AIM: The purpose of this study was to evaluate mini-implants with different dimensions for the following factors: (a) insertion torque, (b) removal torque, (c) fracture torque, (d) shear tension, (e) normal tension and (f) type of fracture. METHODS: Twenty self-drilling mini-implants were used, 10 from SIN and 10 from Neodent, with 1.6mm in diameter and with 8 and 7mm in length, respectively. Out of these 10 mini-implants, 5 did not have a neck and the other 5 had a 2mm neck, and were separated into 4 groups: SIN without neck (SSP), SIN with neck (SCP), Neodent without neck (NSP) and Neodent with neck (NCP). All mini-implants were inserted in 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 by ANOVA. The type of fracture was assessed by a scanning electronic microscope. RESULTS: The NCP group presented a significantly greater insertion torque than all other groups, but all of them fractured during insertion (n = 2) or removal (n = 3). There were no significant differences among groups for removal torque. For group NSP, the fracture torque was significantly smaller than all other groups. All mini-implants suffered ductile fracture. CONCLUSION: Since there were no differences for the mechanical resistance of both brands of mini-implants, varying only in shape, one may conclude that resistance to fracture can be affected by this variable.
Dental implants; Material resistance; Torque; Orthodontic anchorage procedures
