Effects of Lower First Molar Extractions on Third Molar Position in Adolescent Followed by Orthodontic Treatment

Objective: To study the effects of lower first molar extraction on the third molar position in adolescent.Methods: 55 adolescent cases were selected and divided into lower first molar extraction(15 cases),first premolar extraction(20 cases) and non-extraction(20 cases) groups respectively.The pretreatment,posttreatment and after 2 years retaining panoramic radiographs were measured to analyses the change of the third molar position among these groups.Results: There were significant differences in the changes of the third molar eruption space among three groups(P0.05).Space changes in first molar extraction group were larger than that in premolar extraction group and non-extraction group.The changes of lower third molar in first molar extraction group were increased more than that in other groups.After 2 years retaining the changes in eruption space and the angle of first molar extraction group were even larger than other 2 groups.Conclusion: Lower first molar extraction could enlarge the eruption space of third molar and upright the third molar.It was beneficial to third molar eruption.