Recycling of used alginate impression materials into final polishing powder for methacrylate denture base resins

Abstract

Purpose: The purpose of this study was to recycling diatomite from alginate impression materials and investigate its potential as an abrading agent for denture base resins. Materials and Methods: After heating hardened alginate impression materials, a lump-like solid was powdered using a mortar and a pestle. The powder (experimental sand, ES) was characterized by X-ray diffraction (XRD). To explore the suitable ES/wax ratio, three amounts (1, 3, and 5 g, corresponding to samples ES1, ES3, ES5, respectively) were blended with 6 g of casting wax. Casting wax bars without ES were also prepared as the control. In addition, commercial diatomite (reagent-grade diatomite, RD) and a commercial final polishing product for acrylic resin (TE) were examined and compared. A disk-shaped self-curing resin (diameter: 30 mm, thickness: 3 mm) was prepared as a specimen and ground by polishing paper (#800-1,000). Surface gross measurements and surface roughness values after polishing were determined using a gross meter. These surface roughness and gloss data were statistically analyzed by one-way ANOVA and Tukey’s multiple comparison test (α = 0.05). Results: Based on the XRD results, diatomite was successfully detected in the heated alginate impression material. Sample ES3 showed good performance in experimental polishing tools, and its polishing effects were almost identical to those of RD. However, ES3 was inferior to TE in terms of surface gloss, and ES0 exhibited no polishing effect. Conclusion: Within this limited study, diatomite obtained from alginate gel was found to be effective as the final polishing material in denture base resin. (Asian Pac J Dent 2021; 21: 1-6. doi: 10.47416/apjod.21-0278)