Dentoalveolar surgery
Coronectomy of the Lower Third Molar Is Safe Within the First 3 Years

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Purpose

There is no long-term evaluation on the safety of coronectomy of the lower third molar. The aim of this study was to investigate the 3-year morbidity of coronectomy of the lower third molars and to monitor the behavior and migration pattern of the retained roots after coronectomy.

Materials and Methods

This was a prospective cohort study. Patients with lower third molars with specific radiographic sign(s) showing proximity of the roots to the inferior alveolar nerve who underwent coronectomy in a previous randomized clinical trial were reviewed postoperatively in the first week and the third, sixth, 12th, 24th, and 36th months. The morbidities of infection, pain, root eruption, reoperation to remove the root, and the development of any pathology were recorded. The pattern of any root migration was analyzed.

Results

Ninety-eight patients (35 men and 63 women; mean age, 25.7 yrs; standard deviation, 7.9 yrs) with 135 coronectomies completed the 36-month review. None presented with infection or pain from the postoperative third month onward. Root eruption causing sensitivity occurred in 3% (4/135) of the sample and the erupted roots were removed. None of the reoperated cases presented with a postoperative inferior alveolar nerve deficit. No pathology developed in any of the retained roots after coronectomy. Root migration was noted in most cases in the first 12 months, and all roots stopped migrating from the 24th month onward. The mean root migration at 36 months was 2.8 mm (standard deviation, 1.4 mm).

Conclusions

This study confirms that retained roots after coronectomy in the lower third molars produce no complications in terms of infection, pain, or the development of pathologies within the first 3 years. Root eruption can occur in a very small percentage of patients and may require reoperation to remove the root.

Section snippets

Materials and Methods

The preoperative and postoperative assessments and the surgical technique of coronectomy were adopted from the study protocol of a randomized controlled clinical trial comparing coronectomy with the conventional total removal of the lower third molars published by the authors' center in 2009.7 Ethical approval was granted by the local institutional review board (HKU/HA HKW IRB UW 10-001).

Results

Coronectomies were successfully performed in 155 lower third molars in 108 patients. Among these, 98 patients (35 men, 63 women) with 135 coronectomies completed the 36-month follow-up. Fifteen patients with 20 coronectomies refused follow-up during this period owing to work commitments or personal reasons and were excluded from the study. The dropout rate was 12.9% (20/155). The mean age of the patients was 27.6 years (standard deviation [SD], 7.9 yrs). The teeth characteristics and the

Discussion

The randomized clinical trial conducted by the authors' center and several other studies comparing coronectomy with the total removal of the lower third molars have shown, with a sufficient sample size, that an IAN deficit after coronectomy can be significantly decreased in high-risk cases.6, 7, 9, 10 The present study supports that this technique is safe in the long-term up to at least 3 years.

Many clinicians worry about infection of the retained roots after coronectomy in the long-term. Some

Acknowledgments

The authors thank Mr Andy Hon Kwan Chan and Miss Karen Kar Yan Lai for their contributions in data collection and root migration measurement. They also express their gratitude to the postgraduates of the discipline who performed the surgical procedures.

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