Stability of first and second premolars extraction space closure

Introduction: Premolars are the teeth most often extracted to provide space to correct crowding, excessive dental and/or labial protrusion, and to compensate for the sagittal discrepancy. After treatment, the extraction spaces have to remain closed. Nevertheless, several studies have shown a tendency for some relapse even in patients finished with an adequate occlusion. Thus, the objective of this study was to compare the stability of extraction space closure of the first and second premolars. Methods: Dental casts of 72 patients were digitized using a 3-dimensional scanner (R700; 3Shape, Copenhagen, Denmark) and divided into 2 groups. Group 1 (29 patients; mean age, 13.79 years; 4.57 years after treatment; 116 extraction spaces) was treated with first premolar extractions, and group 2 (43 patients; mean age, 15.20 years; 3.97 years after treatment; 100 extraction spaces) was treated with second premolar extractions. Chi-square tests were used to compare the numbers of open and closed extraction spaces after treatment and at the long-term posttreatment stage. t Tests were used to compare the number of spaces posttreatment and at the long-term posttreatment stages. These tests were also performed in subgroups with completely closed extraction sites posttreatment. Results: The groups showed similar numbers of extraction sites reopening. The first and second premolar extraction space closure presents a similar tendency for reopening. Considering only the patients that showed completely closed extraction spaces in the final dental models, maxillary extraction space reopening was larger in the first premolar extraction group. Conclusions: First and second premolar extraction space closure present similar stability.