Lip morphology changes after first premolar extractions in patients with bimaxillary protrusion in North Indian population – A pilot study

Introduction: As we witness the soft-tissue paradigm, treating the face becomes more important than just treating the hard tissue variables. Therefore, it becomes crucial to quantify the soft-tissue response to changes in the hard tissue following orthodontic treatment. Purpose of the Study: To determine lip morphology changes after first premolar extractions in patients with bimaxillary protrusion as ratios of hard and soft-tissue changes. Materials and Methods: The sample consisted of pretreatment and posttreatment lateral cephalograms of 15 subjects with Class I bimaxillary protrusion who had undergone orthodontic treatment with four first premolars extraction and retraction of upper and lower incisors. Pre- and post-treatment lateral cephalograms were traced and superimposed by using SN-7˚ plane. Sixteen linear measurements were made. Statistical analysis was performed to analyze the co-relation between the hard and soft tissue change by Pearson's correlation. Stepwise multiple regression were made to determine factors that related with lip changes. Results: Significant changes after treatment were found both in dental and lip analysis. The equations of upper and lower lip changes in sagittal and vertical dimensions were derived. Conclusion: Stepwise multiple regression analysis revealed that a 1 mm retraction of the maxillary incisor cervical point would produce a 0.59 mm retraction of upper lip and 1 mm retraction of the mandibular incisor cervical point would produce 0.89 mm retraction of the lower lip. The predictability of this study may be helpful for the clinician in predicting the amount of change in profile of the patient post treatment, thus aiding in planning the treatment.