Abstract:

Objective To study the characteristics of the arch form of skeletal Class Ⅲ malocclusion and provide references for diagnosis and treatment plan. Methods 7 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. Results Compared 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）. Conclusion Arch 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.

Key words: arch form, skeletal malocclusion, arch width, arch length