THE EFFECTS OF ORTHODONTIC TREATMENT ON THE ORAL COMMISSURES IN GROWING PATIENTS

Abstract

Objective: The aim of this study was to investigate the effect of extraction and non-extraction orthodontic treatments on oral commissures.Materials & Methods: Pre- and post-treatment 3dMD images of 47 patients aged 10-19 were studied for changes in inner and outer commissure width, philtrum height and buccal corridor width. The subjects either had extractions of all four first premolars, upper first premolars only, or were treated non-extraction. The superimposed 3dMD images were collected and qualitative and quantitative analyses were completed using 3dMD Vultus software. Interincisal angle and upper incisor to NA changes were also calculated using pre- and post-treatment lateral cephalograms. Regression analyses were applied controlling for age, gender, ethnicity, angle classification, and treatment time. Results: While all groups showed a nominal increase in the inner and outer commissure widths from T0 to T1, only the non-extraction group revealed a statistically significant change (p < .05). Buccal corridor width increased in all three groups but was only statistically significant in the extraction of four first premolar extraction group (p < .02). Treatment type had no statistically significant influence on philtrum height and interincisal angle among the three groups. Qualitatively, the commissures exhibited variable changes regardless of treatment type but trended to exhibit more of a positive change for the extraction of upper/lower first premolar group. Conclusion: Extraction of either all four premolars or upper premolars only does not appear to be associated with a measurable change in the commissure width. An increase in buccal corridor width was highly associated with four first premolar extractions and increased with age. Incisor inclination was strongly correlated with four first premolar extractions and resulted in a greater change in outer commissure width. Philtrum height remained relatively unchanged in all three groups accounting for age, treatment time, and gender indicating that this is a relatively stable structure during growth and shows minimal change with orthodontic treatment.