DEDICATÓRIA

Objective: To introduce a new coupling system between screw driver and interference screw, and biomechanical tests that validate the safety of its application. Methods: The new system was submitted to biomechanical torsion assays. Two types of analysis were performed: maximum torque of manual insertion of the screws into bovine bone; destructive assays of torsion of the system using an INSTRON 55MT machine. The same tests were also performed on a control group, using a commercially available interference screw coupling system (Acufex ® ).Results: In the tests on manual insertion of screws in bovine femurs, the average values found with a digital torque meter were 1.958 N/m for Acufex ® and 2.563 N/m for FMRP. Consi- Article received on 9/22/09 and approved on 11/26/10 dering p>0.05, there were no statistical differences between the two groups (p=0.02) in the values for maximum torque of insertion, in the two systems studied. The average values for maximum torque of torsion resisted by the screw were 15N/m for the Acufex ® screw and 13N/m for the FMRP screw, again with no statistical differences between the two groups (p>0.05). In the evaluation of angular deformation, there was also no significant difference between the two screw types (p=0.15). Conclusion: The new coupling system for interference screws developed at FMRP-USP revealed a torsion resistance that is comparable with the system already available on the market and regulated for international use.

Neste estudo objetivamos avaliar a influência do flúor proveniente do fosfato natural de rocha nas propriedades mecânicas dos fêmures de coelhos submetidos a dietas contendo diferentes concentrações de flúor, mediante ensaios mecânicos de flexão em três pontos. Para tanto foram utilizados os fêmures de 40 coelhos machos, albinos, da raça Nova Zelândia. Durante 40 dias, os animais, divididos em cinco grupos, receberam dietas contendo diferentes concentrações de flúor. O ensaio de flexão foi realizado em 77 fêmures para obtenção das seguintes propriedades mecânicas: limite máximo, limite proporcional, rigidez e resiliência. As propriedades mecânicas da deformação proporcional e resiliência apresentaram diferença estatisticamente significante entre os grupos com menor concentração de flúor quando comparados com o grupo 5. Houve redução nos valores para rigidez, carga máxima, mas sem diferença estatisticamente significante, para os grupos com maior concentração de flúor quando comparados com o grupo testemunha, concluindo-se que houve influência do flúor proveniente do fosfato natural de rocha em algumas propriedades mecânicas.