الفهرس 
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Abstract
”Objective : To evaluate and compare the microleakage patterns of adhesive/dentin interface of four different types of adhesives one of them containing bioactive hydroxyapatite nano rods. In time, the nanoleakage pattern and elemental analysis of adhesive/dentin interface were investigated with Scan Electron Microscope immediately after 24h and after 6month storage. Materials and Methods: A total of 120 freshly extracted caries-free human permanent molars were selected and used in this study (n=120). After cleaning and disinfection, they were assigned randomly into four groups. group 1 ; receive one-step self-etch adhesive (Opti Bond™, All-In-One), group 2 ; receive modified-bioactive” adhesive (Opti Bond™, All-In-One containing bioactive hydroxyapatite nanorods), group 3 ; receive MDP containing adhesive (Scotchbond universal), group 4; receive resin modified glass ionomer- based (RMGI) adhesive (Riva Bond LC). For microleakage test (n=80), box- shaped class V cavity was prepared on the buccal surface of each tooth with dimensions 3x3mm, a depth of 2 mm. Then all adhesives were applied and cured with a light emitting diode (LED) unit according to the manufacturer recommendations. The cavities were restored incrementally with a nano hybrid composite restorative material (Filtek Z250 XT, 3M-ESPE, St. Paul, MN, USA). The restored specimens were stored in distilled water for 24 h (n=10) for each subgroup. Half of restored teeth (n=40) were stored in artificial saliva for 6-months to age the adhesive interface and then subjected to thermocycling. The teeth were immersed in 2% methylene blue dye for 24h, and rinsed for 60s with distilled water. The specimens were sectioned buccolingually through the restoration with a precision diamond saw. Microleakage in both occlusal and gingival margins was examined for only one half from each specimen under X30 magnifications using an optical stereomicroscope and the degree of microleakage was measured using scoring criteria. All collected data were tabulated and statistically analyzed using a statistical package with IBM® SPSS® Statistics Version 20 for Windows. Chi-squared test was used to compare between microleakage scores among different adhesive groups. For nanoleakage test, six additional teeth from each group were used (n =24). And four teeth for each group (n=16) were used for elemental analysis of adhesive/dentin interface. After embedding the selected molars in an acrylic resin block, the occlusal enamel and superficial dentin were removed from each tooth, exposing the mid-dentin area. Then all adhesives were applied and cured with a light emitted diode (LED) unit according to the manufacturer recommendations. A nanohybrid composite restorative material was placed incrementally in 4-5 mm height to form a crown segment, each increment with 1mm thickness was light- cured for 20s. To evaluate nanoleakage, all specimens were sectioned, coated with nail-varnish and subjected to ammoniacal silver nitrate solution followed by developing solution. Then all specimens were gold- sputtered and observed in backscattered mode under a high-resolution Scan Electron Microscope and imaged at magnification X500, X1000 and X2000. To analyzed elements of adhesive/dentin interface, the restored specimens were vertically sectioned into two halves. Wet polishing of the cut surface with silicon carbide papers then specimens were ultrasonically cleaned and the adhesive /dentin interface was subjected to EDX analysis with EDX software attached to a field emission scanning electron microscopy. Results : Chi-squared test revealed that the microleakage was significantly affected by the “type of adhesive material” (P ≤ 0.05) and by the “time”. Another Chi-squared test showed that there was no significant difference in microleakage between occlusal and gingival margins among tested groups. Comparison among different adhesive materials and in immediate and delayed groups showed that the microleakage was lowest in the modified adhesive group, while the RMGI group showed the highest microleakage. Silver nitrate uptake could be identified within the resin-dentin interface in all the bonded specimens. EDX elemental analysis revealed that the Ca and P levels at resin- dentin interface in both immediate and delayed groups was the highest in the modified adhesive group, while in the RMGI group was the lowest. Conclusion : Incorporation of bioactive HAP-NR into 1S-SE adhesives decrease microleakage and nanoleakage pattern of resin/dentin interface. Moreover, it improves Ca and P levels at resin / dentin interface.