The elution and breakdown behavior of constituents from various light-cured composites

Abstract

Objectives

Constituents of dental composites can be released from dental fillings after polymerization. The aim of this study was to examine the time-related elution and breakdown of separable constituents of polymerized composites using deuterated solvents.

Method

Elution and breakdown of constituents were investigated with deuterated solvents methanol and water by gas chromatography/mass spectrometry of following composites for 180 days: Filtek™ Supreme XT, Filtek™ Supreme XT Flow, Tetric Ceram ® , Tetric Flow ® , Grandio ® , Grandio ® Flow.

Results

Within 180 days no compounds were formed as the products of breakdown. 19 compounds were identified as elution products: Bis-EMA, TEGDMA, DDDMA, EGDMA, MAA, BPA, CQ, HQME, DMABEE, CSA, BL, TEG, BHT, TINP, TPP, TPSB, DEDHTP, DCHP, ß-PHEA.

The highest concentration of Bis-EMA was measured for Tetric Flow ® in deuterated methanol on day 90 at 36.993 mmol/l and in deuterated water also on day 90 at 0.031 mmol/l.

The highest TEGDMA concentrations were measured for Grandio ® Flow in deuterated methanol on day 60 at 1.322 mmol/l and for Filtek™ Supreme XT Flow in deuterated water on day 3 at 0.689 mmol/l. The highest BPA concentration was measured for Tetric Flow ® in deuterated methanol on day 90 at 1.469 mmol/l. The highest BPA concentration was measured for Grandio ® in deuterated water on day 180 at 0.007 mmol/l.

Significance Examination of time-related elution indicates that various elution products (e.g. Bis-EMA, BPA) were only released in small quantities during the first 90 days, but in high quantities between day 90 and day 180.

Introduction

The use of resin based composites (RBCs) has increased tremendously in the last decade. Though considered by some to be well-tolerated biologically, there are reports in the literature of allergic side effects such as eczema, asthma or lichenoid reactions due to elution of methacrylate . Additionally, reports identify methacrylate as the cause of pulp inflammation . Methacrylates can even get into the circulatory system via the pulp or/and via the intestinal system after absorption from swallowed saliva .

Dentists, dental staff and patients are constantly exposed to methacrylates. During the processing, e.g. in the surgery or in laboratories, these substances also get into the air and can thus be absorbed via the lungs. Certainly the number of dentists and dental staff who suffer from contact allergies and respiratory complaints is increasing .

RBCs are composed of an organic matrix with embedded inorganic fillers . The organic matrix includes monomers (methacrylates) and other additives. The incorporation of inorganic fillers has resulted in materials with higher mechanical properties . In addition to the knowledge about the RBC-composition it is also important to know which of these ingredients are elutable. Only substances which can be released from RBC can cause side effects. One problem of the light-cured dental composite materials is the incomplete polymerization. The lower the degree of conversion of monomers, the higher the amounts of elutable residual monomers from the hardened composite . Variables which have an influence on the degree of polymerization are the composite shade, light energy delivered during curing and distance between the light source and sample surface . Furthermore during the polymerization new reaction products arise which can have a toxic/allergic potential. These can be non-cross-linked released ingredients of RBCs but also products which may be formed with the solvent during the elution process.

In this study the time-dependent elution and breakdown products of various RBCs was assessed using gas chromatography/mass spectrometry.

Deuterated solvents (deuterated water and deuterated methanol) were used to differentiate between elution and breakdown products. The deuteration means the substitution of individual or several hydrogen atoms of product and thus change its physical properties which enables to prove whether it is an elution or a breakdown product. Therefore the null hypothesis tested was that time related exposition of RBCs to deuterated solvents can verify the formation of breakdown products.

Methods

The solvents (deuterated water (D 2 O), deuterated methanol (CD 3 OD)) and reagent products were obtained from Merck, Darmstadt, Germany and of highest purity available.

Preparation of samples

From the six RBCs ( Table 1 ) specimens with a resulting surface of the cylinder of 90.4 mm 3 , of approximately 100 mg (thickness of 1.8 mm, diameter of 6 mm, color A2) were prepared by using a metal ring as sample carrier under laboratory conditions. Between the metal ring and specimens a plastic matrix strip was used (Frasaco, Tettnang, Germany) to avoid contact with the ring and also to dissolve the samples easier from the ring. The specimens were polymerized according to the instructions of the manufacturer of RBCs ( Table 1 ) by using a dental manual light-curing unit (Astralis 10 ® , Ivoclar Vivadent, high intensity halogen light, ca. 1200 mW/cm 2 , the light intensity was measured with Demetron ® Radiometer, Kerr, USA). The light guide tip was held as close as possible to the sample surface.

