Part Iiapplication of Tooth Anatomy in Dental Practice
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APPLICATION OF TOOTH PART II ANATOMY IN DENTAL PRACTICE 195 Scheid_Chap07.indd 195 9/25/2010 10:11:40 AM Scheid_Chap07.indd 196 9/25/2010 10:11:51 AM CHAPTER 7 Periodontal Anatomy First contributing author of this chapter: Dr. Binnaz Leblebicioglu, D.D.S., M.S., Ph.D. is an Associate Professor of Periodontology at The Ohio State University, College of Dentistry, Division of Periodontology. She is a diplomate of the American Academy of Periodontology and currently teaches Periodontology at both predoctoral and graduate levels. Her research is related to periodontal/peri-implant pathogenesis and wound healing. Senior contributing author of this chapter: Dr. Lewis Claman, D.D.S., M.S. is an Associate Professor, Emeritus at the Ohio State University College of Dentistry and has a private practice limited to periodontics. He is a diplomate of the American Board of Periodontology. He was a full time faculty member at Ohio State for 35 years where he was Predoctoral Director of Periodontology from 1997 to 2009. Dr. Claman, who teaches dental photography, has contributed the majority of photo- graphs in this chapter. The periodontal considerations related to external D. Clinical attachment loss (same as clinical morphology and surrounding structures are presented attachment level) in nine sections: E. Bleeding on probing I. Definitions of basic periodontal terms F. Furcation involvement II. The healthy periodontium G. Lack of attached gingiva (previously called a A. Alveolar bone mucogingival defect) B. Tooth root surface H. The plaque score (index) C. Periodontal ligament (abbreviated PDL) V. Relationship of periodontal disease and D. Gingiva restorations (fillings) III. Anatomy of diseased periodontium VI. Relationship of tooth support and root A. Gingivitis morphology B. Periodontitis VII. Influence of root anatomy and anomalies on the C. Gingival recession progression of periodontal disease IV. Periodontal measurements: indicators of disease VIII. Periodontal disease therapies and conditions IX. The influence of root anatomy on periodontal A. Tooth mobility instrumentation, oral hygiene instruction and B. Probe depths periodontal maintenance C. Gingival margin level (gingival recession or non-recession) 197 Scheid_Chap07.indd 197 9/25/2010 10:11:51 AM 198 Part 2 | Application of Tooth Anatomy in Dental Practice OBJECTIVES periodontal health and record these findings on a This chapter is designed to prepare the learner to per- dental chart. form the following: • Describe the relationship of periodontal disease • Identify the components of a healthy periodontium. with restorations placed close to the gingival • List the functions of gingiva, the periodontal liga- attachment (dentogingival junction). ment, alveolar bone, and cementum. • Describe the relationship of root morphology with • Describe and recognize the signs of gingivitis, perio- tooth support. dontitis, and gingival recession. • List contemporary methods of periodontal therapy. • Describe the periodontal measurements that can • Describe challenges for periodontal instrumentation be used to differentiate periodontal diseases from relative to root anatomy. hile the anatomy of the crown is signifi- diseased. An emphasis is placed on periodontal disease cant to tooth function, the root morphol- initiation, the measurements and descriptions that can ogy and healthy surrounding structures be used to differentiate periodontal health from disease, determine the actual support for the and the therapies that can be used to arrest or prevent Wteeth. This chapter focuses on how external root mor- the disease. The important relationship of periodontal phology affects the prevention and progression of disease relative to the placement of fillings and crowns disease of the supporting structures called the periodon- and the relevance of root anatomy to the removal of tium, and how tooth support and stability are affected harmful deposits that can form on the roots are also when the supporting structures of the tooth become introduced. SECTION I DEFINITIONS OF BASIC PERIODONTAL TERMS The following definitions are important to the under- 5. Dental plaque [PLACK] (also known as biofilm): An standing of periodontal disease and related therapies. organized layer consisting mainly of microorganisms Complete definitions can be found in the Glossary of that adhere to teeth (and other oral structures) and Periodontal Terms1 located on the Web site <http://www. contribute to the development of gingival and peri- perio.org/resources-products/Perio-Terms-Glossary.pdf>. odontal diseases, as well as to tooth decay ( dental caries). 