Dental Caries
Dental caries uniquely is prevalent worldwide and the annual oral health costs in Europe are estimated at €79 billion [1]. Essentially, the tooth’s outer covering, dental enamel and subsequently the sub-adjacent dentine are attacked and eventually destroy
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Introduction to Dental Caries Dental caries uniquely is prevalent worldwide and the annual oral health costs in Europe are estimated at €79 billion [1]. Essentially, the tooth’s outer covering, dental enamel and subsequently the subadjacent dentine are attacked and eventually destroyed by bacterially produced acid. If untreated this often results in infection of the alveolar bone of the jaw leading in turn to systemic infection including endocarditis. If the tooth is lost, supporting bone of the tooth socket is also resorbed exposing roots of previously healthy adjacent teeth to further attack by oral bacteria and toothbrush wear. Therapeutic treatment is only possible before the enamel surface is breached, after which restoration materials are inserted following drilling out of porous carious tissue. Since enamel is acellular, enamel caries occurs without the participation of host cells and is essentially a chemical process. Dental enamel comprises ~97 % inorganic crystals of a calcium hydroxyapatite mineral, similar to crystals in dentine, cementum and bone (see chapter “Overview” under part “Teeth and bones”). Enamel crystals are, however, much larger and better formed being 30–50 nm in thickness and width and up to 500 nm in length [2]. Several thousand crystals are packed parallel to each other into 4–5 μm diameter bundles, the C. Robinson Dental Institute, University of Leeds, Clarendon Way, LS2 9LU Leeds, UK e-mail: [email protected]
enamel prisms, extending from dentine towards the enamel surface [3]. Apatite crystals exhibit many ion substitutions (Fig. 1) [4–6]. Important from a therapeutic viewpoint, fluoride ion substitution for hydroxyl ions dramatically reduces acid solubility and facilitates precipitation while carbonate and magnesium have an opposite effect [7]. Fluoride ion stabilises the crystal by reducing lattice energy and improving crystallinity, while carbonate and magnesium distort the regular arrangement of ions leading to instability.
Pathophysiology of Dental Caries and Metabolic Alterations Several hundred species of bacteria are resident in the oral cavity [8]. Of these 30–50 are regarded as cariogenic. The mutans streptococci have received most attention in this respect. Cariogenic bacteria form a biofilm, dental plaque, in the deeper fissures of molar teeth, around contact areas between adjacent teeth (interproximal sites) and at the gum margin. Oral bacteria colonise a protein layer on enamel surfaces, many proteins of which are unique to saliva [9]. This produces a biofilm with channels often extending from saliva to the enamel surface and mushroom-shaped biomass, structures typical of nutrient rich biofilms [10]. Caries is mediated by acid products of plaque biofilm metabolism [11]. Plaque acid initially dissolves the calcium hydroxyapatite crystals at prism and crystal surfaces, which are rich in carbonate [2]. While
E. Lammert, M. Zeeb (eds.), Metabolism of Human Diseases, DOI 10.1007/978-3-7091-0715-7_15, © Springer-Verlag Wien 2014
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