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Schubert, Oliver; Reitmaier, Josef; Schweiger, Josef; Erdelt, Kurt; Gueth, Jan-Frederik (2019): Retentive force of PEEK secondary crowns on zirconia primary crowns over time. In: Clinical Oral Investigations, Vol. 23, No. 5: pp. 2331-2338
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ObjectivesThe purpose of the present study was to evaluate the retentive forces of CAD/CAM-fabricated polyetheretherketone (PEEK) secondary crowns on zirconia primary crowns over an artificial aging period representing 10years of clinical service and compare them to electroformed secondary crowns made from pure gold.Material and methodsImplant-supported zirconia primary crowns (N=20) were CAD/CAM milled and provided either with electroformed secondary crowns (group ZE;N=10) or CAD/CAM-fabricated PEEK secondary crowns (group ZP;N=10). All secondary crowns were attached to a casted tertiary structure to ensure adequate stability. A universal testing machine was used to determine the retentive force values at baseline and after 1, 3, 5, and 10years of simulated aging in the presence of artificial saliva. Data were analyzed applying Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney U test. Level of significance was set at p<0.05.ResultsRetentive forces were not different for the groups ZE and ZP at baseline (median ZE 2.85N;ZP 2.8N;p0.218). Because retentive force values changed significantly over simulation time for group ZE (Kruskal-Wallis;p0.028), the values between the test groups ZE and ZP differed significantly (Mann-Whitney U) at 5years (ZE 3.03N;ZP 2.76N;p0.003) and 10years (ZE 3.1N;ZP 2.78N;p0.011).ConclusionsPEEK secondary crowns exhibit stable retentive force values over 10years of simulated aging showing no signs of deterioration while the retentive force values of electroformed secondary crowns increase over time.Clinical relevancePEEK might be a suitable alternative to proven metallic materials for the fabrication of secondary crowns.