Comparison of 3D facial soft tissue changes following Twin-block and Button & Bead appliances: a single centre randomised clinical trial.

Objectives To determine if the horizontal advancement of soft tissue pogonion was statistically significantly different following treatment with a Twinblock appliance and Button & Bead appliance. Method: Sixty-four children aged 10-14 years were recruited from the Birmingham Dental Hospital. Following randomization thirty-two patients were allocated to either the Twinblock or the Button & Bead appliance group. Records, including threedimensional facial soft tissue images (3dMD), were taken at the start (T0) and and at the end of functional appliance therapy (T1). Results: The overlying soft tissue changes followed the underlying skeletal and dental changes produced by the appliances. There were no statistically significant differences in upper lip movement between the two appliances. There was statistically significantly more anterior horizontal movement at pogonion (p=0.001) and B-point (p=0.012) in the Twinblock group compared to the Button & Bead group. Conclusion: As a result of Twinblock treatment there were minimal changes in upper lip position. In the Button & Bead group there was some retraction and lengthening of the upper lip, this could be clinically significant (>2mm) and mainly in the philtrum region. The horizontal anterior movement of the soft tissue chin region was statistically and clinically significantly greater in the Twinblock group compared to the Button & Bead group. The Button & Bead appliance produced a clinically significant vertical increase in chin and lower lip compared to the Twinblock