Dental Caries

Definition Caries is a disease resulting in the destruction of the hard structure of the teeth

Stages in the development of caries The enamel becomes decalcified A small white spot appear Discoloration becomes pronounced The tooth surface softens and decay penetrates through the enamel into the dentine Caries spreads laterally and in depth Cavitation occurs

The lesion deepens, and pulp becomes affected, first reacting to stimuli (e.g.sweets, temp.), then damaged and dead Bacteria travels down the root canal, out through the apex causing abscesses Hanadi Baeissa

Factors determining the incidence of caries Micro organisms: Acid producing bacteria, especially if they produce extracellular polysaccharides, will increase risk Host factors: Decreased saliva secretion increase incidence Buffering power of saliva to raise pH decrease incidence Hanadi Baeissa

The morphology of the teeth: well spaced teeth decrease incidence, while fissures & pits increase it. The composition of the teeth: certain trace elements decrease incidence (e.g. F, Mb and B), while others (e.g. Cu & Mn) increase it Hanadi Baeissa

Time: frequency of consumption of carbohydrates, and length of time in the mouth are related to incidence. Good oral hygiene can counter act this Substrates for acid production provided in diet

Caries as a disease of civilization Evidence links caries to civilization This is due mainly to changes in dietary habits, e.g. increased carbohydrates intake by Eskimos and eating refined instead of natural forms of carbohydrates by African tribes

Factors in unrefined food lead to decreased incidence of caries Substances that decrease solubility of calcium phosphate More phytate &/or calcium Antibacterial substances Substances that inhibit aggregation of bacteria :- decrease plaque formation Absence of free sugar (most important)

Theories for the cause of caries The proteolytic theory: presence of proteolytic bacteria lead to hydrolysis of protein (collagen) leading to progression of caries The phospho protein theory: phospho protein phosphatse in plaque acts on phosphoproteins in enamel, but this is not tested in humans

The proteolysis-chelation theory: some products of bacterial action on enamel, dentine, saliva & food constituents form complexes with calcium from plaque causing a decrease in the concentration required to maintain saturation, and leading to more solubility

The acid theory of caries: Bacteria in saliva + carbohydrate (sugar) lead to acid production dissolving appetite This the most likely theory

Evidence In thick plaque, pH below critical point pH in carious cavities is lower Caries intensity correlates with acid production and count of acid producing bacteria In germ-free rats, caries was produced by inoculation with acid producing organisms

The importance of diffusion: Since caries is a penetrating lesion, the inward diffusion of the acid must play an important role in its development Evidence shows that the concentration of unionized lactic acid outside the enamel is more important than low pH

Unionized acid diffuses more easily inward, becomes diluted and ionized, allowing reaction with apatite to form free calcium and phosphate These ions diffuse outwards, and may precipitate as CaHPO4, explaining the apparently intact outer layer of enamel over the cavity Therefore, the critical pH may not only be the level at which the environment of enamel becomes unsaturated with apatite, but it also maybe the pH at which sufficient conc. Of unionized lactic acid exists to ensure inward diffusion

The bacteria responsible for caries Two species were isolated from carious mouths and were suggested as causal organisms: Streptococcus mutants, and Lactobacillus acidophilus or odontolyticus Other filamentous bacteria producing lactic acid were isolated from caries lesions of the root surfaces. These bacteria, the genus Actinomyces are of two species Actinomyces viscosus Actinomyces naeslundi , both are found predominantly in the gingival region and cause; inaddition; severe periodontal disease

Relationship between lactobacilli and streptococcus mutans streptococcus mutans alone can produce caries, but the combination is more effective streptococcus mutans stop acid production at pH 4.3, but lactobacilli continue to below pH 4 Therefore, the joint effect is more intense Lactobacilli seems to be involved in the initial attack, and is found at tha front of the lesion

Local effects in caries Caries is localized, indicating the role of local conditions This might be partly due to differences in composition of plaque (bacterial and matrix) Evidence also suggests that different types of bacteria cause caries at different sites (e.g. tetracycline reduces smooth surface caries, to a greater extent than pit and fissure caries

The role of diet in caries Diet has two types of effects Dietary effects: local effects contributing to substrates for bacterial growth & direct interaction with teeth Nutritional effects: effects of assimilated food stuff

1.Dietary effects There is evidence relating consumption of carbohydrates (particularly sucrose) to caries

A- Indirect Evidence for importance of dietary carbohydrates in caries Eskimos, whose diet was formerly almost exclusively of fish, meat and fat, had a low incidence of dental caries while on their primitive diet The prevalence of dental caries in different countries parallels the extent of sugar consumption in those countries

In many areas of Europe where sucrose intake was severely restricted during World War II, caries incidence in children decreased dramatically The study of human biochemical genetics has also provided evidence that sucrose plays a special role in caries. A rare enzyme deficiency involving a lack of fructose-I-phosphate aldolase results in hereditary fructose intolerance. Foods containing fructose cause nausea, vomiting, tremors, and convulsions in affected individuals. As sucrose is a glucose-fructose disaccharide, it also produces these effects, and is avoided by such pateints, who are often found to be caries-free or else have a very low caries prevalence

Amongst present-day children of pre-school age there is a marked correlation between caries experience and the extent of eating between main meals Rampant caries, in which the anterior teeth may be almost completely dissolved away, is found in babies who are given comforters filled with syrup or honey to suck for prolonged periods of time

B- Populations on controlled diets The caries score (decayed, missing and filled teeth, DMFT) was followed over years for different groups given carbohydrates sources of increasing degree of stickiness compared to a control group given a diet low in carbohydrates, with the calories supplied by sugar normally , replaced by margarine

Hanadi Baeissa

A study conducted at an orphanage, indicated that refined carbohydrates increase the caries score. While resident, the children were given a diet that excluded refined carbohydrates , and had low caries score (DMFT), but this increased dramatically after they left and changed their diet to include sugar and refined carbohydrates

Interaction between carbohydrates & dental plaque Epidemiological evidence & experimental studies indicated the following: Carbohydrate free diet thin plaque Presence of sucrose more plaque (gelatinous) Sucrose is more cariogenic than glucose or fructose with respect to smooth surfaces

4. Extra cellular polysaccharides are produced by bacteria from sucrose this help in: Adherence to smooth surface Retain acid in close proximity to tooth surface Shield against buffering by saliva The above are less important in fissures

Other dietary effects Addition of Calcium sucrose phosphate (CaSP) caries Acidic drink could dissolve enamel caries incidence Fibrous food reduce plaque formation , therfore, caries Foods that saliva flow caries e.g. salty foods Foods that pH & increase Ca content caries e.g. cheese

2- Nutritional effects Vitamin D could lead to incidence of caries Some trace elements caries & some it

Minerals associated with increased caries include: Copper, magnesium, Se, zinc, vanadium & lead Minerals associated with decreased caries include : F, Sr, B, K, nickel, Mo, Li Mechanism: suggestion Effect morphology of teeth (rats) Effect crystal structure & solubility

Caries resistance Many factors not strong by themselves combine to caries e.g. Highly buffered saliva with high flow rate Ca, P, HCO3 in saliva High F/CO3 of enamel The most important factor is the type of bacteria presence of antibodies to cariogenic bacteria might help to caries also

Finally the morphology of teeth plays a role Note: Cause of caries differs from person to another

Remineralization Carious lesions up to white spot stage can cease to develop and might disappear Caries progresses by alternate demineralization, when pH falls, and partial remineralization when the pH rises Saliva could remineralization, but F speeds process