الفهرس 
Introduction
Self-etch modeOnly 14 pages are availabe for public view
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Abstract
This in-vitro study was conducted on two different universal adhesives applied in both E&R and SE modes to investigate: a- Changes in surface characterization of dentin and b- Resin/dentin interface nano-leakage. A total of 70 dentin specimens were retrieved from 18 non-carious, non-restored human molar teeth for this study. After extraction, the teeth were cleaned from blood and soft tissues were removed using hand scaler. Hard deposits were removed using ultrasonic scaler. The teeth were stored in distilled water at 4⁰C for no more than 3 months. Distilled water was changed every 48 hours during the storage period.
For AFM evaluation 8 teeth were used; the roots of each tooth were cutoff at the CEJ. Each tooth was sectioned into 2 halves mesio-distally. Each half was re-sectioned again into approximately equal 2 halves in the direction occluso-cervically., resulting in 4 quadrants per each tooth, with total of 30 quadrants. The quadrants were randomly assigned into 6 groups, two control groups (n=10) and four experimental groups (n=20). The ten quadrants for the control groups were sub-divided into two groups (n=5/group) according to the intervention done; group 1: no acid etching and group 2: after application of acid etching. While the twenty quadrants for the experimental groups were sub-divided into four groups (n=5/group) according to two experimental factors investigated: Factor 1: Adhesive type; 2 groups and Factor 2: Application mode; 2 groups. The occlusal enamel was removed using abrasive discs just below the DEJ. The disc was mounted on low-speed hand-piece and enamel removal was performed under copious water irrigation to expose flat dentin surfaces. Dentin surfaces were wet ground over #600 grit SiC for 30 seconds to create standardized smear layers. In self-etching mode, each adhesive was applied directly over dentin surface and air-dried according to manufacturer instructions, while in etch-and-rinse mode; the dentin surface was acid etched for 15 seconds, rinsed with air/water spray for 20 seconds and blot dried using lint-free tissue to keep dentin visibly moist before the application of adhesive according to its manufacturer instructions. Each dentin surface was scanned under AFM to produce an image for the dentin surface. Three different areas of 10μmx10μm for each dentin surface were chosen to calculate both surface area and surface roughness using the recommended software. Fifteen readings (retrieved from 5 specimens) for surface area or surface roughness were collected. The average of the total fifteen readings for both surface area and surface roughness were calculated.
While for nanoleakage evaluation; each tooth was sectioned into 4 quadrants, after removal of the roots, as same for AFM evaluation. 10 teeth were used for nano-leakage evaluation to produce 40 quadrants. The 40 quadrants were randomly assigned into 4 groups (n=10/ group) according to the two experimental factors investigated, Factor 1: Adhesive type (2 groups) and Factor 2: Application mode (2 groups). The occlusal enamel as well as the side enamel of each specimen were removed to create 40 dentin blocks. Pulp chambers, if it was present; sealed using one of the universal adhesives and resin composite. Occlusal dentin of all specimens were wet ground over #600 grit SiC for 30 seconds to create standardized smear layers. Acid etching and adhesive application; either in etch-and-rinse mode or self-etching mode was applied as same as for the AFM evaluation.
Each adhesive was applied on the occlusal surface and light cured using LED light curing unit. Composite build-up was performed in two increments, each for 1.5mm thickness and each increment was light cured for 20 seconds. Dentin/composite specimens were stored in distilled water for 24 hours. After 24 hours, each dentin/composite specimen was finished under ascending grits of sof-lex discs to remove excess composite from the dentin/composite interfaces. Each specimen was covered with 2 layers of nail varnish leaving uncovered 1mm from both composite and dentin margins. Each specimen was immersed in silver nitrate solution in light proof container for 24 hours. After 24 hours, specimens were removed from the solution and rinsed under tap water for 5 minutes. The specimens were immersed in developer solution under fluorescent light for 8 hours and then rinsed under tap water for 5 minutes. Slabs were then imaged using SEM Fig. (13) and the amount of silver granules were quantified using the NIH Image J V1.56 software program (Image J 1.43U, National Institute of Health, USA)(9).
This program allowed transformation of the SEM contents to black or white pixels, which were then counted and compared. The interfacial area present in the SEM was outlined. Silver granules were expressed as a percentage of the interfacial area at SEM image. Ten calculations were used for each group and will be averaged to calculate the mean for each group. Two-Way ANOVA was used to compare between tested Adhesive, Application Mode for mean Surface Roughness (μm) and Surface Area (μm2). The results showed a general significant increase in surface roughness in etch-and-rinse mode of application compared to the self-etch mode, while a One-Way ANOVA was used to compare between different adhesives within other variables followed by Tukey post hoc test for pairwise comparison for mean Surface Roughness (μm) and Surface Area (μm2). The results showed significant increase in surface area of Furturabond compared to that produced by G-permio bond when both adhesives were used in etch-and-rinse mode although there was a non-significant difference in surface roughness.
While Two Way ANOVA used to compare between tested type of bond and mode of application for % area of Nano leakage. Student t-test was used to compare between different type of bond and mode of application for normally distributed quantitative variables. While ANOVA was used for comparing between different interactions for normally distributed quantitative variables and followed by Post Hoc test (Tukey) for pairwise comparison. The results showed a significant difference in % area of nanoleakage; G-permio produced higher % area compared to Futurabond in both modes of application (E&R, SE).