Influence of reverse torque values in abutments with or without internal hexagon indexes Daiane Cerutti-Kopplin, DDS, MSc, a Dimas João Rodrigues Neto, DDS, MSc, b Accácio Lins do Valle, DDS, PhD, c and Jefferson Ricardo Pereira, DDS, MSc, PhD d Faculty of Dentistry, Federal University of Rio Grande do Sul - Porto Alegre, Rio Grande do Sul, Brazil; Dental School, University of Southern Santa Catarina, Santa Catarina, Brazil; Bauru Dental School, University of Sao Paulo, Sao Paulo, Brazil Statement of problem. The mechanical stability of the implant-abutment connection is of fundamental importance for successful implant-supported restorations. Therefore, understanding removal torque values is essential. Purpose. The purpose of this study was to evaluate the reverse torque values of indexed and nonindexed abutments of the Morse Taper system. Material and methods. Twelve Morse taper implants with their respective abutments were divided into 2 groups (n¼6): group NI, nonindexed abutments; and group IN, indexed abutments. Each abutment received a sequence of 2 consecutive torques for insertion (15 Ncm) at an interval of 10 minutes, and 1 reverse torque, all measured with a digital torque wrench. The Student t test with a 5% significance level was used to evaluate the data. Results. Statistical analysis showed no significant difference in reverse torque values between nonindexed and indexed abutments (P¼.57). When comparing insertion torque and reverse torque values between the groups, group NI presented a mean torque loosening percentage of 8% (P¼.013), whereas group IN presented a loosening of 15.33% (P<.001). Conclusion. The use of indexed abutments for the Morse taper system presented similar biomechanical stability when compared with nonindexed abutments, both with a significant reduction in reverse torque values. (J Prosthet Dent 2014;-:---) Clinical Implications Changes to the Morse taper system design, introduced to facilitate prosthetic procedures, could result in stability changes in the implant-abutment complex. The passivity, adaptation, and connection strength of an abutment to the implant are fundamental requirements for treatment success. Dental implants serve to restore the function and esthetics of patients who are edentulous. Various investigators described the successful osteointegration of implant systems, 1-3 with many studies that focused on the develop- ment of new techniques, materials, and designs. In addition, indications have been clarified to optimize the biome- chanical behavior of the implant and its prosthetic components. 4 Passivity, adaptation, and abutment-implant a Doctoral student, Faculty of Dentistry, Federal University of Rio Grande do Sul - Porto Alegre. b Lecturer, Department of Prosthodontics, Dental School, University of Southern Santa Catarina. c Professor, Department of Prosthodontics, Bauru Dental School, University of Sao Paulo. d Associated Clinical Professor and Research Coordinator, Department of Prosthodontics, Dental School, University of Southern Santa Catarina. Cerutti-Kopplin et al