الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
This study included in vitro and in vivo testing. First, in vitro testing involved using forty rectangular ceramic specimens with the standardized dimensions of (12 wx14 lx2 thick.) using two CAD/CAM ceramic materials: Translucent Zirconia (InCoris TZI and hybrid ceramic (Vita Enamic) to its wear and their antagonistic wear behavior. Thirty extracted human permanent molars and thirty deciduous upper second molar were sectioned vertically to utilize the mesio-palatal cusps; forty sectioned cusps were used as an antagonist to each ceramic specimen and twenty cusps as antagonists for sound occlusal tables of respective lower molars. Ceramic specimens were divided into two groups (Zr., and Enamic); each contained 20 specimens of each material, 10 opposed by 10 permanent molar and 10 of each ceramic materials opposing 10 deciduous cusps. Weight loss and surface roughness was measured for each ceramic specimen and molar cusps before after the wear testing in a dual axis chewing simulator. A micro saw (ISOMET 4000) was used to cut ceramic specimens from commercially available ceramic blocks then the cut specimens of Zr. were sintered following its manufacturer’s instructions then all ceramic specimens were finished and polished. Permanent and deciduous molars were sectioned using ISOMET 4000 after being loaded on an acrylic block to handle teeth specimens. A digital caliber was used to confirm the standardization of all ceramic specimens of even dimensions (represent the dimensions of the Teflon housing of the ceramic sample in the chewing simulator). Molars were collected from the faculty of dentistry hospital, Minia University following its ethical guidelines of collecting human remains. Teeth were collected to be free of caries or wear and then kept in distilled water till using them in the wear testing. A weight of 3 kg which is comparable to 49 N of chewing force was used. The test was repeated 150.000 times (cycles) to clinically simulate the one year of chewing in oral conditions. Surface roughness was measured using USB Digital microscope with a built-in camera connected with an IBM compatible personal computer using a fixed magnification of 120X.The images were recorded with a resolution of 1280 × 1024 pixels per image and analyzed using WSxM software. Weight of specimens, sectioned cusps and sound molars was recorded before and after wear testing as well. Statistical analysis showed a significant difference in weight loss of ceramic specimens of the different materials used and in their molar antagonists and the control group after wear testing. For weight loss of tested material (ceramic and control enamel) against permanent enamel; the results of this in vitro study showed that: Zirconia showed the least loss of weight (Mean ± SD: 0.0005±0.001 g) followed by control enamel (0.004±0.0008 g) and Vita-Enamic (0.006±0.001 g) ; For weight loss of tested material (ceramic and control enamel) against deciduous enamel; the results of this in vitro study showed that: Zirconia showed the least loss of weight (Mean ± SD: 0.0005±0.001 g) followed by control enamel (0.05±0.01 g) and Vita-Enamic (0.008±0.002 g); For surface roughness of tested materials (ceramic and control enamel) against permanent enamel; the results of this in vitro study showed that: Zirconia showed the least increase in surface roughness (Mean ± SD: 0.0005±0.001 μm) followed by control enamel (0.004±0.0008 μm) and Vita-Enamic (0.008±0.002 μm); For surface roughness of tested materials (ceramic and control enamel) against deciduous enamel; the results of this in vitro study showed that: Zirconia showed the least increase in surface roughness (Mean ± SD: 0.0005±0.001 μm)
Followed by control enamel (0.01±0.002 μm) and Vita-Enamic (0.001±0.0002 μm); For weight loss of permanent enamel antagonist opposing ceramic and control enamel: Molar cusps opposing Zirconia showed the greatest loss in weight (Mean ± SD: 0.06±0.01 g) followed by control enamel (0.004±0.0008 g) and Vita-Enamic (0.001±0.002 g); For weight loss of deciduous enamel antagonist opposing ceramic and control enamel: Molar cusps opposing Zirconia showed the greatest loss in weight (Mean ± SD: 0.05±0.01g) followed by control enamel (0.02±0.004 g) and Vita-Enamic (0.005±0.001 g). For surface roughness permanent enamel antagonist opposing ceramic and control enamel; the results of this in vitro study showed that: Zirconia showed the least increase in surface roughness (Mean ± SD: 0.005±0.001 μm) followed by control enamel (0.002±0.0004 μm) and Vita-Enamic (0.001±0.0002 μm); For surface roughness of deciduous enamel antagonist opposing ceramic and control enamel; the results of this in vitro study showed that: Zirconia showed the least increase in surface roughness (Mean ± SD: 0.0005±0.001 μm) followed by control enamel (0.004±0.00008 μm) and Vita-Enamic (0.002±0.0004 μm).The results of weight loss and surface roughness was found statistically significant at P value.
