Dental Diseases @) m4 —— wa xO Percent of Persons Is-24 25-29 ME34 3839 0-H 4549 50-54 $8.50 O64 bS-NO- Age Group w4 mn] +6 mm of | Figure 8-3. Percent of persons by severe loss of periodontal attachment (pocket depths measuring 4 mm or more) and age groups as determined from the NIDR survey of employed adults and seniors. Source: National Institute of Dental Research 1987. 05 manana NCHS 1960-62 emums NIDR 1985 ee 2 40 2B S s 30- c i) 3 20 u a. 101, r ' 35-44 45-54 55-64 65-74 Age Group (Years) Figure 8-4. Comparison of the percent of edentulous persons in the 1985-86 NIOR survey to that reported from the NCHS survey of 1960-62. Source: National institute of Dental Research 1987. 351 C Nutrition and Health Fissure Pit Crown (Enamel) Dentinal tubules (Dentin) Gum Pulp Alveolar bone Periodontal ligament Cementum Blood vessel in root canal Figure 8-5. Schematic cross-section of a typical mandibular tooth. The gums recede with age, exposing the cementum of the tooth root. dental organ that produces the tooth enamel and a dental papilla that produces the tooth pulp and the dentin. Cells from the dental follicle form the cementum and periodontal ligament after the tooth has formed. The deciduous teeth begin forming at about 6 weeks in utero, when cells in the primitive oral cavity differentiate to form the dental lamina—the site of development of the tooth buds. The dental lamina is active from the second month of embryonic development, when the first buds for the deciduous teeth are formed, until about the age of 5 years, when the buds for the last permanent molars are initiated. The formation of the tooth crown begins with the secretion of a dentin matrix containing collagen fibrils. Mineral ions then enter the matrix to form small crystals on or between the fibrils. Successive layers of dentin are formed. Enamel formation begins as soon as the first dentin layer has been laid down. Cells of the enamel organ secrete successive layers of a matrix that is chemically different from dentin matrix. Mineral crystals appear in each layer as it is secreted and grow larger as more mineral enters the tissue; matrix proteins and water are removed. This so-called matura- tion of the enamel continues after the full thickness of enamel matrix has 352 Dental Diseases le been laid down. These events occur at different times for the various deciduous and permanent teeth, beginning from a few months before birth until late adolescence. As the tooth erupts into the mouth, it loses the layers of cells and blood vessels that covered the enamel. The enamel, however. continues to mature during the period immediately after tooth eruption and to incorpo- rate minerals (including fluoride) into its structure from saliva, food, and drinking fluids. Otherwise, the enamel of fully erupted teeth is not known to have any metabolic dependence upon nutrients consumed in the diet. The inner surface of dentin adjacent to the pulp remains lined with the cells that formed it, and these cells continue to form secondary dentin at a very slow rate throughout the life of the tooth. Thus, there are different periods in the developmental history of the tooth. During the preeruptive period when the crowns are forming in the jaws (which, for the wisdom teeth, continues into late adolescence), the devel- oping enamel and dentin of the crowns are subject to nutritional deficien- cies or imbalances in the same way as other tissues. In fact, in the enamel the preeruptive period can be divided into two phases, the secretory and the maturation stage. Nutritional deficiencies or excesses may affect either stage separately or both. Hypoplastic lesions in the enamel reflect distur- bances affecting the secretory process. Hypomineralized defects, such as the white spot lesions of fluorosed enamel, give evidence of interference with the maturation process. After eruption, when the crown of the tooth has emerged from the jaw and the enamel is bathed instead by the saliva as well as exposed to micro-organisms and their byproducts, sloughed cells, and food debris, nutritional deficiencies or excesses and dietary habits may affect teeth in a totally different manner. The development and maintenance of the soft tissues and bone that anchor and support the teeth (the periodontium) are also subject to nutritional deficiencies. The periodontium comprises the gingiva (the tissue that cov- ers the alveolar bone