MINISTRY OF HEALTH OF UKRAINE BOGOMOLETS NATIONAL MEDICAL UNIVERSITY Operative Dentistry Department

«Approved» at the meeting of the Operative Dentistry department Report № 11 of January 12, 2016 Head of department ______prof. А.V. Borysenko

GUIDELINES FOR INDEPENDENT WORK OF STUDENTS WHILE PREPARING FOR THE PRACTICAL LESSON

Academic discipline Propaedeutics of operative dentistry

Module № 1 Propaedeutics of operative dentistry

The basic dental tools and equipment. The anatomical Content module № 1 structure of the permanent teeth

Lesson Focus The modern view on the features of histological structure of hard tissues Course ІІ Faculty Dental Number of hours 1

Compiler: prof. Lynovitskay O.V. Methodist: ass.prof. Kolenko Y.G.

Kyiv – 2016

THE MODERN VIEW ON THE FEATURES OF HISTOLOGICAL STRUCTURE OF HARD TISSUES

I. Actuality of theme

Knowledge of histological structure of fabrics of tooth is enamels, dentine and cement – allows with understanding to apply modern stomatological materials, in particular, stoppings materials the use of which is directed on the maintainance of anatomic and functional value of peccant tooth. These knowledges make basis of professional knowledges and skills of doctor-stomatology and are inalienable part of his practical preparation.

II. Educational purpose of employment

General: to learn the histological features of structure of the second teeth. Concrete: To familiarize ((-I):  with the general plan of histological structure of tooth. To know ((-ІI):  histological structure of tooth;  histological structure and clinical value of enamel;  histological structure and clinical value of dentine;  histological structure and clinical value of cement;  histological structure and clinical value of mash. Able ((-IІІ, (-IV):  to draw the structure of endodontium schematically;  to draw the longitudinal microsection of tooth, representing the approximate thickness of enamel, dentine and cement.  to draw the transversal microsection of tooth, representing the approximate thickness of enamel, dentine and cement.

III. Purpose of development of personality (educator purpose)

On material of theme to develop for students sense of responsibility for a rightness, timeliness, and professionalness of leadthrough of therapeutic manipulations; to form the system of legal presentations, related to activity in stomatological industry.

IV. Mezhdistsiplinarnaya integration

Disciplines To know Able

Previous disciplines

Anatomy of man  anatomic structure of tooth To know the anatomic

Занятие №5

 structure of tooth

Histology  histological structure and To draw the schematic clinical value of dentine; histological structure of  histological structure and enamel, dentine, cement clinical value of cement; and endodontium.  histological structure and clinical value of mash.  Inwardly-subject integration

Histological structure of the Features of histological structure of It is correct to describe second teeth the second teeth. histological structure of the second teeth.

V. Table of contents of theme of employment Topic#7: “Contemporary view on the special feature of the histological structure of the hard tooth tissues”.

Histological structure of the tooth tissue

Enamel:

 Enamel prisms;  interprism substance  Gunter-Shreger lines

 Retzius lines  Enamel fascicles,lamines,axles.

Dentine:

 Intracellular fluid;  Dentinal tubules;  Interglobular dentine;  Tom’s granular layer  Predentine;  Parapulpar dentine;  Mantel dentine;

 Peritubular dentine;  Intertubular dentine;  Primary dentine;  Secondary dentine;  Replacing dentine; 3  Scleral dentine. Занятие №5

Cement:

 Non-cellular(primary) cement: o Intracellular fluid; o Has no cells.  Cellular (secondary) cement: o Cementocytes;

o Cementoblasts; o Intracellular fluid.

 Hypercementosis.

Pulp:

 Cells(odontoblasts, fibroblasts macrophages, etc): o Perpherial layer

o Proximal layer: . Outer zone(Veyl zone); . Inner zone; o Central layer.  Intracellular fluid  Petrificators;  Denticles: o Freelylying; o Preside; o Interstitial.

4 Занятие №5

Enamel.Enamel is formed by cells called ameloblasts,which originate from the embryonic germ layer knownas ectoderm. Ameloblasts have short extensions towardthe dentinoenamel junction (DEJ); these are termedTomes processes. Enamel covers the anatomic crown ofthe tooth and varies in thickness in different areas. The enamel is thicker at the incisal and occlusalareas of a tooth and becomes progressively thinneruntil it terminates at the cementoenamel junction.

The thickness also varies from one class of tooth to another,averaging 2 mm at the incisal ridges of incisorsand varying from 2.3 to 2.5 mm at the cusps of premolarsand 2.5 to 3 mm at the cusps of molars. Enamelusually decreases in thickness toward the junction ofthe developmental cuspal lobes of the posterior teeth(premolars and molars), sometimes nearing zero wherethe junction is fissured (noncoalesced). Because enamel is mostly gray and semitranslucent,the color of a tooth depends upon the color of the underlyingdentin, thickness of the enamel, and amount ofstain in the enamel. The amount of translucency ofenamel is related to variations in the degree of calcificationand homogeneity. Abnormal conditions of enamelusually result in aberrant color. Enamel becomes temporarilywhiter within minutes when a tooth is isolatedfrom the moist oral environment by a rubber dam or absorbents.

Thus the shade must be determined beforeisolation and preparation of a tooth for a tooth-coloredrestoration. This change in color is explained by thetemporary loss of loosely bound (or exchangeable) water(less than 1% by weight).

Chemically, enamel is a highly mineralized crystallinestructure containing from 95% to 98% inorganic matterby weight. Hydroxyapatite, in the form of a crystallinelattice, is the largest mineral constituent and is present90% to 92% by volume. Other minerals and trace elementsare contained in smaller amounts. The remainingconstituents of tooth enamel are an organic content ofabout 1% to 2% and a water content of about 4% byweight; these total approximately 6% by volume.

Structurally, enamel is composed of millions ofenamel rods or prisms, which are the largest structuralcomponents, as well as rod sheaths and a cementinginter-rod substance in some areas. Inter-rod substance,or sheath, may be the increased spacing between crystallitesoriented differently to where the "tail" portion ofone rod meets the "head" portion of another. This spacingapparently is partially organic material. The rodsvary in number from approximately 5 million for amandibular incisor to about 12 million for a maxillarymolar. The rods are densely packed and intertwined ina wavy course, and each extends from the DEJ to the externalsurface of the tooth. In general the rods arealigned perpendicularly to both the DEJ and the toothsurface in the primary and permanent dentitions, exceptin the cervical region of permanent teeth where they areoriented outward in a slightly apical direction. In theprimary dentition the enamel rods in the cervical andcentral parts of the crown are nearly perpendicular tothe long axis of the tooth and are similar in their directionto the permanent teeth in the occlusal two thirds ofthe crown. Enamel rod diameter near the dentinal bordersis about 4 /-tm (about 8 M,m near the surface); thisdifference accommodates the larger outer surface of theenamel crown compared to the dentinal surface atthe DEJ.

