In a recent article in the JADA ( Journal of the American Dental Assoc.) the topic of Coronectomy was discussed. Click on the following link:
This was their conclusion based on the systemic review of five databases for the period from 1990 through 2011 : That coronectomy of an impacted mandibular third molar with a high risk of nerve injury is less likely to cause damage to the inferior alveolar nerve when compared with the traditional and complete extraction of the third molar.
However, evidence suggests that even though coronectomy is a good option for high-risk patients, it is technique sensitive and not without complications either.