Inferior alveolar nerve injury resulting from different implant rotary instruments: An ex vivo comparative study in human cadaveric mandibles.

The present study aimed to evaluate the degree of nerve injury on inferior alveolar nerve (IAN) by different implant drills resulting from direct canal intrusion into inferior alveolar canal (IAC). A cadaveric study involving 7 human mandibles was performed to evaluate mechanical injury of canal enclosed IAN resulting from different drills. In group 1, osteotomies were created using different drills with 1 mm of intracanal intrusion, simulating accidental drill intrusion into canal. In group 2, drilling was stopped when the tip has breached into IAC, limited by tactile feedback of operator. The depth and width of nerve defects were assessed using optical coherence tomography. A significant difference in defect depth was found (p < 0.001) in group 1. A sinus lift reamer inflicted the least damage (0.068 ± 0.022 mm). It was also found that the mean defect depth was significantly different when a twist drill was used (p = 0.016). Sinus lift reamer can be used safely for osteotomy preparation in mandible when bone height is limited or when radiographic visualization of canal is poor. Bone corticalization around IAC does not provide adequate protection for IAN in the event of accidental intracanal intrusion.