Effect of orthodontic extraction of mandibular premolars on third molar angulation after treatment with fixed appliances

<jats:title>Abstract</jats:title><jats:sec> <jats:title>Purpose</jats:title> <jats:p>Orthodontic treatment involving premolar extractions might improve the angulation of lower third molars, which are the teeth most often impacted. This study analyzes the impact of first/second lower premolar extraction during orthodontic therapy on the angulation of mandibular third molars.</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>A total of 120 patients treated non-extraction (<jats:italic>n</jats:italic> = 40), with extraction of first (<jats:italic>n</jats:italic> = 40), or second lower premolars (<jats:italic>n</jats:italic> = 40) were included. The mesiodistal angulation of lower third molars relative to the adjacent tooth and their developmental stage were evaluated from posttreatment orthopantomograms. Between-group differences were statistically evaluated at a significance level of 0.05.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>The orthopantomograms of 120 patients (51% female) with a median age of 15.2 years at the time of debonding were evaluated after a mean treatment duration time of 2.9 years. No difference (<jats:italic>P</jats:italic> > 0.05) was seen between the average angulation of the lower third molars of the right (mean = 24.4°, standard deviation [SD] 13.6°) and the left side (mean = 23.6°, SD 14.1°). No differences in the angulation of the lower third molar were found between the non-extraction and extraction groups for the right (<jats:italic>P</jats:italic> = 0.44) or the left side (<jats:italic>P</jats:italic> = 0.22). Likewise, no differences were found when comparing the first and second premolars for the right (<jats:italic>P</jats:italic> = 0.26) or the left side (<jats:italic>P</jats:italic> = 0.10). Premolar extraction was associated with an advanced root development stage of the right third molar (odds ratio 7.1; 95% confidence interval 1.1–48.1; <jats:italic>P</jats:italic> = 0.04), with no differences between extraction of the first or second premolar (<jats:italic>P</jats:italic> = 0.10).</jats:p> </jats:sec><jats:sec> <jats:title>Conclusion</jats:title> <jats:p>Orthodontic treatment involving premolars extractions might be associated with a small acceleration in root development, but not with the angulation, of lower third molars.</jats:p> </jats:sec>