Clinical Comparison of Screw-Retained and Screwless Morse Taper Implant-Abutment Connections: One-year Postloading Results

Purpose: The purpose of this study was to clinically evaluate the screwless Morse taper implant-abutment connection type, in which the retention screw is totally eliminated, in terms of stability, success, periodontal parameters, and marginal bone levels after 1 year of function by comparing it with a passive fit internal implantabutment connection, wherein a space exists between the matching components. Materials and Methods: Each edentulous subject received an implant with a screwless Morse taper connection (MT) in the left canine area of the mandible and an implant with a screw-retained implant-abutment connection (SR) in the right canine area of the mandible. All implants were loaded 6 weeks later. All cases were restored with a cemented bar-retained mandibular overdenture opposing a maxillary complete denture. Clinical recalls at 6 months and 12 months postloading were scheduled and the MT and SR implants were compared in terms of success, survival, primary and secondary implant stability, marginal bone loss, soft tissue response, and mechanical complications. The results were statistically analyzed. Results: A total of 20 subjects were included (10 females, 10 males; average age: 61.60 years) and a total of 40 implants were inserted. No implant failure or technical problem was detected for either MT or SR implants. Marginal bone loss around MT and SR implants did not show any significant differences at 6 weeks after surgery (time of loading) or at 6 months or 12 months postloading (P > .05). Periodontal parameters such as gingival index and probing pocket depth of MT and SR implants likewise did not differ significantly at 6 months and 12 months postloading (P > .05). Primary stability values of MT and SR implants did not differ significantly when measured with the insertion torque device (mean of 68.10 Ncm for MT and 64.20 Ncm for SR implants; P = .564), nor when measured with the electronic percussive testing device (mean of −5.30 for the MT and −5.35 for the SR implants; P = .398). However, MT implants showed lower stability at the time of loading (6 weeks) and 6 months postloading (P = .037 and P = .003, respectively). Stability values did not show any significant differences 12 months postloading (P > .05). Conclusions: Within the limitations of this clinical study, it can be concluded that implants with screwless Morse taper and passive fit internal connections show comparable technical and biologic results after 1 year of function. Keywords: dental implant, Morse taper, screwless Morse taper