Purpose: The purpose of this study was to compare internal Morse taper connections in 2 separate modes: repeated torque/reverse-torque values and compressive bending at a 30-degree off-axis angle.
Materials and methods: Three sample groups (n = 12 in each group)--a solid-screw implant paired with a 5.5-mm solid abutment (SSI), a synOcta implant with a 5.5-mm solid abutment (SOI), and a synOcta implant with a synOcta 5.5-mm solid abutment (SOSA)--were torqued to 35 Ncm, and the reverse torque to remove the abutment was recorded. This was repeated for 3 trials. Additionally, the sample groups were loaded 30 degrees off-axis, and the ultimate compressive values were recorded.
Results: There was a significant difference in the initial reverse-torque values. The SOSA setup showed significantly lower torque than the SOI and SSI setups (P < .05). In addition, the compressive bending test showed that the SOSA setup was significantly different (P < .05) from the SSI and SOI setups. Radiographic survey of the test groups following compressive bending revealed no implant fractures, but bending of the implant-abutment complex occurred.
Discussion: The alteration within the Morse taper did not reduce the strength of the implant-abutment connection, ie, the reduction in surface area did not significantly reduce the torque properties or tensile properties. The new 2-piece synOcta 5.5-mm solid abutment was shown to have a stronger implant-abutment connection when torqued down a second time.
Conclusions: In this in vitro study, alteration of the Morse taper with an internal octagon indexing did not significantly reduce the strength of the implant connection. Sufficient strength was exhibited, which would indicate this implant-abutment design for anterior as well as posterior edentulous sites.