Heat Generation in Bone from Preparation of One-Piece Implants

Objectives: The purpose of this study was to test whether the heat generated while reducing the abutment of a NobelDirect one-piece-implant (OPI) reaches a level to cause impaired bone vitality. Methods: Two size implants were used with diameters of 3.0mm and 5.0mm. These were placed into blocks of bovine femur with two osteotomies 0.5mm adjacent to the OPI and parallel with the long axis of the implant at depths of 3mm and 6mm for measuring temperature change while preparing the abutment. Temperature changes were measured from a baseline temperature of 37°C. Recordings were made during 15 second cutting times (n=10) at each depth for the two implant sizes. Abutments were prepared with a medium grit diamond instrument using a high-speed handpiece and irrigation. Results: The following mean temperature increases were recorded: 1) 1.88°C (SD of 0.256°C) at 3mm depth adjacent to the 3.0mm diameter implant; 2) 1.21°C (SD of 0.272°C) at 6mm depth adjacent to the 3.0mm diameter implant; 3) 0.74°C (SD of 0.253°C) at 3mm depth adjacent to the 5.0mm diameter implant; and 4) 0.59°C (SD of 0.276°C) at 6mm depth next to 5.0mm diameter implant. Conclusions: For the two depths measured with the two implant sizes, temperature increases did not approach levels that would cause loss of bone vitality within the 15 second trial time. The mean temperature increase correlates with the size of implant, with greater temperature change in the smaller implant. Also a correlation with greater temperature increase in the shallower depth measurement (3mm) compared to the more apical temperature reading (6mm). The steady increase in heat generation due to implant preparation underscores the need for further research and protocol development to identify the constant contact time between a rotary instrument and OPIs that could produce detrimental temperature increases.