Investigation of Toxic Effects and Mechanisms of Three Dental Resin Monomers

• Main Authors: Hsiao-Hua Chang, 張曉華
• Other Authors: Jiiang-Huei Jeng
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/44889698559909504247

博士 === 臺灣大學 === 臨床牙醫學研究所 === 98 === Abstract Resin-containing products are extensively applied in dental practice. Monomers released from these materials may cause various adverse biological effects. Among which triethylene glycol dimethacrylate (TEGDMA), 2-hydroxyethyl methacrylate (HEMA) and urethane dimethacrylate (UDMA) are three principal resin monomers and also the major components released from various dental resin materials. The toxic effects and mechanisms of these resin monomers should be elucidated, thereby to improve the safety of utilization. Investigations of cell cycle progression, reactive oxygen species production and glutathione alteration are valuable directions to reveal the mechanism, thus were applied in the presented studies to get insights into the monomer-induced toxicity. Cytotoxic effect was first evaluated. TEGDMA induced growth inhibition in primary human pulp fibroblast (HPF) in a dose-dependent manner, which may be partially explained by induction of cell cycle perturbation. G2/M phase arrest was noted after exposure of HPF to 1 and 2.5 mM of TEGDMA, and S-phase arrest occurred at 5 and 10 mM. Glutathione depletion and ROS production were concomitantly observed. Sub-G0/G1 peaks were noted when HPF were treated with 2.5, 5 and 10 mM of TEGDMA, indicating the potential induction of apoptosis. TEGDMA also induced growth retardation in human Smulow-Glickman gingival cells (S-G cells) in a dose-related pattern, but no obvious phase arrest phenomenon was present. However, sub-G0/G1 peaks occurred in S-G cells when with 2.5, 5 and 10 mM of TEGDMA, similar to what we noticed in HPF. GSH depletion was marked in S-G cells at concentrations of 2.5, 5 and 10 mM, in a dose-relative manner, but at 1 mM TEGDMA exposure, excessive GSH production was noted, which seemed to be an adaptive reaction. ROS production in S-G cells got high at concentration of 1 mM TEGDMA exposure, then decrease with dose increase between 1-5 mM, then went highest at 10 mM. This suggested that the increase of ROS in S-G cells was not mainly caused by GSH depletion. HEMA also produced dose-dependent growth inhibition of HPF and S-G cells, but in a less toxic pattern compared to TEGDMA. In HPF, the cell growth suppression induced by HEMA may well be related to induction of GSH depletion, ROS production, and cell cycle perturbation. When treated with 5 and 10 mM HEMA, G2/M phase arrest was noted, which was concomitant with intracellular glutathione depletion and ROS production. While in S-G cells, the effects induced by HEMA were different. S-phase arrest occurred in S-G cells when treated with 2.5 and 5 mM, while at 10 mM a sub-G0/G1 peak was noted, which might indicate an apoptotic process. Glutathione depletion was marked in S-G cells only at concentrations of 5 and 10 mM, but ROS overgeneration was obvious since 1 mM and rose with dose increase between 1-5 mM, then lessened at 10mM. This suggested the increase of ROS in S-G cells was not mainly caused by depletion of GSH. UDMA elicited growth inhibition of CHO-K1 cells in a clearly dose-dependent manner, and in a much lower concentration compared to TEGDMA and HEMA. Cell cycle perturbation and ROS overproduction were also observed. 0.1 mM UDMA induced S-phase cell cycle arrest, simultaneously the ROS accumulated, and the apoptosis became significant. The effect of glutathione depletion only occurred at cells treated with 0.25 mM UDMA, a highly cytotoxic concentration at which point myriad cells were under apoptosis or necrosis. Thus glutathione depletion might be crucial for the death of CHO-K1 cells. 0.5-10 mM NAC and 250-1000 U/ml catalase obviously attenuated the UDMA-induced toxicity by reducing ROS generation and reverse cell cycle disturbance, and the effects were dose-related. The presented studies helped to elucidate the toxic mechanism of these resin monomers. Although the toxic concentration reported here might not be reached in prudent application, however, in a clinical situation lacking sufficient sound dentin and/or with poorly polymerized material, the unbound monomers may well lead to potential toxic effects as we addressed. Key words: TEGDMA, UDMA, HEMA, cytotoxicity, cell cycle, ROS, GSH