT lineFOR with SALE the arrow OR in DISTRIBUTION Appendix 2k), the distal half of the incisal edge would be perceived as twisted lingually (called a distolingual twist) (Fig. 2-27). This twist is evident in most mandibular lateral incisors in Figure 2-26 and is an excellent way to distinguish mandibular central © Jones & Bartlett Learning, LLC © Jonesfrom lateral& Bartlett incisors Learning,and to distinguish LLC the right from left FIGURE 2-25. It is clear from the mesial view of this mandibular mandibular lateral incisors. NOT FORleft SALE lateral incisorOR DISTRIBUTIONthat there is a pronounced distolingual twist NOT FOR SALE OR DISTRIBUTION (i.e., the distal portion of the incisal edge curves lingually) so that some of the lingual surface is visible from this mesial view. Also, 2. Incisal Ridge Is on or Lingual to Root Axis on notice the slight root depression on the mesial surface. Mandibular Incisors (Incisal View) © Jones & Bartlett Learning, LLCIncisal ridges of both types of ©mandibular Jones incisors& Bartlett are on Learning, or LLC lingual to the midroot axis. If you hold an extracted man- 1. Crown Outline andNOT Incisal FOR Ridge SALE Alignment OR DISTRIBUTION on NOT FOR SALE OR DISTRIBUTION dibular incisor with the root facing directly away from your Mandibular Incisors (Incisal View) sight line, slightly more of the labial than lingual surface The mandibular central incisor is practically bilaterally would be visible if the incisal ridge is lingual to the root axis, symmetrical with little to differentiate the mesial half from especially on the distal half of mandibular lateral incisors due the distal© Jones half. The & Bartlettlabial and lingualLearning, crests ofLLC curvature are to the distolingual© Jones twist. & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

NOT FOR SALE ORTOOTH DISTRIBUTION MESIALNOT ROOT FORDEPRESSION? SALE OR DISTRIBUTIONDISTAL ROOT DEPRESSION?

Maxillary central incisor Not likely No (convex) Maxillary lateral incisor Variable No (convex)

MAXILLARY NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Mandibular central incisor Yes Yes (deeper)

NOTMANDIBULAR FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

General learning guidelines for incisors: 1. Maxillary incisors are not likely to have distal root depressions but could have mesial depressions. 2. Mandibular incisors usually have mesial and distal (deeper) root depressions. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

9781284218251_CH02_049_077.indd 71 25/03/20 4:29 PM 72 PART 1 ■ Comparative Tooth Anatomy

© Jones & FIGURE Bartlett 2-26. Learning, Mandibular central LLC and lateral incisors, incisal views© ,Jones with type traits& Bartlett that distinguish Learning, mandibular LLCcentral from lateral incisors and traits that distinguish right and left sides. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

MDM D © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Central (Right) Lateral (Right)

MANDIBULAR INCISORS: INCISAL VIEWS © Jones & BartlettCentral Learning, (Left) LLC © JonesCentral & Bartlett (Right) Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 24 25 Distal Distal Mesial

TRAITS TO DISTINGUISH© Jones MANDIBULAR & Bartlett Learning, CENTRAL FROMLLC LATERAL INCISOR: ©INCISAL Jones VIEW & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION CENTRAL INCISOR LATERAL INCISOR No distolingual twist of incisal edge Distolingual twist of incisal edge Cingulum is centered Cingulum is off center to distal

TRAITS© Jones TO DIFFERENTIATE & Bartlett Learning, MANDIBULAR LLC RIGHT FROM LEFT ©INCISOR: Jones INCISAL& Bartlett VIEW Learning, LLC CENTRALNOT FORINCISOR SALE OR DISTRIBUTION LATERAL INCISORNOT FOR SALE OR DISTRIBUTION Very symmetrical: cannot tell right from left Distolingual twist of incisal edge Cingulum is off center to distal

© Jones & Bartlett Learning, LLC © Jones FIGURE & 2-28. Bartlett Shovel-shaped Learning, permanent LLC incisors from a young NOT FOR FIGURESALE 2-27. OR The DISTRIBUTION distolingual twist of this right mandibular NOTNative FOR American SALE dentition OR DISTRIBUTION (incisal views). Note the prominent lateral incisor is quite evident. marginal ridges on the lingual surface.

