Monomer elution in relation to degree of conversion for different types of composite.
OBJECTIVE
The aim of this study was to determine the degree of conversion (DC) and the monomer release of three composite types when employed following a layer- and bulk-filling technique.


METHODS
The release of monomers from a 'conventional paste-like' (Filtek Z250), a 'conventional flowable' (Filtek Supreme XTE Flowable) and a 'bulk-fill' flowable composite (Filtek Bulk Fill Flowable) from the same manufacturer (3M ESPE, Seefeld, Germany) was determined. Ten cylindrical specimens per composite were built, either in two 2-mm layers or in one 4-mm bulk. DC was measured at the specimen top and bottom surface using micro-Raman spectroscopy, after which the specimens were immersed in 2 ml absolute ethanol for 24 h at 37 °C. This solution was refreshed weekly during six weeks and the concentration of BisGMA, BisEMA(6), BisPMA, UDMA, TEGDMA and BPA was determined by liquid chromatography/mass spectroscopy.


RESULTS
DC at the specimen top and bottom was similar except for the bulk-fill technique, which resulted in significantly lower DC at the specimen bottom. The release of BisGMA and TEGDMA was initially very high, but rapidly dropped in the second week. In contrast, the release of BisPMA and UDMA increased initially, but then declined towards the sixth week. BisEMA(6) release was relatively steady over time. All composites released small amounts of BPA. The total monomer release was significantly lower for the layer- than the bulk-filling technique.


CONCLUSIONS
The slightly reduced degree of conversion at 4-mm depth resulted in a higher monomer elution when the composite was applied following a bulk-fill application method.


CONCLUSIONS
Applying a flowable and a bulk-fill composite following a bulk-fill application method resulted in a significantly reduced degree of conversion at the bottom of polymerized composite specimens when compared to a layer-application method. This reduced polymerization degree was reflected in significantly increased monomer release.
KU Leuven BIOMAT, Department of Oral Health Sciences, KU Leuven (University of Leuven) & Dentistry, University Hospitals Leuven, Kapucijnenvoer 7, box 7001, 3000 Leuven, Belgium; Department of Operative Dentistry and Endodontics, Faculty of Dentistry, Mahidol University, No.6, Yothi road, Rajthawee, Bangkok 10400, Thailand.
Pong
P
Pongprueksa
KU Leuven BIOMAT, Department of Oral Health Sciences, KU Leuven (University of Leuven) & Dentistry, University Hospitals Leuven, Kapucijnenvoer 7, box 7001, 3000 Leuven, Belgium.
Jan
J
De Munck
Centre for Environmental and Health, Department of Public Health and Primary Care, KU Leuven (University of Leuven), Kapucijnenvoer 35, 3000 Leuven, Belgium.
Radu Corneliu
RC
Duca
Centre for Environmental and Health, Department of Public Health and Primary Care, KU Leuven (University of Leuven), Kapucijnenvoer 35, 3000 Leuven, Belgium.
Katrien
K
Poels
Toxicological Center, University of Antwerp, Universiteitsplein 1, D.S.551, 2610 Wilrijk, Belgium.
Adrian
A
Covaci
Centre for Environmental and Health, Department of Public Health and Primary Care, KU Leuven (University of Leuven), Kapucijnenvoer 35, 3000 Leuven, Belgium.
Peter
P
Hoet
Centre for Environmental and Health, Department of Public Health and Primary Care, KU Leuven (University of Leuven), Kapucijnenvoer 35, 3000 Leuven, Belgium.
Lode
L
Godderis
KU Leuven BIOMAT, Department of Oral Health Sciences, KU Leuven (University of Leuven) & Dentistry, University Hospitals Leuven, Kapucijnenvoer 7, box 7001, 3000 Leuven, Belgium.
Bart
B
Van Meerbeek
KU Leuven BIOMAT, Department of Oral Health Sciences, KU Leuven (University of Leuven) & Dentistry, University Hospitals Leuven, Kapucijnenvoer 7, box 7001, 3000 Leuven, Belgium. Electronic address: kirsten.vanlanduyt@med.kuleuven.be.
Kirsten L
KL
Van Landuyt
D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D058105:Polymerization; D011109:Polymethacrylic Acids / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry; D013499:Surface Properties; D053719:Tandem Mass Spectrometry
D003188:Composite Resins; D003764:Dental Materials; C444701:Filtek Z250; D008689:Methacrylates; D011109:Polymethacrylic Acids; D011140:Polyurethanes; C111840:flowable hybrid composite; C029824:urethane dimethacrylate luting resin; C020946:triethylene glycol dimethacrylate; C041979:2,2-bis-(4-(2-methacryloxyethoxy)phenyl)propane; D000431:Ethanol; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate
BPA; BisEMA(6); BisGMA; BisPMA; Degree of conversion; LC/MS–MS; Monomer elution; TEGDMA; UDMA