Analysis of facial proportions in skeletal Class II subjects treated with Clark's twin block appliance, followed by nonextraction fixed mechanotherapy: A retrospective longitudinal study.

INTRODUCTION: This study aimed to determine the influence of Clark's twin block (CTB) appliance therapy on achieving golden proportion in post-treatment facial profiles in skeletal Class II patients.

METHODS: A retrospective longitudinal study was conducted on a sample of 44 skeletal Class II subjects treated with CTB, followed by nonextraction mechanotherapy. Ricketts' 13 dentoskeletal ratios were measured on pre- and post-treatment lateral cephalograms. Paired Student's t test was used to analyze the existence of golden proportion in the values of the pre- and post-treatment ratios. The influence of pretreatment variables was tested on post-treatment ratio 4 using simple and multiple linear regression analyses.

RESULTS: A statistically significant difference in pre- and post-treatment values was found for ratios 4 (P = 0.02), 9 (P = 0.04), 10 (P < 0.001), and 13 (P = 0.01). Ratios 4, 9, and 13 moved closer to the golden proportion, whereas ratio 10 moved away from the golden proportion after CTB therapy. Simple linear regression analysis showed a statistically significant association of post-treatment ratio 4 with pretreatment ratios 1, 4, 8, 9, and 12. Multiple linear regression analysis showed a statistically significant association of post-treatment ratio 4 with pretreatment ratios 4 and 12.

CONCLUSIONS: Treatment with CTB appliance may well move various facial ratios in individual patients toward the published Ricketts ideals. Ricketts' published golden proportion may be used as one guide when planning for attempted dentofacial change in individual patients.