Bis gma

Bisphenol A–glycidyl methacrylate (BisGMA) and triethylene glycol dimethacrylate (TEGDMA) were purchased from Merck, Darmstadt, Germany. An identical resin matrix containing 60:40 weight ratio of BisGMA: TEGDMA with a photoinitiator system (camphorquinone (0.2 wt %; Merck) and ethyl-4-dimethylamino benzoate (0.8 wt %; Merck)) was used for all materials. Resin was heated to 60 °C prior to admixture of fillers.
Four types of fillers were used in this study, as shown in Table 1.
The materials were mixed in the absence of blue light using an asymmetrical centrifugal mixer (Speed Mixer TM DAC 150 FVZ, Hauschild & Co KG, Hamm, Germany) at gradually increasing speed up to 2700 rpm.
Eight experimental resin composites were prepared, divided into two groups:

Group testing the bimodal approach with 65 wt % total filler load and

Group testing the trimodal approach with 70 wt % total filler load used for investigating 1, 5, and 10 wt % Cu-MBGN composites with silica fillers.

Each group contained both inert control (silica and microfillers; 10-Si and 15-Si) and bioactive control (45S5 BG and microfillers, 10-BG and 15-BG) in adequate amounts corresponding to the total filler load (Table 2).

A dental adhesive was formulated by mixing two methacrylate monomers: bisphenol A glycerolate dimethacrylate (Bis-GMA, Aldrich Chemical Company, St. Louis, Missouri, USA) at 66.66 wt.% and 2-hydroxyethyl methacrylate (HEMA, Aldrich Chemical Company) at 33.33%. Camphorquinone (1 mol%) and ethyl 4-dimethylaminobenzoate (1 mol%) were also used as the photoinitiator and co-initiator, respectively. Butylated hydroxytoluene was used (1 wt.%) as a stabilizer for the inhibition of spontaneous polymerization. These three reagents were also purchased from Aldrich Chemical Company. The adhesive formulated was used as the experimental LiNbO₃-free control adhesive. LiNbO₃ was incorporated in experimental adhesive resins at different concentrations (1 wt.%, 2 wt.%, and 5 wt.%). The particles of LiNbO₃ were milled and sieved (>0.125 mm) and characterized via laser diffraction (CILAS 1180, Orleans, France) for particle size. A light-curing unit (Radii Cal, SDI, Australia) was used for specimens’ photoactivation at 1200 mW/cm². Experimental adhesives were evaluated as illustrated in Figure 2.

Borate glass containing 70% boron oxide, 26% strontium oxide and 4% sodium oxide (mole fraction) was synthesized as per MacDonald et al., and sieved to retrieve <25 μm particles [35 (link)]. Particle size distribution was verified using a laser particle size analyzer, in aqueous dispersant (Mastersizer 3000, Malvern, Malvern, Worcs, UK), and confirmed as d₁₀ = 3.38 μm, d₅₀ = 12.1 μm, d₉₀ = 26.4 μm. A series of 15 two-paste resins (Figure 9, Table 1) were fabricated through varying mixtures of HEMA (Aldrich Chemistry, USA), TEGDMA (Aldrich Chemistry, St. Louis, MO, USA), and BisGMA (Aldrich Chemistry, USA). Benzyl peroxide (BPO, Sigma Aldrich, St. Louis, MO, USA) and N,N-Bis(2-hydroxyethyl)-p-toluidine (DHEPT, Aldrich Chemistry, St. Louis, MO, USA) were added to paste one and two respectively, for each composition, to form a chemical initiation system [54 ]. Resin components were shielded from light to prevent photo initiation of benzoyl peroxide, and placed in a shaking incubator at (37 °C, 2 Hz) overnight to reduce resin viscosity and allow for mixing. Resin mixtures were refrigerated until further use, and hand spatulated with the appropriate weight of glass to form both paste components as needed.

The monomers triethylene glycol dimethacrylate (TEGDMA), 95%, and 2,2-Bis[p-(2′-hydroxy-3′-methacryloxypropoxy)phenylene]propane (Bis-GMA) were both provided by Aldrich, Taufkirchen, Germany. Co-initiator 2-(Dimethylamino)ethylmethacrylate (DMAEMA), 99%, and initiator camphorquinone, 98%, were purchased from J&K Scientific GmbH, (Lommel, Belgium). Commercially available OMMT, Nanomer^® I.34MN, produced by Nanocor Company (Hoffman Estates, IL, USA) and supplied by Aldrich (Taufkirchen, Germany), is an –onium ion modified clay containing 25 to 30 wt % methyl dixydroxyethyl hydrogenated tallow ammonium ion. OMMTs with different intercalating organomodifiers, such as cetyltrimethylammonium chloride (MMT-CTAC), dimethylaminooctadecyl methacrylate (MMT-DMAODM), dimethylaminohexadecyl methacrylate (MMT-DMAHDM), as well as two surface modified analogs, with 3-(trimethoxysilyl)propyl methacrylate, S.MMT-CTAC, and S.MMT-DMAHDM were all prepared in our previous works [49 (link),50 (link)]. The specific chemical structures of all MMT organomofidiers are represented in Figure 1. All other chemicals used were of reagent grade.