Influence of first premolars extraction on vertical dimension in Italian patients with a Class I normo-divergent malocclusion. A retrospective study.

The purpose of this study was to examine the changes in vertical dimension occurring in Class I non-growing patients treated with first four premolars extraction and to test the hypothesis that the vertical dimension collapses after four first premolars extractions. Records of 28 patients (9 males and 19 females) treated with extraction of first four premolars were obtained. Pre-treatment and post-treatment lateral cephalograms were digitized, and 6 linear and 5 angular cephalometric measurements were selected to evaluate vertical changes. Statistical analysis of the data revealed no significant differences between pre-treatment and post-treatment group. Comparison of the treatment results of the pre-treatment and post-treatment cases showed that there weren't vertical changes following the extraction of first premolars. The null hypothesis that premolars extraction results in changes of vertical dimension of occlusion was rejected