A caries susceptibility classification of tooth surfaces by survival time

Individual tooth surfaces have vastly different susceptibilities to caries and this susceptibility also varies over time. The aim of this study was to develop a method of grouping tooth surfaces into a caries susceptibility classification based on their survival experience. The data used in the study were from a 3-year caries clinical trial. The definition of survival time was taken to be the time from the start of the trial to when a surface is recorded as decayed or filled. Cluster analysis was used to divide the tooth surfaces into groups in such a way that surfaces in the same group have similar survival time distributions. The 13 groups identified were ordered from 1 to 13 starting with the group with the shortest survival time, i.e. the occlusal surfaces of the four first molars. Approximately 80% of symmetrical pairs of tooth surfaces were in the same group. The groups obtained using cluster analysis were compared to groups defined using dental/anatomical criteria. It is concluded that the cluster analysis method developed for grouping the tooth surfaces cn provide a useful descriptive measure of caries susceptibility which can be applied to data from any longitudinal study of caries.