Table 1
Investigated dental materials, manufacturer and lot numbers; composition of each material based on manufacturer’s data; curing time recommended by manufacturer.
Composite; manufacturer; LOT Composition of material based on manufacturer’s data Curing time recommended by manufacturer
Filtek™ Supreme XT; 3M ESPE, Seefeld, Germany; 9YC Bis-GMA, UDMA, TEGDMA and Bis-EMA resins; silanized ceramic; silanized silicic acid; water, additives ≥ 20 s in layers of max 2 mm
Filtek™ Supreme XT Flow; 3M ESPE, Seefeld, Germany; 8HG Bis-GMA, TEGDMA and Bis-EMA, silanized ceramic; silanized silicic acid; dimethacrylate-polymer (functionalized); zirconium oxide powder glass (silanized), additives 20 s in layers of max 2 mm
Tetric Ceram ® ; Ivoclar Vivadent, Ellwangen, Germany; M03992 Bis-GMA, UDMA, TEGDMA and bis-EMA, barium glass, ytterbium trifluoride, mixed oxide, prepolymer, additives, catalysts, stabilizers, pigments 10 s at use high intensity halogen light ≥ 1000 mW/cm 2 in layers of max 2 mm
Tetric Flow ® ; Ivoclar Vivadent, Ellwangen, Germany; M10160 Bis-GMA, UDMA and DDDMA, barium glass, ytterbium trifluoride, mixed oxide, highly dispersed silicon dioxide, copolymer, additives, catalysts, stabilizers, pigments 10 s at use high intensity halogen light ≥ 1000 mW/cm 2 in layers of max 2 mm
Grandio ® ; VOCO GmbH, Cuxhaven, Germany; 0916205 Inorganic fillers in a methacrylate matrix (Bis-GMA, TEGDMA), additives 20 s per layer
Grandio ® Flow; VOCO GmbH, Cuxhaven, Germany; 0918340 Inorganic fillers in a methacrylate matrix (Bis-GMA, TEGDMA, HEDMA), additives 20 s per layer
Abbreviations: Bis-GMA, bisphenol-A-glycidyl-methacrylate; TEGDMA, triethylene glycol dimethacrylate; UDMA, urethane dimethacrylate; Bis-EMA, ethoxylated bisphenol-A-dimethacrylate; DDDMA, 1,10-decanediol dimethacrylate; HEDMA, hexanediol dimethacrylate.

Samples of each RBC ( n = 6) were prepared and randomly allocated to one of two groups: 1st group: deuterated methanol; 2nd group: deuterated water. Samples for each medium were incubated in separate vials. The specimens from the first group were incubated in deuterated methanol (100 mg/ml) at 37 °C for 1 d, 3 d, 7 d, 14 d, 30 d, 60 d, 90 d, 120 d, 150 d and 180 d. Caffeine (CF; 0.179 mg/ml) was added to the destruates and each aliquot was analyzed by gas chromatography/mass spectrometry. The medium was not renewed after each period.

The second group was incubated in deuterated water also at 37 °C for 1 d, 3 d, 7 d, 14 d, 30 d, 60 d, 90 d, 120 d, 150 d and 180 d. Caffeine (CF; 0.179 mg/ml) was added to the destruats and each aliquot was analyzed by gas chromatography/mass spectrometry. The medium was not renewed after each period.

GC/MS analysis

The analysis of the eluates was performed on a Finnigan Trace GC ultra gas chromatograph connected to DSQ mass spectrometer (Thermo Electron, Dreieich, Germany). A FactorFour ® capillary column (length 25 m, inner diameter 0.25 mm, coating 0.25 μm; Varian, Darmstadt, Germany) was used as capillary column for GC. The GC oven was heated from 50 °C (2 min isotherm) to 300 °C (5 min isotherm) with a rate of 10 °C/min and 1 μl of the solution was injected with a split of 1:30. Helium was used as carrier gas at a constant flow rate of 1 ml/min. The temperature of the split–splitless injector as well as of the direct coupling to the mass spectrometer was 250 °C. MS was operated in electron ionization mode (EI, 70 eV), ion source was operated at 200 °C; only positive ions were scanned. Scan ran over the range m/z 50–500 at a scan rate of 1 scan/s for scans operated in full scan mode to qualify analytes. The results were referred to an internal CF standard (0.1 mg/ml CF = 100%), which allows to determine the relative quantities of substances released from various resin-based materials. All eluates were analyzed five times. The integration of the chromatograms was carried out over the base peak or other characteristic mass peaks of the compounds, and the results were normalized by means of the internal CF standard. Identification of the various substances was achieved by comparison of their mass spectra with those of reference compounds, the NIST/EPA library, literature data and/or by chemical analysis of their fragmentation pattern . Detection limit for each compound is given in Table 2 .

