OBJECTIVETo study the characteristics of the arch form of skeletal Class III malocclusion and provide references for diagnosis and treatment plan.

METHODS7 indexes in dental casts of 47 patients with skeletal Class III malocclusion and 50 individuals with normal occlusion were measured respectively. And differences between corresponding upper and lower measurements were calculated. Independent samples t-test was employed for comparing between the two groups by SPSS 17.0.

RESULTSCompared with normal occlusion sample, Class III malocclusion group had smaller anterior segment lengths and larger canine angles (P<0.05). Differences between upper and lower first premolar widths were larger in males with skeletal Class III malocclusion. And differences between upper and lower anterior segment lengths were smaller in males with skeletal Class III malocclusion (P<0.05).

CONCLUSIONArch widths of patients with skeletal Class III malocclusion are basically normal. The lengths of anterior segment are smaller and the anterior arch forms are straighter.