Descriptive Study of the Longevity of Dental Implant Drills

Objectives: Atraumatic preparation of the implant osteotomy is critical for osseointegration. Worn dental implant drills have been identified as a potential source of injury to the bone, but manufacturers offer only loose guidelines as to the longevity of their drills. It is left to the clinician to determine the lifespan of the drills, by subjectively evaluating the efficiency of the drill, through a perceived increase in the force required to perform an osteotomy. The aim of this study is to investigate the effects of multiple usages of Straumann, Neoss and Nobel Biocare dental implant drills on bone temperature and to examine the cutting surfaces of these drills under SEM.

Methods: The clinical osteotomy preparation procedure was adapted to the experimental setting to simulate wear on three different manufacturers implant drills, by preparing bovine ribs using a constant drilling force. Thermo-couples were placed in the specimens to record temperature changes. SEM images and elemental spectroscopic analysis of the drills were taken after varying numbers of usages and under varying sterilizing conditions.

Results: Temperatures measured in the bone adjacent to the implant site did not exceed 27.7ºC during the experiment. Spectroscopic elemental analysis indicated that Straumann and Neoss drills were stainless steel and Nobel Biocare drills were tungsten carbide coated stainless steel. The tungsten carbide coated bur had the lowest overall drilling temperatures and showed the least surface corrosion and plastic deformation. SEM analysis showed degradation of the cutting surfaces of the burs although the plastic deformation and surface wear did not appear to affect the cutting temperatures. Surface corrosion was observed on all cutting surfaces.

Conclusions: Drills used for up to 50 osteotomies do not appear to elevate bone temperatures to a harmful level, however drill corrosion from irrigation and sterilization are potentially important in determining the lifespan of implant burs.