A Long-term Epidemiological Study Relevant to Dental Caries Prevalence of Institutionalized Mentally Retarded Individuals

Epidemiological analyses were performed on dental caries prevalence of 1107 mentally retarded individuals at entrance, who were registered with the Niigata prefectural institute of total training for the mentally retarded, Colony Niigata Shiroiwa-no-Sato, during 1971-1988. The subjects represented 9-14% of the severely and profoundly retarded, and 8-12% of the moderately retarded in Niigata prefecture. Dental examination was performed adopting the four-graded diagnostic standard for dental caries using plane mouth mirrors and sickle-shaped explorers under artificial lighting. Data base was constructed from the examination records and statistical analyses were performed. (1) The personal DMF rate in 15 year olds and over was 90-100% in general and the tooth DMF rate showed a tendency to gradually increase with age, and was calculated to reach more than 50% at the end of the 40s from 22-32% in 15-19-year-olds, in three terms, 1971-1975, 1976-1981, 1982-1988, categorized by the subjects' entrance year. (2) The DMFT index showed a tendency to gradually increase with age. The DT index was up to 5.26 in all the age groups but showed no increasing tendency with age. Also there was no increasing tendency with age in the FT index, but there was a long-term increase of 1.20-2.96 in 1971-1975 and 1.67-6.06 in 1982-1988 (over 15 years of age). An increasing tendency of 0.92-2.05 in the MT index with age was remarkable in 15-19-year-olds in all of the three terms, which would make it 11.82 in 40-year-old males and 8.27 in females of the same age in 1982-1988. (3) Yearly variation of DMFT index and average number of examined teeth per person by age and sex was not significant statistically. 684 新潟大学歯学部予防歯科学教室(主 任:堀 井欣一教授) Department of Preventive Dentistry Niigata Univesity School of Dentistry (Direcor Prof Kin-ichi HORII)