Evaluation and Comparison of Marginal Adaptation of Computer-aided Design and Manufacturing Monolithic Polyether Ether Ketone and Zirconia Crown after 6 Months of Simulated Clinical Use: An In vitro Pilot Study

Context (Background): Marginal adaptation is a key determinant of the longevity and clinical success of fixed dental prostheses. Polyether ether ketone (PEEK), a high-performance polymer, has recently gained interest as an alternative to zirconia due to its favorable mechanical, esthetic, and biological properties. Aims: To evaluate and compare the marginal adaptation of computer-aided design and manufacturing (CAD-CAM) monolithic PEEK and zirconia crowns cemented on natural teeth after simulating 6 months of clinical service. Settings and Design: An in vitro comparative pilot study was conducted using 28 extracted mandibular molars divided into two groups ( n = 14): Group I (PEEK) and Group II (Zirconia). Materials and Methods: Crowns were fabricated using CAD-CAM and cemented with self-adhesive resin cement. All specimens underwent thermocycling (120,000 cycles) and cyclic loading, followed by silver nitrate dye penetration. Sectioned specimens were examined under a scanning electron microscope (SEM) to assess vertical and horizontal marginal gaps. Statistical Analysis Used: Data were analyzed using SPSS v20. Normality was tested with the Shapiro–Wilk test, showing nonnormal distribution. The Mann–Whitney U test compared groups, with significance set at P < 0.05 (α = 0.05). Results: Group I (PEEK) showed mean horizontal and vertical marginal gaps of 35.09 ± 16.79 μm and 32.71 ± 17.85 μm, respectively, while Group II (Zirconia) showed 25.88 ± 23.45 μm and 26.53 ± 8.69 μm. Differences were statistically insignificant ( P > 0.05). Conclusions: Both PEEK and zirconia exhibited clinically acceptable marginal adaptation after simulated clinical aging. PEEK demonstrates comparable marginal accuracy to zirconia and can serve as a viable restorative alternative.