Résumé
Background: Extraction of all 1st premolars in the orthodontic treatment of Class II div 1 malocclusion has been associated with a decrease in vertical dimension of occlusion thus predisposing the patient to TMJ disorders. Objectives: To evaluate the vertical changes occurring in patients having class II div 1 malocclusion, treated orthodontically with 1st premolar extractions & compare these changes with those occurring in patients treated orthodontically without extractions. Method: Pre-treatment & Post-treatment Lateral Cephalogram radiograph of 11 patients having CL-II div1 malocclusion treated without extraction and 16 patients treated with the extraction of all 1st premolars were analyzed and compared to observe the changes in the anterior facial height. Result: the orthodontic treatment of Cl-II div 1 malocclusion cases treated with a non-extraction approach leads to a statistically significant increase in the anterior facial height due to the downward & backward rotation of the mandible. The cases treated with the extraction of all 1st premolars also show the statically significant increase in the anterior facial height but this increase was less than that observed for the non-extraction group. Conclusion: this study does not support the theory that the first premolar extractions reduce the vertical dimension of occlusion and predispose the extraction patients to TMJ disorders.