1. Periodontium [pair e o DON she um] (or Periodontal 6. Dental calculus [KAL kyoo les] (tartar): A hard Ligament Apparatus): The tissues that surround, mass that forms on teeth (or tooth substitutes) due envelop, or embed the teeth (Fig. 7-1) including the to calcification of dental plaque. gingiva, cementum (covering the tooth root), peri- 7. Periodontics: That specialty of dentistry that odontal ligament, the supporting (alveolar) bone, encompasses the prevention, diagnosis, and treat- and the alveolar mucosa. ment of diseases of the supporting tissues of the 2. Gingivitis [jin ji VIE tis]: Inflammation (disease) of teeth or their substitutes; the maintenance of the the gingiva. health, function, and esthetics of these structures 3. Periodontitis [per e o don TIE tis]: Inflammation (dis- and tissues; and the replacement of lost teeth and ease) of the supporting tissues of the teeth called the supporting structures by grafting or implantation of periodontium. (A spread of inflammation of the gin- natural and synthetic devices and materials. giva into the adjacent bone and periodontal ligament 8. Periodontist: A dental practitioner who, by virtue usually results in a progressively destructive change of special knowledge and training in the field, limits leading to loss of bone and periodontal ligament.) his or her practice or activities to periodontics. 4. Periodontal diseases: Those pathologic processes affecting the periodontium, most often gingivitis and periodontitis. Scheid_Chap07.indd 198 9/25/2010 10:12:01 AM Chapter 7 | Periodontal Anatomy 199 Gingival sulcus (a potential space) Junctional Free Gingiva Gingival margin epithelium Free gingival groove Connective tissue attachment Keratinized with free gingival fibers epithelium Alveolar crest fibers Alveolar crest Attached Gingiva Horizontal fibers Cortical plate Mucogingival (shaded red) junction Oblique fibers Alveolar Mucosa Alveolar bony socket (lamina dura lining) Cheek (is a red line) Periodontal ligament fibers Apical fibers Marrow spaces Trabecular bone FIGURE 7-1. Cross section of a tooth within its periodontium. Mesial side of a mandibular left first premolar suspended in its alveolus by groups of fibers of the periodontal ligament. Periodontal ligament fibers include the apical, oblique, horizontal, and alveolar crest fibers. Other fibers include free gingival fibers, and a sixth group (not visible in this view) called transseptal fibers that run directly from the cementum of one tooth to the cementum of the adjacent tooth at a level between the free gingiva and alveolar crest fibers. The fibers of the periodontal ligament are much shorter than depicted here, averaging only 0.2 mm long. SECTION II THE HEALTHY PERIODONTIUM The periodontium is defined as the supporting tissues B. TOOTH ROOT SURFACE of the teeth including surrounding alveolar bone, the Tooth roots are covered by a thin layer of cementum. gingiva, the periodontal ligament, and the outer layer of the tooth roots (all identified in Fig. 7-1). C. PERIODONTAL LIGAMENT A. ALVEOLAR BONE (ABBREVIATED PDL) The right and left maxillae bones together, and the man- The periodontal ligament is a very thin ligament com- dible, both have a process of bone called the alveolar posed of many fibers that connects the outer layer of [al VEE o lar] process that surrounds the roots of all the tooth root (which is covered with cementum) healthy teeth in that arch. The root of each erupted tooth with the thin layer of dense bone (lamina dura) lining is embedded in an individual alveolus [al VEE o lus] each alveolus or tooth socket. The groups of fibers (plural alveoli) or tooth socket whose shape corresponds of the periodontal ligament represented in Figure 7-1 closely with the shape of the roots of the tooth it sur- are greatly enlarged. The entire thickness of the lig- rounds. Each alveolus is lined with a thin compact layer ament would normally be less than one fourth of a of bone seen on a radiograph (x-ray) as the lamina dura. millimeter. Scheid_Chap07.indd 199 9/25/2010 10:12:01 AM 200 Part 2 | Application of Tooth Anatomy in Dental Practice D. GINGIVA The gingiva [JIN je va] is the part of the oral tissue (oral mucosa) covered by keratinized epithelium. It covers the alveolar processes of the jaws and surrounds the portions of the teeth near where the root and crown join (cervical portion). The gingiva is the only visible part of the periodontium that can be seen in the mouth during an oral examination. 1. APPEARANCE OF HEALTHY GINGIVA Healthy gingiva varies in appearance from individual to individual and in different areas of the same mouth. It is usually pink or coral pink (Fig. 7-2), but in many per- FIGURE 7-3. sons with darkly colored and black skin, and in many Gingiva with heavy melanin (brownish) persons of Mediterranean origin, healthy gingiva may pigmentation, normal for many ethnic groups. (Note that there have brown masking pigmentation