Preparation of Dental Polymeric Nano-Adhesives with Silica Nano-Porous (MCM-41) as Novel Fillers for Improving the Adhesive Mechanical Properties: Synthesis and Application

The primary aim of dental adhesives is to provide retention to composite fillings or composite cements. In addition to withstanding mechanical forces, and in particular shrinkage stress from the lining composite, a good adhesive also should be able to prevent leakage along the restoration's margins. With the recent improvements in dental adhesive, the behavioral characteristics of adhesive dentistry have received an increasing consideration. Nanotechnology created a new vision in the formation and evaluation of modified materials. The mechanical efficiency of nano-filler may in some situation be extraordinary to other filler size. The three-point bending test has been performed in the past by some researchers, for investigating the mechanical properties of dental adhesives. In these researches, the influence of inorganic filler particles of adhesive and composites on flexural strength and flexural modulus is shown increasing modulus with inorganic fillers.  This study evaluates that the incorporation of silica nano-porous (MCM-41) as filler synthesized by sol-gel method, into an experimental dental polymeric adhesive, improves the mechanical properties of the polymeric adhesive layer.Methods. MCM-41 filler was prepared by sol-gel method. Adhesive precursor (2,2-Bis[p-(2-hydroxy-3-methacryloxypropoxy)-phenyl] propane (Bis-GMA), 1,6-bis-[2-methacryloyloxyethoxycarbonylamino]-2,4,4-trimethylhexane (UDMA), 2-hydroxyethyl methacrylate (HEMA), 2-ethyl-2-(hydroxymethyl)-1,3-propandiol trimethacrylate (TMPTMA) and ethanol) were mixed. Then, MCM-41 with different wt.% (0-5.00 %), camphorquinone (CQ) and N,N-Dimethyl aminoethyl methacrylate (DMAEMA) were added to the above mixture and the mixture was placed under vacuum in a suitable temperatures.The resulting MCM-41 powder was characterized using FTIR, SEM, BET. The flexural modulus of seven adhesive systems containing different MCM-41 were evaluated by three-point bending test. Results. The improved properties of the new adhesive system might be due to the high surface area and high porosity of the MCM-41. FT-IR spectrum of the filler is shows the peaks corresponding to the MCM-41 filler structure. The characteristic peaks of Si-O-Si appear at about 462, 794 and 1076 cm−1. Also, the peaks of Si-OH located at 3100-2700 cm−1. BET-plot of MCM-41 show that filler is place in the nano-porous categories and BJH-plot illustrate this filler has a pore-size diameter 2.66 nm. SEM observation showed size of the MCM-41 filler, is about 37.29 nm. The results established that dental polymeric adhesive containing 1% of filler has highest flexural modulus.