Objectives: Passive fit entails an ideal situation, with a minimum of stress generation when a prosthetic superstructure is mounted onto osseointegrated implants. Stress may have an adverse effect on bone-remodelling around implants, on the implants themselves, components and superstructures. So far passive fit was investigated in laboratory tests. Measurements of stress are difficult and expensive to perform clinically. Therefore a new cost-effective method to measure the passive fit in vivo is needed. Methods: 15 patients with a total of 42 Straumann®-Implants were enrolled in this study. All patients had osseointegrated implants for at least 6 months. All subjects received screw retained cast gold frameworks. 7 Patients were treated with conventional and 8 with the Cresco Ti Precision®-method. Radiographs with the right angle technique were taken. The tightening of occlusal screws was performed with a drilling equipment (OsseoCare DEC 601, Nobel Biocare, Göteborg, Sweden) and simultaneously the applied torque was measured. The maximum torque was set to 35 Ncm. According to the Sheffield test the screws were screwed in one way direction. Each measurement was repeated three times. Results: All three measurements within one subject showed the same stress pattern. But there was a large variation between the patients. Four radiographs exhibited signs of misfit between implant and framework. In this cases the applied torque increased by 2.3 Ncm on the average. Frameworks fabricated by the Cresco Precision®-method showed significantly lower torque (p<0.001). Conclusion: The intraoral measurement of torque while tightening the occlusal screws of cast frameworks in one direction is a save and cost-effective method to measure and evaluate clinically the passive fit. This method may enable the clinician to evaluate different precisioning systems. Torque control measurements could be introduced as an initial parameter for longitudinal monitoring of implant supported reconstructions.

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