Edition V13N05 | Year 2008 | Editorial Article | Pages 76 to 87
Objective: Evaluate mini-implants of different sizes for the following factors: (a) insertion torque, (b) removal torque, (c) fracture torque, (d) shear tension, (e) normal tension and (f) type of fracture. Method:Twenty self-drilling mini-implants were used, 10 manufactured by SIN and 10 by Neodent, measuring 8 and 7 mm in length, respectively and all with 1.6 mm in diameter. Out of these 10 mini-implants, for each brand, 5 did not have a neck and the other 5 had a 2 mm neck, and were separated into 4 groups: SIN without neck (S), SIN with neck (SN), Neodent without neck (N) and Neodent with neck (NN). All mini-implants were inserted into bone cortex and removed with a low speed handpiece connected to a digital torquimeter. The mini-implants were also submitted to a fracture test. The insertion, removal and fracture torques, as well as the calculated shear and normal tensions were compared between all groups using ANOVA. The type of fracture was assessed by a scanning electron microscope. Results: The NN group presented a significantly greater insertion torque than all other groups, although all of them fractured during insertion (n=2) or removal (n=3). There were no significant differences between groups for removal torque. For group N, the fracture torque was significantly smaller than all other groups. All mini-implants suffered ductile fracture. Conclusion: Since there were no differences in the mechanical resistance of both brands of mini-implants, which varied only in shape, one may conclude that resistance to fracture can be affected by this variable.