A cephalometric study on effectiveness of orthodontic treatment of bimaxillary protrusion with premolar extraction - a retrospective study

Objectives: This study was designed to evaluate for an appropriate treatment plan (extraction or non-extraction) for reducing the dental and soft tissue procumbency of bimaxillary protrusion individuals and also to compare the pre and post-treatment values of the two groups to provide an evidence based approach of premolar extraction in treating bimaxillary protrusion individuals. Method: The sample consisted of 30 bimaxillary protrusion patients treated with four premolar extraction and 30 treated with non-extraction line of treatment between the ages of 15-30 years taken from the archives of Department of Orthodontics and Dentofacial Orthopaedics, M.S.Ramaiah Dental College & Hospital, Bangalore. Pre and post-treatment lateral cephalograms were evaluated using a series of 27 linear and angular measurements, and the effect of orthodontic correction was determined using different statistical tests. Results: Pre-treatment (T1) characteristics of bimaxillary protrusion individuals demonstrated increased procumbency due to decreased interincisal angle, increased (upper incisor to SN angle, lower incisor to mandibular plane, upper incisor to NA linear and angle, lower incisor to NB linear and angle, upper incisor to APog and lower incisor to APog) in extraction as well as non-extraction groups but the variation was more in extraction group than non-extraction group. Soft tissue parameters like upper lip to E-line, lower lip to E-line and nasolabial angle showed significant statistics post-treatment with extraction and insignificant statistics with non-extraction. Pretreatment mean values of all four measurements of alveolar width were less in bimaxillary protrusive sample while upper and lower alveolar heights were found to be greater in both groups. Conclusion: The comparison of skeletal, dental and soft tissue post-treatment (T2) values between extraction and non- extraction group demonstrated that premolar extraction is more effective in reducing the dental and soft tissue procumbency in bimaxillary protrusion patients as compared to non-extraction mode of treatment. Hence it was concluded that only borderline bimaxillary protrusion cases can be treated with non-extraction line of treatment.