Discoloration of new commercially thermoplastic denture base resin

Recently, thermoplastic resin is being used more frequently as an esthetic denture without a metal clasp. Reports indicate that some thermoplastic resins discolor easily over short-term use. This study evaluated the discoloration properties of new commercial thermoplastic resins.

Method:

Three thermoplastic resins [Estheshot Bright (Polyethylene Terephthalate; PET, i-CAST, Japan), Reigning N (Polycarbonate, Toshinyoko, Japan), Bioplast (polyamide, High Dental, Japan), Aclytone (acrylic, High Dental, Japan)] and auto-polymerized acrylic resin [ParaXpress, Hereus Kluzer] as a control were used in this study. Thermoplastic and auto-polymerized acrylic resin plates (10.0×10.0×2.5 mm) were made, and their surfaces were abraded using emery paper (1200 grit). Each material was immersed in four solutions, such as curry (yellow), coffee (brown), edible dye (green), and wine (red) at 50 °C for seven days. Color changes (Δa, Δb, ΔEab) were measured using a reflectance spectrophotometer (SE2000, Nippon Denshoku, Tokyo, Japan) before and after the specimens were immersed in the solutions. The results (n=5) were analyzed using one-way analysis of variance (ANOVA) and Tukey’s multiple comparison test (α=0.05).

Result:

Polyamide had a higher degree of color change (ΔEab) than the other thermoplastic resins and acrylic resin in all color solutions (p<0.05). Of the polycarbonate, the highest color changes were most notable in curry and coffee relative to wine and edible dye (p<0.05).

Conclusion:

As anticipated, polyamide was more susceptible to color change than the other thermoplastic denture base resins. All color solutions (yellow, brown, green, and red) showed the similar discoloring effects on all thermoplastic resins except polycarbonate.