The hardest substance of the human body is enamel. Hardnessmay vary over the external tooth surface accordingto the location; also, it decreases inward, with hardnesslowest at the DEJ. The density of enamel also decreasesfrom the surface to the DEJ. Enamel is a very brittlestructure with a high elastic modulus and low tensilestrength, which indicates a rigid structure. However,dentin is a highly compressive tissue that acts as a cushionfor the enamel. Enamel requires a base of dentin towithstand masticatory forces. Enamel rods that fail topossess a dentin base because of caries or improperpreparation design are easily fractured away fromneighboring rods. For maximal strength in tooth preparation,all enamel rods should be supported by dentin.

Human enamel is composed of rods that in transversesection are shaped with a rounded head or body sectionand a tail section, which forms a repetitive series of interlockingprisms. The rounded head portion of eachprism (5 pm wide) lies between the narrow tail portions(5 pm long) of two adjacent prisms. Generally,the rounded head portion is oriented in the incisal or occlusaldirection; the tail section is oriented cervically.

The structural components of the enamel prism aremillions of small, elongated apatite crystallites that arevariable in size and shape. The crystallites are tightlypacked in a distinct pattern of orientation that givesstrength and structural identity to the enamel prisms.The long axis of the apatite crystallites within the centralregion of the head (body) is aligned almost parallel tothe rod long axis, and the crystallites incline with increasingangles (up to 65 degrees) to the prism axis inthe tail region. The susceptibility of these crystallites toacid, either from an etching procedure or caries, appearsto be correlated with their orientation. Whereas the dissolutionprocess occurs more in the head regions of therod, the tail regions and the periphery of the head regionsare relatively resistant to acid attack. The crystallitesare irregular in shape, with an average length of1600 A and an average width of 200 to 400 A. Each apatitecrystallite is composed of thousands of unit cellsthat have a highly ordered arrangement of atoms. Acrystallite may be 300 unit cells long, 40 cells wide, and20 cells thick in a hexagonal configuration.

An organic matrix or prism sheath also surrounds individualcrystals. This appears to be an organically richinterspace rather than a structural entity.Enamel rods follow a wavy, spiraling course, producingan alternating arrangement for each group or layerof rods as they change direction in progressing from thedentin toward the

5 Занятие №5 enamel surface where they end a fewmicrometers short of the tooth surface. Enamel rodsrarely run a straight radial course because it appearsthere is an alternating clockwise and counterclockwisedeviation of the rods from the radial course at all levels ofthe crown. They initially follow a curving path throughone third of the enamel next to the DEJ. After that, therods usually follow a more direct path through the remainingtwo thirds of the enamel to the enamel surface.

There are groups of enamel rods that may entwine withadjacent groups of rods, and they follow a curving irregularpath toward the tooth surface. These comprisegnarled enamel, which occurs near the cervical regions andthe incisal and occlusal areas. Gnarled enamel isnot subject to cleavage as is regular enamel. This type ofenamel formation does not yield readily to the pressureof bladed, hand cutting instruments in tooth preparation.The changes in direction of enamel prisms that minimizecleavage in the axial direction produce an opticalappearance called Hunter-Schreger bands.

These bands appear to be composed of alternate lightand dark zones of varying widths that have slightly differentpermeability and organic content. These bandsare found in different areas of each class of teeth. Sincethe enamel rod orientation varies in each tooth, Hunter-Schreger bands also have a variation in the number presentin each tooth. In the anterior teeth they are locatednear the incisal surfaces. They increase in numbers andareas of the teeth from the canines to the premolars. Inthe molars the bands occur from near the cervical regionto the cusp tips. The orientation of the enamel rod headsand tails and the gnarling of enamel rods providestrength by resisting, distributing, and dissipating impactforces.

Enamel tufts are hypomineralized structures ofenamel rods and inter-rod substance that project betweenadjacent groups of enamel rods from the DEJ. These projections arise in the dentin, extendinto the enamel in the direction of the long axis of thecrown, and may play a role in the spread of dentalcaries. Enamel lamellae are thin, leaflike faults betweenenamel rod groups that extend from the enamel surfacetoward the DEJ, sometimes extending into the dentin. They contain mostly organic material,which is a weak area predisposing a tooth to the entryof bacteria and dental caries. Odontoblastic processessometimes cross the DEJ into the enamel; these aretermed enamel spindles when their ends are thickened. They may serve as pain receptors, therebyexplaining the enamel sensitivity experienced by somepatients during tooth preparation.

Enamel rods are formed linearly by successive appositionof enamel in discrete increments. The resultingvariations in structure and mineralization are called theincremental striae of Retzius and can be consideredgrowth rings. In horizontal sections of atooth, the striae of Retzius appear as concentric circles.In vertical sections, the lines transverse the cuspal andincisal areas in a symmetric arc pattern descendingobliquely to the cervical region and terminating at theDEJ. When these circles are incomplete at the enamelsurface, a series of alternating grooves, called the imbricationlines of Pickerill, are formed. The elevations betweenthe grooves are called perikymata; these are continuousaround a tooth and usually lie parallel to thecementoenamel junction and each other.

There is a structureless outer layer of enamel about 30f.m thick found most commonly toward the cervicalarea and less often on cusp tips. There are no prism outlinesvisible, and all the apatite crystals are parallel toone another and perpendicular to the striae of Retzius.

It appears that this layer is more heavily mineralized.Microscopically, the enamel surface initially has circulardepressions indicating where the enamel rods end.These concavities vary in depth and shape, and theymay contribute to the adherence of plaque material,with a resultant caries attack, especially in young people.However, the dimpled surface anatomy of theenamel gradually wears smooth with age.

The interface of the enamel and dentin is called thedentinoenamel junction. It is scalloped or wavyin outline, with the crest of the waves penetrating towardthe enamel. The rounded projections of enamel fitinto the shallow depressions of dentin. This interdigitationseems to contribute to a firm attachment betweendentin and enamel. The DEJ is also a hypermineralizedzone about 30 /.tm thick.Deep invaginations occur in pit-and-fissure areas ofthe occlusal surfaces of premolars and molars; such invaginationsdecrease enamel thickness in these areas.

These fissures act as food and bacterial traps that maypredispose the tooth to dental caries. Occlusalgrooves, which are sound, serve an important function asan escape path for the movement of food to the facialand lingual surfaces during mastication. A functionalcusp that opposes a groove occludes on the enamel inclineson each side of the groove and not in the depthof the groove. Therefore this arrangement leaves aV-shaped escape path between the cusp and its opposinggroove for the movement of food during chewing.Grooves or fissures are formed at the junction of the developmentallobes of the enamel. Sound coalescence of thelobes results in grooves; faulty coalescence results in fissures.

Enamel is incapable of repairing itself once destroyedbecause the ameloblast cell degenerates following formationof the enamel rod. The final act of the ameloblastcell is secretion of a membrane covering the end of theenamel rod. This layer is referred to as the Nasmythmembrane, or the primary enamel cuticle. This membranecovers the newly erupted tooth and is worn away bymastication and cleaning. The membrane is replaced byan organic deposit called a pellicle, which is a precipitateof salivary proteins. Microorganisms may invade thepellicle to form bacterial plaque, a potential precursor todental disease.

