Influence of Ceramic Thickness and Ceramic Materials on the Fracture Resistance of Overlays

Description :

The study aims to compare the fracture resistance of various molar-form monolithic ceramic overlay materials fabricated using CAD/CAM technology and to analyze the influence of their thicknesses. The primary objective is to evaluate the influence of the materials’ thicknesses on the fracture resistance between the different CAD/CAM materials. The secondary objective is to assess the influence of the ceramic material on the fracture resistance of overlays. The study will be conducted on freshly extracted human mandibular molars with certain inclusion criteria, and it will use three different types of machinable CAD/CAM blocks. There will be 2 major groups: one Lithium Disilicate (LD) ceramic group IPS e.max CAD (Ivoclar, Vivadent) and one Nanohybrid (NH) ceramic group CERASMART® (GC Dental products). For each of the restoration groups, molar overlays with minimum thicknesses of 0.7, 1.0 and 1.5 mm will be fabricated using a CAD/CAM system with the groups LD1.0 and NH1.0 taken as control groups. After the cementation of the restorations, they will be subjected to thermal aging (thermocycling) prior to the loadbearing test. Afterward, a statistical analysis of the fracture resistance of the overlays will be conducted, taking into consideration both inter-group and intra-group variations in the thicknesses of the materials used. Why only 2 groups? Because the main focus of the study is the material’s thickness and here is an article published in 2015 titled "The Influence of Ceramic: Thickness and Ceramic Materials on Fracture Resistance of Posterior Partial Coverage Restorations." This article only studied two ceramic materials: Lithium disilicate glass ceramic IPS e.max and leucitereinforced glass ceramic IPS Empress, with two thicknesses: 1 mm and 2 mm (Bakemann et al.). Why only Thermocycling? Here is another article that studied the fracture resistance of indirect restorations after thermocycling only: "Effect of Inlays, Onlays, and Endocrown Cavity Design Preparation on Fracture Resistance and Fracture Mode of Endodontically Treated Teeth: An In Vitro Study" (Kassis et al.)