Structural and Mechanical Investigation of Class I Biomimetic Composite Dental Filling by X-ray Computed Tomography, Scanning Electron Microscopy, and Microtensile Bond Strength Testing

Nowadays, short fiber-reinforced composites are broadly used in modern restorative dentistry. The tensile strength, Young's modulus, density, and polymerization shrinkage of these materials are developed to mimic the original teeth tissue best. The shrinkage, however, will occur during any polymerization process, which can cause residual stress and gap formation between the tooth and the filling. These can lead to the propagation of cracks, reduction in the adhesive bond strength, or even cause separation in the restoration. During this research, a biomimetic dental restoration was created on a surgically removed third molar with EverX short-fiber reinforced dental composite by bulk-filling technique. The restored tooth sample was examined by X-ray computed tomography to obtain a 3D image of the whole restoration. The volume of the used adhesive, the material discontinuities, and internal cavities were determined. A cut-out slice was further investigated by scanning electron microscopy to examine the adhesive layer thickness, the gap formation, and the quality of the filling. Finally, microtensile specimens were machined to evaluate the bond strength between the tooth dentin and the filling material.