The effect of orthodontic extraction protocol on vertical skeletal relationships: A retrospective study

Extractions may be helpful in the relief of crowding and in incisal retraction. While extractions may help to control the vertical dimension, their effect is not clear-cut. Four premolar extractions (FPE) may be more potent in reducing the vertical dimension than two upper premolar extractions (UPE), although research to support this contention is lacking.

The aim of this study is to evaluate the effect of orthodontic extraction protocols on vertical skeletal relationships.

A retrospective study involving participants either undergoing UPE or FPE-based treatment and non-extraction-based controls was performed. All cephalometric outcome measures were assessed before (T0) and after (T1) orthodontic treatment. The effect of extraction pattern on vertical skeletal dimension in terms of mandibular planes angle (MMPA) and anterior facial height (AFH) was assessed using a multivariable analysis.

A total of 168 patients (86 males, 82 females) with a mean age of 13.69±5.03years were included. The MMPA reduced marginally in all three groups. Based on multivariable analysis adjusted for age, lower crowding at baseline, sex, and MMPA at baseline, the extraction pattern did not exert a significant effect on post-treatment MMPA (UPE group: coef.=-0.31; 95% CI: -1.06, 0.43, P=0.40; FPE group: coef.=-0.40; 95% CI: -1.75, 0.96; P=0.56) compared to non-extraction protocols. Similarly, the extraction pattern did not have a significant effect on post-treatment AFH (UPE group: coef.=0.50; 95% CI: -0.73, 1.73, P=0.42; FPE group: coef.=1.59; 95% CI: -0.65, 3.83; P=0.16).

Based on the findings of the present retrospective study, neither statistically nor clinically significant differences in the vertical skeletal relationships were introduced across UPE, FPE, and non-extraction groups. Post-treatment MMPA and AFH were significantly associated solely with their pre-treatment values.