Effect of Surface Coating, Thermocycling, and Staining Solutions on the Color Stability of CAD-CAM Polymethyl Methacrylate Interim Fixed Restorations.

Abstract

Objective: To examine factors affecting color change in computer-aided design and computer-aided manufacturing (CAD-CAM) polymethyl methacrylate (PMMA) interim fixed restorations, including resin coating, fabrication methods, staining solutions, and thermocycling.

Materials and methods: A total of 144 CAD-CAM PMMA specimens-both 3D-printed and milled types (n = 72 each)-were divided into non-coated and resin-coated subgroups (n = 36 each). After 5000 thermocycling cycles, specimens (n = 12) were immersed in coffee, cola, or red grape juice for 28 days. Color measurements were taken before and after coating, after thermocycling, and after immersion at 7, 14, and 28 days using a spectrophotometer. Color difference (∆E) values were analyzed using paired t-tests and multiple linear regression (α = 0.05).

Results: 3D-printed PMMA exhibited significantly greater color change than milled PMMA after 7 days of immersion, with no significant differences observed at later intervals. Resin glaze coatings reduced color changes in both CAD-CAM PMMA materials under thermocycling and staining exposure. Coffee had the most significant impact on color change. Thermocycling caused color changes in both CAD-CAM PMMA materials, with 3D-printed PMMA showing more significant discoloration.

Conclusions: Fabrication methods, surface coatings, staining solutions, and thermocycling influence the color stability of CAD-CAM PMMA. Resin glaze coatings effectively reduce discoloration under both thermocycling and staining conditions.

Clinical significance: Resin coatings significantly reduce color change in both 3D-printed and milled interim fixed PMMA restorations, particularly in the 3D-printed PMMA, and can maintain clinically acceptable color stability for approximately 7 months in the oral environment.