b. Proteolytic Concept. According to the proteolytic (effecting the digestion of
proteins) concept, proteolytic bacteria attack the organic material in the enamel rods
(which is mostly protein) along certain tracts called lamellae. Dissolution of the organic
material in these lamella tracts eventually allows bacterial penetration to the underlying
dentin.
c. Combined Concepts. According to both concepts, dental caries is the result
of microbial activity on the teeth. The process of dental caries may be a combination of
both concepts, with the acidogenic concept accounting for dissolution of mineral content
and the proteolytic concept accounting for destruction of organic content of the tooth.
1-17. CARIES IN ENAMEL
The organisms that produce acid are contained in mucinous plaques that adhere
to the surface of the enamel. Common sites of plaque adherence are pits, fissures,
interproximal areas, and along the free margin of the gingiva, particularly on the facial
surface of the tooth. The enamel rods of a tooth are cemented together by a substance
that dissolves more readily than the rods themselves and, thus, according to the
acidogenic concept, the first effect in enamel caries is probably the dissolution of this
cementing substance. The first visible evidence of caries is a slightly whitened area on
the surface of the tooth (decalcification). This area is very easily overlooked,
particularly when the teeth are wet. Drying of the tooth surface makes these areas far
more visible. From the small areas on the surface of the tooth, caries continues its
progressive destruction. As the acid dissolves the cementing substances, the enamel
rods are left without support and break away. Since enamel contains a minimal amount
of organic material, the primary acid effect on the enamel cementing substance results
in loss of enamel structural support. Without support, the enamel rods break away,
allowing progressive formation of a cavity within the enamel, until ultimately dentin is
also involved. In summary, caries first penetrates the enamel and dentinoenamel
junction. Then it spreads laterally and deeper within the dentin toward the pulp. Thus,
what may appear to the patient as a small surface cavity may in fact be a very extensive
involvement of the tooth structure. See figure 1-1.
MD0511
1-8