Color changes of polyetheretherketone (PEEK) and polyoxymethelene (POM) denture resins on single and combined staining/cleansing action by CIELab and CIEDE2000 formulas.

PURPOSE: The purpose of study was to investigate the long-term effect of staining and/or cleansing solutions on the color stability of two non-metal removable partial denture materials. METHODS: One hundred disks (25x3mm) of polyoxymethylene (POM) and polyetheretherketone (PEEK) were immersed in water, wine, coffee, cleanser and combo bath, simulating normal daily use. Color parameters in the CIELAB system was measured every 30 cycles up to 240 using a contact colorimeter and color differences estimated using DeltaE(ab) and DeltaE(00) formulas. Two-way repeated measures ANOVAs and regression analyses were performed at alpha=0.05. RESULTS: Regression analysis indicated a strong R(2) between color changes and number of cycles, for both materials. Tests of within-subjects effects for the DeltaE(ab) revealed significant differences among cycles and between the materials in the wine and coffee baths (p<0.001). Significant materialXcycles interactions were also recorded with all staining baths. DeltaE(00) values were lower than DeltaE(ab) up to 63.6%. Tests within and between-subjects effects for the DeltaE(00) gave similar but not the same with DeltaE(ab) results. CONCLUSIONS: DeltaE(00) found to correlate well with DeltaE(ab). Long term exposure of both materials showed a progressive discoloration in all except control baths. POM discolored more than PEEK in coffee, and combo baths but not in cleanser. Discoloration was smaller in combo bath (where a cleanser was also used) indicating the effectiveness of a cleanser to prevent long term discoloration of both materials.