Relationship between human enamel structure and the formation of caries-like lesions in vitro

Caries-like enamel lesions were produced in deciduous and permanent human teeth by exposure to acidified hydroxymethyl-cellulose gel, pH 4.5, for 21 days. Mean lesion depth was significantly greater in deciduous than in permanent enamel, in agreement with previous studies. The greater lesion depth in deciduous enamel was associated with greater mean prism-junction density and mean volume fraction of interprismatic enamel, as measured by planimetry of scanning electron micrographs. The greater susceptibility of deciduous enamel appears to be due to greater porosity. The order of lesion depths in vitro among permanent teeth suggests that in vivo the pattern of caries incidence among the various tooth types is governed mainly, not by intrinsic susceptibility but by other factors, such as morphology and salivary composition and flow rate. Some of the variation in caries incidence between individuals and between contralateral teeth may, however, be due to variations in intrinsic susceptibility.