Abstract: Objective To study the influence of different thicknesses and materials on the fracture resistance of inlays and the change of stress distribution, to provide experimental basis and support for restoration with inlays in clinic. Methods The standard preparation of inlay of the right lower first molar was selected, and the model was obtained by scanning. The thickness of the inlay was adjusted by software, and the metal dies were made by 3D printing. IPS e.max and Vita enamic were selected as inlay materials. Fracture resistance was tested on the inlays after bonding. CBCT data of lower right first molars of a healthy adultwas selected to carry out the digital model simulation. The stress distribution of inlay and remaining teeth with different thicknesses and materials were observed and analyzed. Results There were differences in fracture resistance among IPS e.max groups (P<0.05), and the largest fracture resistance was at 2.0 mm. There were differences among Vita enamic groups (P<0.05), and the largest fracture resistance was at 2.5mm. IPS e.max had higher fracture resistance (P<0.05) when the inlay thickness was 2.0 mm. In three-dimensional finite element analysis, the equivalent stress of IPS e.max inlays was larger than Vita enamic under the same thickness. The equivalent stress of residual enamel in IPS e.max group was lower than that of healthy teeth, while in Vita enamic group, the equivalent stress of residual enamel increased when the thickness was 2.0 mm and 2.5 mm. The peak equivalent stress of dentin restored with both materials was larger than that of intact dentin, but the peak equivalent stress of residual dentin decreased with the increase of thickness. Conclusion IPS e.max inlay with 2.0 mm has the largest fracture resistance. The fracture strength of IPS e.max is larger than that of Vita enamic and bears more stress than Vita enamic, which is more conducive to the preservation of the remaining tooth hard tissue.

Key words: Key words: Inlay, Fracture resistance, Thickness, Material, Three-dimensional finite element analysis