Assessment of Dental Caries Increments II. A Comparison of the R.I.D. and DMFS Indexes

¹ University of Oregon Dental School, and Reed College, Portland, Oregon

1. Six-month dental caries increments of forty children with permanent dentitions are presented and compared by using three different indexes—the R.I.D. index, the DMFS index, and the ratio of DMFS to the surfaces available.

a) The R.I.D. index was shown to have a coefficient of correlation of 0.93 when compared with the increment of DMF surfaces for the interval.

b) The R.I.D. index was shown to have a coefficient of correlation of 0.97 when compared with the ratio of the increase in DMF surfaces to the number of surfaces available for dental caries. The reasons for this higher correlation are discussed.

2. The dental caries increments of sixty-seven children with mixed dentitions are presented and compared in terms of the R.I.D. and DMFS indexes.

a) A correlation coefficient of 0.70 was shown between these two indexes for this group.

b) The significance of the difference between these two indexes used to express increments of dental caries in mixed-dentition periods is discussed.

3. The R.I.D. was shown to have a close relationship with the DMF surface increments for individuals with permanent dentitions over a 3-year period. The relationship between these two indexes for a 3-year period for children in the mixed-dentition period was shown to be similar in pattern but different in the total measure of caries activity.

4. The R.I.D. index is suggested as an instrument to express dental caries increments in a manner which will allow comparison of increments of dental caries of individuals or groups of different ages and different dentitions, i.e., deciduous, mixed, and permanent.