Abstract: PURPOSE: To Investigate the changes of Bolton index, maxillary and mandibular teeth size and teeth size discrepancy (TSD) in the youth and middle- aged and elderly people. METHODS: One hundred ninety-one youth dental plaster casts from malocclusion patients and 63 middle-aged and elderly people with snoring or obstructive sleep apnea-hypopnea syndrome (OSAHS) patients were selected. 12 teeth size between the upper and lower first molar, width of maxillary lateral incisor, Bolton anterior and overall ratios and teeth size discrepancy were measured and calculated. Statistical analysis was performed using SPSS 13.0 software package. RESULTS: ①There was no significant difference between the 2 groups in Bolton anterior and overall ratios ( P>0.05 ).②The mean size of the upper lateral tooth in the youth was larger than the middle-aged and elderly people( P<0.01 ).There was no significant difference in 6 upper or lower anterior teeth size between canine and 12 mandibular teeth size between first molar in 2 groups, but the mean teeth size in the middle-aged and elderly people was smaller.③The prevalence of anterior and overall TSD in the youth was 31.4% and 42.4%,while it was 19.05% and 15.9% in the middle-aged and elderly group. ④There was significant difference(P<0.05 ) between 2 groups in width of upper lateral incisor, which was 7.46mm in the youth and 7.20 mm in the middle-aged and elderly group. ⑤Prevalence of laminal width of upper lateral incisor in patients with teeth size discrepancy was low. CONCLUSIONS: Bolton index does not change by age. Although the teeth size in middle-aged and elderly group are smaller than the youth group, the total reduction is little without clinical significance. The laminal width of upper lateral incisor isn’t the main cause for anterior or overall dental size discrepancy.

Key words: Malocclusion, Bolton index, Teeth size discrepancy, Snoring, Obstructive sleep apnea /hypopnea syndrome