الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Fissure sealant has been proven to be effective preventive measure that dramatically reduces caries in occlusal surfaces of posterior teeth. Recently, bioactive fissure sealants have evolved which are able to regenerate dental hard tissue after acid attack and inhibit bacterial growth. In this study, the antibacterial activity and mechanical properties of fluoride-releasing resin based sealant, surface pre-reacted glass filler containing sealant and amorphous calcium phosphate containing sealant were assessed and compared. Bacteriological estimation of fissure sealants in this study was performed using agar diffusion test at Microbiology Department, Faculty of Medicine, Mansoura University. Mitis salivarius agar media were prepared according to manufacturers` instructions. Plates were inoculated with 200 μL of Streptococcus mutans strain. Sealant specimens were prepared using a plastic mould and placed on freshly inoculated plates and incubated for 48hr. Then, inhibition zones were measured using digital caliper and expressed in millimeters by subtracting the sealant diameter from the average zone of inhibition. Evaluation of mechanical properties was carried out at Dental Biomaterial Department, Faculty of Dentistry, Tanta University. Regarding shear bond strength evaluation, 30 non carious human premolars were embedded in cold curing methyl methacrylate resin. Sealants were applied on the proximal enamel surfaces through the plastic ring and cured according to the manufacturer’s instructions. Shearing force was applied perpendicular to the prepared sealant surfaces using universal testing machine. The load of failure was divided by bonding area to express the bond strength in MPa. As regards diametrical tensile strength, sealant specimens were prepared using a plastic mould of 4mm diameter and 6 mm height. Strength was measured using universal testing machine by directing the force against the lateral surface of the specimen until fracture occurs. Regarding microhadness, sealant specimens were prepared in a round mould of 8 mm diameter and 2 mm thickness. A load of 200g were applied to the surface of the specimens for 10 seconds using Digital Display Vickers Micro-hardness Tester. The diagonals length of the indentations was measured by built in scaled microscope. The results of the present study revealed that fluoride releasing resin based sealant has superior antibacterial activity than PRG containing sealant and ACP containing sealant. Regarding shear bond strength, PRG filler containing fissure sealant has higher strength. On the other hand, there was no statistically significant difference between fluoride releasing sealant and ACP containing sealant. The result also showed that PRG containing sealant has lower diametrical tensile strength. Moreover, diametrical strength of fluoride releasing sealant and ACP containing sealant are not significantly different. Additionally, amorphous calcium phosphate containing sealant has higher microhardness than PRG containing sealant. On the other side, fluoride releasing sealant has lowest microhardness value. Ch.VII Based on this study’s results, the following conclusions can be obtained: 1. All of the tested materials are capable of inhibiting Streptococcus mutans growth. 2. The fluoride releasing resin based sealant has a higher antibacterial effect than sealant containing S-PRG filler and amorphous calcium phosphate containing sealant. 3. PRG filler containing fissure sealant has the highest shear bond strength value compared to that of fluoride releasing resin based sealant and amorphous calcium phosphate containing sealant. 4. The diametrical tensile strength of PRG filler containing fissure sealant is lower than that of fluoride releasing resin based sealant and amorphous calcium phosphate containing sealant. 5. Amorphous calcium phosphate containing fissure sealant shows a superior surface micro hardness characteristics compared to fluoride releasing resin based sealant and PRG filler containing fissure sealant.