| Purpose and background:With the increase in the demand for oral aesthetics,the use of all-ceramic materials has become very common.Computer aided design /computer aided manufacture(CAD / CAM)ceramic materials are also favored by more and more patients.The optical performance of all-ceramic prosthetics plays an important role in dental aesthetic restoration.More and more attention has been paid to the color stability and semi-permeability of restorations.These optical properties are critical to the clinical repair effect of all-ceramic restorations.A variety of factors can affect the optical properties of the restorations in the oral cavity,such as eating habits,surface roughness and temperature of the restorations.The purpose of this experiment is to evaluate the effects of cold and heat cycles on the surface roughness,color,and transparency of two CAD / CAM materials with different surface treatments,and provide a certain reference for the clinic.Method:Prepare 56 pieces of lithium disilicate glass ceramics(UP.CAD HT A2)and resin infiltrating ceramics(VITA Enamic A2),place the test piece under running water and use 600 mesh,800 mesh,1000 mesh,1200 mesh water-resistant silicon carbide sand in sequence The paper is polished,and it is prepared into a test piece with a size of 10 mm × 5 mm × 2mm,and the thickness error of the test piece is controlled within 0.02 mm with an electronic digital display vernier caliper.After making all the test pieces,put them in deionized water,rinse them with ultrasound for 5 minutes,and dry them with absorbent paper.Randomly divide the specimens into 8 groups(n = 6),one extra specimen in each group is reserved for electron microscopy scanning before cold and hot cycles,and different surface treatments are performed for each group,respectively:(1)blank control group without surface treatment;(2)Polishing group polishes the test piece from coarse to fine according to the requirements(≤10000r / min),each polishing for 30s;(3)glazing group glazes the test piece according to the requirement,evenly brushing with glaze brush until it is even Up to the surface(Up.CAD porcelain furnace sintering glaze,810 ℃,sintering 15min;Vita Enamic light curing glaze,wavelength 395-480 nm,illumination 20s);(4)polishing glaze group according to the above steps to polish glaze;The process is completed by one person.8 groups of samples were put into a cold and hot cycle machine(5 ℃ and 55 ℃ hot and cold water)for 10,000 cold and hot cycle aging.Use a surface roughness measuring instrument and a spectrophotometer to measure the surface roughness value(Arithmetical mean deviation of the profile,Ra)and color parameters(L *,a *,b *)before and after the cooling and heating cycle,and calculate the color difference(color difference,ΔΕ)and transparency(Translucency Parameter,TP).Scanning electron microscopy was used to observe the surface morphology of each group before and after cooling and heating cycles.SPSS23.0 software was used to perform two-factor analysis of variance and Tukey’s multiple test on the experimental results,and the test level was two-sided α = 0.05.Results:1.After the hot and cold cycles,the Ra value of each group has an upward trend.The Ra value of the VITA Enamic group is greater than the UP.CAD group.The UP.CAD polishing and glazing group shows the lowest Ra value,and the cold and heat cycles have a small effect on the Ra value of the group.The VITA Enamic glazing group and the polishing glazing group have the lowest Ra value.The Ra value of the group is relatively close(P﹥0.05),but the Ra value of the polished and glazed group has the smallest change after the hot and cold cycles.2.Scanning electron microscopy was observed.There were many scratches in the blank control group of Up.CAD,but fewer scratches in the polishing group,while smooth surfaces were observed in the glazed group and polished glazed group.The effect of cold and hot cycling on the blank control group was more obvious.The surface of the VITA blank control group had more pores,and the pores in the polishing group were relatively reduced.A smooth surface with no pores was observed in the glazed group and the polished glazed group.After the hot and cold cycles,the smoothness of the glazed group and the polished glazed group decreased,and the pores in the polished group increased relatively,while the changes in the blank control group were the most obvious.3.After the hot and cold cycles,each group showed varying degrees of color change.The blank control group is the most obvious.TheΔΕ = 1.93 ± 0.01 in the Up.CAD group and ΔΕ = 2.17 ± 0.02 in the VITA group,but the ΔΕ values of the two materials are similar.The TP value of the Up.CAD polishing group is the highest,while the glazed group shows the lowest TP value.After the cooling and heating cycle,the TP value of the polished and glazed group is more stable,while the blank control group has a significantly lower TP value than other groups;The value change is similar to it,but the TP value of each group is lower than the Up.CAD group.Conclusion:1.Different surface treatments can affect the surface roughness of VITA Enamic and Up.CAD,and the Ra value of the polished and glazed group is the lowest.2.The transparency of the two materials can be affected by the type of surface treatment.Glazing can cause the TP value of the two materials to decrease.Polishing can increase the TP value to a certain extent.The semi-permeability and color stability of Up.CAD are better than VITA Enamic.3.The hot and cold cycling can cause the Ra value of VITA Enamic and Up.CAD to become larger and the TP value to decrease.Each group showed different degrees of color change,but all were within the clinically acceptable range(ΔΕ <3.3),and the color stability of the polished and glazed group was the best. |
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