IADR Abstract Archives
in Vivo Ageing of Dental Zirconia Ceramics: Is it Clinically Relevant?
Objectives: To assess clinical relevancy of in vivo aging of 3Y-TZP ceramics in the oral environment with the emphasis on the roles of the comparison to in vitro aging extrapolations and the zirconia`s surface state.
Methods: 3Y-TZP disk specimens, varying sintering protocols, grain sizes, and surface states (as-sintered, polished and airborne-particle-abrasion) were incorporated in lingual flanges of complete dentures of 12 edentulous volunteers for up to 48 months. In vitro hydrothermal aging at 134 °C was also performed. In addition, the extent of ageing was assessed from five 3Y-TZP implants (ZiUnite with a porous coating) explanted from prospective clinical investigations due to periimplant bone breakdown after 37, 40, 52, 64 and 181 months. XRD, conventional SEM and FIB-SEM tomography were employed for evaluation.
Results: The ageing kinetics of 3Y-TZP disk specimens were almost 3-times faster than the in vivo predictions. As expected, 3Y-TZP with lower amount of alumina were slightly more susceptible to ageing. In the case of implants with porous surface coating, all explanted specimens exhibited extensive surface t-m transformation, pronounced micro-cracking and subsequent coating degradation.
Conclusions: Biomedical grade 3Y-TZP is susceptible to in vivo ageing, depending on the composition and surface state. Concerning disk-shaped specimens, the extent of degradation did not yet constitute grounds for clinical concern after 4 years in vivo, but the ageing kinetics were faster than the generally accepted in vivo predictions. In the case of assessed implants, the porous coatings were highly prone to ageing and the related cracking of the coatings were thus linked to brittle fractures. It is hypothesized that these changes possibly contributed to bone loss, loss of osseointegration and subsequent implant failure.
Methods: 3Y-TZP disk specimens, varying sintering protocols, grain sizes, and surface states (as-sintered, polished and airborne-particle-abrasion) were incorporated in lingual flanges of complete dentures of 12 edentulous volunteers for up to 48 months. In vitro hydrothermal aging at 134 °C was also performed. In addition, the extent of ageing was assessed from five 3Y-TZP implants (ZiUnite with a porous coating) explanted from prospective clinical investigations due to periimplant bone breakdown after 37, 40, 52, 64 and 181 months. XRD, conventional SEM and FIB-SEM tomography were employed for evaluation.
Results: The ageing kinetics of 3Y-TZP disk specimens were almost 3-times faster than the in vivo predictions. As expected, 3Y-TZP with lower amount of alumina were slightly more susceptible to ageing. In the case of implants with porous surface coating, all explanted specimens exhibited extensive surface t-m transformation, pronounced micro-cracking and subsequent coating degradation.
Conclusions: Biomedical grade 3Y-TZP is susceptible to in vivo ageing, depending on the composition and surface state. Concerning disk-shaped specimens, the extent of degradation did not yet constitute grounds for clinical concern after 4 years in vivo, but the ageing kinetics were faster than the generally accepted in vivo predictions. In the case of assessed implants, the porous coatings were highly prone to ageing and the related cracking of the coatings were thus linked to brittle fractures. It is hypothesized that these changes possibly contributed to bone loss, loss of osseointegration and subsequent implant failure.