Effect of layer thickness on the elution of bulk-fill composite components.
An increment layering technique in a thickness of 2mm or less has been the standard to sufficiently convert (co)monomers. Bulk fill resin composites were developed to accelerate the restoration process by enabling up to 4mm thick increments to be cured in a single step. The aim of the present study is to investigate the effect of layer thickness on the elution of components from bulk fill composites.



The composites ELS Bulk fill, SDR Bulk fill and Venus Bulkfill were polymerized according to the instruction of the manufacturers. For each composite three groups with four samples each (n=4) were prepared: (1) samples with a layer thickness of 2mm; (2) samples with a layer thickness of 4mm and (3) samples with a layer thickness of 6mm. The samples were eluted in methanol and water for 24h and 7 d. The eluates were analyzed by gas chromatography/mass spectrometry (GC/MS).



A total of 11 different elutable substances have been identified from the investigated composites. Following methacrylates showed an increase of elution at a higher layer thickness: TEGDMA (SDR Bulk fill, Venus Bulk fill), EGDMA (Venus Bulk fill). There was no significant difference in the elution of HEMA regarding the layer thickness. The highest concentration of TEGDMA was 146μg/mL for SDR Bulk fill at a layer thickness of 6mm after 7 d in water. The highest HEMA concentration measured at 108μg/mL was detected in the methanol eluate of Venus Bulk fill after 7 d with a layer thickness of 6mm.



A layer thickness of 4mm or more can lead to an increased elution of some bulk fill components, compared to the elution at a layer thickness of 2mm.
Department of Operative/Restorative Dentistry, Periodontology and Pedodontics, Ludwig-Maximilians-University of Munich, Goethestr. 70, 80336 Munich, Germany; Walther-Straub-Institute of Pharmacology and Toxicology, Nussbaumstr. 26, 80336 Munich, Germany.
Lena
L
Rothmund
Department of Operative/Restorative Dentistry, Periodontology and Pedodontics, Ludwig-Maximilians-University of Munich, Goethestr. 70, 80336 Munich, Germany; Walther-Straub-Institute of Pharmacology and Toxicology, Nussbaumstr. 26, 80336 Munich, Germany.
Franz-Xaver
FX
Reichl
Department of Operative/Restorative Dentistry, Periodontology and Pedodontics, Ludwig-Maximilians-University of Munich, Goethestr. 70, 80336 Munich, Germany.
Reinhard
R
Hickel
Department of Operative/Restorative Dentistry, Periodontology and Pedodontics, Ludwig-Maximilians-University of Munich, Goethestr. 70, 80336 Munich, Germany; Walther-Straub-Institute of Pharmacology and Toxicology, Nussbaumstr. 26, 80336 Munich, Germany.
Panorea
P
Styllou
Department of Operative/Restorative Dentistry, Periodontology and Pedodontics, Ludwig-Maximilians-University of Munich, Goethestr. 70, 80336 Munich, Germany; Walther-Straub-Institute of Pharmacology and Toxicology, Nussbaumstr. 26, 80336 Munich, Germany.
Marianthi
M
Styllou
Walther-Straub-Institute of Pharmacology and Toxicology, Nussbaumstr. 26, 80336 Munich, Germany; Bundeswehr Institute of Pharmacology and Toxicology, Neuherbergstr. 11, 80937 Munich, Germany.
Kai
K
Kehe
Department of Operative/Restorative Dentistry, Periodontology and Pedodontics, Ludwig-Maximilians-University of Munich, Goethestr. 70, 80336 Munich, Germany; Walther-Straub-Institute of Pharmacology and Toxicology, Nussbaumstr. 26, 80336 Munich, Germany.
Yang
Y
Yang
Department of Operative/Restorative Dentistry, Periodontology and Pedodontics, Ludwig-Maximilians-University of Munich, Goethestr. 70, 80336 Munich, Germany; Walther-Straub-Institute of Pharmacology and Toxicology, Nussbaumstr. 26, 80336 Munich, Germany. Electronic address: christof.hoegg@lrz.uni-muenchen.de.
Christof
C
Högg
D003188:Composite Resins; D008422:Materials Testing; D008689:Methacrylates; D058105:Polymerization
D003188:Composite Resins; D008689:Methacrylates
Bulk-fill composite; Comonomer; Elution; Layer thickness