The aim of this study is to evaluate the fracture toughness and hardness of Vita Suprinity with and without cyclic loading and thermocycling(An in-vitro study)-24 plates of 3mm thickness were cut by an isomet cutting machine. All the specimens were sintered and then auto-glazed according to manufacturer's instructions.-All specimens were stored in distilled water at 37oC for 24 hours in sealed containers in incubator.-Half of the specimens were exposed to thermal cycling with number of cycles was 500 cycle (46) , Dwell times were 25 s. in each water bath with a lag time10 s. and The low-temperature point was 5 0C). The high temperature point was 55 0C. (46-47) and also were exposed to cyclic loading in chewing simulator machine in which Twelve specimens of experimental ceramic group were exposed to the mouth-motion fatigue at load of 50 N for 20,000 cycles with a frequency of 1.6 Hz-The other half was left with its glazed surface without any aging procedure thermocycling and cyclic loading.-Surface hardness and fracture toughness were measured before and afterstorage where the surface hardness was measured through Vicker‘s indentation: three indentations were made in each sample and the mean was calculated for each using this equation.HV=1.854 P/dFracture toughness was calculated by the indentation method through this equation.KIC = 0.016(E/H)-The basis of the indentation technique is a series of cracks that form under heavy loading for a certain duration in a brittle material around a Vickers diamond indenter. When viewed superiorly the cracks appear to emanate from each of the corners of the indentation. The size of these cracks expressed by the surface dimension ―c,‖ increases with an elevating indentation load and is an inverse function of fracture toughness. The data was obtained and the results were tabulated.ResultsIt is found that regarding Vickers hardness after aging (thermomechanical loading) control group recorded statistically non-significant higher mean value of Vickers hardness than experimental group, regardless to aging, totally it is found that the difference between control group and experimental group was statistically not significant and irrespective of material group, totally it was found that aging procedure affected on Vickers hardness mean value significantly.It was found that the highest mean value of hardness recorded at baseline then after water storage while the lowest mean ± SD value of hardness recorded after thermomechanical aging. The difference was statistically significant.We concluded that regarding the fracture toughness after aging, it as found that experimental group recorded statistically significant higher mean value of fracture toughness than control group ,regardless to aging, totally it as found that control group recorded higher mean value of fracture toughness than experimental group mean value. The difference between both groups was statistically significant, and irrespective of material group, totally it was found that aging procedure affected on fracture toughness mean value nonsignificantly.It is found that the highest mean value of fracture toughness recorded at baseline then after thermo-mechanical aging while the lowest mean ± SD value of fracture toughness recorded after water storage. The difference was statistically significant.ConclusionsWithin the limitations of this study, the following conclusions could be drawn as follows:•Ageing procedure with thermocycling and cyclic loading negatively affected the surface hardness for Vita Suprinity.•Ageing procedure with thermocycling and Fatigue with mechanical cycling for 20,000 times has on effect on fracture toughness of Vita