Clinical effectiveness of the Twin block appliance in the treatment of Class II Division 1 malocclusion

Abstract

The aim of the present study was to assess clinical effectiveness of Class II Division 1 malocclusion treatment with Twin block appliance.

Material and methods: Analysis of cephalometric radiographs of 34 Class II Division 1 patients treated with Twin block appliance was performed before and after treatment. A control group was generated from the normative growth data published by Bhatia and Leighton. The treatment effect was 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.

Results: Mean mandibular length as measured from point Art to point Pog increased by 6.4 mm in the Twin-block group compare with 4.1 mm in the control group. The overjet during treatment was reduced by 4.9 mm. Relative to the maxilla upper incisor tipped backward by 6.7 degrees and in the control group natural growth proclined them by 2.4 degrees. Lower incisor after the treatment tipped forward and the angle between long axis of lower incisor and mandibular plane increased by 3.3 degrees, whereas in the control group they stay almost in the same position, proclination only 0.7 degrees.

Conclusions: Twin block appliance clinically significantly increases mandibular length (net effect 2.3 mm) and reduce overjet (net effect 4.9 mm). Modification of the Twin block appliance by acrylic extension to cover the edges of lower incisors reduce dentoalveolar tipping and maximize skeletal changes.