THE EFFECT OF PREMOLAR EXTRACTIONS ON TOOTH-SIZE DISCREPANCY

The purpose of this study is to investigate whether the extraction of four premolars as a requirement of orthodontic therapy is a factor in the creation of tooth size discrepancies, and to determine whether any tooth extraction combinations create more severe discrepancies. The s tudy is carried out on the pretreatment dental casts of 50 patients wi th malocclusions. The dental casts were selected according to the main criteria. No tooth-size discrepancy between the mandibular and maxill ary dental arches should exist before treatment. Pretreatment mesiodis tal dimensions of mandibular and maxillary teeth were measured, record ed on a computer program, and subjected to Bolton's analysis. Hypothet ical tooth extractions were performed on each patient by the following combinations: all first premolars, all second premolars, upper first and lower second premolars, and upper second and lower first premolars . The resultant measurements were again subjected to Bolton's analysis to see whether a tooth-size discrepancy had been created. The results were evaluated statistically by the use of paired samples t test. The difference between the pretreatment and postextraction Bolton values was found statistically significant for the first premolar extraction and insignificant for the others. The removal of the four first premol ars created the most severe tooth-size discrepancy, whereas the extrac tion of all four second premolars created fewer discrepancies and the smallest range in the size of discrepancies. The results of this study indicate a new point of view to the question of which teeth to extrac t when evaluated for tooth size aspect only.