Effect of orthodontic treatment with 4 premolar extractions compared with nonextraction treatment on the vertical dimension of the face: A systematic review.

INTRODUCTION: Our aim was to assess the available evidence for the effects of orthodontic treatment with 4 premolar extractions on the skeletal vertical dimension of the face compared with nonextraction treatment. METHODS: Electronic database searches (MEDLINE, EMBASE, Cochrane Oral Health Group's Trials Register, and CENTRAL) of published and unpublished literature and hand searches of eligible studies were performed, with no language or publication date restrictions. Two authors performed data extraction independently and in duplicate. Risk of bias was assessed. RESULTS: After application of the eligibility criteria, 14 studies were included in this systematic review. All were retrospective. Risk of bias ranged from moderate to critical. Ten studies investigated patients with various skeletal vertical patterns and classes of malocclusion and found no difference between extraction (Ex) and nonextraction (Nonex) treatment in regard to the vertical dimension. Only 2 studies found statistically significant increases in the nonextraction groups, one in N-Me (Ex: +1.5 mm; Nonex: +5.5 mm; P <0.05) and one in SN-GoGn (Ex: -0.9 degrees ; Nonex: +0.8 degrees ; P <0.05), but without a concurrent significant change in other vertical measurements such as FMA. Two other studies showed opposite findings regarding N-Me (Ex: +2.3 mm; Nonex: +0.9 mm; P <0.05) and FMA (Ex: +0.3 degrees ; Nonex: -2.0 degrees ; P <0.05). CONCLUSIONS: Although the quality of evidence ranged from moderate to low, there was considerable agreement among these studies, suggesting that orthodontic treatment with 4 premolar extractions has no specific effect on the skeletal vertical dimension. Thus, an extraction treatment protocol aiming to reduce or control the vertical dimension does not seem to be an evidence-based clinical approach.