Abstract
The novelty of this study consists in the formulation and characterization of three experimental dental composites (PM, P14M, P2S) for cervical dental lesion restoration compared to the commercial composites Enamel plus HRi® - En (Micerium S.p.A, Avengo, Ge, Italy), G-ænial Anterior® - Ge, (GC Europe N.V., Leuven, Belgium), Charisma® - Ch (Heraeus Kulzer, Berkshire, UK). The physio-chemical properties were studied, like the degree of conversion and the residual monomers in cured samples using FTIR-ATR (attenuated total reflectance) and HPLC-UV (ultraviolet detection), as well as the evaluation of the mechanical properties of the materials. The null hypothesis was that there would be no differences between experimental and commercial resin composites regarding the evaluated parameters. Statistical analysis revealed that water and saliva storage induced significant modifications of all mechanical parameters after three months for all tested materials, except for a few comparisons for each type of material. Storage medium seemed not to alter the values of mechanical parameters in comparison with the initial ones for: diametral tensile strength (DTS-saliva for Ge and PM, compressive strength (CS)-water for Ch, DTS-water and Young’s modulus YM-saliva for P14M and YM-water/ saliva for P2S (p > 0.05). Two of the experimental materials showed less than 1% residual monomers, which sustains good polymerization efficiency. Experimental resin composites have good mechanical properties, which makes them recommendable for the successful use in load-bearing surfaces of posterior teeth.
Highlights
The results reveal statistically significant lower percentages of residual double bonds (RDB) in experimental composites, compared with the values obtained for commercial ones [12]
The determination of RDB and the amount of residual monomers in dental composites are of great importance, as these parameters could be regarded as prognostic factors of the behaviour of dental restorations
Fewer residual double bonds were found to be present in experimental resin composites than in commercial ones
Summary
Resin composites have been proposed as an alternative to amalgam, gold and ceramic restorations because of their aesthetic and toxicological considerations [1,2].From a clinical point of view, posterior teeth restoration composites require good mechanical properties, such as a high viscosity of the composites and reduced polymerization shrinkage to avoid the degradation and fractured restoration marginal.Materials 2019, 12, 2109; doi:10.3390/ma12132109 www.mdpi.com/journal/materialsThe variation of forces in the case of posterior composites can be explained by differences, such as the chemical composition (of the organic phase and inorganic phase), distribution and size of the inorganic particles. [3].The higher is the fillers volume, the higher is the surface hardness and the compressive strength, and the increase of the elastic modules, which reduces the flowing ability [4].Studies show that this does not compensate the polymerization shrinkage, leading to high intrinsic stress, but there is a positive correlation between diametrical tensile strength and compressive strength [5].A restorative composite with high, mechanical properties should be resistant to masticatory forces in clinical situations [6]. The higher is the fillers volume, the higher is the surface hardness and the compressive strength, and the increase of the elastic modules, which reduces the flowing ability [4]. Studies show that this does not compensate the polymerization shrinkage, leading to high intrinsic stress, but there is a positive correlation between diametrical tensile strength and compressive strength [5]. A restorative composite with high, mechanical properties should be resistant to masticatory forces in clinical situations [6]. Scientific manipulation of resin composite composition and improvements in manufacturing technologies could enhance the mechanical properties and stability of the restorations
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