Mechanical properties of polymethyl methacrylate as a denture base: Conventional versus CAD-CAM resin e A systematic review and meta-analysis of in vitro studies

摘要

Statement of problem. The development of polymethyl methacrylate (PMMA) computer-aided design and computer-aided manufacturing (CAD-CAM) resin blocks with reported improved mechanical properties has simplified complete denture production. However, whether the objective of improved mechanical properties has been achieved compared with conventional heat-polymerized PMMA is not yet clear. Purpose. The purpose of this systematic review and meta-analysis was to evaluate the mechanical properties of denture base resins manufactured by conventional heat-polymerization and by CAD-CAM in terms of flexural strength, flexural modulus, and surface roughness. Material and methods. Electronic databases (PubMed/MEDLINE, Scopus, Web of Science) were independently searched by 2 researchers for relevant studies published up to November 2020. The population, intervention, comparison, and outcome (PICO) question was, "Does the conventionally manufactured, heat-polymerized PMMA resin, as a denture base, demonstrate the same mechanical properties as the CAD -CAM resin block?" In addition, a meta-analysis was based on the inverse variance method. Flexural strength, flexural modulus, and surface roughness were analyzed through the continuous outcome evaluated by mean difference and standard deviation, with 95 confidence intervals. To evaluated heterogeneity, the I2 value (50=moderate and >75=high) and the P value were considered. P<.10 indicated statistical difference for heterogeneity. The effects of meta-analysis were based on the results of heterogeneity as per the studies. Results. Thirteen in vitro studies were included in the analysis. A total of 507 specimens were evaluated, 222 conventional and 285 CAD-CAM. In terms of flexural strength, the data showed no significant difference when conventional heat-polymerized PMMA was compared with CAD -CAM PMMA resins (P=.06; mean difference=18.28; 95 confidence interval:-0.42 to 36.97). In terms of flexural modulus, there was a significant difference for the CAD-CAM PMMA group (P=.01; mean difference=589.22; 95 confidence interval: 117.95 to 1060.48). In terms of surface roughness, a significant difference was observed between the groups (P=.02; mean difference=-0.53; 95 confidence interval:-0.97 to-0.09) with the conventional heat-polymerized PMMA resin having higher surface roughness values. Conclusions. The mechanical properties of CAD-CAM PMMA resins were generally improved when compared with heat-polymerized polymethyl methacrylate resin. (J Prosthet Dent 2022;128:1221-9)