Implant design affects the fracture resistance of zirconia implants

Researchers have compared different zirconia implant systems to examine how implant design influences fracture resistance after simulated clinical loading.

A new in vitro study investigated how one-piece and two-piece zirconia implant designs performed after being exposed to repeated loading in a moist environment, simulating functional conditions in the mouth. The study was carried out in collaboration with Malmö University, with supervision and experimental work conducted at NIOM.

The study forms part of the doctoral research of Abdulaziz Gul, who is scheduled to defend his PhD thesis in October. The project was supervised by NIOM CEO and Professor Per Vult von Steyern, together with associate professor Evaggelia Papia and professor Jonas Bector from Malmö University.

Senior scientist Siamak Eqtesadi and engineer Magnus Anderson contributed to the experimental work and testing performed at NIOM.

“Zirconia implants are attracting increasing interest, and reliable knowledge about their mechanical performance is important. This study shows that implant design plays a key role and provides valuable information for future clinical evaluation of these systems,” says NIOM CEO Per Vult von Steyern.

What did the researchers investigate?

The researchers tested five zirconia implant configurations according to the international ISO 14801 standard. The implants were exposed to 2 million cycles of dynamic loading in water at 37 °C and were then subjected to static load-to-fracture testing.
The study included one-piece implants, bone-level two-piece implants, and tissue-level two-piece implants. The two-piece designs were tested with either ceramic or titanium abutment screws.

What did the researchers find?

All implant systems survived the dynamic preloading phase without failure. However, clear differences were observed during the subsequent fracture test.

Tissue-level two-piece implants showed the highest fracture resistance, followed by one-piece implants. Bone-level two-piece implants showed the lowest fracture resistance among the tested designs. Within the two-piece implant groups, tissue-level designs performed better than bone-level designs.

The results also showed that implant-level design had a stronger effect on fracture resistance than the abutment screw material. No significant difference was found between ceramic and titanium abutment screws within the same implant level.

What are the key findings?

The evaluated zirconia implant systems demonstrated fracture resistance levels that support further clinical investigation.

The study showed that tissue-level two-piece zirconia implants had the most favorable mechanical performance, while bone-level two-piece implants were more sensitive to design-related mechanical limitations.

The choice between ceramic and titanium abutment screws appeared to have less influence on fracture resistance than the overall implant design.

Fracture patterns differed between implant designs. One-piece implants mainly fractured in the coronal thread region, bone-level two-piece implants mainly showed platform fractures, and tissue-level two-piece implants showed combined fracture patterns.

Micro-Raman analysis showed that the zirconia material remained predominantly tetragonal after testing, although localized monoclinic phase formation was detected depending on implant design and loading history.

Overall, the study contributes new knowledge about the mechanical behaviour of zirconia implant systems and may support future development and clinical evaluation of ceramic dental implants.