Modification On BIS-GMA Based Dental Adhesive With Mussel-Inspored Bioadhesion Molecule

Inspired by the adhesion behavior of marine mussels, which demonstrte excellent bonding strength on various substrates in humid environment, an idea that using a bioadhesion molecule to modify adhesives for dental restoration was proposed in this study. Dopa was identified the key molecule responsible for the excellent bonding ability of mussels. Therefore, dopamine (DA), an analogue of dopa, was applied to synthesize a new functional photocurable monomer (DA-GMA) by reacting with glycidyl methacrylate (GMA). Then the DA-GMA was added into bisphenol A GMA (Bis-GMA)-based adhesive for the purpose to investigate the effect of DA-GMA on the polymerization, the bonding strength and the biocompatibility of the adhesive. To investigate the effect of molecular structure of DA modified methacrylate on the properties of Bis-GMA-based adhesive, a new methacrylate (OEMP) was obtained by reacting hydroxyethyl methacrylate (HEMA) with epoxy chloropropane. And the DA-OEMP was obtained and studied similarly to those of DA-GMA. The main work and achievements are listed as below.(1) The synthesis of DA-GMA was systematically studied by adjusting the key reaction parameters including the feeding ratio of DA to GMA, the reaction temperature and time, as well solution pH. Under the optimized condition, the obtained DA-GMA was identified having the characteristic structures of both DA and GMA by Fourier transform infrared spectrascopy (FTIR) and'H nuclear magnetic resonance spectroscopy (1H NMR). By adding different amount of DA-GMA into the Bis-GMA-based adhesive, the conversion of C=C groups was monitored with real-time FTIR. The result revealed that the catechol group in DA had some inhibition effect on the photopolymerization of the adhesive, that the addition amount of DA-GMA should be controlled under 0.4 wt.%. Further study on the bonding strength by using pull-out test, the highest bonding strength was confirmed at the addition of 0.4 wt.% DA-GMA, which was comparable to that of the commercial 3M adhesive. Cytotoxicity assay was conducted by culturing L929 fibroblasts in extracts of photocured adhesives containing different amounts of DA-GMA, and the results demonstrated the addition of 0.4 wt.% DA-GMA would not cause adverse effect on the biocompatibility of Bis-GMA-based adhesives.(2) Similarly, the synthsis of DA-OEMP was optimized. The difference between the DA-GMA and DA-OEMP was that an extra short -OCH2CH2- segment was in the latter compound. By adding different amount of DA-OEMP into the Bis-GMA-based adhesive, the photo-initiated polymerization, the bonding strength and the cytotoxicity of resulted adhesives were assessed by real time FTIR, pull-out test and in vitro cell culture. It was found that all the features of these DA-OEMP-added systems were quite similar to those of the DA-GMA-added systems when DA-OEMP and DA-GMA were added at the same amount. The results suggested that such a difference in molecular structure did not have significant effect on the properties of adhesives. A possible reason might be their limited addition amounts.In conclusion, the Bis-GMA adhesive containing 0.4 wt.% of DA-GMA or DA-OEMP had achieved comparable bonding strength to that of commercial 3M adhesive, and displayed potentials in clinical application.