UCSF

Abstract: Introduction: Facial convexity related to bimaxillary

protrusion is prevalent in many populations. Underlying skeletal

protrusion combined with increased dentoalveolar protrusion contributes to facial muscle imbalance and lip incompetence which is undesirable for many patients. This study evaluates the relationship between soft and hard tissue changes in an orthodontically treated Asian population. Methods: Twenty-four consecutive non-growing Asian patients (mean age=24), diagnosed with severe bimaxillary dentoalveolar protrusion, were evaluated using pre- and post-treatment cone beam CT (CBCT). Patients were treated with four first premolar extractions followed by anterior retraction using either skeletal or intraoral anchorage. Serial CBCT radiographs were registered on the entire cranial base and fossa. Soft and hard tissue changes were determined through landmark displacement and color mapping. Results: Upper lip retraction was concentrated between the

nasolabial folds and commissures. Lower lip retraction was accompanied by significant redistribution of soft tissue at pogonion. Soft tissue changes correlated well with regional facial muscle activity. Significant retraction (2-4 mm) of soft tissue occurred beyond the mid-sagittal region. Use of skeletal anchorage resulted in 1.5 mm greater lower lip retraction than intraoral anchorage, with greater retraction of the upper and lower incisor root apices. Conclusions: Profound soft tissue changes accompanied retraction of the anterior dentition using both treatment

modalities.