Is There a Need for Standardization of Tightening Force Used to Connect the Transducer for Resonance Frequency Analysis in Determining Implant Stability?

Purpose: The purpose of this in vitro study was to determine the minimum placement torque required to attach the transducer (measuring peg) to the implant to provide an accurate assessment of implant stability using resonance frequency analysis. Materials and Methods: One hundred 4 × 11-mm screw-shaped titanium implants were inserted into a uniform polyurethane block with similar density to bone in a standardized surgical protocol. The implants were distributed into 10 groups, with 10 implants each (G1 to G10). In G1, the transducer was manually attached by a female operator and in G2 by a male operator using the manual connector provided by the manufacturer. For the remaining groups (G3 to G10), the transducers were placed using a connector adapted to a digital torque wrench with different torque settings: 3 Ncm (G3), 4 Ncm (G4), 5 Ncm (G5), 6 Ncm (G6), 10 Ncm (G7), 13 Ncm (G8), 17 Ncm (G9), and 20 Ncm (G10). Stability was measured for all groups using the Osstell equipment (Diagnosis of Integration) and the implant stability quotient (ISQ) annotated for statistical comparison between the groups. Results: The mean ± standard deviation ISQ values for groups G1 to G10 were 9.50 ± 5.54, 19.05 ± 2.67, 29.25 ± 4.22, 26.55 ± 5.37, 40.90 ± 0.99, 69.60 ± 2.41, 71.30 ± 0.82, 71.20 ± 1.32, 72.40 ± 0.97, and 70.90 ± 0.88, respectively. Statistical comparisons determined that the amplitudes of the confidence intervals, relative to the standard deviations, were lowest for groups G5, G7, G8, G9, and G10. For the means, the lowest amplitudes of the confidence intervals were observed in G6, G7, G8, G9, and G10. When checking the conjugated confidence intervals (mean and standard deviation), the results were homogenous for G7, G8, G9, and G10. When the torque of 20 Ncm was reached, the connection between the transducer and the implant failed. Conclusion: In this in vitro model experiment, transducer torques between 10 and 17 Ncm appear to be adequate for accurate measurement of implant stability, allowing more precise comparisons without damaging the prosthetic connection in the implant. Keywords: dental implants, in vitro techniques, primary implant stability, resonance frequency analysis