[Bolton tooth-size discrepancy among different skeletal malocclusion groups].

Purpose: To evaluate the differences in tooth size ratios and distributions of Bolton anterior and overall ratios among different skeletal malocclusions.

Methods: 180 subjects were involved in this study, each malocclusion group consisted of 60 subjects(30 males and 30 females). The mesio-distal width from left first molar to right first molar was measured, Bolton anterior and overall ratios were calculated. Student's t test, ANOVA, LSD and chi2 test were performed for statistical analysis with SPSS15.0 software package.

Results: No statistically significant sex difference was found in anterior or overall ratio in any malocclusion. Significant difference was found for all ratios between skeletal Class III and skeletal Class I, so with skeletal Class II. No significant differences in all ratios between skeletal Class I and Class II were noted. Significant difference was found in the distribution of subjects with anterior and overall ratio discrepancies between skeletal Class III and skeletal Class II.

Conclusions: The mean anterior and overall ratios for skeletal Class III malocclusions are significantly greater than those for skeletal Class I and Class II. The number of subjects with anterior ratio discrepancies for skeletal Class III malocclusions are larger than that for skeletal Class I and Class II malocclusion.