Factors influencing caries etiology

ALSO SEE KEYES' CIRCLE.

A)Host factors
1) tooth factors:
a. Composition : surface enamel due to dense
mineralization and high F-
content more resistant to caries than
subsurface layers of enamel.

b. Morphology: more chances of caries if deep ,
narrow occlusal fissures or buccal or lingual pits present

2) saliva factors:
a. composition :
a1) inorganic: less chances of caries if higher Ca2+
and PO43- concentration
a2) organic: less chances of caries with higher
ammonia and urea content

b. pH : decrease in pH of saliva below 5.5 (k/a critical
pH) predispose to caries.
The remarkable buffering-capacity of saliva (due to HCO3-/H2CO3 and phosphate buffer systems) controls the marked fall in pH, thus preventing caries formation.


c. Position: more chances of caries if malaligned , rotated teeth.

c. quantity: decreased amount or absence ( xerostomia)
increases the risk of caries.

d. viscosity

e. antibacterial properties :
due to the presence of
lysozyme (cleaves the N-acetyl glucosamine and N-acetyl muramic acid components of bacterial cell wall)
and salivary peroxidase system ( salivary peroxidase and thiocyanate/SCN- components of saliva interferes with glycolytic pathway of bacteria)



3) systemic factors
a) heredity :
even though no strong evidence has been found connecting caries-susceptibility with heredity, studies have shown
“high DMF” father and “high DMF” mother produced offspring with a “high DMF” rate
And “low DMF” parents produced offspring with “low DMF” rates.
b) Pregnancy and lactation:
despite the popular belief, there is NO evidence suggesting increase in caries in pregnancy (unless the mother has neglected her general oral health care).

B)Diet factors:
a. physical nature of diet:
person taking food with more fibre-content less
susceptible to caries than those taking soft, refined
(worse if sticky) food

b. local factors

b1) carbohydrate content:
though all forms of fermentable sugar leads to caries , there is always a higher risk of caries with free sucrose than starches.
Because sucrose in addition to its acid- byproduct produced during fermentation also aids in plaque development and adherence of cariogenous microbes to the tooth surface.
However starches due to large molecular structure, shows limited diffusion and hence can not directly enter the plaque .



b2) vitamin content
vitamins like (vit.D, vit.K and vit.B6) have been found to decrease the incidence of caries,
vit. B-complex deficiency has shown decrease in the rate of caries
whereas even though it is well-established that vit C-deficiency causes severe periodonta land pulpal changes , no evidence of decrease in caries by Vit C-supplement has been reported.
however a more extensive study to confirm the link between vitamins and caries is still desireable.
b3) fluorine content:
even though there is reduced incidence of caries with F-in drinking water, there is no significant caries reduction with dietary fluoride (because of its metabolic unavailabilty).



C)Cariogenic potential of the microorganism

Available data strongly suggest an active involvement of Streptococcus mutans in caries initiation (especially in pit and fissure caries, and smooth-surface caries; and to some extent the root surface caries)
On the other hand, oral actinomyces like
Actinomyces viscosus, and
Actinomyces neslundii, have a more important role in root surface caries.
Also A. neslundii, Lactobacillus spp. And other filamentous rods have been implicated in dep dentinal caries.