The clinical study involved using twenty adult subjects (Age: 18-25) and twenty pediatric subjects (Age: 7-9) to receive a single all ceramic crown on a lower molar where the opposing teeth on the same side to be unrestored with sound enamel and the contralateral unrestored teeth of upper and lower arches acting as a control. Informed assents and consents were obtained from adult subjects and the parents of pediatric subjects, and the procedure was explained to them. It was assured that subjects included in this study were healthy with no parafunctional habits. Subjects were randomly allocated to receive either a Zirconia crown or a hybrid ceramic crown. Two CAD/CAM ceramic materials: Translucent Zirconia (InCoris TZI and hybrid ceramic (Vita Enamic). After preparation of teeth following the manufacturers instruction for each material, teeth were scanned using an intraoral scanner then milled crowns were adhesively cemented using dual-cured resin cement. After cementation, both arches were scanned using an intraoral scanner after cementation (baseline) and after one year follow-up period. Scanned arches were stored as STL files and baseline and follow-up scans were superimposed for comparison using WearCompare software. Volume loss (mm3) and wear rate () were measured as a measure of wear behavior of ceramic crowns, antagonist enamel and control side. The results of the clinical trial in adult subjects for ceramic crowns showed that: Zirconia crowns against permanent enamel showed the least change in volume (Mean ± SD: 0.34± 0.018 mm3) and vertical loss (wear rate) (Mean ± SD: 27±2.5 μm) followed by control enamel (Mean ± SD: 0.43±0.05 mm3) (Mean ± SD: 40.2±8.2 μm) and Vita-Enamic crowns (Mean ± SD: 0.93±0.044 mm3) (Mean ± SD: 83.2±9.7 μm). The results of the clinical trial in pediatric subjects for ceramic crowns showed that: Zirconia crowns showed the least change in volume (Mean ± SD: 0.13± 0.019 mm3) and vertical loss (wear rate) (Mean ± SD: 8.2±2.5 μm) followed by Vita-Enamic control enamel (Mean ± SD: 0.49±0.1 mm3) (Mean ± SD: 43.7±5.9 μm) and control enamel (Mean ± SD: 0.87±0.07 mm3) (Mean ± SD: 88±8.7 μm). The results of the clinical trial in adult subjects for permanent enamel antagonists against ceramic crowns and control enamel showed that: Permanent enamel cusps opposing Zirconia crowns showed the greatest volume loss (Mean ± SD: 0.66± 0.07 mm3) and vertical loss (wear rate) (Mean ± SD: 61±3.7 μm) followed by control enamel (Mean ± SD: 0.46±0.04 mm3) (Mean ± SD: 39±3.5 μm) and Vita-Enamic crowns (Mean ± SD: 0.20±0.03 mm3) (Mean ± SD: 19±4.7 μm).The results of the clinical trial in adult subjects for deciduous enamel antagonists against ceramic crowns and control enamel showed that: Deciduous enamel cusps opposing Zirconia crowns showed the greatest volume loss (Mean ± SD: 1.4± 0.2 mm3) and vertical loss (wear rate) (Mean ± SD: 100.4±9.7 μm) followed by control enamel (Mean ± SD: 0.92±0.06 mm3) (Mean ± SD: 86.8±6.7 μm) and Vita-Enamic crowns (Mean ± SD: 0.40±0.07 mm3) (Mean ± SD: 37.4±9 μm). The results of weight loss and surface roughness was found statistically significant at P value.