Monitoring of caries progression in permanent and primary posterior approximal enamel by bitewing radiography.

The work which has monitored caries progression in posterior approximal enamel surfaces by reference to the size of radiolucency seen on bitewing radiographs is reviewed. There are wide variations in the degree of standardisation achieved, in the composition of the study groups and in the duration of the studies. There is a paucity of information relating to adults, the elderly, groups with low caries prevalence, and fluoridated communities. The results indicate that for the majority approximal caries progresses slowly, and large numbers of lesions remain unchanged for long periods. The available results are compared using the mathematical model of a negative exponential. The 'mean' time during which a lesion remains radiographically confined to the enamel is of the order of 3-4 yr, although in caries active individuals much shorter times are reported. Some clinical implications are suggested and the need for further research using comparable methods is stressed.