Abstract: Objective: To investigate the effects of different treatments for full bony impacted wisdom teeth on the prognosis of adjacent second molar with external root resorption. Methods: 52 asymptomatic second molars were included with external root resorption caused by full bony impacted teeth, and then divided into two groups--test group (extraction of the impacted wisdom teeth) and control group (reservation of the impacted wisdom teeth)-according to the willing of fully informed patients. As long-term follow-up was taken, symptoms and signs were recorded and comparatively analyzed, including the progress of external root resorption, pulp vitality, distal probing depth (PD) of the second molar. Results: No continuous progress of external root resorption was observed in both the test group and the control group. Pulp symptoms were observed in 5 teeth in test group in which 2 teeth were proved transient sensitivity, 2 teeth with pulp necrosis were applied root canal therapy and 1 teeth were extracted finally. Pulp symptoms were not observed in other 27second molars. The postoperative distal PD of the second molars in the test group became deeper with significant difference; while in the control group, there was no significant difference in the distal PD before and after the follow-up. The difference of the changes of the distal PD between the two groups was statistically significant. Conclusion: Removal of the full bony impacted teeth might not be the only option for the compromised adjacent teeth with external root resorption. To the cases that the impacted wisdom must be extracted, the pulp of adjacent second molars should also be protected during operation.

Key words: external root resorption, impacted tooth, pulp vitality