RESUMO
The use of natural and bio-inserts in composite resin restorations was introduced in an attempt to reduce polymerization shrinkage, by minimizing the volume of the composite material used, which is the forerunner of composite failures. The question ,whether they can bond perfectly to composites to prevent them acting as stress raisers, was always in mind. Also their influence on the fracture resistance and leakage of the restorations was to be tested accounting for their influence on minimizing shrinkage. A group of natural silicates, sulfates and carbonates beside biogenic aragonite derived from fish bones were used as natural inserts. The used silicate minerals were represented mainly by Quartz [Tectosilicates] while the sulfates were represented by celestite [SrSO4], and the used carbonates minerals were biogenic aragonite, magnesite and dolomite. These inserts were treated with silane and Vivadent bonding agent to improve the bond strength with the associated composite material. Shear bond strength of the inserts, after the different treatments, to composites was evaluated. The treated samples were subjected to Petrographic, and SEM investigations to evaluate their effects on the hermetic seal of the composite resin restorations. The fracture resistance of the teeth with the class five composite restorations was tested. The study also included testing micro-leakage in class V composite restorations including the inserts inside using the image analysis system and stereomicroscope. It was concluded that the use of natural and bio-inserts in composite restorations enhanced the fracture resistance of the tooth restoration complex and minimized micro-leakage, which can be secondary influences to lower polymerization shrinkage. Silane treated inserts were more efficient in achieving their goal than the ones treated with dentin bonding agents. The aragonite inserts were statistically significantly more effective than the other four types