Surface Wear and Retention Force of Zirconia and PEKK Implant-retained Crowns.

Purpose: The aim of this study was to evaluate the surface wear and retention force of telescopic attachments made of zirconia primary crowns and poly-ether- ketone -ketone (PEKK) secondary crowns for 2-implant retained mandibular complete overdentures.

Materials and methods: Ten healthy completely edentulous patients aged 55-60 years were selected for this study. Each patient received two implants in the mandibular canine regions. Maxillary conventional complete dentures were constructed against implant-retained mandibular overdentures for all patients. Zirconia- PEKK telescopic attachments were fabricated to retain the overdentures where primary copings were constructed of zirconia and secondary ones were constructed of PEKK. Retention force and surface wear were evaluated at the time of overdenture insertion (T0), and after 6 months of overdenture use (T6).

Results: The results revealed less wear of zirconia copings compared to PEKK ones at T0 and T6. However, both materials showed insignificant wear after 6 months of overdenture use. A significant increase in retention force was observed after 6 months of overdenture use.

Conclusion: Within limitations of this study, PEKK may be considered a promising alternative material for telescopic secondary crowns construction combined to zirconia primary ones, regarding the wear resistance and the satisfactory retention forces.