Effect of layer thickness on residual monomer release in polymerization of bulk-fill composites

• Published in: Polymers & polymer composites Vol. 29; no. 9_suppl; pp. S296 - S305
• Main Authors: Kılıç, Vahti, Hurmuzlu, Feridun, Ugur, Yılmaz, Cangul, Suzan
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01.11.2021; Sage Publications Ltd
• Subjects: Biocompatibility; Bisphenol A; Bulk polymerization; Calibration; Composite materials; Curing; Dentists; Elution; Ethanol; Layering; Light emitting diodes; Monomers; Polymerization; Resins; Stainless steels; Thickness; Viscosity; United States > US; Switzerland; Japan; Germany; Bulk-fill composite; photopolymerization; layer thickness; residual monomer; HPLC
• ISSN: 0967-3911; 1478-2391
• DOI: 10.1177/0967391121999588

The aim of the present study was to investigate and compare the quantity of residual monomers leached from the bulk-fill composites with different compositions polymerized at varying layer thickness. Three bulk-fill (X-tra-fil, Beautifil Bulk Restorative, Fill-Up) and a nanohybrid composite (Filtek Z550) were used for the study. The composite resin samples were prepared with a stainless steel mold. For each composite, two groups were constructed. The samples in the first group were prepared using the 2 + 2 mm layering technique. In the second group, the composite samples were applied as a 4 mm-thick one layer and polymerized. Then, each composite samples were kept in a 75% ethanol solution and residual monomers released from composite resins were analyzed with an HPLC device after 24hour and 1 month. The data were analyzed using Kruskal-Wallis and Mann-Whitney U tests. Except the Fill-Up, all of residual monomer elution from the bulk-fill composites was significantly affected by the layer thickness (p < 0.05). The greatest monomer release was detected at 1 month after polymerization as a single 4 mm layer for Beautifil Bulk Restorative. Fill-Up composite showed similar residual monomer release in polymerization at different layer thicknesses compared to other composite resins. In the 2 + 2 mm layering technique, the least monomer elution was detected in the Filtek Z550 composite group. While Bis-GMA was the most released monomer in X-tra fil composite, UDMA was the most released monomer in all other composite resins. During polymerization of the bulk-fill composite, the layer thickness of the composite applied may affect the amount of residual monomers released from the composite resins. Conventional composites may release less monomer than bulk-fill composites when used with layering.