الفهرس 
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Abstract
Statement of the problem
Color stability of shade guides may be affected by sterilization and different disinfection methods. However, there is paucity of information regarding the effect of sterilization on the color stability of the shade guides.
Aim of the study
The purpose of this in vitro study was to evaluate the effect of autoclave sterilization and 3 chemical disinfectants on the color stability of 2 commonly used shade guides (Vitapan classical shade guide, A-D shade guide IvoclarVivadent) after one year of simulated usage.
Materials and Methods
The total number of specimens representing the 2 shade guides were divided into 2 main divisions (Vita and Vivadent) each division was then divided into 4 groups based on the treatment method as follows: Group A: sodium hypochlorite solution 5%, group B: Cavicide disinfection solution, group C: Micro 10 Enzyme solution and group D: sterilization. The CIE lab values of all shade guide tabs were measured with VITA Easy Shade spectrophotometer before and after disinfection or sterilization to calculate E.
In order to simulate 1 year of usage, first and third shade guides were immersed into their respective solutions for 5minX365, According to Cavicide manufacturer’s instructions group B specimens were subjected to spraying with the surface disinfectant Cavicide for 480 ,and the fourth shade guide was autoclaved at 134°C/10minX365. In order to measure the color changes (E) of all the shade guides’ tabs after 1 year of simulated usage, CIE Lab values were compared with initial measurements by using CIE color difference formula:
“E= ([L1-L2]2+[a1-a2]2+[b1-b2]2)1/2”
Results
The mean E values of the 4 groups were as follows:( in Vitapan classical shade guides sodium hypochlorite solution5% E=1.12, Cavicide E=0.78, Micro 10 Enzyme E=1.82 and autoclave E=0.98. In A-D shade guides sodium hypochlorite solution 5% E=0.97, Cavicide E=1.26, Micro 10 Enzyme E=1.01, Autoclave E=1.06.
Conclusions
Within the limitations of this study Cavicide disinfection solution and sterilization did not produce a perceivable color change with Vitapan classical shade guide (E<1).Sodium hypochlorite solution was the only treatment method that did not produce a perceivable color change with A-D shade guide (E<1).