Abstract:

Objective To analysis the sum and frequencies of Bolton toothsize discrepancies Angle Class Ⅰ,Ⅱ,Ⅲ malocclusion patients.Methods Measured each tooth crown mesialdistal size between the first molar of 439 dental plaster casts of malocclusion patients and obtained the sums of six anterior toothsize and twelve toothsize between the first molar of upper or lower and calculated the anterior and total toothsize discrepancies by Bolton rate standards, then statistic analysises were done.Results Patients whose sums of anterior toothsize discrepancy were pass 1.5 mm or less than 1.5 mm was 14.02% in Angle Class Ⅰ malocclusion patients and 9.49% in Class Ⅱ and 19.32% in Class Ⅲ. Patients whose sums of tolal toothsize discrepancy were pass 1.5 mm or less than 1.5 mm was 19.63% in Angle Class Ⅰ malocclusion patients and 15.33% in Calss Ⅱ and 20.45% in Class Ⅲ. The upper sum of anterior toothsize of Class I malocclusion patients whose sums of anterior toothsize discrepancies were pass 1.5 mm or less than 1.5 mm was always smaller than normal and the lower sum was always larger The sums of anterior toothsize discrepancy of Class Ⅰ、Ⅱ、Ⅲ and total toothsize discrepancy of Class Ⅰ were always between 1.5 mm～2.5 mm or 2.5 mm～1.5 mm. Patients whose sums of anterior toothsize discrepancy were pass 3.5 mm or less than 3.5 mm was 2.34% in Class Ⅰ malocclusion patients and 0 in class Ⅱ and 0 in class Ⅲ. Patients whose sums of totoal toothsize discrepancy were pass 3.5 mm or less than 3.5 mm was 4.21% in Class Ⅰ and 1.46% in Class Ⅱ and 4.54% in Class Ⅲ.Conclusion Toothsize discrepancy of malocclusion patients was not the general cause of malocclusion.

Key words: malocclusion, Bolton index, dental-size discrepancy (DSD)