9781284218251_CH02_049_077.indd 72 25/03/20 4:29 PM CHAPTER 2 ■ Morphology of the Permanent Incisors 73

There is great morphologic variation in the maxillary lateral incisor. It may be missing© Jonesaltogether; & it Bartlett may resemble Learning, a small LLC LEARNING© EXERCISE Jones & Bartlett Learning, LLC slender version of a maxillaryNOT FORcentral SALEincisor; itOR may DISTRIBUTION be quite NOT FOR SALE OR DISTRIBUTION asymmetrical; or it may be peg shaped (as seen later in the Assign a Universal number to a handheld incisor: chapter on anomalies). Suppose a patient just had all of his or her permanent Racial differences in the maxillary incisor teeth have teeth extracted. Imagine being asked to find tooth 8 from been reported in dental literature. Shovel shape is the among a pile of 32 extracted teeth on the oral surgeon’s term© commonly Jones &used Bartlett to designate Learning, incisor teeth LLC that have tray because© youJones wanted & toBartlett evaluate a Learning, lesion seen on LLC the prominentNOT marginalFOR SALE ridges OR and DISTRIBUTIONa deep fossa on their lin- radiographNOT on the FOR root of SALE that incisor. OR How DISTRIBUTION might you go gual surfaces (Fig. 2-28). A high incidence of shovel-shaped about it? Only after you have written down your own incisors has been observed in Mongoloid people, includ- ideas, then consider the following steps: ing many groups of American Indians.4,6,7,9 (Mongoloid • From a selection of all permanent teeth (extracted teeth pertains to a major racial division marked by a fold from or tooth models), select only the incisors (based on class © Jones &the Bartlett eyelid over Learning, the inner canthus, LLC prominent cheekbones,© Jonestraits & Bartlett). Learning, LLC NOT FORstraight SALE black OR hair,DISTRIBUTION small nose, broad face, and yellowishNOT FOR• Determine SALE whether OR DISTRIBUTIONeach incisor is maxillary or mandibular complexion. Included are Mongols, Manchus, Chinese, using arch traits. Review Table 2-2 if needed. You should Koreans, Arctic coastal populations, Japanese, Siamese, never rely on only one characteristic difference between Burmese, Tibetans, and American Indians.) White and teeth to name them; rather, make a list of many traits that apply to a maxillary incisor, as opposed to only one black people are reported to have less frequent occurrences © Jones & Bartlett Learning, LLCtrait that makes you think it© belongs Jones in the& Bartlettmaxilla. This Learning, LLC of this characteristic. way, you can act as a detective and become an expert at A study of the skullsNOT of FORAmerican SALE Indians OR who DISTRIBUTION lived recognition at the same time.NOT FOR SALE OR DISTRIBUTION in Arizona about 1100 ad has disclosed the occurrence of • Once you determine that the tooth is maxillary, position incisor teeth that have a mesial marginal ridge on the labial the root up; if it is mandibular, position the root down. surface and a depression, or concavity, on the mesial part • Use appropriate traits in order to identify the facial surface. of the labial surface just distal to this ridge.10 In these teeth, This will permit you to view the tooth as though you were the distal© Jones part of &the Bartlett labial surface Learning, is rounded LLCin an unusual looking into© Jones a patient’s & mouth. Bartlett Learning, LLC manner.NOT Such FOR teeth SALE have been OR referred DISTRIBUTION to as “three-quarter • Next, usingNOT type FOR traits, determineSALE OR the typeDISTRIBUTION of incisor you double shovel shaped,” a descriptive, if ponderous, term. are holding (central or lateral). Refer to the tables and Labial “shoveling” has also been reported in some Arctic teeth in the figures throughout this chapter as needed. • Next, determine which surface is the mesial. Refer to coastal populations. figures throughoutthis chapter as needed. While viewing There is more uniformity of shape in the mandibular © Jones & Bartlett Learning, LLC © Jonesthe & incisor Bartlett from Learning,the facial and LLCpicturing it within the incisor teeth than in other teeth. In some Mongoloid people, appropriate arch (upper or lower), the mesial surface can NOT FORthe SALE cingulum OR DISTRIBUTIONof mandibular incisors is characteristicallyNOT FORbe positionedSALE OR toward DISTRIBUTION the midline in only one quadrant, marked by a short deep groove running cervicoincisally. This the right or left. groove is often a site of dental caries. • Once you have determined the quadrant, assign the Later, in the chapter on anomalies, you will read about appropriate Universal number for the incisor in that more variations: peg-shaped incisors, fused mandibular inci- quadrant. For example, the central incisor in the upper sors, congenitally missing© Jonescentral incisors, & Bartlett and even Learning, a lateral LLCright quadrant is tooth 8. © Jones & Bartlett Learning, LLC incisor merged distally NOTto the canine.FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

