RESUMO
OBJECTIVE: To investigate the long-term stability of a metal-free zirconia two-piece implant assembled with a carbon fiber-reinforced (CRF) screw by means of transformation propagation, potential changes in surface roughness, the gap size of the implant-abutment connection, and fracture load values. METHODS: In a combined procedure, two-piece implants made from alumina-toughened zirconia were dynamically loaded (107 cycles) and hydrothermally aged (85°, 60days). Implants made from titanium (Ti) and a titanium-zirconium (TiZr) alloy with a titanium abutment screw served as control. Transformation propagation (ATZ) and gap size of the IAC were monitored at cross-sections by scanning electron microscopy (SEM). Furthermore, changes in surface roughness of ATZ implants were measured. Finally, implants were statically loaded to fracture. Linear regression models and pairwise comparisons were used for statistical analyses. RESULTS: Independent of the implant bulk material, dynamic loading/hydrothermal aging did not decrease fracture resistance (p=0.704). All test and control implants fractured at mean loads >1100N. Gap size of the IAC remained stable (<5µm) or decreased. None of the CFR screws fractured during static or dynamic loading. Monoclinic layer thickness of ATZ implants increased by 2-3µm at surfaces exposed to water, including internal surfaces of the IAC. No changes in surface roughness were observed. SIGNIFICANCE: Combined hydrothermal aging and dynamic loading did not affect the above-mentioned parameters of the evaluated two-piece ATZ implant. Mean fracture loads >1100N suggest a reliable clinical application.