OBJECTIVETo analysis the sum and frequencies of Bolton tooth-size discrepancies Angle Class I, II, III malocclusion patients.

METHODSMeasured each tooth crown mesial-distal size between the first molar of 439 dental plaster casts of malocclusion patients and obtained the sums of six anterior tooth-size and twelve tooth-size between the first molar of upper or lower and calculated the anterior and total tooth-size discrepancies by Bolton rate standards, then statistic analyses were done.

RESULTSPatients whose sums of anterior tooth-size 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 total tooth-size 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 Class II and 20.45% in Class III. The upper sum of anterior tooth-size of Class I malocclusion patients whose sums of anterior tooth-size 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 tooth-size discrepancy of Class I, II, III and total tooth-size 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 tooth-size 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 total tooth-size 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.

CONCLUSIONTooth-size discrepancy of malocclusion patients was not the general cause of malocclusion.