Table 2
Abbreviations of compounds found in RBCs; limit of detection (mmol/l).
Compound abbreviation Compound Limit of detection
Bis-EMA (basic monomer) Ethoxylated bisphenol-A-dimethacrylate 0.003
TEGDMA (comonomer) Triethylene glycol dimethacrylate 0.001
DDDMA (comonomer) 1,10-Decandiol dimethacrylate 0.0005
EGDMA (comonomer) Ethylene glycol dimethacrylate 0.004
MAA (comonomer) Methacrylic acid 0.001
BPA (decomposition product of monomers) Bisphenol A 0.00008
CQ (photoinitiator) Camphorquinone 0.0006
HQME (inhibitor) Hydroquinone methyl ether 0.0003
DMABEE (coinitiator) 4- N , N -dimethylaminobenzoic acid butyl ethoxy ester 0.0003
CSA (reaction product of CQ) Campheracid anhydride 0.0008
BL (photoinitiator) Benzil 0.0005
TEG (decomposition product of TEGDMA) Triethylene glycol 0.002
BHT (inhibitor, antioxidant) 2,6-Di- t -butyl-4-methyl phenol 0.00005
TINP (photostabilisator) 2(2′-Hydroxy-5′-methylphenyl)benzotriazol, tinuvin p 0.0004
TPP (catalysator residual of Bis-GMA synthesis) Triphenyl phosphane 0.001
TPSB (catalysator residual of Bis-GMA synthesis) Triphenyl stibane 0.0006
DEDHTP (softener) Diethyl-2,5-dihydroxiterephthalate 0.0002
DCHP (softener) Dicyclohexyl phthalate 0.0004
ß-PEA ß-phenoxyethylacrylate 0.0007

Calculations and statistics

The results are presented as means ± standard deviation (SD). The statistical significance ( α = 0.05) of the differences between the experimental groups was tested using the two-way analysis of variance (ANOVA) .

Methods

The solvents (deuterated water (D 2 O), deuterated methanol (CD 3 OD)) and reagent products were obtained from Merck, Darmstadt, Germany and of highest purity available.

Preparation of samples

From the six RBCs ( Table 1 ) specimens with a resulting surface of the cylinder of 90.4 mm 3 , of approximately 100 mg (thickness of 1.8 mm, diameter of 6 mm, color A2) were prepared by using a metal ring as sample carrier under laboratory conditions. Between the metal ring and specimens a plastic matrix strip was used (Frasaco, Tettnang, Germany) to avoid contact with the ring and also to dissolve the samples easier from the ring. The specimens were polymerized according to the instructions of the manufacturer of RBCs ( Table 1 ) by using a dental manual light-curing unit (Astralis 10 ® , Ivoclar Vivadent, high intensity halogen light, ca. 1200 mW/cm 2 , the light intensity was measured with Demetron ® Radiometer, Kerr, USA). The light guide tip was held as close as possible to the sample surface.

Table 1
Investigated dental materials, manufacturer and lot numbers; composition of each material based on manufacturer’s data; curing time recommended by manufacturer.
Composite; manufacturer; LOT Composition of material based on manufacturer’s data Curing time recommended by manufacturer
Filtek™ Supreme XT; 3M ESPE, Seefeld, Germany; 9YC Bis-GMA, UDMA, TEGDMA and Bis-EMA resins; silanized ceramic; silanized silicic acid; water, additives ≥ 20 s in layers of max 2 mm
Filtek™ Supreme XT Flow; 3M ESPE, Seefeld, Germany; 8HG Bis-GMA, TEGDMA and Bis-EMA, silanized ceramic; silanized silicic acid; dimethacrylate-polymer (functionalized); zirconium oxide powder glass (silanized), additives 20 s in layers of max 2 mm
Tetric Ceram ® ; Ivoclar Vivadent, Ellwangen, Germany; M03992 Bis-GMA, UDMA, TEGDMA and bis-EMA, barium glass, ytterbium trifluoride, mixed oxide, prepolymer, additives, catalysts, stabilizers, pigments 10 s at use high intensity halogen light ≥ 1000 mW/cm 2 in layers of max 2 mm
Tetric Flow ® ; Ivoclar Vivadent, Ellwangen, Germany; M10160 Bis-GMA, UDMA and DDDMA, barium glass, ytterbium trifluoride, mixed oxide, highly dispersed silicon dioxide, copolymer, additives, catalysts, stabilizers, pigments 10 s at use high intensity halogen light ≥ 1000 mW/cm 2 in layers of max 2 mm
Grandio ® ; VOCO GmbH, Cuxhaven, Germany; 0916205 Inorganic fillers in a methacrylate matrix (Bis-GMA, TEGDMA), additives 20 s per layer
Grandio ® Flow; VOCO GmbH, Cuxhaven, Germany; 0918340 Inorganic fillers in a methacrylate matrix (Bis-GMA, TEGDMA, HEDMA), additives 20 s per layer
Abbreviations: Bis-GMA, bisphenol-A-glycidyl-methacrylate; TEGDMA, triethylene glycol dimethacrylate; UDMA, urethane dimethacrylate; Bis-EMA, ethoxylated bisphenol-A-dimethacrylate; DDDMA, 1,10-decanediol dimethacrylate; HEDMA, hexanediol dimethacrylate.

