الفهرس 
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Abstract
The aim of this study was to evaluate the effect of addition of 5 wt% BAG nanoparticles to a commercially available unfilled universal multimode adhesive on its degree of conversion, viscosity, pH, contact angle, ion release and bioactivity.
Microtensile bond strength test of the unmodified and modified adhesive was done in E&R and SE mode and tested after 2 different storage intervals, and failure mode analysis was assessed.
Moreover, hybrid layer evaluation was done using SEM at 1000x, as well as nanoleakage assessment using SEM and EDX.
For the degree of conversion, testing was done using FTIR spectroscopy for both groups (unmodified unfilled adhesive and adhesive modified with 5% BAG NPs) before and after curing of the adhesive layer.
For the viscosity measurement, 0.5 ml from each adhesive was measured using a rheometer, and 5 readings were taken for each group.
Regarding the pH measurement, drops of each adhesive were placed in a pH meter and the readings were recorded.
Calcium ion release testing was done by forming adhesive discs of 1 mm thickness and 5 mm diameter that were suspended in test tubes containing deionized water. Ion chromatography was used to measure the amount of calcium ion release from both adhesives after 4 predetermined storage intervals (1 day, 7 days, 14 days and 28 days).
Bioactivity testing was done by forming adhesive discs in the same as maneuver used for the calcium ion release test. Discs were stored in SBF solution which was changed daily and SEM images at 1000X were taken after each predetermined storage interval (1day, 7days, 14 days and 28 days).
For the µTBS test, twenty-four recently extracted sound third molars were distributed on the 8 groups (Unmodified adhesive in E&R mode, Unmodified adhesive in the SE mode, 5% BAG modified adhesive in the E&R mode and 5% BAG modified adhesive in the SE mode, for two storage intervals; 1 day and 6 months). The teeth had their occlusal enamel removed. Dentine was demineralized, then the bonding procedure or composite was done. Half of the teeth were tested after 1 day and the other half after 6 months. The teeth were then sectioned into 1mm2 beams, and the test was performed using a universal testing machine in tensile mode. Fracture mode analysis was performed using a stereomicroscope at 40X magnification.
Two representative beams were taken from each group for the assessment and evaluation of the hybrid layer using SEM at 1000x.
For the nanoleakage testing, sixteen recently extracted premolars were distributed on the 8 groups, same as the microtensile bond strength testing. The teeth had their occlusal enamel removed. Dentine was demineralized, then the bonding procedure or composite was done. Half of the teeth were tested after 24 hours and the other half after 6 months.
After the predetermined storage period, teeth were coated with acid resistant nail varnish except for the dentin-composite interface and then immersed in silver nitrate solution. Specimens were then sectioned to obtain dentin-composite slabs, that were then assessed for the amount of Ag ion penetration using SEM and EDX.
Conclusions
Within the limitations of the present study, the following conclusions could be drawn:
• Modifying the unfilled universal multimode adhesive with 5 wt% BAG nanoparticles would not deteriorate its degree of conversion, viscosity or wettability to dentin.
• The pH of the unfilled universal multimode adhesive increases upon addition of 5% BAG.
• A continued calcium ion release can be achieved by modifying the unfilled universal multimode adhesive with 5% BAG, with a promising potential for apatite formation overtime.
• Application of the unfilled adhesive in the etch and rinse mode gives better immediate bond strength to dentin compared to the selective etch mode, yet upon storage, both etching modes are comparable regarding their bond strength to dentin.
• Modifying the unfilled universal multimode adhesive with 5% BAG can be considered a promising approach for enhancing its bond durability to demineralized dentin, along with a decrease in nanoleakage over time.