Effect of the lower premolar extraction on third molar eruption

Objective: To evaluate the eruption of mandible third molar in orthodontic patients with non-extraction or extraction of the lower premolars.Methods: We selected 3 group of the orthodontic patients.One group consisted of 23 subjects(12 males,11 females,average age 13.5 years) with non-extraction.One group consisted of 23 subjects(12 males,11 females,average age 13 years) with lower first premolar extraction.One group consisted of 21 subjects(11 males,10 females,average age 14.07 years) with lower second premolar extraction.The panoramic radiography was taken.The lower third molar angulation and eruption space were measured before and after the orthodontic treatment.The comparison of treatment changes in 3 groups were performed by means of a paired-sample t test using SPSS 17.0 software package.Results: The RS,LS,Rratio and Lratio increased significantly after treatment in patients with lower first premolar extraction(P0.01).The RM3 and LM3 increased(P0.05) and RS,LS,Rratio and Lratio increased significantly(P0.01) after treatment in patients with lower second premolar extraction(P0.05).Conclusion: The mandibular third molars show improvement in eruption space and inclination in the orthodontic patients with lower premolar extraction.