Maximum insertion torque of a novel implant-abutment-interface design for PEEK dental implants

Frequent reports attest to the various advantages of tapered implant/abutment interfaces (IAls) compared to other types of interfaces. For this reason, a conical IAI was designed as part of the development of a PEEK (polyetheretherketone)-based dental implant. This IAI is equipped with an apically displaced anti-rotation lock with minimal space requirements in the form of an internal spline. The objective of this study was the determination of the average insertion torque (IT) at failure of this design, so as to determine its suitability for immediate loading, which requires a minimum IT of 32 N cm. 10 implants each made of unfilled PEEK, carbon fiber reinforced ("CFR") PEEK ( > 50 vol% continuous axially parallel fibers) as well as of titanium were produced and tested in a torque test bench. The average IT values at failure of the unfilled PEEK implants were measured at 22.6 +/- 0.5 N cm and were significantly higher than those of the CFR-Implants (20.2 +/- 2.5 N cm). The average IT values at failure of the titanium specimens were significantly higher (92.6 +/- 2.3 N cm) than those of the two PEEK variants. PEEK- and CFR-PEEK-implants in the present form cannot adequately withstand the insertion force needed to achieve primary stability for immediate loading. Nevertheless, the achievable torque resilience of the two PEEK variants may be sufficient for a two-stage implantation procedure. To improve the torque resistance of the PEEK implant material the development of a new manufacturing procedure is necessary which reinforces the PEEK base with continuous multi-directional carbon fibers as opposed to the axially parallel fibers of the tested PEEK compound.