6 Занятие №5

Although enamel is a very hard, dense structure, it ispermeable to certain ions and molecules, permittingboth partial and complete penetration. The route of passageappears to be through structural units that are hypomineralizedand rich in organic content, such as rodsheaths, enamel cracks, and other defects. Water playsan important role as a transporting medium throughsmall intercrystalline spaces. Enamel permeability decreaseswith age because of changes in the enamel matrix,though basic permeability is maintained; this decreaseis referred to as enamel maturation.

Enamel is soluble when exposed to an acid medium,but the dissolution is not uniform. Solubility of enamelincreases from the enamel surface to the DEJ. When fluoridesare present during enamel formation or are topicallyapplied to the enamel surface, the solubility ofsurface enamel is decreased. Fluoride concentration decreasestoward the DEJ. Fluoride additions can affectthe chemical and physical properties of the apatite mineraland influence the hardness, chemical reactivity, andstability of enamel while preserving the apatite structures.Trace amounts of fluoride stabilize enamel bylowering acid solubility, decreasing the rate of demineralization,and enhancing the rate of remineralization.Evidence also shows that topical fluorides alter the oralbacterial flora, thereby increasing resistance to dentalcaries.

An established operative technique involves acidetching the enamel surface for the micromechanical"bonding" of composite restorative materials or pitand-fissure sealants directly to the etched surface. Theetchant usually is a 35% to 50% solution of phosphoricacid. This etching produces an irregular and pitted surfacewith numerous microscopic undercuts by an un-even dissolution of enamel rod heads and tails. Composite or pit-and-fissure sealant is bonded to the enamelsurface by resin tags formed in the acid-etched enamelrod structures. Therefore the structure of enamel can be anasset when it is subjected to purposeful and controlled acid dissolution of the enamel rods to providethis microretention for composite or sealant.

Pulp-Dentin Complex.Dentin and pulp tissues arespecialized connective tissues of mesodermal origin,formed from the dental papilla of the tooth bud. Thesetwo tissues are considered by many investigators as asingle tissue, which thus form the pulp-dentin complex,with mineralized dentin comprising the mature endproductof cell differentiation and maturation. Dentin isformed by cells called odontoblasts. Odontoblasts areconsidered part of both dentin and pulp tissues becausetheir cell bodies are in the pulp cavity but their long,slender cytoplasmic cell processes (Tomes fibers) extendwell into the tubules in the mineralized dentin. It is because of these odontoblastic cell processesthat dentin is considered living tissue with the capabilityto react to physiologic and pathologic stimuli. Suchstimuli can result in changes throughout the life of the dentin forms the largest portion of the tooth structure, extending almost the full length of the tooth. Externally,dentin is covered by enamel on the anatomic crown and cementum on the anatomic root. Internally, dentin forms the walls of the pulp cavity (pulp chamber and pulp canal[s]).

The odontoblasts begin dentin formation immediately before enamel formation by the ameloblasts. Dentinogenesis begins with the odontoblasts layingdown a collagen matrix, moving from the dentinoenameljunction inward toward the pulp. Mineralizationof the collagen matrix gradually follows its secretion.The most recently formed layer of dentin is alwayson the pulpal surface. This unmineralized zone ofdentin is immediately next to the cell bodies of theodontoblasts and is called predentin. Dentin formationbegins at areas subadjacent to the cusp tip or incisalridge and gradually spreads to the apex of the root. Unlike enamel, dentin formation continuesafter tooth eruption and throughout the life of the pulp.

The dentin forming the initial shape of the tooth iscalled primary dentin and is usually completed 3 yearsafter tooth eruption (for permanent teeth).The dentinal tubules are small canals that extend acrossthe entire width of dentin, from the dentinoenamel ordentinocemental junction to the pulp. Each tubule contains the cytoplasmic cell process(Tomes fiber) of an odontoblast. Each dentinal tubule islined with a layer of peritubular dentin, which is muchmore mineralized than the surrounding intertubular dentin.

The surface area of dentin is much larger at the dentinoenamelor dentinocemental junction than it is on thepulp cavity side. Since the odontoblasts form dentinwhile progressing inward toward the pulp, the tubulesare forced closer together. The number of tubules increasesfrom 15,000 to 20,000/mmz at the DEJ to 45,000 to 65,000/mmz at the pulp. The lumen of the tubulesalso varies from the DEJ to the pulp surface. In coronaldentin, the average diameter of tubules at the dentinoenameljunction is 0.5 to 0.9 /-tm, but this increases to2 to 3 /.Lm at the pulp.

The course of the dentinal tubules is a slight S-curvein the tooth crown, but the tubules are straighter in the incisal ridges, cusps, and root areas. The endsof the tubules are perpendicular to the dentinoenameland dentinocemental junctions. Along the tubule wallsare small lateral openings called canaliculi. As the odontoblasticprocess proceeds from the cell in the pulp tothe DEJ, lateral secondary branches extend into thecanaliculi and appear to communicate with lateral extensionsof adjacent odontoblastic processes. Near theDEJ the tubules (with processes seen in young teeth) divideinto several terminal branches, thus forming an intercommunicatingand anastomosing network.

After the primary dentin is formed, dentin depositioncontinues at a reduced rate even without obvious externalstimuli, though the rate and amount of this physiologicsecondary dentin varies considerably among individuals.In secondary dentin the tubules take a slightlydifferent directional pattern in contrast to primarydentin.

7 Занятие №5

Secondary dentin forms on all internalaspects of the pulp cavity, but in the pulp chamberin multirooted teeth it tends to be thicker on the roofand floor than on the side walls.

Reparative dentin (tertiary dentin) is formed by replacementodontoblasts (termed secondary odontoblasts) in responseto moderate-level irritants, such as attrition,abrasion, erosion, trauma, moderate-rate dentinalcaries, and some operative procedures. It usually appearsas a localized dentin deposit on the wall of thepulp cavity immediately subadjacent to the area on thetooth that has received the injury (a dentin deposit underneaththe affected tubules). For example,reparative dentin usually is formed when teeth are mechanicallypreparedto within 1.5 mm of the pulp.

Thecut fibers (odontoblastic processes) die along with thecorresponding odontoblasts, leaving dead tracts (describedin the next paragraph). In about 15 days newodontoblasts are differentiated from mesenchymal cellsof the pulp, and these replacement odontoblasts laydown the reparative dentin. Reparative dentin is confinedto the localized irritated area of the pulp cavitywall, becomes apparent microscopically about 1 monthfrom the inception of the stimulus, is structurally andchemically different from primary and secondarydentin, and, being highly atubular, is impervious tomost irritants. Reparative or tertiary dentin is a defensereaction to an area of moderate- intensity injury.