process and surrounds the top of the tooth), the periodontal ligament (the soft connective tissue that surrounds the roots of the teeth and joins the root cementum and the alveolar bone), the root cementum (a specialized calcified tissue that covers the tooth root), and the alveolar bone (the bone that forms and supports the sockets of the teeth). The bony tissue of the alveolar process is dependent on the presence of teeth. The alveolar bone grows in response to dental eruption, is modified by dental changes, and resorbs when the teeth are lost as a result of 353 C Nutrition and Health advanced dental caries and/or periodontal disease. The resorption of al- veolar bone ridges (residual ridge resorption) has been described as an oral disease entity (Atwood 1971). Throughout life, the oral soft tissues undergo rapid rates of turnover and repair, and the continued presence of optimum levels of nutrients is neces- sary to maintain proper oral health and to resist disease. Dental Caries Once a tooth is fully erupted, it becomes subject to the influence of chewing, acids in the mouth, and bacterial plaque. Dental caries begins with dissolution of the mineral surface of the tooth by acid produced from fermentable carbohydrate (e.g., sugar) by dental plaque bacteria. Next, the dissolution advances further into the enamel, first appearing as a white spot, and subsequently into the dentin and eventually into the pulp. If left untreated, the result is destruction of the crown and root system, tooth loss, and resorption of the surrounding bone (Newbrun 1978). The decay that begins in pits and fissures, on the smooth surfaces, or on exposed roots of the teeth is invariably due to the combined effects of bacterial infection and host and dietary factors over time (Wei, Fomon, and Anderson 1977; Shaw 1978, 1987). Patients with reduced salivary flow are also at increased risk (Mandel 1983). Of the many bacteria found in tooth plaque, Streptococcus mutans is considered the primary etiologic agent in coronal caries (Loesche 1986; Shaw 1987). This bacterium is unique in that it produces enzymes that convert table sugar (sucrose) into long sticky polysaccharides. The poly- saccharides promote firm attachment and accumulation of the bacteria in dental plaque (Gibbons and van Houte 1978). If not removed, the bacteria metabolize sugars (including sucrose) and produce acids that dissolve minerals from the teeth and begin the decay process. Root caries, decay of tooth root cementum following recession of gum tissues, has been regarded as an independent type of caries (Nikiforuk 1985). However, a relationship between root caries and coronal caries has been reported recently (Vehk- alahti 1987). Decay also occurs around restorations where plaque is diffi- cult to remove. Whereas sugars facilitate the action of cariogenic bacteria, saliva is a major impediment to the pathogenesis of these bacteria (Vogel 1985; Mandel 1986). This fluid, secreted by the major and minor salivary glands, coats the tissues of the mouth and provides protection against bacteria that cause disease. The saliva contains molecules that when adsorbed to the tooth can influence attachment of bacteria to this surface and, when present in the 354 Dental Diseases ie fluid, can clump bacteria together such that they cannot attach to the teeth but rather are cleared from the mouth by swallowing. Saliva also contains enzymes and proteins with antibacterial activity that inhibit bacterial growth or kill bacteria. In addition to these defense mechanisms, saliva can contain antibodies that attack specific kinds of bacteria. Another important function of saliva is that it supplies the calcium and phosphorus, minerals important in the remineralization of tooth surfaces that have lost mineral due to acid attack. Several types of interventions might prevent tooth decay. The most impor- tant diet-related interventions are fluoridation of drinking water and con- trol of sugar intake, but other approaches such as oral hygiene, application of plastic sealants, use of topical fluorides, and various chemotherapeutic agents have also been shown to be effective (Navia 1985). The efficacy of a caries vaccine that would prevent infection by cariogenic bacteria is under investigation (Navia 1985; Krasse, Elmilson, and Gahnberg 1987). Periodontal Disease Periodontal disease encompasses pathologic changes of the gingiva, peri- odon