Despite the great need and applicability of different orthodontic treatments, it is necessary to recognize its negative aspects. Most of the treatments include cementation of orthodontic brackets and other metal accessories on tooth surface. All these bonded items in the oral cavity, hinder hygiene, and generate large accumulation of biofilm which is responsible for problems like dental caries and periodontal disease. Recently, the chemical composition of dental materials has been explored to obtain some specific properties. Applications for antimicrobial polymers have been studied by industry and health sciences to minimize microorganisms' contamination and infections. Regarding to composite resins for bonding fixed appliances in orthodontics, antibacterial property is desirable due to plaque accumulation and cleaning difficulties.In 2012, Gong Shi-qiang et. al. tested a new class of methacrylate macromonomers, methacryloxy quaternary ammonium silicates (QAMSs) containing 3-(trimethoxysilyl)propyldimethyloctadecyl ammonium chloride (SiQAC). In this study it was shown that QAMSs are antimicrobial macromonomers and when copolymerized with Bis-GMA forms a hybrid interpenetrating inorganic-organic network and its antimicrobial properties are maintained.Thus the aim of this study will be to evaluate the antimicrobial effect and the mechanical properties of Transbond XT Light Cure resin (3M ESPE) incorporating 3 wt% and 6 wt% of quaternary ammonium silicates methacryloxy (QAMSs) Antibacterial properties will be tested with Streptococcus mutans UA159 grown in TYE (Tryptone-Yeast Extract, Difco) supplemented with 1% sucrose. A plating method is performed to quantify the CFU / mL of each experimental group. There are going to be 5 groups (n=5) analyzed in circular samples of 8 mm in diameter and 2mm thick: A - Absolute QAMSs (n=5);B - Bovine Teeth (n=5);C - Transbond XT Light Cure Adhesive resin (n=5);D - Transbond XT Light Cure Adhesive resin + 3 wt% QAMSs (n=5);E - Transbond XT Light Cure Adhesive resin + 6 wt% QAMSs (n=5).This tests will be done triplicate in 3 different moments (24h, 48h and 72h)To test mechanical properties, there are going to be 3 groups:Group1: Transbond XT Light Cure Adhesive (n = 7);Group 2: Transbond XT Light Cure Adhesive + 3 wt% QAMSs (n = 7);Group 3: Transbond XT Light Cure Adhesive + 6 wt% QAMSs (n = 7) . Degree of Conversion (GC); Sorption (Wsp) and Solubility (Wsl); Ultimate Bond Strength and Shear Bond Strength Tests will be done after 24h of storage. The DC of the composites will be evaluated for the three groups (n = 7) by means of Fourier transform infrared spectrometer. The samples for DC test are 8 mm in diameter and 2mm thick circular samples. Wsp and Wsl will be measured through periodic weighing on an analytical weighing machine. The samples for Wsp e Wsl are 5 mm in diameter and 0,5 mm thick circular samples For Ultimate Bond Strength and Shear Bond Strength tests Instron universal testing machine will be used. The samples for Ultimate Bond Strength test are in hourglass shape, 10 mm length x 1 mm width x 1 mm thickness. For Shear Bond Strength test, metallic brackets will be bonded in bovine dental enamel (n=10) using the respective composite resin, storage for 24h and the brackets will be removed by Instron universal testing machine. Data will be tabulated and analyzed by a statistical consultant.
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