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Nanoleakage of different composite restoration systems

Objective This study was carried out to investigate the nanoleakage of different composite restoration systems (composite materials and its recommended adhesives). Patients and methods Thirty intact, noncarious human premolars were selected. Root apices of all teeth were sealed with wax. For each tooth, the roots were inserted into self-curing resin mold, with the long axis perpendicular to the acrylic resin base. Standardized class V cavities were prepared above the cemento-enamel junction by 1 mm, on the buccal surfaces of the teeth. The prepared teeth were divided randomly into three equal groups (10 each) according to restorative systems used: group 1: nanohybrid composite system, group 2: bulk-fill composite system, and group 3: flowable composite system. Each group was equally divided into two subgroups (five each) according to the thermal and load cycling treatments (A and B). All specimens were examined at the occlusal margins and cervical margins (divisions 1 and 2). All specimens were coated with two layers of nail varnish except for 1 mm, around the restoration margins and immersed in a 50% (w/v), sectioned in bucco-lingual direction and processed for scanning electron microscopy and energy dispersive analysis radiograph. Results The bulk-fill composite system (group 2) recorded the higher silver weight percentage mean value followed by nanohybrid composite system (group 1) while the flowable composite system (group 3) recorded the lowest silver weight percentage mean value in both cases whether the restorations were thermal and load cycled or not. However, a statistically significant difference was recorded in the three tested groups when subgroup A was compared to subgroup B in each group. Moreover, the results indicated that the mean value of nanoleakage at the cervical margins (division 2) in all groups (1, 2, and 3) and subgroups (A and B) recorded a higher significant nanoleakage than the occlusal margins (division 1) except group 2B which recorded no significant difference with a P value of 0.147. Conclusion The flowable composite system recorded the lowest silver weight percentage mean values. Thermal and mechanical stresses increase nanoleakage significantly.