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© Jones & Bartlett REVIEWLearning, Questions LLC about Incisors© Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION For each of the traits listed below, select the letter(s) of the permanent incisor(s) that normally exhibit(s) that trait. More than one answer may apply. a. Maxillary central incisor b. Maxillary lateral© incisor Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC c. Mandibular centralNOT incisor FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION d. Mandibular lateral incisor 1. Mesiodistal dimension of the crown is larger than the labiolingual dimension. a b c d 2. The incisal ridge exhibits a distolingual twist. a b c d 3. The© Jones root is very & narrowBartlett mesiodistally Learning, with LLCmesial and distal root depressions.© Jones & Bartlett Learning,a b LLCc d NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 4. The incisal edge is positioned more to the lingual of the root axis line. a b c d 5. The distal proximal crest of curvature is more cervical than the mesial height of contour. a b c d 6. This ootht has the widest (mesiodistally) incisor crown. a b c d © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC 7. This ootht has the shortest root relative to its crown. a b c d NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 8. This ootht is the most symmetrical incisor. a b c d 9. This ootht has the largest curvature of the mesial cervical line. a b c d 10. This ootht has the narrowest incisor crown (mesiodistally). a b c d

NOT FOR SALE OR DISTRIBUTION10–c 9–a; 8–c; 7–a; 6–a; d; b, 5–a, d; 4–c, d; NOT3–c, d; FOR2–a, b; SALE1–a, OR DISTRIBUTION ANSWERS:

9781284218251_CH02_049_077.indd 74 25/03/20 4:29 PM CHAPTER 2 ■ Morphology of the Permanent Incisors 75

1. The only way to master the many traits of the incisors presented in this chapter is to be able to picture each trait in your mind for each type© of Jones incisor and & Bartlettfor each side Learning, of the mouth. LLC Therefore, even though you ©have Jones probably & already Bartlett looked Learning, LLC carefully at each illustrationNOT FOR in this SALE chapter, OR at thisDISTRIBUTION time, reread the legends and study eachNOT figure FORin this SALEchapter. IfOR any DISTRIBUTION facts are unclear, review the portion of the chapter that referred to that figure. Also, use the front and back of Appendix pages 1 and 2 to review all identified traits of incisors. 2. While you are recording which teeth are present in the mouth of Mrs. Jenny James, you notice that she has only three mandibular incisors. How might you determine which specific mandibular incisors are still present? Think of things ©you Jones have learned & Bartlett about incisors, Learning, and try toLLC recall facts you may already know© Jones about landmarks& Bartlett in the Learning, mouth. LLC 3. NOTLook at FOR your mouth SALE in theOR mirror DISTRIBUTION while you place your anterior maxillaryNOT and mandibular FOR SALE teeth ORedge toDISTRIBUTION edge, and align the arch midlines (the proximal contacts between central incisors) over one another. If your teeth are of average shape and alignment, notice that the distal outline of each maxillary central incisor extends distal to its opposing mandibular central incisor because the maxillary central is wider. Also, notice that the maxillary central incisors are wider and larger than the maxillary lateral incisors and that the maxillary central incisors and maxillary lateral incisors are wider © Jones & Bartlettthan either Learning, the mandibular LLC central or lateral incisors. ©Finally, Jones note &that Bartlett the mandibular Learning, central incisorsLLC appear slightly NOT FOR SALEnarrower OR andDISTRIBUTION smaller than the adjacent mandibular lateralNOT incisors. FOR SALE OR DISTRIBUTION 4. Using a good light source (like a small flashlight), a large mirror (magnifying if possible), and a small, clean disposable dental mirror, carefully compare the maxillary and mandibular incisors in your own mouth while referring to the traits in Table 2-2 from the labial view and lingual view that can be used to differentiate maxillary from mandibular incisors. Write down© Jones each trait & that Bartlett can be useful Learning, to differentiate LLC the maxillary from the ©mandibular Jones incisors& Bartlett in your Learning, LLC own mouth, and alsoNOT make FOR note SALE of any of OR the traitsDISTRIBUTION in the text book that do not apply in yourNOT mouth. FOR SALE OR DISTRIBUTION 5. Perform a computer search for images of “close-ups of celebrity teeth,” and answer the following questions for at least five of the images. Remember that many of these celebrities have had major cosmetic dental work, so you may not be viewing their original teeth. a. Are their maxillary central incisors wider than their maxillary lateral incisors? ©b. JonesCan you &see Bartlett evidence of Learning, formation from LLC three facial lobes on any of their© Jones anterior & teeth? Bartlett Learning, LLC NOTc. Try FORto find SALE at least OR one DISTRIBUTIONpicture where you can see the mandibular NOTincisors, FOR and SALEanswer these OR DISTRIBUTIONquestions. Are the mandibular incisors narrower than the maxillary incisors? Are their mandibular centrals narrower than the laterals? Do you see any spaces (diastemas) between teeth? If not, try looking for images of Madonna, the early years, for the diastema between her central incisors (which she had closed during her later years). 6. Search the Internet for images of “orthodontics before and after,” and answer the same questions as in exercise © Jones & Bartlett#4 above Learning, for the “before” LLC pictures and for the “after” ©pictures. Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

