Removal torque study of two different implant surfaces: an experimental study in the rabbit tibia

Several strategies have been employed to modify the surface texture, and thus increase the surface area of implants, with the aim of enhancing the reaction of bone to the implant. Increased surface roughness may increase installation torque and thus appear to increase the initial stability of an implant. Objectives: This study was undertaken to compare removal torque of two different implant surfaces. Methods: Eight machined and 8 sandblasted and acid-etched T.B.R implants (Benax, Ancona, Italy) were used in this study. Four New Zealand white rabbits, weighing 2.5 to 3.5 kilograms, were used in this study. The implants were inserted into the tibia; each rabbit received 4 implants, two test (sandblasted and acid-etched) and two control (machined). No rabbits died in the study. All animals were killed after two months. Each implant was surgically exposed via sharp dissection to bone and clinically examined. The coverscrew was removed and an implant removal mount was securely fastened engaging the external hex. The leg was stabilized and the implant was removed under reverse torque rotation with a manual torque meter (Somfy Tec, Milano, Italy). Results: Mean torque values for machined and sandblasted acid-etched titanium implants at two months were 16.07±0.67 N-cm; 30.63±3.41 N-cm, respectively. Analysis of torque removal measurements revealed a statistically significant difference (P<0.001) between machined and sandblasted acid-etched titanium. Conclusion: In conclusion the present study demonstrated that a relation exists between surface roughness and removal torque values and is probable to influence the anchorage of implants by altering the surface structure morphology.