الفهرس 
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Abstract
According to the objectives of this study, three different disinfectant materials were tested for their influence on the dimensional stability of addition silicone impression material. The null hypothesis for the present evaluation assumes that there is no difference between the four research groups in terms of their dimensional stability, which means that the influence of different disinfectants materials was not considered.
All impressions were scanned using CBCT scanner directly after taking them under the specific conditions: 80 kV, 1 mA, 0.125mm voxel size, 100X 50 mm field of view, as well as 0.125mm voxel size. The DICOM file collected by The CBCT images were underwent reconstruction into 3D pictures, which have been then translated into the stereolithography format employing a 3D imaging software application. (Blue Sky Plan®). then eight impressions were stored in dry condition without disinfection as a control group I, while group II, impression was disinfected by 0.525% sodium hypochlorite, group III impression was disinfected by ozonated water, group IV impression was disinfected by gaseous ozone.
All four groups were rescanned by CBCT Scanner after being disinfected by different materials, A set of CBCT images was collected, and hence the negative form of the impression image was converted into the positive form using a computer program to produce the final digital model and four linear measurements of inter-abutment distance (A1-A2, B1-B2); cross arch distance (A1-B1, A2-B2) of each digital model were made to evaluate the dimensional stability. The data were analyzed via Statistical software.
The impressions disinfected by gaseous ozone showed better dimension stability than the other two groups when statistically significant difference was found between II &III disinfectant’s groups. The overall dimensional changes were analyzed Statistically and showed clinically insignificant. Since it was at the lowest possible level and was beyond the permissible thresholds of changes of less than 0.5 %, as stated by the ADA standards for elastomeric impression materials.