REFERENCES 7. De Voto FCH, Arias NH, Ringuelet S, et al. Shovel-shaped incisors in a northwestern Argentine population. J Dent Res 1. Hanihara K. Racial characteristics© Jones in& theBartlett dentition. Learning, J Dent Res LLC © Jones & Bartlett Learning, LLC 1968;47:820. 1967;46:923–926. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 8. Taylor RMS. Variations in form of human teeth: I. An 2. Ash MM, Nelson SJ. Wheeler’s dental anatomy, physiology and anthropologic and forensic study of maxillary incisors. J Dent occlusion. Philadelphia, PA: Saunders, 2003. Res 1969;48:5–16. 3. Kraus RE, Abrams L. Kraus’ dental anatomy and occlusion. 9. Dahlberg AA. The dentition of the American Indian. In: Oxford, UK: Wolfe Publishing, Ltd., 1992. Laughlin WS, ed. The physical anthropology of the American 4. Carbonelli VM. Variations in the frequency of shovel-shaped © Jones & Bartlett Learning, LLC Indian. New© Jones York, NY: &The Bartlett Viking Fund, Learning, 1949. LLC incisors in different populations. In: Brothel DR, ed. Dental NOT FOR SALE OR DISTRIBUTION 10. Snyder RG.NOT Mesial FOR marginal SALE ridging OR of incisorDISTRIBUTION labial surfaces. anthropology. London, UK: Pergamon Press, 1963:211–234. J Dent Res 1960;39:361. 5. Brabant H. Comparison of the characteristics and anomalies of the deciduous and the permanent dentitions. J Dent Res GENERAL REFERENCES 1967;48:897–902. 6. De Voto FCH. Shovel-shaped incisors in pre-Columbian Goose DH. Variability of form of maxillary permanent incisors. © Jones & BartlettTastilian Indians. Learning, J Dent Res LLC 1971;50:168. © JonesJ Dent & ResBartlett 1956;35:902. Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

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Statistics obtained from Dr. Woelfel’s original research on B. The crown of the maxillary lateral incisor averages teeth have been used to draw conclusions throughout this about 2.0 mm narrower mesiodistally than on the cen- chapter and were referenced© Jones with & superscript Bartlett lettersLearning, that LLC tral incisor, and the root© is Jones0.4 mm longer. & Bartlett Learning, LLC refer to the data stated here. Data from his original research C. The maxillary lateral incisor root is 0.4 mm longer are presented in TablesNOT 2-5A and FOR 2-5B SALE. OR DISTRIBUTIONthan on the maxillary NOTcentral. FOR The SALEaverage root-to-OR DISTRIBUTION crown ratio for 295 maxillary lateral incisors was 1.37. A. The crown of the maxillary central incisor averages The average root-to-crown ratio for 398 maxillary 11.2 mm long incisocervically, making it the longest central incisors was 1.16. incisor crown. This crown averages 2.6 mm longer D. The maxillary central incisor root at the cervix averages ©incisogingivally Jones & Bartlett than mesiodistally. Learning, LLC © Jones & Bartlett Learning, LLC about 6.4 mm wide mesiodistally and faciolingually. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

TABLE 2-5A Size of Maxillary Incisors (Millimeters)

Crown length 11.2 longest incisor crown 8.6–14.7 9.8 7.4–11.9 Root length © Jones &13.0 Bartlett Learning, LLC 6.3–20.3 13.4© Jones & Bartlett9.6–19.4 Learning, LLC Overall length NOT FOR SALE23.6 OR DISTRIBUTION16.5–32.6 22.5NOT FOR SALE17.7–28.9 OR DISTRIBUTION Root-to-crown ratio 1.16 1.37 Crown width (mesiodistal) 8.6 7.1–10.5 6.6 5.0–9.0 Root width (cervix) 6.4 5.0–8.0 4.7 3.4–6.4 © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC FaciolingualNOT FOR crown SALE size OR DISTRIBUTION7.1 6.0–8.5NOT FOR SALE6.2 OR DISTRIBUTION5.3–7.3 Faciolingual root (cervix) 6.4 5.1–7.8 5.8 4.5–7.0 Mesial CEJ curve 2.8 greatest CEJ curve 1.4–4.8 2.5 1.3–4.0 Distal CEJ curve 2.3 0.7–4.0 1.9 0.8–3.7 © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION TABLE 2-5B Size of Mandibular Incisors (Millimeters)