Thus when moderate-level stimuli are applied todentin, such as moderate-rate caries or attrition, the affectedodontoblastic processes may die with the associatedodontoblasts. These areas of dentin are called deadtracts and extend from the external dentin surface to the pulp. The tubules are empty and thus appear blackwhen ground sections of dentin are viewed microscopicallywith transmitted light. Dead tracts are sealed off atthe pulpal surface by reparative dentin formed by replacementodontoblasts. While dead tracts are commonlyassociated with areas of caries or attrition, theyhave occurred in unerupted incisors and teeth thatshow few, if any, obvious external defects. Dead tractsmay be considered in some circumstances as a form ofage-related change associated with the death of odontoblasts.

Usually this occurs in areas of the pulp where theodontoblasts have been crowded into narrow pulphorns. In dried, ground sections of normalteeth the odontoblastic processes contract and mayallow the tubules to fill with air, giving the appearanceof a dead tract. However, a true dead tract can be distinguishedby a deposit of reparative dentin on the pulpalsurface.

Sclerotic dentin results from aging or mild irritation(such as slowly advancing caries) and causes a changein the composition of the primary dentin. The peritubulardentin becomes wider, gradually filling the tubuleswith calcified material, progressing pulpally from theDEJ. These areas are harder, denser, less sensitive,and more protective of the pulp against subsequentirritations. Sclerosis resulting from aging is physiologicdentin sclerosis; sclerosis resulting from a mildirritation is reactive dentin sclerosis. Reactive dentin sclerosisoften can be seen radiographically in the form of amore radiopaque (lighter) area in the S-shape of thetubules. Eburnated dentin refers to the outward (exposed)portion of reactive sclerotic dentin, where slowcaries has destroyed formerly overlying tooth structure,leaving a hard, darkened, cleanable surface.

The composition of human dentin is approximately75% inorganic material, 20% organic material, and 5%water and other materials. Dentin is less mineralizedthan enamel but more mineralized than cementum orbone. The mineral content of dentin increases with age.

This mineral phase is composed primarily of hydroxyapatitecrystallites, which are arranged in a less systematicmanner than enamel crystallites. Dentinal crystallitesare smaller than enamel crystallites, having alength of 200 to 1000 A and a width of about 30 A, similarto the sizes seen in bone and cementum. The organicphase of dentin consists primarily of collagen.

Dentin is significantly softer than enamel but harderthan bone or cementum. The hardness of dentin averagesone fifth that of enamel, and its hardness near theDEJ is about three times greater than near the pulp.Dentin becomes harder with age, primarily due to increasesin mineral content. While dentin is a hard, mineralizedtissue, it is somewhat flexible, with a modulus ofelasticity of 1.67 X 106 PSI. This flexibility helps supportthe more brittle, nonresilient enamel. Often small "crazelines" are seen in the enamel that indicate minute fractures of that structure. These craze lines usually are notclinically significant unless associated with cracks in theunderlying dentin. Dentin is not as prone to cleavageas is the enamel rod structure. The tensile strength ofdentin is approximately 40 MPa (6000 PSI), which is lessthan cortical bone and approximately one half thatof enamel. The compressive strength of dentin is muchhigher-266 MPa (40,000 PSI).

During tooth preparation, dentin is usually distinguishedfrom enamel by: (1) color, (2) reflectance, (3)hardness, and (4) sound. Dentin is normally yellowwhiteand slightly darker than enamel. In older patientsdentin is darker, and it can become brown or black incases where it has been exposed to oral fluids, oldrestorative materials, or slowly advancing caries. Dentinsurfaces are more opaque and dull, being less reflectiveto light than similar enamel surfaces, which appearshiny. Dentin is softer than enamel and provides greateryield to the pressure of a sharp explorer tine, whichtends to catch and hold in dentin. When moving an explorertine over the tooth, enamel surfaces provide asharper, higher-pitched sound than dentin surfaces.

8 Занятие №5

Sensitivity is encountered whenever odontoblastsand their processes are stimulated during operative procedures, even though the pain receptor mechanismappears to be within the dentinal tubules near thepulp.

A variety of physical, thermal, chemical, bacterial, andtraumatic stimuli are transmitted through the dentinaltubules, though the precise mechanism of the transmissiveelements of sensation has not been conclusively established.The most accepted theory of pain transmissionis the hydrodynamic theory, which accounts for paintransmission through small, rapid movements of fluidthat occur within the dentinal tubules.Because manytubules contain mechanoreceptor nerve endings nearthe pulp, small fluid movements in the tubules arisingfrom cutting, drying, pressure changes, osmotic shifts,or changes in temperature account for the majority ofpain transmission.

Dentinal tubules are normally filled with odontoblasticprocesses and dentinal fluid, a transudate of plasma.When enamel or cementum is removed during toothpreparation, the external seal of dentin is lost and thetubules become fluid-filled channels from the cut surfacedirectly to the pulp. Fortunately, pulpal fluid has aslight positive pressure that forces fluid outward towardany breach in the external seal. Permeability studiesof dentin indicate that tubules are functionally muchsmaller than would be indicated by their measured microscopicdimensions as a result of numerous constrictionsalong their paths. Dentin permeabilityis not uniform throughout the tooth. Coronaldentin is much more permeable than root dentin. Thereare also differences within coronal dentin.

Dentin permeability is primarily dependent on the remainingdentin thickness (i.e., length of the tubules) andthe diameter of the tubules. Since the tubules areshorter, become more numerous, and increase in diametercloser to the pulp, deep dentin is a less-effective pulpalbarrier than is superficial dentin near the dentinoenamelor dentinocemental junctions.

Dentin must be treated with great care during restorativeprocedures to minimize damage to the odontoblastsand pulp. Air-water spray should be used whenevercutting with high-speed handpieces to avoid heatbuildup. The dentin should not be dehydrated by compressedair blasts; it should always maintain its normalfluid content. Protection is also provided byjudicious use of liners, bases, dentin-bonding agents,and nontoxic restorative materials. Restorations mustadequately seal the preparation to avoid microleakageand bacterial penetration.

Whenever dentin has been cut or abraded, a thin alteredlayer is created on the surface. This smear layer isonly a few micrometers thick and is composed of denaturedcollagen, hydroxyapatite, and other cutting debris. The smear layer serves as a natural bandageover the cut dentinal surface because it occludes manyof the dentinal tubules with debris called smear plugs. While the smear layer is a good protectivebarrier, it has a relatively weak attachment to the dentinand is subject to dissolution by acids.

