Effect of the Degree of Conversion on Mechanical Properties and Monomer Elution from Self-, Dual- and Light-Cured Core Composites

Abstract

The objective of this work was to measure and correlate the degree of conversion (DC), mechanical properties and monomer elution from self-, dual- and light-cured core composites. Five samples of each of the following materials were prepared for each test: Clearfil (Core, Photo Core, Automix), Bisco (Core-Flo, Light-Core and Bis-Core). DC was determined using FTIR, compressive and flexural strength and modulus of elasticity using a universal testing machine and microhardness using Vickers hardness. Elution was measured using HPLC. One-way ANOVA with Tukey’s post-test and Pearson’s correlation were used to statistically analyze the data. DC of Clearfil-Dual (70.1%) and Clerafil-Photo (66.8%) were higher than Clearfil-Self (55.4%) and all Bisco materials (51.4–55.3%). Flexural strength of Clearfilwas higher than that of Bisco composites. The Microhardness of Clearfil-Dual (119.8VHN) and Clearfil-Photo (118.0VHN) were higher compared to other materials. The greatest elution was detected from self-cured materials. DC positively correlated to microhardness and compressive/flexural strength and negatively to BisGMA elution. Clearfil-Photo and Automix showed higher conversion, lower monomer elution and, generally, better mechanical properties. Self-cured composites should not be recommended for routine clinical use as their performance was inferior to dual- and light-cured composites. Microhardness may be used as an indicator of elution.

Monomer elution model of composite resin material

“…Its novelty stems from the development of a mathematical model that precisely describes the dynamics of monomer release from composite resin. While other authors have proposed different mechanisms underlying this process, as leaching was measured after 28 days only 6 (i.e., rather than at three different time intervals, as was done in this research), the obtained results represent the total amount of leached monomers, rather than delineating the evolution of this process over time. By performing measurements at several time points, it is possible to more precisely determine the release dynamics, as well as obtain the amount of monomer released at every stage, as indicated by other authors.…”

“…5 Incomplete composite resin polymerization and monomer leaching thus compromise clinical outcomes. Specifically, these adverse processes not only undermine the mechanical durability of the restoration, [6][7][8] but can also negatively impact the material biocompatibility (e.g., by exerting cytotoxic, genotoxic, mutagenic or estrogenic effects). In some patients, allergic reactions can also occur, such as allergic contact dermatitis and asthma.…”

“…5,6,15,16 Considering the harmful effects of substances leached from composite resins for tooth restoration, these phenomena have been extensively studied. [5][6][7][8][9][10][11][12][13][14][15][16][17] However, to our knowledge, a mathematical model describing the leaching of BisGMA monomer from composite resin has never been developed.…”

Effects of Sr/F-Bioactive Glass Nanoparticles and Calcium Phosphate on Monomer Conversion, Biaxial Flexural Strength, Surface Microhardness, Mass/Volume Changes, and Color Stability of Dual-Cured Dental Composites for Core Build-Up Materials

“…In general, composites with high DC may exhibit a low risk of releasing the unreacted toxic monomers from the materials [ 53 ]. The concerns of released monomers included cytotoxic, teratogenic, estrogenic, mutagenic, genotoxic effects, and allergic reactions depending upon the released substances [ 54 ].…”

Novel Polymerization of Dental Composites Using Near-Infrared-Induced Internal Upconversion Blue Luminescence

“…On the other hand, the microhardness tests show advantages in their simple techniques and ability to mutually assess DC and physical information [37][38][39]. Microhardness values have been proven to correspond with those spectroscopic methods and also correlate to mechanical properties including wear resistance, mechanical strengths, and stiffness of RBCs [40][41][42]. The depth profiles of microhardness are especially useful to investigate the extent of polymerization [37,43,44].…”