Limiting factors in the site distribution of dental caries.
From records of 32 067 dentate persons from low fluoride communities in South Yorkshire, England, clinical dental caries has been scored at the distal and mesial sites of permanent canines, first and second premolars, and first and second molars, in relation to age. For those teeth with distal or mesial caries or both, the average number of distal and mesial sites attacked per DF tooth is calculated. The ratio observed generally reaches a stable value as age increases and is lowest for mandibular canines (1.10 from 15 years of age and above) and highest for mandibular first molars (1.46 from 30 years and above). For second premolars--both maxillary and mandibular--the ratio reaches a maximum at 30-39 years, and then falls with increasing age. Because the ratio generally attains an effective ceiling with increasing age at a level well below 2, and because it is characteristic of the tooth-type, host factors would seem to be implicated. The data corroborate the authors' hypothesis that the site-specificity of dental caries is genetically-determined and that the timing of attacks in a given environment is governed largely by endogenous factors.