Effect of Pre-Heating on the Monomer Elution and Porosity of Conventional and Bulk-Fill Resin-Based Dental Composites

Abstract

The pre-heating of dental resin-based composites (RBCs) improves adaptability to cavity walls, reducing microleakages. However, the rapid cooling of the pre-heated RBC may change the polymerization kinetics, and thus the final network configuration of the RBC. It is well known that unreacted monomers remaining in the set RBC can leach into the oral cavity. However, it is still not clear how the pre-heating and cooling of RBCs alter monomer elution (ME). Thus, the purpose was to determine the ME from room-temperature and pre-heated RBCs, in addition to determining the closed porosity (CP) volume. Bulk-filled RBCs and layered conventional RBC samples were prepared. The pre-polymerization temperature was set at 24 °C and 55/65 °C. The ME from RBC samples was assessed with high-performance liquid chromatography using standard monomers. CP was measured with micro-computed tomography. ME decreased significantly from bulk fills and increased from layered samples as a result of pre-heating. Pre-heating was unfavorable in terms of CP in most RBCs. Based on the effect size analysis, ME and CP were greatly influenced by both material composition, pre-polymerization temperature, and their interaction. While the pre-heating of high-viscosity bulk-fill RBCs is advantageous from a clinical aspect regarding biocompatibility, it increases CP, which is undesirable from a mechanical point of view.

Effect of repeated preheating on monomer elution from a bulk-fill composite resin

“…In the present study, preheating of bulk-fill composites significantly reduced the amount of monomer elution, which is consistent with previous studies. 11 , 29 Dunavári et al 29 found that preheating significantly reduced the amount of UDMA and BisGMA monomer elution from Filtek One Bulk Fill Restorative composite resin, similar to the present study. In contrast, monomer elution increased when conventional composite resins were preheated.…”

“…In the present study, elution of BisGMA was also detected; even though it was not listed in the monomers specified by the manufacturer, UDMA elution was higher than that in previous studies. 28 , 29 BisGMA exhibits high viscosity owing to its high molecular weight and strong intramolecular hydrogen bonding ability. However, the lower viscosity and higher double bond concentration of UDMA results in a high degree of conversion and crosslinking density.…”

Does Preheating Influence the Cytotoxic Potential of Dental Resin Composites?

“…A recent study found distinct monomer release from preheated conventional RBCs stratified in 2 mm layers compared to 4 mm thick bulk-fill RBCs [ 16 ]. The extent of leached monomers from the tested room temperature bulk-fill RBC samples was significantly greater compared to the preheated specimens.…”

“…The extent of leached monomers from the tested room temperature bulk-fill RBC samples was significantly greater compared to the preheated specimens. In contrast, stratified conventional RBCs showed an increased monomer elution from the preheated samples [ 16 ]. However, it was concluded that the absolute amount of eluted resinous substances was strongly dependent on the RBC’s composition and not related to the mode of application [ 16 ].…”

“…In contrast, stratified conventional RBCs showed an increased monomer elution from the preheated samples [ 16 ]. However, it was concluded that the absolute amount of eluted resinous substances was strongly dependent on the RBC’s composition and not related to the mode of application [ 16 ]. Eluted resin monomers may have side effects such as skin, mucous membranes, and eye irritation [ 17 ].…”