Abstract
Objectives: To evaluate and compare the flexural strength and the elastic moduli of three provisional crown materials (methyl methacrylate based autopolymerized resin, bis acryl composite based autopolymerized resin and urethane dimethacrylate based light polymerized resin) after storing in artificial saliva and testing at intervals of 24 hours and 7 days. Study design: A metal master mould with four slots of dimensions 25x2x2 mm was fabricated to obtain samples of standard dimensions. A total of 135 specimens were thus obtained with 45 each of three provisional materials. Further 15 samples of each group were tested after storing for one hour at room temperature and again at intervals of 24 hours and 7 days after storing in artificial saliva. Three point flexural tests were carried out in the universal testing machine to calculate the flexural strength and the elastic modulus. The changes were calculated and data was analyzed with Fisher’s test and ANOVA. Results: The flexural strength of the methyl methacrylate resin reduced significantly while bis-acrylic composite resin showed a significant increase in its flexural strength after storing in artificial saliva for 24 hours and the values of both remained constant thereafter. Contrary to these findings, light polymerized resin showed a significant decrease in flexural strength after storing in artificial saliva for 24 hours and then significantly increased in flexural strength after 7 days. However the changes in the values for elastic modulus of respective materials were statistically insignificant. Conclusion: Methacrylate based autopolymerizing resin showed the highest flexural strength and elastic moduli after fabrication and after storing in artificial saliva and for 24 hours and 7 days. Bis-acrylic composite resin showed the least flexural strength and elastic moduli. Key words:Provisional restorations, interim restorations, Methyl Methacrylate, composite restoration, flexural strength, elastic moduli.
Highlights
Provisional crowns and fixed partial dentures (FPDs) are essential components of fixed prosthodontic treatment (1)
The arrival of newer composite resin based provisional restorative materials to an area dominated by polymethyl methacrylate has lent a freedom of choice to the practitioner
With the data obtained from this study on measuring the flexural strength and elastic moduli of provisional restorative materials, it was observed that methacrylate based autopolymerized resin showed superior flexural strength and elastic moduli in comparison to both light polymerized and bis-acrylic composite based autopolymerized resin after fabrication and after storage, while the bis-acrylic composite based resin exhibited the least flexural strength and elastic moduli amongst the three
Summary
Provisional crowns and fixed partial dentures (FPDs) are essential components of fixed prosthodontic treatment (1). Definitive crown and fixed partial denture (FPD) restorations are usually a multiple-dental-visit procedure which requires that the interim restoration mimic the planned final restoration independent of the restorative material(s) used for that restoration (2). Temporary materials have changed immensely since their early days in the 1930s- from acrylics and premade crown forms to newer bis-acryl materials and computer-aided design/computer-aided manufacturing (CAD/ CAM) generated restorations (5). Though extensive research has been done regarding the fracture resistance of various available provisional restorative materials there is a paucity of information in the literature regarding the flexural strength and elastic moduli of provisional restorative materials in simulated in vivo conditions. This study has embarked upon the investigation of the flexural strength and elastic modulus of three common provisional crown materials in simulated intra oral conditions. The aim of this study was to evaluate and compare the flexural strength and elastic moduli of three provisional crown materials (methyl methacrylate based autopolymerized resin, bis acryl composite based autopolymerized resin and urethane dimethacrylate based light polymerized resin) at room temperature and study the change in flexural strength and elastic moduli of these three materials after storing in artificial saliva for 24 hours and 7 days
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