A comparative study of dental arch widths: extraction and non-extraction treatment

The aim of this study was to determine the pre- and post-treatment width changes in the canine, premolar and molar regions in subjects treated with extraction of four first premolars, non-extraction, and non-extraction with rapid maxillary expansion (RME). Pre- and post-treatment orthodontic study models of 60 females (13.83 +/- 2.77 years) and 24 males (14.33 +/- 2.67 years) who underwent comprehensive orthodontic therapy were evaluated. Forty-two were treated non-extraction with fixed appliance therapy, 15 non-extraction with RME, and 27 with extraction of the first premolars. In addition to standard descriptive statistical calculations, one way ANOVA was used for comparison of the groups, and the post hoc Tukey multiple comparison test for comparison of the subgroups. The results revealed that the distance between the upper canines was not affected by the treatment modality. Upper premolar and molar arch widths increased more in the non-extraction subjects when compared with those with extractions, with the greatest increase in patients with RME. In the lower canine area the extraction group showed the widest arch width at the end of treatment. There was also a 0.60 mm decrease in the lower canine width in the non-extraction group. A decrease was found in lower inter-premolar and molar distances due to consolidation of the extraction spaces. When making a decision between non-extraction with maxillary expansion and extraction treatment modalities in borderline cases where there is constriction in the upper inter-premolar distance, apart from taking profile values into consideration, it should be borne in mind that expansion treatment can be helpful in achieving a wider arch form.