COMPARISON OF OVERALL AND POSTERIOR BOLTON RATIOS OF SKELETAL CLASS II MALOCCLUSION BEFORE AND AFTER DIFFERENT COMBINATIONS OF FOUR PREMOLAR EXTRACTIONS IN A PAKISTANI POPULATION

Abstract

Objectives: To fi nd whether diff erent premolar extraction patterns change the overall Bolton ratio from 91.30%, and the posterior Bolton ratio from 105.27% among the Pakistani population in a skeletal class II malocclusion.
Materials and Methods: This Quasi Experimental study was conducted at at the Orthodontics Department of Khyber College of Dentistry, Peshawar on 30 dental models of skeletal class II patients. A Digital Vernier Caliper was used to measure the mesiodistal widths of the teeth me-sial to the second molar. Overall and posterior Bolton ratios were calculated before and after hypothetical extractions of the premolars. One-sample-t test was used to see if there was any significant diff erence between the overall and posterior Bolton ratios of the Bolton study and our study. Paired-samples-t test was used to fi nd the change in Bolton ratios before and after extractions. P value of ≤0.05 was considered signifi cant.
Results: The mean overall and posterior Bolton ratios were 91.57±1.21% and 103.36±2.82%, respectively. Following premolars’ extractions in the pattern: all fi rst premolars, upper first with lower second premolars, upper second with lower fi rst premolars and all second premoalrs, the overall ratio decreased signifi cantly (p <0.05) to 90.29±1.54%, 90.55±1.61%, 89.47±1.62% and 89.72±1.59%, respectively, whereas the posterior ratio for all fi rst premolars and upper fi rst with lower second premolar extractions increased signifi cantly to 105.27±3.18% and 105.88±3.71% (p <0.05).
Conclusion: Premolar extractions in skeletal class II malocclusion cause a signifi cant decrease in the overall Bolton ratio. The all fi rst premolars and upper fi rst with lower second premolar extractions pattern cause a signifi cant increase in the posterior Bolton ratio.