Effect of Bi-jaw Premolar Extractions on Tooth Size Discrepancy in an Indian Population having Class I Malocclusion: An in vitro Study

Aim: To evaluate the effect of bi-jaw premolar extractions on Bolton tooth size discrepancy in patients of Indian origin, all of which exhibited a bilateral Angle’s class I molar relationship. Materials and methods: Ninety sets of pretreatment study casts, which constituted the sample for the study, were divided into three groups, namely, Bolton small (BS), Bolton normal (BN), and Bolton big (BB). Simulated bi-jaw extraction of premolars was carried out in four different combinations for each set of study cast. The four values of Bolton’s overall ratio (BOR) thus obtained were compared with the original BOR value. Results: The BOR value reduced when subjected to any of the four combinations of bi-jaw premolar extractions. Conclusion: Premolar extraction in any combination inevitably changes the BOR value, which potentially affects the settling of occlusion toward the finishing stages of orthodontic treatment. Clinical significance: The present study provides an insight into the choice of bi-jaw premolar extraction combination for each of the three groups in patients exhibiting class I malocclusion in the Indian population.