الفهرس 
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Abstract
The current in vitro study was designed to evaluate the effect of salivary contamination either before or after the acidic primer application on the marginal adaptation of class V cavities restored with three different types of glass ionomer restorations. Forty five, caries-free, freshly extracted human sound molars from middle aged patients were collected. A Class V cavity preparation was done on the buccal or lingual surface of each tooth with cylindrical diamond bur under air-water cooling. The dimensions of the cavity were 3-mm in width (mesio _distaly), 2-mm in depth and 3-mm in length (occluso_cervicaly) with the occlusal margin in enamel and the gingival margin located in dentin. The prepared teeth were randomly divided into nine groups (5 teeth each) corresponding to different glass ionomer materials and saliva contamination timing. Groups 1, 2, 3: restored with conventional glass ionomer cements (GC Fuji IX GP). Groups 4, 5, 6: restored with resin modified glass ionomer cements (GC Fuji VIII GP). Groups 7, 8, 9: restored with nano filled resin modified glass ionomer cements ( Ketac TM Nano). Groups 1,4,7: acting as control groups. Groups 2,5: the cavities were contaminated with saliva before the conditioner application. group 8: the cavities were contaminated with saliva before the primer application. Groups 3,6: the cavities were contaminated with saliva after the conditioner application. group 9: the cavities were contaminated with saliva after the primer application. Samples in each group were thermal cycled in a thermo-cycling apparatus consisting of 1000 cycles simulating about 2 years of clinical service, alternating between 5oc-55oc with 30 seconds immersion time and 30 seconds transfer time. Samples were processed for SEM evaluation to examine the restoration margins at (60x and 120x) magnification. The degree of marginal gap was determined as the ratio of gap length to the total marginal length and converted to a percentage. The marginal gap was measured for all the samples using AutoCAD software. SEM examination revealed that no marginal gaps were detected at the enamel-GIC interface in the different tested groups that were not subjected to salivary contamination. It also revealed that small marginal gaps were detected at the cementum-GIC interface in the different tested groups that not subjected to salivary contamination. While in the samples that were subjected to salivary contamination there were marginal gaps formation. Gaps show higher scores when contamination occurred after primer applications than when contamination occurred before primer application. It was found that, the highest mean value of open margin was recorded for group 3 restored with GC Fuji IX after salivary contamination recoding 8.65 mm ± 0.391, while the lowest mean marginal gap length value was found at group 7 restored with Ketac Nano without salivary contamination recording 0.894 mm ± 0.259.