Reliable dentin bonding of composite restorations hasbeen a difficult goal for dental manufacturers. Whilesome manufacturers claim their products create chemicalbonds to dentin, most experts agree that the primarymechanism of attachment is mechanical interlocking.Most dentin-bonding systems have acids that removethe smear layer and partially demineralize the intertubulardentin. In most systems these acidic componentsare weaker than the 37% phosphoric acid commonlyused to etch enamel surfaces. When viewedunder high magnification, dentin without a smear hasmany irregularities for micromechanical retention. Ideally, such etchants remove the smear layer butleave the smear plugs because they greatly reducedentin permeability and sensitivity. Etchants should notexcessively damage exposed collagen fibers becausemuch of the bond strength develops from resin encapsulatingthese fibers. After the acids, hydrophilic adhesiveresins are applied that penetrate into the inherentlymoist dentin surfaces and copolymerize with the compositerestoration. While some of the bond formsfrom resin "tags" extending into the dentinal tubules,most of the bond strength develops from resin that penetratesand adapts to the demineralized intertubulardentin and exposed collagen fibers. The resultant resininterdiffusion zone is often termed the hybrid layer.

While dentin bond strengths have improved, they arevariable because of the dentin substrate. Bond strengthsfor superficial dentin close to the dentinoenamel ordentinocemental junctions are greater than those fordeep dentin. In deep dentin the greater number oftubules and the larger diameter of tubules reduce theamount of intertubular dentin available for bonding.

An important aspect of current dentin-bondingagents is their ability to seal cut dentinal surfaces andthus reduce permeability and microleakage. Many dentistsuse dentin-bonding products to seal and desensitizedentin surfaces in all tooth preparations and in unrestoredClass V cervical abrasion and erosion defects.

The dental pulp occupies the pulp cavity in the tooth.Each pulp organ is circumscribed by the dentin and islined peripherally by a cellular layer of odontoblasts adjacentto the dentin. Anatomically the pulp organ is dividedinto: (1) coronal pulp located in the pulp chamberin the crown portion of the tooth, including the pulphorns that are directed toward the incisal ridges andcusp tips; and (2) radicular pulp located in the pulpcanal(s) in the root portion of the tooth. The radicularpulp is continuous with the periapical tissues by connectingthrough the apical foramen or foramina of theroot. Accessory canals may extend from the pulpcanal(s) laterally through the root dentin to the periodontaltissues. The shape of each pulp conforms generallyto the shape of each tooth.

9 Занятие №5

The dental pulp is composed of myelinated and unmyelinatednerves, arteries, veins, lymph channels, connectivetissue cells, intercellular substance, odontoblasts,fibroblasts, macrophages, collagen, and finefibers. The central area of the pulp contains the largeblood vessels and nerve trunks. The pulp is circumscribedperipherally by a specialized odontogenic areamade up of the odontoblasts, the cell-free zone, and thecell-rich zone.

The pulp is a unique, specialized organ of the humanbody serving four functions: (1) formative or developmental,(2) nutritive, (3) sensory or protective, and (4)defensive or reparative. The formative function is theproduction of primary and secondary dentin by theodontoblasts. The nutritive function supplies nutrimentsand moisture to the dentin through the bloodvascular supply to the odontoblasts and their processes.

The sensory function provides sensory nerve fiberswithin the pulp to mediate the sensation of pain. Dentinreceptors are unique because various stimuli elicit onlypain as a response. The pulp usually does not differentiatebetween heat, touch, pressure, or chemicals. Motorfibers initiate reflexes in the muscles of the blood vesselwalls for the control of circulation in the pulp. Finally,the defensive function of the pulp is related primarily toits response to irritation by mechanical, thermal, chemical,or bacterial stimuli. Such irritants can cause the degenerationand death of the affected odontoblasticprocesses and corresponding odontoblasts and the formationof replacement odontoblasts (from undifferentiatedpulpal mesenchymal cells) that lay down irregularor reparative dentin. The deposition of reparativedentin acts as a protective barrier against caries and variousother irritating factors. This is a continuous but relativelyslow process, taking 100 days to form a reparativedentin layer 0.12 mm thick. In cases of severeirritation the pulp responds by an inflammatory reactionsimilar to that for any other soft tissue injury. However,the inflammation may become irreversible and canresult in the death of the pulp because the confined,rigid structure of the dentin limits the inflammatory responseand the ability of the pulp to recover.

If, however, the irritant is very mild, such as thatcaused by cutting the odontoblastic processes more than1.5 mm external to the pulp at high speed with airwatercoolant during tooth preparation, no replacementodontoblasts are formed; thus no reparative dentin iscreated, even though the processes and correspondingodontoblasts have died. Therefore there is no barrier(except for the smear layer) between the dead tracts remainingand the pulp. This may explain why manyteeth have pulpal problems following tooth preparationand restoration. However, newer dentin-bonding systemslook promising for sealing the cut dentinal surfacesand preventing postoperative sensitivity.

A knowledge of the contour and size of the pulp cavityis essential during tooth preparation. In general, thepulp cavity is a miniature contour of the external surfaceof the tooth. Size varies among the various teeth inthe same mouth and among individuals. With advancingage, the pulp cavity usually decreases in size. Radiographsare an invaluable aid in determining the sizeof the pulp cavity and any existing pathologic condition. Also with advanced age, the pulp generallybecomes more fibrous because of past episodes of variousirritations, and it may contain pulp stones or denticles.

The latter are nodular, calcified masses usually appearingin the pulp chamber but also in the pulp canal.These may either be attached to the pulp cavity wall orfree in the mass of pulp tissue.

Clinical interpretation of pain from pulpal inflammationis somewhat empiric, but it is nonetheless importantto the successful practice of operative dentistry.One of the primary services rendered by the dentist isdiagnosis and relief of pain of pulpal origin.When an irritant (e.g., sugar, cold, acid from caries)first contacts dentin, the patient may be alerted by atwinge of pain. This pain is usually only momentary,ceasing if the irritant is removed. If such irritation continuesor the irritant is applied repeatedly, hyperemia (increasedblood flow and volume) and inflammation ofthe pulp can result, which will cause the pain elicitedfrom the irritation to linger a few seconds. The reactionis because the pulp is contained by unyielding dentinalwalls; thus drainage of the increased blood is limited bythe constricted apical foramen. As long as an irritant,such as touching ice to the tooth, causes pain thatlingers no more than 10 to 15 seconds after removal ofthe irritant, resolution of the hyperemia by immediaterestorative treatment is a possibility; such hyperemia istermed reversible pulpitis.

When pulpal pain, either spontaneous or elicited byan irritant, lingers more than 15 seconds, infection of thepulp often has occurred and resolution by operativedentistry treatment is usually doubtful; root canal therapyis advised for this pulpal condition, termed irreversiblepulpitis, if the tooth is to be maintained in thedentition. When this condition is untreated, suppurationand pulpal necrosis follows, characterized by spontaneous,continuous throbbing pain or pain elicited byheat that can be relieved by cold and later characterizedby no response to any stimulus. Pulpal necrosis istreated by root canal therapy or tooth extraction.A primary objective during operative proceduresmust be preservation of the health of the pulp. The successfulmanagement of the disease process by propertreatment of the pulp organ is discussed further in laterchapters.