Samples of each RBC ( n = 6) were prepared and randomly allocated to one of two groups: 1st group: deuterated methanol; 2nd group: deuterated water. Samples for each medium were incubated in separate vials. The specimens from the first group were incubated in deuterated methanol (100 mg/ml) at 37 °C for 1 d, 3 d, 7 d, 14 d, 30 d, 60 d, 90 d, 120 d, 150 d and 180 d. Caffeine (CF; 0.179 mg/ml) was added to the destruates and each aliquot was analyzed by gas chromatography/mass spectrometry. The medium was not renewed after each period.

The second group was incubated in deuterated water also at 37 °C for 1 d, 3 d, 7 d, 14 d, 30 d, 60 d, 90 d, 120 d, 150 d and 180 d. Caffeine (CF; 0.179 mg/ml) was added to the destruats and each aliquot was analyzed by gas chromatography/mass spectrometry. The medium was not renewed after each period.

GC/MS analysis

The analysis of the eluates was performed on a Finnigan Trace GC ultra gas chromatograph connected to DSQ mass spectrometer (Thermo Electron, Dreieich, Germany). A FactorFour ® capillary column (length 25 m, inner diameter 0.25 mm, coating 0.25 μm; Varian, Darmstadt, Germany) was used as capillary column for GC. The GC oven was heated from 50 °C (2 min isotherm) to 300 °C (5 min isotherm) with a rate of 10 °C/min and 1 μl of the solution was injected with a split of 1:30. Helium was used as carrier gas at a constant flow rate of 1 ml/min. The temperature of the split–splitless injector as well as of the direct coupling to the mass spectrometer was 250 °C. MS was operated in electron ionization mode (EI, 70 eV), ion source was operated at 200 °C; only positive ions were scanned. Scan ran over the range m/z 50–500 at a scan rate of 1 scan/s for scans operated in full scan mode to qualify analytes. The results were referred to an internal CF standard (0.1 mg/ml CF = 100%), which allows to determine the relative quantities of substances released from various resin-based materials. All eluates were analyzed five times. The integration of the chromatograms was carried out over the base peak or other characteristic mass peaks of the compounds, and the results were normalized by means of the internal CF standard. Identification of the various substances was achieved by comparison of their mass spectra with those of reference compounds, the NIST/EPA library, literature data and/or by chemical analysis of their fragmentation pattern . Detection limit for each compound is given in Table 2 .

Table 2
Abbreviations of compounds found in RBCs; limit of detection (mmol/l).
Compound abbreviation Compound Limit of detection
Bis-EMA (basic monomer) Ethoxylated bisphenol-A-dimethacrylate 0.003
TEGDMA (comonomer) Triethylene glycol dimethacrylate 0.001
DDDMA (comonomer) 1,10-Decandiol dimethacrylate 0.0005
EGDMA (comonomer) Ethylene glycol dimethacrylate 0.004
MAA (comonomer) Methacrylic acid 0.001
BPA (decomposition product of monomers) Bisphenol A 0.00008
CQ (photoinitiator) Camphorquinone 0.0006
HQME (inhibitor) Hydroquinone methyl ether 0.0003
DMABEE (coinitiator) 4- N , N -dimethylaminobenzoic acid butyl ethoxy ester 0.0003
CSA (reaction product of CQ) Campheracid anhydride 0.0008
BL (photoinitiator) Benzil 0.0005
TEG (decomposition product of TEGDMA) Triethylene glycol 0.002
BHT (inhibitor, antioxidant) 2,6-Di- t -butyl-4-methyl phenol 0.00005
TINP (photostabilisator) 2(2′-Hydroxy-5′-methylphenyl)benzotriazol, tinuvin p 0.0004
TPP (catalysator residual of Bis-GMA synthesis) Triphenyl phosphane 0.001
TPSB (catalysator residual of Bis-GMA synthesis) Triphenyl stibane 0.0006
DEDHTP (softener) Diethyl-2,5-dihydroxiterephthalate 0.0002
DCHP (softener) Dicyclohexyl phthalate 0.0004
ß-PEA ß-phenoxyethylacrylate 0.0007
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Nov 25, 2017 | Posted by in Dental Materials | Comments Off on The elution and breakdown behavior of constituents from various light-cured composites
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