Effect of orthodontic removal of mandibular first molar on the position change of third molar

To investigate the effects of the first molar on the eruption of the third molar by comparing the changes of the third molar position after orthodontic treatment in different tooth extraction modes.

39 cases of adolescent patients were selected and divided into three groups: the first molar extraction, first premolar extraction and non-extraction. The pretreatment, posttreatment panoramic radiographs were measured to analyze the change of the third molar position among these groups.

There were significant differences (P ＜ 0.05) in the average annual variation of the third molar eruption space and angle. The changes in first molar extraction group were larger than that in premolar extraction group and non-extraction group. The average annual variation of the third molar eruption space, three groups were (2.38 ± 1.62) mm, (1.61 ± 0.90) mm and (1.08 ± 1.49) mm; the average annual variation of eruption angle, the three were 1.89° ± 1.93°, 1.37° ± 1.16° and 0.83° ± 1.74°.

Compared with conventional treatment, mandibular first molar extraction can significantly increase the third molar eruption space and improve its eruption angle, which is beneficial to the eruption of the third molar.