Assessment of Retention of CAD-CAM Milled PEKK vs PEEK Double Crown-retained Removable Partial Dentures: A Randomized Clinical Trial.

AIM AND OBJECTIVE: To assess and compare the dislodging force of double crown-retained removable partial dentures (RPDs) made from polyetherketoneketone (PEKK) and polyetheretherketone (PEEK) at insertion (baseline) and one year after clinical functional use. MATERIALS AND METHODS: A total of 18 patients with maxillary symmetrical Kennedy class I with the second premolars being the last standing abutment were selected. The patients were randomly assigned into two groups according to the materials used for the construction of the double crown-retained RPD. Group I: Double crown-retained RPDs were made from PEKK. Group II: Double crown-retained RPDs were made from PEEK. For both groups, the primary copings were made from zirconia (ZrO(2)). The dislodging force was measured using a digital force gauge at baseline and one year after clinical functional use. An independent t-test was used for intergroup comparisons and a paired t-test for intragroup comparisons. RESULTS: when comparing both groups at baseline, there was no significant difference between the two groups, but after one year, Group I had a significantly higher dislodging force value than Group II. Individually, there was an increase in dislodging force in both groups one year after clinical functional use, which was statistically significant for Group I. CONCLUSION: After clinical functional use, double crown-retained RPDs made from PEEK in combination with ZrO(2) primary copings demonstrate a minimal increase in dislodging force, while those made of PEKK demonstrate a significant increase in dislodging force. CLINICAL SIGNIFICANCE: All patients were satisfied with the retention and esthetics of their dentures. Polyetherketoneketone double crown-retained RPDs demonstrate better retention one year after clinical functional use.