Mechanical resistance of screwless morse taper and screw-retained implant-abutment connections

ObjectiveThe screwless morse taper (SMT) implant-abutment connection is an alternative to conventional external or internal screw-retained (ISR) connections. The aim of this in vitro study was to evaluate mechanical resistance of the SMT connection and to compare it with three different ISR connections. Materials and MethodsFour implant systems were tested in this study: SMT system; Tasarimmed Octo (Istanbul, Turkey), ISR systems; Straumann Bone Level (Basel, Switzerland), Biohorizons Internal (Birmingham, AL, USA), and Dentsply Friadent Xive (Mannheim, Germany). Overall, 64 specimens with stylized single crowns were prepared: 32 for dynamic loading (DL) and 32 for static loading (SL). DL was carried out using a chewing simulator with 120N at 1.75Hz for 1.2x10(6) cycles, and SL was performed with a universal testing machine at a crosshead speed of 2mm/min with an angulation of 30 degrees. Cycles until failure from DL and fracture/bending loads at SL were recorded. Statistical analyses were made with Dunn's multiple comparison. ResultsMedian cycles until failure in DL were as follows: Octo 86,354 (24,810-153,875), Straumann 1,200,000 (1,156,618-1,200,000), Biohorizons 539,719 (437,224-858,732), Xive 139,411 (139,411-139,411). Median fracture/bending loads in Newton at SL were as follows: Octo 429.6 (404.5-482.7), Straumann 574.6 (544.6-629.9), Biohorizons 548.7 (532.9-567.3), Xive 431.5 (412.5-520.5). There were significant differences between the implant systems under both loading conditions (P0.05) revealing that the Octo implant system's SMT connection showed significantly lower cycles to failures and lower fracture/bending loads compared with the ISR connections of the Straumann and Biohorizons implant systems. However, there was no significant difference compared with the Xive implant system. ConclusionThe mechanical resistance of the screwless morse taper implant system is lower than that of the ISR implant systems that might result in more frequent clinical complications.