Evaluation of Surface Roughness of PEEK and Laser-Sintered Cobalt – Chromium Subjected to Different Polishing Protocols and Thermocycling ( An in vitro study )

Objective Surface roughness of dental materials is a critical determinant of their clinical performance. This in-vitro study aimed to evaluate and compare the surface roughness (Ra) of polyetheretherketone (PEEK) and cobalt–chromium (Co–Cr) alloys following different polishing protocols and subsequent thermocycling. Materials and Methods Eighty disk-shaped specimens were fabricated from PEEK and Co–Cr and allocated into four groups (n = 20 each): PEEK + EVE Diacomp Plus, PEEK + Ivoclar Universal Paste, Co–Cr + Ivoclar Universal Paste, and Co–Cr + Renfert Saphir Paste. Surface roughness was measured at baseline, after polishing, and after thermocycling (10,000 cycles, 5–55 °C). Data were analysed using mixed-design ANOVA with Pillai’s Trace for within-subject effects and Games–Howell post hoc tests (α = 0.05). Results Co–Cr specimens showed significantly higher baseline Ra (19.25 ± 5.24 µm) compared with PEEK (2.30 ± 0.22 µm; p < 0.001). Polishing significantly reduced Ra across all groups (PEEK: 0.5802 ± 0.09 µm, Co-Cr 0.57 ± 0.13 µm; p < 0.001), with no significant difference between materials (p = 0.63). After thermocycling, Ra increased in all groups, with PEEK exhibiting the highest values (1.02 ± 0.31 µm; p < 0.001). Conclusion Both PEEK and laser-sintered Co–Cr presented rough surfaces post-fabrication. Polishing protocols effectively reduced Ra; however, thermocycling increased roughness in all groups. Co–Cr demonstrated greater resistance to surface degradation compared with PEEK. Although the polished Ra values exceeded ideal smoothness levels, they remain within the range commonly achieved for prosthetic polymers and metal frameworks. These findings highlight the importance of material selection and polishing protocols in long-term clinical performance.