Purpose: The purpose of this study is to investigate the effect of premolar extractions on Bolton index.
Methods: 213 plaster casts were divided into Bolton big, normal and small groups according to Bolton normal value and one standard deviation. Bolton overall ratios and number of patients in each group were measured and compared between parameters before and after hypothetical premolar extractions.
Results: The Bolton overall ratios in each group were smaller after premolar extractions than those before extractions. Part of patients in the Bolton normal group and big group were changed into Bolton small group and normal group after premolar extractions, respectively.
Conclusion: The Bolton overall ratios decreased after premolar extractions.