الفهرس 
Composition of composite resins
Various advances in composite resinsOnly 14 pages are availabe for public view
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Abstract
This in vitro study was performed to evaluate the effect of flowable composite and glass ionomer liner on the marginal integrity of Class II composite resin restorations. The samples consisted of 30 extracted human sound molars of an age ranging between 25 and 50 years .The teeth were disinfected in the 0.5% Chloramine-T solution for one week and then, kept in the normal saline solution. Each tooth was fixed with sticky wax to the base of plastic cylinder. The cylinder was filled with self-curing acrylic resin so that only root was embedded. Simple Class II cavity with parallel walls was prepared. The cervical margin was established 1.5 mm above the cemento- enamel junction. The overall dimensions and depth of the cavities were standardized as follow: 4 mm length occlusocervically, 4 mm width buccolingulaly and 2 mm depth axially.Total Etch (37% phosphoric acid) was applied on enamel and subsequently on dentin; for 15 seconds, rinsing for 20 seconds. Universal Tofflemire’s matrix retainer and metal band were used to restore the missing wall of cavity. Futurabond U was applied to the walls of cavities, rubbed for 20 seconds by using disposable micro brush. Lightly air drying then cured for 30 seconds with a light emitting diode (LED) curing unit.The samples were divided into the groups randomly − group 1: Futurabond U was applied then the cavities were restored with Xtra Fil bulkfill composite. − group 2: Futurabond U was applied then Xtra base flowable composite (1mm thickness) was applied, followed by Xtra Fil bulk fill.− group 3: Ionoseal glass ionomer was applied as a base (1mm thickness), then Futurabond U was applied ,followed by Xtra Fil bulk fill. All specimens were subjected to 500 thermo cycles between 5°C and 55°C, 30 s dwell time and a transfer time of 15s. Impressions of the specimens were made using a Polyvinyl Siloxane material (light body). The impressions were then poured with epoxy resin. These replicas were left 24 h for complete setting. Then, Gold sputtered to render the surface electrically conductive. These replicas were examined under Scanning Electric Microscope (SEM). Results were expressed as percentage of open margins for the total margin length for proximal and cervical margins and also the width of the gap was measured. All data was collected, tabulated and statistically analyzed using software statistical package for social sciences (SPSS) version 25.Comparing the total gap length through different groups, there is a significant difference between groups with p-value 0.001*, where the group 1 has the biggest marginal gap length 0.75 and the smallest marginal gap length belongs to group 2.