Study Of Color Stability Of Four Heat-curing Denture Base Resins With Different Brands

Currently, poly(methyl methacrylate)(PMMA) resin and its modified products arewidely used and according to curing type, they are divided into heat-polymerizing acrylicresins, auto-polymerizing acrylic resins and light-polymerizing acrylic resins three categories.Heat-cured denture base resin is an important component in removable partial dentures andcomplete dentures, and has been widely used in the clinic because of its good physical andchemical properties in the oral environment, suitable aesthetics and easy manipulation.Many studies have shown that denture resin base has water absorption and solubility inthe oral environment, and with the water molecules in and out, the residual monomer in theresin will be released and lead to the change of physical, chemical and biological properties,thereby affecting service life. In recent years, with the improvement of people’s livingstandards, patients with dental restoration aesthetic demand are increasing. The color ofdenture resin base material will change under different conditions, the patients often replacedentures due to their aesthetic issues. Therefore the color stability of denture resin base in theoral environment is very important.The purpose of this study was to detect the changes of color and gloss of fourcommercial heat-curing denture base resins in different solution for different storage timewith purpose of evaluating the color stability of four commercial heat-curing denture baseresins and debating the relation of water absorption and solubility, gloss and color stability ofdenture base resins. The information obtained here will help optimize maintenance ofdentures and also inform choice of denture materials.Currently, the surface color of dental materials can be measured with a colorimeter, aspectrophotometer, or by digital photography and computer technology. In this experiment we measured the color and gloss used a PR-715spectrophotometer and vanceometer. In thisexperiment, four heat-cured denture base resins New Century, Meliodent, Nissin andBasis-Hi were heated and cured in accordance with the manufacturer’s instructions. Eachmaterial had twenty-five specimens and was divided into five groups. Subsequently thesurfaces of specimens were polished using the same way then were soaked in red wine, cola,coffee and tea. The specimens were taken out from the soak solutions at1,28and84days,the color and gloss of the specimens was measured.The water sorption and solubility valuesof the four denture base resins were measured in accordance with the ISO1567:1999standard.The results showed that New Century, Meliodent and Basis-Hi resins became darker atprolonged immersion time, Heraeus resins showed more significant changes. Fourcommercial heat-curing denture base resins were immersed in red wine, coke, coffee and teafor1,28and84d, the values of ΔE of the Heraeus resin materials immersed in red wineincreased most significantly and there were significant differences（P<0.05）. The values ofΔE of the Heraeus and New Century resin materials immersed in red wine are up3.7, whichregarded as clinically unacceptable. The values of ΔE of the Nissin resin materials immersedin coke, coffee and tea for1,28and84d changed little and here were no significantdifferences（P>0.05）. The values of gloss of the Heraeus resin materials immersed in redwine for84d reduced and there were significant differences（P<0.05）. The water absorptionof Heraeus resin was higher than the other resins and there were significant differences（P<0.05）.Through statistical analysis on the color and gloss of four commercial heat-curingdenture base resins were immersed in red wine, coke, coffee and tea for1,28and84d and thewater sorption and solubility values of materials, the following conclusions could be drawn:1. The color stability of dental base resin materials is associated with different thedenture base resins, soak solution and storage time，the stability of the Nissin resin materials is the highest.2. The color change of denture resin base material is related to water absorption andsolubility and gloss of the material. The color change of the Heraeus resin materialsimmersed in red wine for84d is significant. There is correlation that its higher waterabsorption and larger gloss decline values.