第 1 大臼歯の萌出および齲蝕罹患に関する疫学的研究

抄録

Almost all reports of research on first molars indicate the importance of their ability or capacity to function as a biologic unit of the dental mechanism. However, first molars have the highest dental caries prevalence in the life time. The purpose of this study was to determine their eruption and caries prevalence to obtain data for its prevention. 1. The results were as follows : Lower first molars tended to show higher rates than upper first molars for both males and females at the ages from 5 to 9. After 10 years old, all first molars showed complete eruption (eruption index 3). At the ages from 8 to 9, the males showed higher rates than the females. 2. Eruption pattern : The A type was more frequent in the males at the ages from 5 to 7. After 10 years old, all subjects showed the P type. At the ages from 6 to 7, the A type was most frequent, followed by the P and the G type. 3. Symmetry of eruption pattern : Symmetry of eruption pattern was most frequent for lower first molars at lower ages for both males and females. The females showed a greater tendency toward symmetry at the ages from 6 to 7, but the tendency was reversed at the ages from 8 to 9. 4. Number of DMFT : The males showed higher values at the ages from 5 to 6, but after 7 years old, the females showed higher values, especially in 8-year-old group. 5. DMFT rate : The males showed higher values at the ages from 5 to 6, but after 8 years old, the females showed higher values, especially in groups 8 and 11 years old. 6. DMFS : The males showed higher values at the ages from 5 to 6, but after 8 years old, the females showed higher values, especially in 8-year-old group. 7. Caries prevalence pattern : The A type was greater in the females at the ages from 5 to 7. After 8 years old, the females tended to show lower rates. The P type appeared in 6-year-old group. The females in 12-year-old group showed 100%. 8. Symmetry of caries prevalence pattern : Symmetry of the pattern was seen highest in the lower first molars in all ages. It tended to increase with age. 9. Actual dental health capacity : The males showed lower rates than the females in 6-year-old group. After 8 years old, the females showed lower rates. The rates tended to decrease with age for both males and females.