Influence of premolar extractions on tooth size discrepancy. part one: analysis of Bolton index.

The purpose of this study is to determine the influence on four premolar extractions for upper and lower anterior tooth size discrepancy (for total Bolton index (TBI=Overall ratio) and for Bolton value (BV)) and to find out the differences of four first and second premolar extractions tooth size discrepancies (TSD). 148 pretreatment dental casts have been examined. It has been determined that upper teeth of 93 patients suited lower teeth sizes (normal TBI - 91.3%+/-1.91), 27 patients had upper teeth wider than lower ones (low TBI<89.39%) and 28 patients had wider teeth in lower jaw (high TBI>93.21%). In this study the influence of four hypothetical first and second premolar extractions (1. all first premolars, 2. all second premolars, 3. upper first and lower second premolars, 4. upper second and lower first premolars) on TSD frequency appearance and size has been estimated. After performing the analysis it was estimated that in normal Bolton index group TSD is more frequent, when four first premolars are extracted (p<0.05 after comparing with extraction of four second premolars). When TBI is high, in all four hypothetical teeth extraction variations TBI remain increased, which determine 100% TSD. In low TBI group TSD is more usual when four-second premolars are extracted (p<0.01, after comparing with teeth extractions using 1-st or 3-rd method).