Cephalometric evaluation of the Twin-block appliance in the treatment of Class II Division 1 malocclusion with matched normative growth data.

Cephalometric radiographs were taken before and after treatment with the Twin-block appliance on 30 consecutive patients with Class II Division 1 malocclusions. A control group was generated from published normative data such that each treated case was matched individually for age, sex, and treatment time. The cephalometric change during treatment was compared to the natural growth change in the matched control group using a Mann-Whitney U-test for statistical significance. The treatment effect was also calculated by subtracting the natural growth change from the treatment change. This was then compared to twice the method error to see if the treatment change was clinically significant. There was both a statistically and clinically significant reduction in overjet, angle ANB, increase in angle SNB, and mandibular length together with a reduction in upper incisor angle. None of the other cephalometric parameters measured showed a significant change.