Caries saliva factors

The clinical evidence presented in section 1.2 unequivocally supports an inverse association between calculus and caries experience for subjects of similar age. There are many possible reasons for this finding. In section 1.4 a variety of saliva and plaque factors were discussed which have been shown to influence mineralisation processes in vitro or to have the potential to influence such processes. A number of studies have sought correlations between particular factors and either calculus or caries almost none involved both. 

In summary, the data for calcium and inorganic phosphate levels in saliva and plaque tend to support an inverse association with caries and a direct association with calculus, as predicted on mechanistic grounds. However, statistically significant trends are rare, which suggests that these factors alone cannot account for the inverse relationship between caries and calculus. 

A natural defence mechanism of the body against disease is the production of antibodies against bacteria. An antibody against oral bacteria, immunoglobulin A (IgA), is found in saliva. However, correlations between IgA levels to S mutans, the bacterium most closely associated with caries, and caries experience are inconsistent [106]. In his 1998 review of antimicrobial factors in saliva, Tenovuo concluded that naturally evoked salivary antibodies do not have enough power to influence caries development in adolescents and adults [107],... 

We believe that more scientifically rigorous investigations are warranted in order to understand better the key causal factors in the caries-calculus relationship. For example, moderately sized (but balanced) sub-groups of children should be chosen with different distinct calculus/caries characteristics. Their saliva and plaque should then be examined using the most appropriate proven methodologies for factors of interest. In order to account for the time dependencies of these factors, sampling would best be done on repeated occasions and, especially in the case of saliva, at consistent times of the day. 

Dawes C An analysis of factors influencing diffusion from dental plaque into a moving film of saliva and the implications for caries. J Dent Res 1989 68 1483-1488. 

A simplified description of the etiology of dental caries involves metabolism of sugars by oral microorganisms to acids which gradually dissolve tooth enamel. However, it is now recognized that a number of dietary factors and nutrient interactions can modify the expression of dental caries (Herod, 1991). The cariogenic potential of food is infiuenced by its composition, texture, solubility, retentiveness, and ability to stimulate saliva flow (Morrissey et al, 1984). 

Dextrans are reported to interact with salivary proteins, " certain oral bacteria, and phosphate ions. It may be envisaged that each of these components could be actively incorporated into the matrix of a plaque that contains a dextran-gel network. The incorporation of proteins and phosphate ions, moreover, would impart a charge to this network thus, in addition to preventing the free exchange of macromolecules between saliva and the tooth surface, the dextran gel would have the capacity to control the rate at which calcium and phosphate ions leave the tooth surface, and this appears to be an important factor in the formation of natural, subsurface, caries lesions. In contrast, the diffusion of small, neutral molecules into plaque does not appear to be prevented by the dextran gel, as electron micrographs of plaques differentially stained for carbohydrates indicated that both endocellular and exocellular reserve-carbohydrates depleted by bacterial metabolism are rapidly re-formed in the presence of dietary sucrose. ... 

Saliva is a crucial factor for protection of the oral environment. The rate of oral clearance of sugar and acid is inversely related to the onset and progression of dental caries, as shown particularly in persons with severe hyposalivation. 

Dental calculi, i.e. calcifications of the dental plaque biofilm, contain various calcium phosphates, since these inorganic ions are provided by saliva or crevicular fluids. Although the pattern of calcification of oral microorganisms, either intra- or extracellularly, is mainly a characteristic of each bacterial species or strain [75], it may be influenced by nutritional factors, such as saliva proteins, as well [76]. The interactions of saliva with dental calculi and its role in preventing dental caries by controlling the enamel de- and remineralisation processes have been reviewed [19]. 

Over the years, many attempts have been made to relate the composition of the saliva to both the nature of the diet and the incidence of caries, but it is now realized that so many factors influence its composition that, unless these are strictly controlled, it is not possible to correlate one set of findings with another. If any such relationship exists, the rate of flow and hence the buffering power of the saliva would appear to be the factors most likely to affect the ability of bacterially produced acids to attack the mineral elements of the teeth. 

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