Evaluation of Color Stability of PEEK and PEKK Dental Materials: A Systematic Review.

OBJECTIVES

Polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) are two members of the polyaryletherketone (PAEK) family. PEEK is a high-performance thermoplastic material increasingly used in dental restorations due to its favorable mechanical properties and biocompatibility. However, its long-term clinical esthetic success significantly depends on color stability upon exposure to different coloring materials. In this systematic review, we aimed to investigate the present in vitro literature on the color stability of dental PEEK and PEKK materials when exposed to staining agents, artificial aging, and cleaning procedures.

MATERIALS AND

METHODS

A comprehensive search in PubMed, Embase, Scopus, and MEDLINE databases was conducted up to May 15, 2026, following PRISMA guidelines. After evaluation and an updated search, 27 studies met the inclusion criteria.

RESULTS

The results indicated that PEEK generally exhibits superior color stability compared to other polymeric materials like polymethyl methacrylate (PMMA), composite resins, and polyamide. In direct comparisons, PEKK demonstrated better color stability than PEEK, attributed to its lower water sorption. Turmeric and green tea caused the most severe discoloration (ΔE > 3.3), while coffee, wine, and Cola produced moderate to minimal changes. Thermocycling and thermomechanical aging adversely affected PEEK, especially in ceramic‑filled variants. Surface finishing was critical-specific polishing protocols maintained color stability within clinical thresholds, whereas glazing offered no significant advantage. Cleaning methods varied in efficacy; ultrasonic and Air Flow were more effective than brushing, but sodium hypochlorite and chlorhexidine caused pronounced discoloration. While PEEK shows acceptable color stability under most conditions, it remains more susceptible to discoloration than ceramics like zirconia.

CONCLUSION

The findings highlight the importance of material composition, surface treatment, and maintenance protocols in optimizing the esthetic performance of PEEK restorations. The limited evidence on PEKK suggests superior color stability over PEEK, warranting further investigation. Long‑term clinical studies are essential to validate these in vitro findings and to establish maintenance protocols.