A Cephalometric Evaluation of Vertical Changes Following First Premolar Extraction

Objectives: There is disagreement concerning the effect of therapeutic premolar extractions on the vertical dimension (VD). It has been suggested that orthodontic forward movement of the posterior teeth after first premolar extraction leads to reduction in VD. The purpose of this study was to examine cephalometrically the dentofacial vertical changes in Class I Indian subjects treated with and without extractions.

Methods: The sample consisted of 120 lateral cephalograms obtained from 60 Class I normodivergent malocclusion patients (SN-GoGn,32°±1°). They did not have severe anteroposterior (0° < ANB < 5°) and vertical discrepancies (0mm < overbite < 6mm). The extraction group included 31 patients (26 female, 5 male; pretreatment age, 17.19±3.89 years) with maxillary and mandibular first premolar extractions. The nonextraction group included 29 patients (18 female, 11male; pretreatment age, 18.48±3.61 years). All subjects were treated by using standard edgewise appliances and frictionless mechanics. A coordinate system with the Frankfort horizontal plane and a mandibular fiduciary line was used for the cephalometric calibration. To determine VD changes due to treatment and to compare differences between the 2 groups, paired and unpaired t tests were performed, respectively. When non-normality was observed, the results were ascertained by nonparametric tests such as the Mann-Whitney test (for unpaired) and the Wilcoxon test (paired).

Results: Both groups had increases in linear VD (P<.05), but the change was comparatively greater in extraction group (P<.05). Mesial movement of the maxillary and mandibular posterior teeth was coincidental with the extrusion to such an extent that it increased the VD, although the FMA remained unchanged during treatment.

Conclusion: Extraction of teeth only to increase the overbite or decrease the mandibular plane angle might not be justified.