Preparation of Bis-GMA-Free Dental Restorative Composites with Dendritic Macromer (G-IEMA)

A comparative study on the mechanical and antibacterial properties of BPA-free dental resin composites

OBJECTIVE

The commonly used base monomer utilized in resinous commercial dental restorative products is bis-GMA which is derived from bisphenol-A (BPA) - a well-known compound which may disrupt endocrine functions. To address concerns about its leaching into the oral environment and to optimize the quality of dental composites, a BPA-free alternative base monomer, fluorinated urethane dimethacrylate (FUDMA), was designed by modifying a UDMA monomer system.

METHODS

Nine groups of composites were prepared by mixing the base monomers and TEGDMA in a ratio of 70/30 wt% to which were added silanized glass particles (mean diameter: 0.7 µm) in 3 different volume fractions (40, 45, and 50 vol%). Bis-GMA and UDMA base monomers were used as control groups in the same ratios. Various properties including degree of conversion (DC), flexural strength (FS) and flexural modulus (FM), water sorption (WS), solubility (SL), surface hardness and roughness, and initial adhesion property against S.mutans were investigated. One-way analysis of variance followed by Bonferroni test at α = 0.05 was used to analyze the results.

RESULTS

A significant difference in FS between FUDMA-based composite with 40 vol% filler (120.3 ± 10.4 MPa) and Bis-GMA-based composite with the same filler fraction (105.8 ± 10.0 MPa) was observed but there was no significant difference among other groups. The UDMA based group exhibited the highest WS (1.3 ± 0.3 %). Bis-GMA showed greater initial bacterial adhesion but was not statistically different from the other groups (p = 0.082).

SIGNIFICANCE

FUDMA-based resin composites exhibit comparable mechanical and bacterial adhesion properties compared with Bis-GMA and UDMA-based composites. The FUDMA composites show positive outcomes indicating they could be used as substitute composites to Bis-GMA-based composites.

New dimethacrylate monomers based on phenolphthalein and resveratrol for the application of dental materials

Potential estrogenic effects and changes in fertility are some of the health problems associated with bisphenol A (BPA) derivatives used to produce some polymers, including dental materials that contain Bis-GMA. Those issues drove this study proposing the synthesis of methacrylate resveratrol and phenolphthalein monomers that, combined with diluent monomers, generate copolymers. Their key characteristics were determined and analyzed on the chemical structure-property perspective considering monomer planarity and flexibility based on molecular dynamic simulations.

METHODS

Methacrylate resveratrol ((E)-5-(4-(methacryloyloxy)styryl)-1,3-phenylenebis(2-methylacrylate)), EMPM) and methacrylate phenolphthalein ((3-oxo-1,3-dihydroisobenzofuran-1,1-diyl)bis(4,1-phenylene)bis(2-methylacrylate)), DIFPM) were synthesized through the reaction of precursors with methacryloyl chloride. After monomers purification and spectroscopic characterization (FTIR and NMR), the following copolymers were produced: DIFPM/TEGDMA and Bis-GMA/TEGDMA, EMPM/HEMA and Bis-GMA/HEMA. Microhardness, degree of conversion, water sorption and contact angle data were statistically analyzed through one-way ANOVA and Tukey's test (p ≤ 0.05).

RESULTS

The DIFPM molecular structure's reduced flexibility proved to be an important factor to inhibit TEGDMA cyclization. In turn, the EMPM molecule's high planarity modified the spatial organization of the HEMA copolymer, altering the water diffusion and, therefore, the water sorption when compared to Bis-GMA copolymers.

CONCLUSION

The scientific findings contribute to better understand the effect of monomer chemical structures, molecular geometry, and planarity on some physicochemical properties of copolymers. Knowledge that can contribute to the design of new monomers to replace Bis-GMA.

Preparation of a Bis-GMA-Free Dental Resin System with Synthesized Fluorinated Dimethacrylate Monomers

With the aim of reducing human exposure to Bisphenol A (BPA) derivatives in dentistry, a fluorinated dimethacrylate monomer was synthesized to replace 2,2-bis[4-(2-hydroxy-3-methacryloy-loxypropyl)-phenyl]propane (Bis-GMA) as the base monomer of dental resin. After mixing with reactive diluent triethyleneglycol dimethacrylate (TEGDMA), fluorinated dimethacrylate (FDMA)/TEGDMA was prepared and compared with Bis-GMA/TEGDMA in physicochemical properties, such as double bond conversion (DC), volumetric shrinkage (VS), water sorption (WS) and solubility (WSL), flexural strength (FS) and modulus (FM). The results showed that, when compared with Bis-GMA based resin, FDMA-based resin had several advantages, such as higher DC, lower VS, lower WS, and higher FS after water immersion. All of these revealed that FDMA had potential to be used as a substitute for Bis-GMA. Of course, many more studies, such as biocompatibility testing, should be undertaken to prove whether FDMA could be applied in clinic.

Preparation and characterization of Bis-GMA free dental resin system with synthesized dimethacrylate monomer TDDMMA derived from tricyclo[5.2.1.0(2,6)]-decanedimethanol

As a substitute for 2,2-bis[4-(2-hydroxy-3- methacryloxypropoxy)phenyl] propane (Bis-GMA) in dental materials, a new dimethacrylate monomer TDDMMA without bisphenol-A structure was synthesized through the reaction between tricyclo[5.2.1.0(2,6)]- decanedimethanol and 2-isocyanatoethyl methacrylate. The TDDMMA was mixed with triethylene glycol dimethacrylate (TEGDMA) to prepare Bis-GMA free dental resin. Physicochemical properties, such as double bond conversion (DC), polymerization shrinkage (VS), water sorption (WS) and solubility (SL), flexural strength (FS) and modulus (FM) and fracture energy of TDDMMA/TEGDMA resin system were investigated. Bis-GMA/TEGDMA resin system was used as a control. The results showed that, compared with Bis-GMA/TEGDMA resin system, TDDMMA/TEGDMA resin system had comparable VS and several advantages like higher DC, lower SL and better mechanical properties after water immersion.