الفهرس 
Loss of tooth structureOnly 14 pages are availabe for public view
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Abstract
The present study aims to evaluate the effect of extension of endocrown and ferrule effect on the internal and marginal adaptation of anterior endocrown made of Nanoceramic composite blocks.
Twenty eight freshly extracted human upper anterior teeth with comparable dimensions were used in this study. The twenty eight teeth were divided into two groups of 14 teeth each. Samples of group A received endocrown with short extension (2mm) while group B received endocrown with long extension (5mm). Each of the two groups was further divided into two subgroups of 7 samples each. Subgroup 1 is prepared with ferrule while subgroup 2 without ferrule.
Groups A1 and B1 were decoronated 2mm above CEJ to provide ferrule. While groups A2 and B2 were decoronated at the level of CEJ. All samples then were endodontically treated and all samples were individually mounted vertically in polymethyl methacrylate (PMMA) resin blocks to a depth of 2 mm apical to the CEJ, to facilitate handling.
CNC machine was used to prepare the extension inside the root canal, 2mm depth in groups A1 & A2, and 5 mm depth in groups B1 and B2. The ferrule design in groups A1 and B1 was also prepared by CNC machine by making a deep chamfer finish line of 1mm thickness and 2 mm height with 6 degree taper.
Teeth were then scanned, endocrowns were designed and milled using CAD/CAM cerec 3 milling machine.
The internal and marginal fitness was measured using replica technique. The prepared teeth were carefully filled with a light body silicone impression material (Elite HD, Zermakh SpA) and then enendocrowns were seated on them with maximum hand pressure to simulate cementation. After complete setting of the impression material, the endocrowns were carefully removed. The thin layer of impression material, representing the discrepancy between the endocrowns and abutment teeth, was stabilized with more viscous silicone material in a different color (Putty impression material (elite HD, zermakh SpA). After setting of the putty material, both silicone materials were removed carefully as one piece from the prepared teeth.
All replicas were cut with a razor blade along the abutment axis in buccolingual direction. Replicas are then examined under digital microscope. At magnification of 50x and images were taken using a connected digital camera and transferred to software Image J version 2006.02.01 on DELL compatible personal computer. Six measuring points were measured for groups A1 and B1 (groups with ferrule effect) and 4 measuring points were measured for groups A2 and B2 (groups with no ferrule effect). Data obtained were collected, tabulated and then subjected to statistical analysis.
General Linear Model GLM procedure was used for testing the significance of the main effects; ferrule effect, length of endocrown extension and their interaction, on the internal fitness. (Univariante Analysis of Variance ANOVA with two fixed effects).
The results revealed that the ferrule effect with short extension endocrown showed the best internal and marginal fitness with significant effect of ferrule and no significant effect of extension but high significant effect of interaction between them on internal fitness. Ferrule and extension was not significant in case of marginal fitness.
Also, the results reported a minimum film thickness at the margin and maximum thickness at the occlusal point of measurement in all samples of groups.