Retention force of all-zirconia, all-polyetheretherketone, and zirconia-polyetheretherketone telescopic attachments for implant-retained overdentures: In vitro comparative study

Abstract

Aim: The aim was to evaluate and compare retention forces of all-zirconia (ZrO2), all-polyetheretherketone (PEEK), and ZrO2-PEEK Computer-Aided-Designing computer-Aided -Manufacturing (CAD-CAM) telescopic attachments for two implant-retained mandibular overdentures. Materials and Methods: Fifteen identical acrylic resin models of the edentulous mandibular arch without alveolar undercuts were fabricated. Two implants were inserted in the canine region of each model. According to the material of telescopic attachment, models were divided into three groups: all ZrO2 (ZZ): primary and secondary crowns were made of ZrO2, all PEEK (PP): primary and secondary crowns were made of PEEK, and ZrO2-PEEK (ZP): primary crowns were made of ZrO2 and secondary ones were made of PEEK. Identical experimental overdentures were constructed for all models. For measuring the retention force, a universal testing machine was used to apply a pull-off test in presence of artificial saliva between the crowns. The achieved maximum values of retention force were recorded at the beginning of the study (initial retention) and after 540 cycles of insertion and removal simulating 6 months of the clinical service (final retention). Results were statistically analyzed, analysis of variance (P < 0.05). Results: ZP group reported the highest initial force values for all groups. The final retention values of PP and ZP groups were significantly decreased than initial values, while the insignificant loss of retention was observed with ZZ group (P = 0.06). Independent samples test showed a significant difference in both initial and final retentions between each two groups. Conclusion: Within the limitations of this study, ZrO2 is more preferred as a secondary telescopic crown against a primary ZrO2 one. Despite the loss of retention by time, PEEK can still be used as a secondary telescopic crown against ZrO2 or PEEK primary crowns regarding the acceptable initial and final retention values.