While some procedures require clinicians to drill into bone, further damage is always a risk due to mechanics and temperature. Researchers from the University of the Pacific’s Arthur A. Dugoni School of Dentistry and School of Engineering and Computer Science, however, recently examined multiple factors in drilling to determine best practices to ensure safety.
The researchers looked at thrust force, torque, heat accumulation and dissipation, cutting direction, bone density, the thickness of the bone’s outer layer, drill rotation and feed rate, drill bit shape, angles and wear, and drilling techniques. A set of recommendations then emerged from this review.
First, the researchers noted that a point angle of 70 to 90 or 120 to 140 and a clearance angle of 12 to 15 can provide less friction with unworn cutting edges. They also recommend a helix angle of 24 to 36 to reduce the risk of chip clogging, as these chips can significantly increase both friction and temperature if they aren’t evacuated efficiently.
Also, the researchers said that using coolant fluid for external irrigation prevent chip clogging and reduce temperature elevation, further assisting in chip evacuation. Plus, intermittent drilling can improve chip evacuation, particularly from deeper holes. For implantation, predrilling can significantly reduce the maximum forces and temperature. The inner diameter of the insertion screw should be used as the diameter of the pilot hole in predrilling.
While a larger and more comprehensive study would be the next step, the researchers said, they believe dentists can start using these recommendations now. The study, “Parameters affecting mechanical and thermal responses in bone drilling: A review,” was published by the Journal of Biomechanics.