Abstract
Aim: The aim was to evaluate the physical properties of denture base resin in two different media such as artificial saliva and chlorinated water by using thermal gravimetric analysis (TGA) & differential thermal analysis (DTA).
 Materials and Methods: 40 samples divided into 2 groups of 20 samples each. One group was stored in artificial saliva the other group was stored in chlorinated water of 3ppm concentration. Total number of 40 acrylic blocks was grouped as Group I & II. Scrapings were taken from the blocks of both the Group I & II. Samples of artificial saliva and chlorinated water were subjected to thermal behavior by TGA and DTA.
 Results: TGA Thermograph of Group I shows broad endothermic peak at 282.90C to 357.70C and exothermic peak at 535.40C to 602.20C. TGA Thermograph of Group II shows broad endothermic peak at 336.20C to 362.20C and exothermic peak at 535.60C to 643.90C. The phase change corresponding to the weight change is shown in DTA thermograph. The thermograph of TGA/DTA shows changes in thermal behavior in both the medium.
 Conclusion: Changes in the physical properties of denture base resin such as transition temperature and phase changes were evaluated by thermal analysis. Chlorine being highly reactive will react with the double bonds of polymethylmethacrylate (PMMA). Blocking of double bond can affect the physical properties of denture base resin.
 Keywords: Polymethylmethacrylate, Differential thermal analysis, Thermal analysis, Denture base resin.
Highlights
Polymethylmethacrylate (PMMA) is formed by polymerization of monomer by emulsion method of polymerization
Materials and Methods: This study was performed to analyze the thermal behavior of denture base resin was stored in artificial saliva and 3ppm concentration of chlorine
Chlorine being highly reactive will react with the double bonds of PMMA
Summary
Polymethylmethacrylate (PMMA) is formed by polymerization of monomer (methylmethacrylate) by emulsion method of polymerization. It has a main carbon skeleton with pendant hydrogen (H), methyl (CH3) and carboxymethyl (COOCH3) arranged in alternative manner. The diffusion co-efficient of typical heat cure denture base resin is 1.08 X10m/sec at 370C. It has been estimated that for each 1 percent increase in weight due to the absorbed water acrylic resin expands linearly by 0.23%. In modern days it has become a routine to use hard water, chlorinated water due to insufficient water supply especially in countries like India, chemicals present in the water will diffuse along with the water molecule and can even interact with the polymer chain
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