Hardness difference between thermo-cured polymethylmethacrylate (PMMA) and milled PMMA used in fixed temporary prostheses.

Abstract

One of the major challenges faced by dentists when creating provisional restorations is selecting a material that provides and meets the best properties, such as hardness, wear resistance, fracture resistance, color stability, tissue compatibility, among others. The most commonly used material is known as polymethyl methacrylate (PMMA), which is an acrylic resin that was previously available for use through conventional self-curing and heat-curing techniques. Nowadays, thanks to technological advancements, we have milled PMMA used in CAD/CAM techniques (Computer-Aided Design and Computer-Aided Manufacturing). The study of the hardness of heat-cured PMMA and milled PMMA for the fabrication of provisional restorations is important from a functional perspective, as these restorations are constantly exposed to functional loads. Objective: To determine the difference in hardness between heat-cured polymethyl methacrylate and milled PMMA used in fixed provisional prostheses. Materials and methods: A search was conducted in the PubMed and Google Scholar databases, under inclusion criteria: systematic reviews, meta-analyses, and in vitro studies published from 2014 to 2024. Results: Of the 68 studies identified, 9 articles were selected. It was demonstrated that milled PMMA presents higher hardness values compared to heat-cured PMMA. Conclusions: Provisional restorations fabricated using CAD/CAM milling show a superior hardness difference and multiple advantages, which are attributed to their composition and the type of processing before milling.