226 CENTRALS 234 LATERALS

DIMENSION MEASURED© Jones &AVERAGE Bartlett Learning, LLC RANGE AVERAGE© Jones & BartlettRANGE Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Crown length 8.8 6.3–11.6 9.4 7.3–12.6 Root length 12.6 7.7–17.9 13.5 9.4–18.1 Overall length 20.8 16.9–26.7 22.1 18.5–26.6 Crown© Jones width (mesiodistal) & Bartlett Learning,5.3 narrowest LLC adult crown 4.4–6.7© Jones & Bartlett5.7 Learning,4.6–8.2 LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Root width (cervix) 3.5 2.7–4.6 3.8 3.0–4.9 Faciolingual crown size 5.7 4.8–6.8 6.1 5.2–7.4 Faciolingual root (cervix) 5.4 4.3–6.5 5.8 4.3–6.8 © Jones & BartlettMesial CEJ curveLearning, LLC 2.0 © Jones & 1.0–3.3Bartlett Learning,2.1 LLC 1.0–3.6 NOT FOR SALEDistal CEJ OR curve DISTRIBUTION 1.6 NOT FOR SALE0.6–2.8 OR DISTRIBUTION1.5 0.8–2.4

9781284218251_CH02_049_077.indd 76 25/03/20 4:30 PM CHAPTER 2 ■ Morphology of the Permanent Incisors 77

© Jones & BartlettAll other Learning, types of maxillary LLC teeth have roots that© JonesI. The& Bartlett crown of Learning,the maxillary LLCcentral incisor averages NOT FOR SALEare thicker OR DISTRIBUTION faciolingually than mesiodistally by 1.1 toNOT FOR1.5 SALE mm wider OR mesiodistallyDISTRIBUTION than faciolingually. The 3.4 mm. crown of the maxillary lateral incisor averages only E. Dr. Woelfel examined the maxillary incisors on casts 0.4 mm wider mesiodistally than faciolingually. of 715 dental hygiene students and found that 32% J. The narrowest tooth in the mouth is the mandibular of the central incisors and 27% of the lateral incisors central incisor and averages only five eighths, or 62% have some degree© ofJones shoveling. & Bartlett The rest hadLearning, smooth LLC as wide as the maxillary© central Jones incisor. & Bartlett Learning, LLC concave lingual NOTsurfaces FOR without SALE prominent OR DISTRIBUTIONmarginal K. Dr. Woelfel found two NOTshallow FOR labial SALE developmental OR DISTRIBUTION ridges or deep fossae. depressions on 48% of 793 mandibular central inci- F. Inspection of 506 maxillary central incisors by sors and on 51% of 787 mandibular lateral incisors. Dr. Woelfel revealed 36% with no accessory lingual L. The root-to-crown ratio for both types of mandibu- ridges, 27% with one small ridge, 28% with two acces- lar incisors is 1.43 compared to 1.16 for the maxillary ©sory Jones ridges, & 9% Bartlett with three Learning, ridges, and only LLC three teeth central© incisor Jones and & 1.37 Bartlett for the maxillary Learning, lateral. LLC NOTwith fourFOR small SALE ridges. OR DISTRIBUTION M. The NOTcurve of FOR the CEJ SALE on the OR mesial DISTRIBUTION of the mandibu- G. Inspection of 488 maxillary lateral incisors by lar central incisor averaged 2.0 mm, which is 0.4 mm Dr. Woelfel revealed 64% with no lingual accessory greater than on the distal. On the mandibular lateral lingual ridges, 32% with one small accessory ridge, incisor, the mesial CEJ curvature is 0.6 mm greater and only 4% with two ridges. than the distal. © Jones & BartlettH. The largest Learning, curvature LLCof a proximal cervical line aver©- JonesN. The& Bartlett cervix of theLearning, root of the LLC both types of mandibu- NOT FOR SALEages OR 2.8 mmDISTRIBUTION on the mesial of a maxillary central inciNOT- FORlar SALE incisor ORaverages DISTRIBUTION 2.0 mm wider faciolingually than sor, and the distal curve is only 2.3 mm. The curvature mesiodistally. of the mesial of the maxillary lateral incisor averages O. Both types of mandibular incisor crowns average 2.5 mm or one fourth of the crown length. 0.4 mm wider labiolingually than mesiodistally.

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