Caries Management - Science and Clinical Practice. Группа авторов

L. Structural analyses of plaque and caries in relation to the morphology of the groove-fossa system on erupting mandibular third molars. Caries Res 1997;31(5): 336–348

      43. Carvalho JC, Thylstrup A, Ekstrand KR. Results after 3 years of non-operative occlusal caries treatment of erupting permanent first molars. Community Dent Oral Epidemiol 1992;20(4): 187–192

      44. Ekstrand KR, Kuzmina IN, Kuzmina E, Christiansen ME. Two and a half-year outcome of caries-preventive programs offered to groups of children in the Solntsevsky district of Moscow. Caries Res 2000;34(1):8–19

      45. Wakita M, Kobayashi S. The three-dimensional structure of Tomes’ processes and the development of the microstructural organisation of tooth enamel. In: Suga S, ed. Mechanisms of Tooth and Enamel Formation. Berlin: Quintessenz;1983:165

      2 Etiology and Pathogenesis of Caries

      Peter Shellis

       Microbiology of Caries

       Chemistry of Dental Minerals

       Solubility, Dissolution, and Crystal Growth

       Minerals of Dental Tissues

       Fluoride and Calcium Phosphate Chemistry

       The Cariogenic Challenge

       Chemistry of Caries

       Enamel Lesion Formation

       Dentin Lesion Formation

       Fluoride and Lesion Formation

       Remineralization and Lesion Arrest

       Dental Erosion

As described in Chapter 1, teeth are continuously bathed in saliva, one of the main functions of which is to minimize mineral dissolution and precipitation within the mouth^1,2: both can be harmful to the teeth and other oral tissues. Saliva can ameliorate the effects of challenges that tend to dissolve tooth tissue, such as consumption of acidic foods, because it has an approximately neutral pH, is reasonably well buffered, and contains mineral ions. In dental caries, this homoeostasis is overcome by acid-generating metabolic processes in localized accumulations of bacteria. This in turn causes loss of mineral from the hard tissues, which destroys their integrity and eventually impairs their function.

      Most of the surface of a tooth is kept free of bacteria by friction from the tongue, cheeks, and foodstuffs. However, bacteria colonize areas of the surface protected from these frictional forces (plaque stagnation areas) and form a film of closely packed bacteria known as dental plaque^3,4 within which is created a unique microenvironment, partly isolated from the saliva and immediately adjacent to the tooth surface. The human diet includes a variety of easily-fermentable carbohydrates: monosaccharides such as glucose and fructose; disaccharides such as sucrose and maltose; and oligosaccharides such as those found in honey. In this chapter, these will be collectively referred to as ‘sugar’ and specific carbohydrates will be named. On each occasion when sugars are ingested, they are metabolized by plaque bacteria and this results in the accumulation of organic acid end products and hence causes a temporary reduction in plaque pH. Such an episode can pose a “cariogenic challenge” since, if the plaque pH falls low enough, mineral within the underlying dental hard tissue can dissolve. The progressive loss of mineral through dissolution by plaque acid (demineralization) during repeated cariogenic challenges is the primary process in dental caries.

      This basic etiology is summarized by the well-known Venn diagram of Keyes⁵ (Fig. 2.1), which illustrates the interaction of the three factors “tooth,” “bacteria,” and “diet.” While the combination of two factors will produce a contribution (e.g., bacteria + tooth → plaque; bacteria + diet → acid), the interaction of all three is required for caries initiation. Lesions are initiated only at sites where plaque accumulates. In economically developed populations, primary caries lesions are initiated in children on the enamel surface: most commonly in occlusal pits and fissures, less often on approximal surfaces, and rarely on smooth surfaces. In young adulthood, approximal caries increases. In older people, root surfaces exposed by gingival recession are sites for new primary lesions, and the margins of restorations are sites for secondary or recurrent caries lesions.⁶

      Caries tends to progress relatively slowly (over months or years) and in the early stages demineralization produces subsurface lesions which can in principle be arrested or reversed. Between cariogenic challenges, plaque pH returns toward “resting” levels which are approximately neutral, and this allows the possibility that mineral ions in plaque can contribute to re-deposition of mineral within the caries lesion: a process known as remineralization. Thus, the caries process is not one-directional but involves a dynamic process of mineral loss and regain⁷ (Fig. 2.2). If the balance between these processes favors demineralization, caries lesions progress and ultimately the damage to the tissue, due to mechanical breakdown (enamel) or to bacterial action (dentin), becomes irreversible. Restoration or extraction then becomes the only treatment option.

      Fig. 2.1 Venn diagram summarizing the etiology of caries. The diagram demonstrates that caries requires both the presence of acidogenic bacteria and availability of a diet from which the bacteria can produce acid, in conjunction with acid-susceptible dental tissues.⁵

      Despite this apparently simple etiology, caries is regarded as a multifactorial disease, for two main reasons. First, despite much research, it has not been proven whether it is caused by one specific pathogen or by several bacteria. Second, the risk of caries occurrence, and the rate at which the disease progresses, are influenced by a large number of factors.^6,8 These form a hierarchy at individual, behavioral, and social levels:

      • Individual factors: the oral bacterial flora; the solubility of tooth mineral; hard tissue structure; salivary flow rate and composition

      • Behavioral factors: frequency with which foods containing fermentable carbohydrate are consumed; frequency and effectiveness of oral hygiene; pattern of dental check-ups

      • Social factors, such as level of education and socioeconomic status, influence aspects of individual behavior which impinge on caries. Caries incidence in children is strongly influenced by the level of care provided by those looking after them, especially with respect to diet, attention to oral hygiene, and attendance at the dentist. Care provision is in turn influenced by the care-giver's background.