الفهرس 
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Abstract
This in vitro study was carried out to evaluate the microtensile bond strength and the interfacial micromorphology of resindentin interface after chemomechanical caries removal using Carisolv and NmonochloroD2 aminobutyrate (NMAB) solution and after conventional caries removal with low speed bur. A total of 120 mandibular molar teeth with grossly carious lesions were used in this study. The occlusal enamel of the carious teeth were removed exposing flat dentin surfaces containing the carious lesion. The teeth were grouped into 3 equal groups of 40 each according to the method of caries removal used; Carisolv system, NMAB system and conventional method (using a round diamond bur rotated in a low speed hand piece as a control group). Following caries removal, teeth of each group were subdivided into 2 subgroups each of 20 according to the adhesive system used; Syntac single component adhesive system and Excite adhesive system. A composite buildup was made on each tooth in layers of Tetric Ceram dental composite cured with light curing unit. The microtensile bond strength test:? 15 specimens of each subgroup were used for microtensile bond strength test. After thermocycling (between 5oc to 55oc for 500 cycles using 30 seconds dwell time ), the composite/adhesive/dentin complex of each specimen was sectioned into 1X1 mm2 sticks using a diamond disk in a low speed contra angle under continuous water spray. The sticks were fixed into a specially designed attachment of LLOYD Universal testing machine and the tensile force was applied at a cross head 2mm/min. The force causing failure was recorded and divided by the bonded surface area to obtain the microtensile bond strength in MPa. The results were then tabulated and subjected to statistical analysis using two way ANOVA and ttest for significance. The mode of failure of each debonded specimen was evaluated using a stereomicroscope. Evaluation of resindentin interfacial micromorphology 5 specimens of each subgroup were used for the interfacial micromorphology examination. The teeth with their composite build ups were sectioned into buccolingual direction, each section was polished using 600,800 and 1000 abrasive papers and then demineralized using HCl and deproteinized using NaOCl. The specimens were dried, sputter coated then photographed using Scanning Electron Microscopy. The conclusions of the present study were: 1?Chemomechanical caries removal method gave higher bond strength values of composite to remaining dentin compared with conventional mechanical method with bur when the same type of adhesive system used. 2?The bond strength of dental composite to dentin is affected by the type of adhesive system. 3 The thickness of hybrid layer of adhesive systems has no effect on the bond strength of composite restoration to dentin. Recommendations Chemomechanical caries removal is recommended to be used in specific conditions such as deep caries decreasing the risk of pulp exposure due to its selective nature in removing caries, inaccessible areas in the oral cavity decreasing the need of drilling and in medically compromised patients to eliminate the use of local anesthesia.