ABSTRACT
The polymerization initiators for resins cured using visible light usually consist of a photosensitizer, primarily camphorquinone (CQ), and a reducing agent, which is often a tertiary amine (DMPT, DMAEMA), while the initiator used for self-curing resins consists of benzoyl peroxide (BPO) and a tertiary amine (DMPT). The genotoxicities of camphorquinone (CQ), benzoyl peroxide (BPO), dimethyl-para-toluidine (DMPT), 2-dimethylamino-ethyl-methacrylate (DMAEMA), and 1-allyl-2-thiourea (ATU) were examined using the bioluminescent bacterial genotoxicity test. 4-Nitroquinoline-N-oxide (4NQO) was prepared for comparison with these chemicals. Acetone solutions of the five polymerization initiators and 4NQO were prepared. Benzoyl peroxide (BPO), dimethyl-para-toluidine (DMPT), and 1-allyl-2-thiourea (ATU) showed significant genotoxic activity at 24 h in the bioluminescent bacterial genotoxicity test, at concentrations of approximately 5 microM, 4 mM, and 1 mM, respectively. 2-Dimethyloamino-ethyl-methacrylate (DMAEMA) did not have genotoxic activity and CQ had questionable genotoxic activity. In comparison, 4NQO had strong genotoxicity, at 4 microM, roughly the same as that of BPO. Therefore, BPO should be used carefully in clinical dentistry.
Subject(s)
Biocompatible Materials/toxicity , Composite Resins/toxicity , Dental Materials/toxicity , Mutagenicity Tests , 4-Nitroquinoline-1-oxide/chemistry , 4-Nitroquinoline-1-oxide/toxicity , Acetone/chemistry , Benzoyl Peroxide/chemistry , Benzoyl Peroxide/toxicity , Biocompatible Materials/chemistry , Camphor/analogs & derivatives , Camphor/chemistry , Camphor/toxicity , Dose-Response Relationship, Drug , Ethylamines/chemistry , Ethylamines/toxicity , In Vitro Techniques , Inhibitory Concentration 50 , Light , Methacrylates/chemistry , Methacrylates/toxicity , Molecular Structure , Photosensitizing Agents/toxicity , Quinolones/chemistry , Quinolones/toxicity , Reducing Agents/chemistry , Reducing Agents/toxicity , Solutions/chemistry , Sulfonium Compounds/toxicity , Thiourea/analogs & derivatives , Thiourea/chemistry , Thiourea/toxicity , Toluidines/chemistry , Toluidines/toxicityABSTRACT
OBJECTIVES: This study was performed to determine the compositions of commercial temporary restorative resins and to evaluate the leachability of plasticizer and residual monomer from them. METHODS: The chemicals in four commercial temporary restorative resins (Dura Seal, Fit Seal, Plast Seal Quick, and Poly Seal) were detected by GCMS and HPLC. The amounts of plasticizers and residual monomers that leached from cured resin samples immersed in ethanol for 1 h to 14 d were determined by HPLC. RESULTS: Phthalate esters used as plasticizers contained 40-55 wt% either di-n-butyl phthalate (DBP) or butyl phthalyl butyl glycolate. The resin monomer included methyl methacrylate (MMA) or a mixture of MMA and 2-hydroxyethyl methacrylate (HEMA); 1,3-butanediol dimethacrylate was added as a cross-linking agent. Each resin contained 40-60 wt% monomer. The amounts of phthalate esters leached increased with immersion time up to 7 d, reaching 120-190 microg/mg, and did not change subsequently. The residual monomers leached gradually for up to 3d and did not change subsequently. The amount of leached residual monomer (MMA, HEMA) was 20-90 microg/mg after 3d storage. More than 50% of the leachable plasticizers and monomers were eluted from the cured resins within 24 and 3 h, respectively. CONCLUSIONS: The amounts of leached plasticizers and residual monomers were extremely large compared with the concentrations of endocrine disrupters and their potentially genotoxic effects. Therefore, it is very important to evaluate the leachability of these compounds from temporary restorative resins.
Subject(s)
Acrylic Resins/chemistry , Dibutyl Phthalate/analogs & derivatives , Methylmethacrylate/chemistry , Plasticizers/chemistry , Butylene Glycols/chemistry , Chromatography, High Pressure Liquid , Dental Restoration, Temporary , Dibutyl Phthalate/chemistry , Diffusion , Gas Chromatography-Mass Spectrometry , Humans , Materials Testing , Methacrylates/chemistry , Polymethyl Methacrylate/chemistry , Resins, Synthetic/chemistry , Time FactorsABSTRACT
Thermal analysis was used to measure the characteristics of dental resins cured with the use of a new light-activation unit equipped with high illuminant blue light-emitting diodes (LEDs). The characteristics were compared with those of resins cured with the use of two conventional halogen lamp units. The prepared base monomer consisted of a mixture of Bis-GMA and TEGDMA (60:40 by weight), with 0.5 wt% CQ/DMPT or CQ/DMAEMA. The two experimental visible-light-cured resins were polymerized for 40 s. Differential scanning calorimetry (DSC) was used to examine the thermal characteristics of the cured resins. The activation energy for the decomposition of the dental resin was calculated from the peaks of the endothermic curves obtained when the specimens were heated at three different rates (5, 10, and 15 C/min) during DSC. The activation energies calculated for the LED-cured specimens were more than 220 kJ/mol; specimens cured with the use of the halogen units had activation energies of less than 192 kJ/mol. The Knoop hardness number (KHN) of the same specimens was measured, and was higher with the blue LED units than with halogen lamp units. Therefore, dental resins cured using blue LEDs have a higher degree of polymerization and more stable three-dimensional structures than those cured with halogen lamps.
