Abstract
Unreacted monomers eluted from resin-based restorative materials have been considered a reason of local and systemic adverse reactions. This study was designed to determine the effect of finishing and polishing procedures on the elution of Bis-GMA, TEGDMA, UDMA, and HEMA monomers from compomer and bulk-fill composite resins. Bulk-fill composite (3M ESPE GmbH, Seefeld, Germany) and compomer (Dentsply DeTrey GmbH, Konstanz, Germany) specimens with 3 × 4 mm diameters were prepared. The specimens were randomly divided into two groups, and finishing-polishing procedures were applied only to the experimental groups. Release of residual monomers was analyzed by using High-Performance Liquid Chromatography (HPLC) after 24, 48, and 72 hours. Repeated measures ANOVA and Tukey post hoc tests were used for comparisons. Finishing and polishing procedures had a significant effect on reducing the quantity of UDMA release in the Filtek™ Bulk Fill composite and Bis-GMA, HEMA, and TEGDMA in the Dyract XP compomer (p < 0.05). The restorative materials investigated here are not chemically stable after polymerization, and concentrations of eluted monomers may reach critical toxicity levels even after one restoration placement. Finishing and polishing procedures are mandatory to reduce residual monomers.
Highlights
In the early 1990s, polyacid-modified composite resins are introduced to combine the superior mechanical properties of composite resins and fluoride release of glass-ionomer cements to overcome the disadvantages such as water sensitivity and physical strength of glass ionomer cements [1]
It is known that atmospheric oxygen inhibits the polymerization of monomers. This results in an “oxygen inhibition layer (OIL)” on the surface of resin-based restorative materials which are rich in unreacted monomers [6]
High-Performance Liquid Chromatography (HPLC) analysis demonstrated that residual monomers were leached from resin-based restorative materials and the quantity of residual monomers could be reduced with finishing and polishing procedures
Summary
In the early 1990s, polyacid-modified composite resins (compomers) are introduced to combine the superior mechanical properties of composite resins and fluoride release of glass-ionomer cements to overcome the disadvantages such as water sensitivity and physical strength of glass ionomer cements [1]. The polymerization of resin-based restorative materials is the end product of a chemical reaction between the methacrylate resin monomers that results in the formation of a rigid and highly cross-linked polymer network [5]. It is known that atmospheric oxygen inhibits the polymerization of monomers This results in an “oxygen inhibition layer (OIL)” on the surface of resin-based restorative materials which are rich in unreacted monomers [6]. The degree of conversion of monomer to polymer in resin-based restorative materials varies between 55% and 80%, and this rate decreases to 35% in the presence of an OIL [7]. OIL could be minimized by blocking air contact with the use of matrix strips or glycerin before curing; since there is oxygen already present within the resin material, the most effective method to eliminate the OIL is to finish and polish the surface after curing [8, 9]. Finishing and polishing procedures are essential for the elimination of the resin-rich outer surface [8,9,10,11,12]
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