Primary stability analysis of the torque-resistant orthodontic miniscrew anchorage

Abstract

Though miniscrews are widely used as a temporary anchorage device, research focusing on the primary stability of miniscrew loading torque force is limited. This study is aimed to design a novel torque-resistant miniscrew used as orthodontic anchorage (TRO-screws) and to compare the difference of primary stability between TRO-screws and commercial miniscrew anchorage (COM-screws) using torque tests and resonance frequency analysis (RFA). Fresh swine ribs were cut into pieces of 20 mm × 13 mm × 11 mm, and each piece was implanted with one screw after a 1.5 mm-deep hole with a diameter of 1.0 mm was pre-drilled. There were 20 TRO-screws and 20 COM-screws. Maximum insertion torque (MIT) and maximum removal torque (MRT) were measured. The implant stability quotient (ISQ) was recorded parallel to and perpendicular to the long axis of teeth respectively. The measurement was repeated three times for each direction, and the ISQ values were averaged and recorded as the ISQpar, ISQper, and ISQm. The mean values of MIT for TRO-screws and COM-screws were 11.86±1.58 N cm and 10.36±1.42 N  cm. The mean values of MRT for TRO-screws and COM-screws were 8.45±2.24 N cm and 6.76±1.78 N cm. The mean values of ISQ for TRO-screws and COM-screws were 61.80±2.9 and 58.15±2.98. These indicated that TRO-screws were more stable than COM-screws. We found that the primary stability of the TRO-screw was better than that of the COM-screw.