Cementum. Cementum is the hard dental tissue coveringthe anatomic roots of teeth and is formed by cellsknown as cementoblasts, which develop from undifferentiatedmesenchymal cells in the connective tissue of thedental follicle. Cementum is slightly softer than dentinand consists of about 45% to 50% inorganic material(hydroxyapatite) by weight and 50% to 55% organicmatter and water by weight. The organic portion is primarilycomposed of collagen and protein polysaccharides.Sharpey's fibers are the portions of the

10 Занятие №5 collagenousprincipal fibers of the periodontal ligament embeddedin both the cementum and alveolar bone to attach thetooth to the alveolus. Cementum is avascular.The cementum is light yellow and slightly lighter incolor than dentin. It has the highest fluoride content ofall mineralized tissue. Cementum is also permeable to avariety of materials. It is formed continuously throughoutlife, because a new layer of cementum is depositedto keep the attachment intact as the superficial layer ofcementum ages. Two kinds of cementum are formed:acellular and cellular. The acellular layer of cementum isliving tissue that does not incorporate cells into its structureand usually predominates on the coronal half ofthe root; cellular cementum occurs more frequently on theapical half. Cementum on the root end surrounds theapical foramen and may extend slightly onto the innerwall of the pulp canal. Cementum thickness can increaseon the root end to compensate for attritional wearof the occlusal/incisal surface and passive eruption ofthe tooth.

The cementodentinal junction is a relatively smootharea in the permanent tooth, and attachment of cementumto the dentin is firm but not understood completely.The cementum joins the enamel to form the cementoenameljunction, which is referred to as the cervical line.In about 10% of teeth, enamel and cementum do notmeet, and this can result in a sensitive area. Abrasion,erosion, caries, scaling, and the procedures of finishingand polishing may result in denuding the dentin of itscementum covering, which can cause the dentin to besensitive to several types of stimuli (e.g., heat, cold,sweet and sour substances). Cementum is capable of repairingitself to a limited degree and is not resorbed undernormal conditions. Some resorption of the apicalportion of the root often occurs during physiologictooth movement.

Cementum is a hard tissue with a calcified intercellularsubstance covering the anatomic roots of teeth; it hasbeen discussed previously in this chapter.The alveolar process, a part of the maxilla andmandible, forms, supports, and lines the sockets intowhich the roots of the teeth fit. Anatomically, no distinctboundary exists between the body of the maxilla or themandible and the alveolar process. The tissue elementsof the alveolar process are the same as for bone foundelsewhere. The alveolar process is thin, compact bonewith many small openings through which blood vessels,lymphatics, and nerves pass. As previously stated,both cementum and the alveolar bone contain Sharpey'sfibers, the ends of the principal fibers of the periodontalligament. The inner wall of the bony socket consists ofthe thin lamella of bone that surrounds the root of thetooth (and gives attachment to Sharpey's fibers). It istermed the alveolar bone proper. The second part of thebone is called supporting alveolar bone, which surroundsthe alveolar bone proper and supports the socket. Supportingbone is made up of two parts: (1) the corticalplate, consisting of compact bone and forming the inner(lingual) and outer (facial) plates of the alveolar process,and (2) the spongy base that fills the area between theplates and the alveolar bone proper. Bone is composedof approximately 65% inorganic and 35% organic material.

The inorganic material is hydroxyapatite; the organicmaterial is primarily type I collagen (88% to 89%),which is surrounded by a ground substance of glycoproteinsand proteoglycans.Clinically, the level of the gingival attachment andgingival sulcus is an important factor in restorative dentistry.

Soft tissue health must be maintained by the teethhaving correct form and position if apical recession ofthe gingiva and possible abrasion and erosion of theroots are to be prevented. The margin of a tooth preparationshould not be positioned subgingivally (at levels betweenthe marginal crest of the free gingiva and the base of the sulcus)unless dictated by caries, previous restoration, esthetics,or other preparation needs.

ENAMEL OF TEETH An enamel covers a crown and partly neck of tooth. It is located over a dentine. Chemical structure: water – 3,8% (about 1% free water); organic matters – 1,2%; inorganics – 95%, among them calcium – 37% and phosphorus – 17%. Inorganic компоненты of enamel is presented the crystals of гидроксиапатитов, fluorapatites and карбонатапатитов. An enamel does not contain a cage, there are not nervous completions and blood vessels in it, it is not able to grow and regenerate. Structural-functional unit of enamel is an enamel prism. Structural компонентами of enamel prisms are the well-organized placed палочковидные crystals of apatite. Enamel prisms are dissociated from each other a less минерализованным interprism matter. On the microsections of enamel of tooth its optical heterogeneity is marked:

11 Занятие №5 1. Bars of Guntera-Shregera. If to examine the longitudinal microsection of enamel in the reflected light, then on it it is possible to look after light and dark bars which alternate between itself and go from enamel-dentinal connection to the surface of enamel. 2. Lines of Rettsiusa. On the longitudinal cuts of enamel yellow-brown or brown bars, going more sheerly, are often visible, than bars of Guntera-Shregera, and crossings them under an acute angle. Explain the presence of these bars the recurrence of минерализации of enamel in the process of its development and power influences on a tooth. Enamel plates (ламеллы) are the thin leaved structures of слабоминерализованной enamel, containing the albumens of enamel and organic matters. Enamel bunches are long ribbons of less минерализованной enamel, which grow on 1/3 thicknesses of enamel from enamel-dentinal connection and oriented athwart to him. Enamel spindles are the thin «blind» ductings which contain completions of одонтобластов. In the moment of odontiasis, his enamel is covered a cuticle, formed the редуцированным epithelium of enamel organ. On the enamel of tooth пеликула appears is transparent organic tape which consists of albumens and glycoproteins of mouth liquid.

DENTINE It is hard, cell-free, минерализованная fabric of tooth, which 70-72% inorganics (аппатиты, mainly гидроксиапатит) and salts (phosphates of calcium and magnesium, calcium фторид), 20% organic matters (mainly collogen) and 10% waters, enter in the complement of. A dentine contains followings basic structural компоненты: минерализованное basic matter of dentine, which is pierced by dentinal tubes (tubulis) with the sprouts of одонтобластов and маломинерализованный предентин. The sprouts of одонтобластов (fibres of Tomsa), surrounded a dentinal liquid, are located in dentinal tubes. A dentinal liquid is the transudate of peripheral blood vessels of mash and on albuminous composition similar to plasma of blood. A dentine, located between dentinal tubes, is named интертубулярным (межканальцевым). The минерализованное basic matter of dentine contains collogen fibres and протеогликанами, related to the crystals of гидроксиапатита is presented. Inside of dentine, adjoining to the endodontium, маломинерализованна and named предентином. Peritubulyarniy a dentine is the most минерализованный dentine, with the negligible quantity of organic matters. In a dentine select two слоя, which differ direction of collogen fibres and degree of минерализации:

12 Занятие №5 1. Cloak dentine. Cloak dentine of прилежит to the enamel and forms an original depreciation gasket for it. He минерализован a bit less than, what other layers of dentine. Basic formed компонентами of cloak dentine are fibres of Korfa. These fibres are oriented a bit athwart to enamel-dentinal connection. The deposit of inorganic components (apatite) takes place both on fibred компонентах and between them. 2. Okolopul'parnyy dentine. Okolopul'parnyy a dentine takes place between a cloak dentine and предентином. Collogen fibres (Ebnera) are similar to the fibres of Korfa of cloak dentine and take place not parallell to the walls of dentinal tubes, but anymore tangentially. A dentine, appearing during a dentinogenesis to прорезывания of teeth, is named the dentine of development (primary dentine). After прорезывания of teeth, in the cavity of mouth from the side of mash a dentine with the structure changed a bit, named the second dentine, begins to be put aside. He is two kinds: - regular (functional, physiology) - irregular (заместительный dentine, tertiary dentine) Інтерглобулярний a dentine is areas little or almost quite неминерализованного basic matter of dentine, limited characteristic spherical surfaces. Dentinal tubes pass through them. A склерозированный (transparent) dentine is a dentine with облитерированными by dentinal tubes and гиперминерализованными sprouts of одонтобластов. Enamel-dentinal connection (enamel-dentinal border) has a toothed, undulating kind.

ENDODONTIUM An endodontium is located in the cavity of crown and in the root ductings. It is the specialized loose connecting fabric which contains many blood vessels and nervous fibres. In an endodontium select three слоя: 1. The peripheral layer of mash (одонтобластный) is presented the compact layer of одонтобластов (дентинобластов), located in a few rows (from 1 to 8) on a border with предентином athwart to his internal surface. Of the circulatory system capillaries and nervous fibres bed between them. 2. The intermediate layer of mash (субодонтобластный) is developed only in коронковой mash and consists of external and internal areas. - external area of intermediate layer (layer of Veylya) - ZI of intermediate layer 3. The central layer of mash contains фибробласты, histocytes, адвентициональные cages, collogen and ретикулярные fibres, and also intercellular matter. Large blood and lymphatic vessels, bunches of nervous fibres, are located in this layer.

13 Занятие №5 Mash, being in the cavity of crown of the tooth, limited a dentine and enamel, is named коронковой. Mash of the root ductings – root. They have a row of differences depending on placing, form, structure and function. The process of formation of dentine can take place directly in the layer of mash – дентиклы is formed. They can be formed the high-organized dentine or irregular dentine. Select: свободноразмещенные, пристеночные and interstitial дентиклы. Educations, being the accumulation of crystals of different mineral salts of calcium, name concrements.

CEMENT OF TOOTH It is dense, минерализованная fabric, covering subgingival part of tooth – his root and neck. In area of neck of tooth cement can cover an enamel (60-65% cases), come to its border (30%) or not come to the enamel (5%). On chemical composition cement is similar to the bone, consists of organic matters (22%), waters (32%) and 56 % mineral matters: mainly гидроксиапатит, salts of calcium and other oligoelementss. A collogen is the basic of principle organic component of matrice. The feed of cement is carried out from the side of периодонта due to diffusion. Thickness of cement in area of neck of tooth 0,015 мм, in middle part of root are 0,02-0,03 мм Depending on a structure and composition select two type of cement: - cellular (second) cement; - cell-free (primary) cement. The маломинерализованный matrice of cement beds between a кальцифицированным matrice and layer of цементобластов – прецемент. Surplus formation of cement is гиперцементоз.

14 Занятие №5 VI. Plan and organizational structure of employment

An educational Distributing of Basic stages of employment, their purpose is in Methods of control and Materials of the methodical № time functions and maintenance the levels of teaching providing (in minutes) mastering

I. Preparatory stage

1 Organizational measures - Greeting, verification of Academic magazine presence of students and necessary educational 2 minutes materials, original appearance et cetera

Raising of educational aims and - - "Educational aims", "Actuality of 2-3 minutes 2 motivation theme"

3 Control of initial level of knowledges, skills, abilities: 20 minutes

3.1. Anatomic structure of tooth. ІІ Individual theoretical Question. questioning. Tables, pictures, sliding seats, 3.2. Histological structure and Decision of typical tasks ІІ phantoms, remote teeth. clinical value of enamel. mastering level. Typical tasks ІІ mastering level. Decision of test tasks ІІ Test tasks ІІ mastering level. 3.3. Histological structure and mastering level. Writing theoretical tasks. clinical value of dentine. Writing theoretical control.

3.4. Histological structure and clinical value of cement.

3.5. Histological structure and clinical value of mash.

15 Занятие №5 II. Basic stage

4 Forming of professional skills and abilities: 90 minutes

4.1. To draw the schematic structure III, IV Method of forming of abilities: Algorithm for forming of professional of endodontium. the professional training is in abilities. Plaster casts, equipment. the decision of offtype clinical Text offtype situatioonal tasks. situations 4.2. To draw the longitudinal

microsection of tooth, representing the thickness of enamel, dentine and cement approximately.

4.3. To draw the transversal microsection of tooth, representing the thickness of enamel, dentine and cement approximately.

IІI. Final stage

5 Control and correction of level of III Methods of control of skills: Job performances. 20 minutes professional skills and abilities. individual control of skills or Text situatioonal tasks of the III levels. their results. Tests of the III levels Methods of control of abilities: decision of offtype situatioonal tasks, test control of the III levels.

6 Working out the totals of - Evaluation of success of - employment (theoretical, practical, student (diagnostics of level organizational). of knowledges, skills and abilities). 7 Home task - - Reference map for independent work with literature.

16 Занятие №5 VIІ. Materials of the methodical providing of employment

VII.1. Control materials for the preparatory stage of employment VII.1.1. Theoretical questions ((-II) 1. Describe a histological structure and clinical value of enamel. 2. Describe the chemical structure of enamel. 3. Name and describe structural-functional unit of enamel. 4. Describe a histological structure and clinical value of dentine. 5. Describe the chemical structure of dentine. 6. Describe a histological structure and clinical value of cement. 7. Describe the chemical structure of cement. 8. Describe a histological structure and clinical value of mash. VII.1.2. Tests ((-I) №1. Where placed одонтобласты? A. in the superficial layer of dentine; B. in the deep layers of dentine; C. on the border of dentine and mash; D. in a околопульпарном dentine; E. in the superficial layers of mash. Answer: Е. №2. The basic morphon of enamel is: A. гидроксиапатит; B. enamel prisms; C. collogen fibres; D. fibres of Tomsa; E. enamel веретна. Answer: In №3. The most sensible areas of hard fabrics of tooth are: A. enamel-dentinal connection; B. enamel; C. cloak dentine; D. околопульпарный dentine; E. cement. Answer: And №4. Composition of enamel: A. 95-98,5 % mineral matters, 3% waters and organic matters; B. 90% mineral matters, 10% waters and organic matters; C. 100% mineral matters; D. 85% mineral matters, 15% waters and organic matters; E. 92% mineral matters, 5% waters and 3% organic matters; Answer: And VII.1.3. Tests ((-II) №1. As what connections mineral matters are in the enamel of tooth: 1. фосфорнокислые salts of sodium; 2. calcium chloride;

