Abstract
Epidemiological analyses in connection with DMFT index and length of stay were performed on 948 subjects receiving further dental examinations beyond an initial admission examination among 1107 mentally retarded individuals who were admitted to the Niigata Prefectural Institute of Total Training for the Mentally Retarded, Colony Niigata Shiroiwa-no-Sato during the years 1971-1988.
(1) The 948 subjects were distributed into 3 groups based on the length of stay, i. e., 1-5, 6-10, and 11 years and longer. The DMFT index showed a tendency of increasing with age in all 3 groups. The DT index showed values blow 2.46 in 15-year-olds and over, and decreased in longer stays. The FT index in all of the 3 groups classified by length of stay was in the range of 3.31-7.60 in almost all age groups (over 15 years of age). The MT index was 1.66-3.17 in 20-24-year-olds and 2.00-11.00 for subjects in their 40's in all of the 3 groups classified by length of stay.
(2) In the DMFT index by sex in 1971-1975 newcomers, females had a higher index than males, and it was the same in 1976-1981. This difference may disappear as the length of stay increased, and the difference in the MT index by sex, also higher in females, was gone within 5 years of admission. The difference in the DMFT index by sex in 1976-1981 newcomers disappeared within 5 years. No difference was noted afterwards in 1982-1988 newcomers.
(3) While the DMFT index remained stable, a decrease in the DT index and a corresponding increase in the FT index was seen in females as the length of stay increased. In males the DMFT index was raised by an increase in the FT index as the length of stay increased.
However, this increase in the FT index immediately after admission in males was accompanied by gradual decreases in the DT and MT indices and consequently by a decrease in the DMFT index in 1971-1975 newcomers when they stayed longer than 6 years, as compared to the data of 1977-1988 admissions as a control.
