الفهرس 
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Abstract
Bioactive restorative Activa is an esthetic, durable material; having the strength and physical properties compared to dental resin composites, plus bioactive properties of glass ionomers, and hydrophilic property, suggesting less bacterial adhesion. The aim of this study was to assess the microleakage, fracture toughness and wear resistance of Activa and compare it to the nono-hybrid composite resin (Tetric ® N-Ceram).
Our work was divided into two groups, according to the material used; group A: Activa bioactive restorative (Pulpdent), group B: Tetric® N-Ceram Bulk-Fill (Ivoclar-Vivadent). Each group was subdivided into three subgroups according to the performed test. The Microleakage test was assessed by bacterial leakage, twenty extracted premolar teeth were selected, ten for subgroup A1, and ten for subgroup B1. Subgroup A1was filled with Activa from the subpulpal wall to the occlusal surface that was adjusted for 4mm, the same procedure was performed for subgroup B1 using the Tetric® N-Ceram. The bacterial leakage of all premolars was assessed in a microbiological laboratory test and the leaked bacteria were counted by a quantitative culture through serial dilution method.
Fracture toughness of subgroups (A2, B2) was tested by fabrication of eight bar specimens of each material. Custom made rectangular Teflon mold with a sharp steel (Razor) blade was used to fabricate the specimens with a centrally placed notch. A universal testing machine was used to apply a central load to each specimen in a three point bending mode at a cross head speed of 0.5 mm/min, where the maximum load to failure was recorded and the fracture toughness was calculated using the following equation: KIC = (3PLa1/2 / 2bw2) f (a/w).
Wear test of subgroups (A3, B3) was accomplished by fabrication of eight disc specimens from each material using a custom made Teflon mold. 15,000 brushing strokes with vertical load of 2kg were performed in a tooth brushing simulator. Surface roughness before and after brushing, and wear depth of the disc specimens were estimated using 3D laser scanning confocal microscope. Also, it provided qualitative (2D and 3D pictures) analysis of the surface topography.
Our results within subgroups A1, B1 for testing microleakage showed that Activa revealed bacterial microleakage demonstrated by turbidity in nine out of ten samples while Tetric N-Ceram revealed turbidity in eight out of ten samples, but the difference was statistically insignificant. Also regarding the day of leakage between Activa and Tetric N-Cearm, the difference was statistically insignificant, and the serial dilution count of the leaked bacteria, also the difference was statistically insignificant.
The results within subgroups A2, B2 for testing fracture toughness revealed that subgroup A2 showed a higher mean value of fracture toughness than subgroup B2 and the difference was statistically significant.
The results within subgroups A3, B3 for the wear test obtained by confocal microscope; showed that subgroup A3 mean value of surface roughness before brushing was less than subgroup B3 and the difference was statistically significant. Subgroup A3 brushed side showed less mean value of surface roughness than subgroup B3 but the difference was statistically not significant.
Tooth brushing had significantly increased the surface roughness between the brushed and unbrushed sides of subgroup A3 and the difference was statistically significant, and for subgroup B3 where the difference was also statistically significant.
Subgroup A3 showed higher roughness percentage change than subgroup B3 where the difference was statistically significant.
Subgroup A3 showed less wear depth than subgroup B3 specimens where the difference was statistically significant.
Activa showed a comparable microleakage to nano hybrid composites, higher fracture toughness and less wear depth. These findings nominate Activa as a restorative material replacing the brittle composite materials.