17 Занятие №5 3. potassium фосфорнокислый; 4. calcium carbonate; 5. гидроксиапатиты; 6. карбонатапатиты; 7. хлорапатиты; 8. fluorapatites. Right answer: 5, 6, 7, 8. №2. A dentine can be: 1. primary; 2. заместительный; 3. cellular; 4. second; 5. склерозированный; 6. peripheral. Right answer: 1, 2, 4, 5. №3. Write what fabrics of tooth (enamel, dentine, cement) the followings structures belong to: Histological structures Fabrics of tooth

Primary dentine

Grainy layer

Diazony

Lines of Guntera-Shregera

Lines of Rettsiusa

Cell-free cement

Tsementotsity

Fibres of Korfa

Cuticle

Sklerozirovannyy dentine

Sharpeevskie of fibre

Note: the name of fabrics of tooth a student inscribes independently. VII.1.4. Tasks ((-II) №1. What basic structural компоненты of dentine you know?

18 Занятие №5 №2. That is between the shell of sprout of одонтобласта and минерализованной wall of dentinal tube? №3. What are histological varieties of basic matter of dentine? №4. What functions of cement you know? Answers to the tasks Task 1. A dentine contains followings basic structural компоненты: dentinal tubes (tubulis) with the sprouts of одонтобластов, кальцифицированный matrice (actually basic matter of dentine) and маломинерализованный предентин. Task 2. In obedience to the last information on the transversal cut of dentinal tubes the sprouts of одонтобластов do not occupy all road clearance of tube. The неминерализованный matrice of dentine takes place between the shell of sprouts and минерализованной wall of tubes. He looks something like предентин and can remain неминерализованным during all existence of sprout. Task 3. Depending on the degree of минерализации classify the sometimes (not conventionally) минерализованное basic matter of dentine on низькоминерализованное, средне- and высокоминерализованное. A высокоминерализованное оновное matter surrounds dentinal tubes (tubulis) and forms, thus, their walls is a перитубулярний dentine. A matrice with the middle degree of минерализации beds between the перитубулярним dentine of contiguous tubes, from where and his name – межканальцевый or интертубулярный dentine. Predentin which reminds a matrice with low минерализацией as a narrow bar beds in dentinal tubes between a перитубулярным dentine and sprout of одонтобласта is a околоотростковый dentine. Task 4. Cement is component part of dental vehicle, retaining tooth, providing attaching to him of fibres of периодонта; protects the dentine of root from damages; executes репаративные functions; put aside in the area of apex of root, provides the maintainance of general length of tooth, compensating elimination of enamel.

VII.2. Materials of the methodical providing of the basic stage of employment VII.2.1. Reference map for forming of professional abilities and skills

Sequence of Warning in relation to self- Educational task implementation control

To represent the To represent the bars The bars of Guntera-Shregera longitudinal of Guntera-Shregera look as dark and light bars which microsection of alternate between itself and go tooth. from enamel-dentinal connection to the surface of enamel.

19 Занятие №5 To represent the lines The lines of Rettsiusa cross the of Rettsiusa bars of Guntera-Shregera under an acute angle.

To represent a cloak The fibres of Korfa are oriented dentine athwart to enamel-dentinal connection.

To represent a Collogen fibres (Ebnera) bed not околопульпарный parallell to the walls of dentinal dentine tubes, but anymore tangentially.

To represent the To represent the lines Have the appearance of concentric transversal of Rettsiusa rings. microsection of tooth.

VII.3. Control materials for the final stage VII.3.1. Offtype situatioonal task ((-IV) №1. On the roentgenologic picture of overhead sixth teeth on the left it is possible to see in the cavity of tooth the area of darkening a size 1х1 мм, which adjoins with the wall of cavity of tooth. A периодонтальная crack in area of a 26 tooth is differentiated along the whole length. On your opinion, that is this darkening? Answer: This darkening can be пристеночный дентикл. This education can be the rounded or wrong form, which consists of dentine or дентиноподобной fabric.

VІI.4. Materials of the methodical providing самоподготовки of students VII.4.1. Reference map for organization of independent work of students with educational literature on the topic: «Feature of histological structure of enamel, dentine cement and endodontium»

Educational task Pointing Notes

To learn:

Describe a histological To describe a histological structure structure and clinical value and clinical value of enamel. of enamel.

20 Занятие №5 Describe the chemical To describe the chemical structure of structure of enamel. enamel.

Will offer structural- To name and describe structural- functional unit of enamel. functional unit of enamel.

Describe a histological To name a histological structure and structure and clinical value clinical value of dentine. of dentine.

Describe the chemical To describe the chemical structure of structure of dentine. dentine.

Describe a histological To describe a histological structure structure and clinical value and clinical value of cement. of cement.

Describe the chemical To describe the chemical structure of structure of cement. cement.

Describe a histological To describe a histological structure structure and clinical value and clinical value of mash. of mash.

VІІІ. Literature on the topic of employment Basic

1. Practical work of з терапевтичної стоматології (фантомний course) / A.V.Borisenko, L.F.Sіdel'nіkova, M.Yu.antonenko, Yu.g.kolenko, O.O.Shekera. – Kiїv, 2011. – 512 p. 2. Danilevs'kiy M.F., Borisenko A.V., Polіtun A.M., Sіdel'nіkova L.F., Nesin O.F. Terapevtichna стоматологія: Pіdruchnik; At 4 т. – Fantomniy course / M.F.Danilevs'kiy, A.V. Borisenko, A.M. Polіtun, L.F. Sіdel'nіkova, O.F. Nesin – Kiїv: Medicine, 2007. – 304 p. 3. Danilevskiy N.F., Borisenko A.V., Politun A.M., Sidel'nikova L.F., Nesin A.F. Therapeutic stomatology: Textbook; In 4 т. – Propedevtika of therapeutic stomatology. it is Kiev: Medicine, 2011. – 400 p. 4. Borovskiy E.V., Ivanov V.S., Banchenko g.v. and other Therapeutic stomatology. – M.: the Medical agency of news, 2004. – 840 p. 5. Nikolaev A.I., Tsepov l.m. Practical therapeutic stomatology. – M.: MEDpress-inform, 2007. – 928 p. Additional

21 Занятие №5 1. Bykov V.L. Histology and embryology of organs of cavity of mouth of man. – SPb.: Special literature, 1999. – 247 p. 2. Falin L.I. Histology and embryology of cavity of mouth and teeth. – M.: Gosmedgiz, 1963. – 220 p. Electronic sources 1. http://www.mednovosti.by/journal.aspx?article=2765 2. http://eurodent.su/topbibl/topterstomat/itemlist/category/37-gist_zub 3. http://www.whitetooth.ru/articles/gistologiya_tkaney_zuba_-_iz_chego_sostoyat_zuby.html

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