الفهرس 
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Abstract
This in vitro study was conducted to investigate the effect of Silver Diamine Fluoride (SDF) application on: a- Surface characterization of demineralized dentin using environmental scanning electron microscope and b- The micro shear bond strength of 2 universal adhesives to demineralized dentin. A total of 80 dentin specimens were retrieved from 40 non carious, non-restored human molar teeth for this study. After extraction, the teeth were cleaned from blood and soft tissue was removed using hand scaler. Hard deposits were removed using ultrasonic scaler. The teeth were stored in distilled water at 4⁰C not more than 3 months. Distilled water was changed every 48 hours during the storage period.
For ESEM evaluation 40 teeth were used; the roots of each tooth were cut off at the CEJ. Each tooth was sectioned into 2 halves mesio-distally; resulting in 2 halves per each tooth, with total of 80 halves. The 80 halves were divided into 2 groups (n= 40 halves) according to the type of dentin (either demineralized or sound). Each group was subdivided into 2 subgroups (n= 20) according to SDF application (either with SDF or No SDF)
The dentin Specimens (n=40 halves) were placed in artificial demineralizing solution for 72 hours. A small cotton pellet or brush was used to paint approximately one DROP of SDF onto the middle dentine of each half for at least one minute then air-dry. After the lesions have been exposed to SDF for the determined period of time, the SDF was rinsed off for 30 seconds with distilled water. Each dentin surface was scanned under ESEM to obtain images of dentin surface.
For Micro shear bond strength evaluation, the subgroups were then subdivided into 2 classes (n= 10) according to type of universal adhesive (universal adhesive 1 or universal adhesive 2). Specimens were then embedded in acrylic blocks in which the dentin surfaces were facing upwards Each adhesive was applied directly over dentin surface and prior light curing empty micro cylinders were placed on dentin surface then light cured using LED light curing unit for 20 seconds. Nano-hybrid resin composite was packed into cylinder lumen using a thin periodontal probe then light cured using LED light curing unit. A scalpel was used to remove the micro cylinder. In this manner, a very small cylinders of resin, approximately 1.5 mm in diameter and 2mm in height, were bonded to the dentin specimens. After 24 hours, each acrylic block containing the embedded dentine specimen with its bonded composite was mounted in the universal testing machine (Instron 3382, Canton, MA, USA). Forces were applied to the dentin-composite bonded interface at a crosshead speed of 1 mm per min until fracture occurred.
On comparing the ESEM images of sound dentin to demineralized dentin upon SDF application, it was found that SDF was deposited on side walls of dentinal tubules in sound dentin while it was deposited inside the opened dentinal tubules in demineralized dentin. Three-way ANOVA test was assessed to show the effect of the interaction between SDF application, type of dentin and type of bonding agent on micro-shear bond strength of resin composite to dentin. The results showed that the interaction had no significant effect on micro-shear bond strength of composite.
Student t-test was used to compare the effect of SDF application on Micro Shear bond strength (MPa) within each universal adhesive in sound and demineralized dentin groups. Results showed that there was no significant difference on micro-shear bond strength upon SDF application in both universal adhesives whether in sound or demineralized dentin. Moreover, by comparing the results of the 2 different universal adhesives to each other regarding SDF application; it was shown that there was no significant difference whether SDF was applied or not on sound or demineralized dentin.
Furthermore, Student t-test was used to compare the effect of SDF application and type of dentin on Micro Shear bond strength (MPa) within each universal adhesive groups. The results revealed that in Futurabond M+ groups, there was a significant difference between sound and demineralized dentin groups treated by SDF while no significant difference was found in All-Bond Universal groups
Conclusions:
Within the limitations of this study, it can be concluded that:
1- Demineralization allows more SDF penetration into dentinal tubules.
2- The Decrease in the pH of universal adhesive positively affects the micro shear bond strength of SDF- treated demineralized dentin.
Recommendation:
Further investigations are needed regarding quantitative measurement of depth of SDF penetration in dentin and its effect on micro shear bond strength after aging in addition to elemental analysis for products resulted from SDF application. Additional investigations needed to be done on the Nano particles of SDF.