A prospective evaluation of factors affecting occlusal stability of Class II correction with Twin-block followed by fixed appliances.

INTRODUCTION

Modified Twin-block therapy followed by fixed appliances (TBFA) is a standard treatment modality in Class II malocclusion; however, there is little information regarding the stability of this approach. We aimed to assess the stability of Class II correction with TBFA and to evaluate factors that may affect stability.

METHODS

A prospective evaluation involving convenience sampling of 64 participants treated with TBFA was undertaken over 12 months. Study models and lateral cephalometric radiographs were obtained to record overjet and molar relationship, Peer Assessment Rating score, and skeletal parameters, and a new objective buccal segment interdigitation scoring system was developed. Multivariate logistic regression analysis was used to assess the stability of anteroposterior occlusal correction and the degree of buccal interdigitation, pretreatment skeletal discrepancy, and change in overjet during treatment.

RESULTS

Mean overjet reduction of 6.22 mm arose during treatment, with the canine and molar relationships improving by 3.34 mm and 2.67 mm, respectively. In the 12 months posttreatment, a relapse of 0.67 mm and 0.06 mm in overjet and molar relationship, respectively, was observed, with 25% of subjects having overjet relapse of >1 mm. There is weak evidence that the treatment-induced change in overjet is linked with overjet relapse (P = 0.05; odds ratio, 0.67; 95% confidence interval, 0.44, 1.01). No significant relationship was observed, however, between anteroposterior stability and buccal segment interdigitation (P = 0.99), pretreatment skeletal discrepancy (P = 0.10) or prescribed retention regime (P = 0.63).

CONCLUSIONS

Overall, acceptable levels of stability were observed, although appreciable relapse was noted in 25% of participants. Neither the degree of buccal segment interdigitation nor pretreatment skeletal discrepancy was predictive of anteroposterior occlusal stability.