Effect of the second premolar extraction on third molar eruption

Objective To investigate the effects of orthodontic treatment for 4 second premolars extractions on the angulations and eruption spaces of third molars. Methods Totally 41 adolescents were chosen and divided into second premolar extraction and nonextraction groups,with 21 and 20 patients respectively. The angulational changes and eruption spaces of third molars were evaluated on the panoramic radiographs taken before and after orthodontic treatment. Results Compared to nonextraction group,second premolar extraction group demonstrated statistically significant differences for all third molar eruption spaces(P 0.001)and the upper third molar eruption angulation(P 0.05),but no statistically significant difference for lower third molar eruption angulation(P 0.05). Conclusion Second premolar extraction could increase the eruption spaces of third molars,and make the upper third molar eruption angulation more upright.