الفهرس 
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Abstract
The present in vitro investigation was designed to study the effect of some technical variables and resin phase modification on micro leakage of direct resin composite restorations.
The aim of the study was in three folds, the first was to investigate the influence of using different application techniques; bulk filling technique, horizontal filling technique, and oblique incremental filling technique. The second, was to study the effect of the modifications of resin matrix i.e., the use of low–shrinkage composite (InTen-S) material versus microhybrid composite resin restorations on the marginal sealing of both occlusal and gingival margins at six month storage. The third was to study the effect of different adhesive systems: two steps, self-etching. Primer adhesive system (6th generation) AdheSE and single step, self-etching primer adhesive system (7th generation) on the marginal sealing G-bond.
A total of 240 freshly extracted molars were used for preparation of 240 standardized class V cavity in the buccal surface of all the teeth, the occlusal margin was in enamel, while gingival margin was prepared in the root surface. The teeth were divided into two major equal groups (120 each). The teeth were divided into two major equal groups of 120 each. According to the resin formulation of composite resins. In the first group, the cavity was restored with microhybrid composite (Tetric Ceram). While in the second group, the cavities were restored with low-shrinkage composite. (InTen-S) each group was subdivided into three equal subgroups of 60 teeth each, according to the three type of insertion techniques either bulk, horizontal or oblique.
Each subgroup were divided again into two division (20 each ) relative to adhesive systems, either 6th generation, two steps, self relative to adhesive system, or 7th generation, single step, self etching-primer adhesive system AdheSE. All the teeth were examined, and assessed at both margin either, enamel or dentine for the tooth composite restorations interface after six months.
Another 30 composite samples were done using circular Teflon mold of 3 mm depth and 6 mm diameter. Those specimens were divided into two major equal groups (15 specimens each) according to composite resin materials. Each group will be subdivided into three equal subgroups (5 specimens each) according to the type of insertion technique which used either bulk, horizontal, or oblique. After Finishing and polishing of restoration. The apical foramen was occluded for each tooth. The entire tooth was painted with two coats of nail varnish to within 1 mm of the restorations margins, stained with dye, sectioned into the cavities were restored with low-shrinkage composite. (InTen-S) each group was subdivided into three equal subgroups of 60 teeth each, according to the three type of insertion techniques either bulk, horizontal or oblique.
Each subgroup were divided again into two division (20 each ) relative to adhesive systems, either 6th generation, two steps, self relative to adhesive system, or 7th generation, single step, self etching-primer adhesive system AdheSE. All the teeth were examined, and assessed at both margin either, enamel or dentine for the tooth composite restorations interface after six months.
Another 30 composite samples were done using circular Teflon mold of 3 mm depth and 6 mm diameter. Those specimens were divided into two major equal groups (15 specimens each) according to composite resin materials. Each group will be subdivided into three equal subgroups (5 specimens each) according to the type of insertion technique which used either bulk, horizontal, or oblique. After Finishing and polishing of restoration. The apical foramen was occluded for each tooth. The entire tooth was painted with two coats of nail varnish to within 1 mm of the restorations margins, stained with dye, sectioned into halves and observed with stereomicroscope at X30 magnification and scored for the degree of dye penetration at the occlusal and gingival margin of the restorations.
A photographic record of each specimen was obtained and scored for the degree for dye penetration at the occlusal and gingival margin of the restorations. Image analysis for each 30 specimens were performed using image analysis software to calculate the surface area of gap formation in µm, also the length of the dye penetration along the cavity walls and margin was measured at the occlusal and gingival margin. The result revealed that there was significant increase in both gap surface area and linear dye penetration in cavities restored with microhybrid composite, than that restored with low-shrinkage composite. Also there were significant increase in both gap surface area and linear dye penetration between the cavities and specimens restored with bulk technique than that restored with incremental filling technique. Also there were no significant difference between cavities used either two step self-etch AdheSE or that used one-step self-etch G-bond in there marginal leakage.