Changes in Strength Parameters of Composite Cements as Affected by Storage Temperature—A Review of the Literature

Abstract

Fixed restorations are now among the most common restorations in modern dental prosthodontics. The current view in prosthodontics of maximum preparation economy is causing an increased interest in the mechanical properties of cements. Among the most important properties of materials used for indirect cementation are mechanical properties, i.e., hardness and compressive strength. These properties can change as a result of changes in physical factors. The purpose of this study was to analyze the available literature on the effect of conditioning temperature of cements used for cementation of indirect fixed restorations on the durability of their bonding to dental tissues and their mechanical and physical properties. The following databases were used: Mendeley, PubMed, ResearchGate, National Library of Medicine, and Google Scholar. Analysis of the available literature was carried out according to the Prisma diagram program. Forty-eight articles were selected, which were the following types of studies: clinical reports, research article, and review articles. Some studies indicated that mechanical properties, such as flexural strength, polymerization shrinkage, and conversion factor, did not change after heating the composite material. According to some researchers, preheating the composite material increased its conversion degree, which consequently led to an increase in hardness and fracture toughness, an increase in flexural strength and an increase in elastic modulus, and an increase in abrasion resistance. Studies on changes in the mechanical and physical properties of composite materials, as well as composite cements, have not always provided clear answers, as there are still no laboratory and clinical studies that fully confirm the benefits of heating composite cements. Conducting studies evaluating the effect of elevated storage temperature on the strength parameters of cements, in conjunction with the type of material and its composition, could provide answers to many clinical questions that are still unresolved. If the benefits of heating cements were unequivocally confirmed in laboratory studies, this could open up many possibilities for improving the retention of fixed prosthetic restorations.

Examining the Impact of Preheating on the Fracture Toughness and Microhardness of Composite Resin: A Systematic Review

“…Additionally, three studies reveal no statistically significant difference in microhardness values [5,10,30]. Moreover, six studies report both an increase in microhardness and fracture toughness [4,6,11,14,24,29]. Furthermore, one study indicates an increase in microhardness, but no statistically significant difference in fracture toughness [32].…”

“…However, heating the composite resin results in an increase in microhardness at both the top and bottom surfaces, as elevated material temperature leads to more polymerization and hardening [36]. It is worth noting that some studies observed increased microhardness at temperatures ranging from 50°C to 60°C, while others showed either decreased or insignificant effects at different temperatures [6,9,16,22,24].…”

“…These variations could be attributed to several factors, including the presence of residual tensions induced by high temperatures. Such tensions have the potential to influence both the hardness of the material and its bonding characteristics [6]. This underscores the complexity of the interaction between preheating and microhardness in resin composites.…”

“…Therefore, it becomes essential to evaluate the mechanical characteristics of preheated resin composites, understanding how heat influences their resistance to fracture, attrition, and mastication forces. Existing research on this topic has yielded ambiguous and contradictory outcomes [6]; it appears that preheating or precooling procedures do not exert any discernible impact on the hardness and additional mechanical properties of resin composites [5].…”