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Coronectomy with graft reduces bony socket defects

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Coronectomy with bone graft reduces periodontal pockets on adjacent mandibular second molars – a 5-9 year follow-up of 78 adult patients




To determine whether coronectomy with bone graft (CWG) improves distal periodontal support of adjacent mandibular second molars in adults, and to determine the rate of potential root migration following CWG. 




Removal of impacted mandibular third molars with roots approximating the inferior alveolar nerve poses risks of injury and temporary or permanent sensational deficits. The reported rate of such injuries is significant at between 1 to 5%. Coronectomy addresses this concern by removing only the crown of the impacted tooth, leaving the roots untouched and untreated in the bone.


While symptomatic impacted teeth require surgical attention, studies also indicate that increased age (>25 years old) contributes to inadequate post-operative bone fill in the third molar socket, compromising the periodontal health on the distal of second molars. Furthermore, there are indications that a layer of bone placed above the remnant roots prevents migration and is considered advantageous in preventing subsequent infection.





Clinical and radiographic records of 78 CWG patients with 5 to 9 years of follow-up were evaluated. Data surveyed included pre-operative probing depths on the distal of the second molars, pre-operative CBCT scan, annual post-op probing depths, and a 2-year post-op CBCT scan. Panoramic radiographs were obtained at post-op years 1, 3, 4, 5, and more. 


All coronectomy procedures were conducted via the previously established “second molar mesial papilla-sparing marginal incision with distobuccal release” (MPMI) that was followed by a full thickness mucoperiosteal flap elevation. The resection was conducted at least 5mm inferior to the alveolar bone crest, ensuring that the entirety of the crown has been removed below the cementoenamel junction. Approximately 1.0 to 1.2cc of mineralized allograft of 200um – 1000um particle size was placed over the remaining roots and the bony crypt closed primarily with running, continuous 3-0 chromic gut sutures.




In all patients, the remnant roots remained in their immediate post-surgery position, no post-surgical infections were encountered, and no patients required secondary procedures to remove the retained roots. Patients with 5-9mm pre-op distal second molar probing depths normalized to the 3-4mm range. Overall, CWG predictably reduces periodontal pockets on the distal of adjacent mandibular second molars caused by impacted third molars. Placement of a bone graft in the coronectomy defect also appears to prevent root migration and surgical site infection, which lessens the number of surgical interventions required.



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