Orthodontic Extractions: Differential Treatment with First and Second Premolar Extractions

The majority of American youths have malocclusions that would benefit appreciably from orthodontic treatment, and the arch-size to tooth-size discrepancy often is so great that at least 1/3 of orthodontic patients are treated with premolar extractions. Objective: We tested whether (as claimed) the location of the major occlusal problem (ie, anterior crowding versus sagittal buccal problems) influenced the extraction of maxillary P1 versus P2 teeth. Methods: The maxillary dental casts of 122 orthodontic cases with premolar extractions were studied. Homologous dental and distal-medial palatal rugae landmarks were located on the pre- and posttreatment casts, then occlusal photographs were made at 2X and the landmarks were digitized as Cartesian coordinates, with computer-generated distances. Dental changes were measured as mesiodistal distances parallel with the midpalatal raphe. Results: There was no premolar crown size difference between groups, though P1 was larger than P2 in both groups. Cases treated with P1 extractions exhibited (1) more anterior crowding, greater overjet, but less sagittal disharmony at pretreatment and (2) greater retraction of the anterior segment and canine movement during treatment. Intercanine width was expanded significantly in both groups, though the mean change of 0.7 mm is inconsequential clinically. Overjet and BSR were indistinguishable between groups at posttreatment. Facial harmony was better in the P2 extraction cases at pretreatment, and more of the extraction space was used to resolve sagittal buccal problems in the present sample. In both samples, more of the premolar extraction space was used to retract the anterior teeth than to move the buccal teeth mesially. Conclusion: Our quantitative study confirmed the qualitative claims in the orthodontic literature regarding criteria used to differentially diagnosis and treatment plan patients with malocclusions who require premolar extractions. Supported by NIH DE07258.