ABSTRACT
This study was designed to study the effect of different surface treatments on ceramic/ cement bond strength
Material and Methods: Sixty six disc shaped Duceram LFC as well as 66 Inceram samples [3mm thickness and 6 mm diameter] were constructed and divided into 3 groups according to the type of surface treatment employed. Group 1 was Al[2]O[3] blasted, group 2 was HF etched and group 3 was copper coated. Each group of the tested ceramic was divided into 2 subgroups according to the type of cement used. Subgroup 1: twin samples were cemented with glass ionomer cement, subgroup 2: twin samples were cemented with resin cement. A stereomicroscope was used to measure the surface roughness of the differently treated ceramics and calculated the interfacial mean pore count and average pore size of cemented samples. A scanning electron microscope was used to study the surface topographic changes of the differently treated ceramics and calculated the interfacial mean pore count and average pore size of cemented samples. A scanning electron microscope was used to study the surface topographic changes of the differently treated ceramics. Shear bond strength values were measured using a universal testing machine. For the copper coated samples, optical measurement were taken using a spectrophotometer [N = 5 for each material] and color change delta E was calculated. All data were statistically analyzed using ONE WAY ANOVA
Results: The highest bond strength was obtained with the blasted and copper coated groups of the tested ceramics when glass ionomer cement was used. With resin cement, the HF etched Duceram and the blasted Inceram groups exhibited the highest shear bond values due to the increased surface roughness [Ra]. However the blasted Inceram recorded the highest shear bond values compared to the HF etched and copper coated groups with resin cement. Spectrophotometric measurements revealed no color changes [delta E] before and after copper coating
Conclusions: blasting and copper coating Duceram LFC and Inceram exhibited a high shear bond values with glass ionomer cement. Blasting or HF etching is recommended for Duceram LFC when resin cement is to be used. However, blasting of inceram is recommended when resin cement is to be used
ABSTRACT
Objective: To evaluate the fit of crowns constructed from metal ceramic nicke-chromium alloy, gold electroformed and Cerec 3 restoration systems
Materials and methods: A total of thirty crowns were fabricated in this study: two main groups: fifteen anterior and fifteen posterior crowns. Each group was divided into three subgroups, each of five crowns were designed as follows: five nickel-chromium ceramo-metallic crowns, five gold electroformed ceramo-metallic crowns and five Cerec 3 [all-ceramic] crowns. The vertical gap distance defined as the marginal opening between the prepared die margin and the most apical surface of the cast crowns was measured before and after porcelain application using a traveling microscope
Results: for the metal ceramic crowns before porcelain application both systems showed clinically accepted range of marginal gap but the gold-electroformed system showed better marginal fit. After porcelain application the metal ceramic systems showed distortion in marginal fit than before porcelain application. The gold-electroformed anteriors system was significantly distorted more than the nickel-chromium and Cerec 3 systems. The posterior crowns were insignificantly different from each other and within the clinical acceptable range for marginal gap
Conclusion: 1- The posterior crowns are within the clinical acceptable range for marginal fit for all systems before and after porcelain application. 2- The nickel-chromium and the gold-electroformed systems are within the clinical acceptable range for marginal fit before porcelain application. 3- The high temperature used during the firing of porcelain affect the marginal fit of a metal-ceramic restorations. 4- The distortion in the marginal fit of anterior crowns was pronounced for the gold-electroformed system after porcelain application. 5-CAD/CAM [Cerec 3] crowns represent good technology compare to other fabricated techniques
ABSTRACT
Objectives: to evciluate the microstructure of the recently developed glass ceramic [Leucite-Egypt] using scanning electron microscope and its shear bond strength to commercially available nickel chromium alloy
Materials and methods: for microstructure investigation four metal discs in dimension 3mm in diameter and 1.5mm in thickness [nickel chromium] were cast, 2 for each ce-rami: material [Leucite-Egypl and Vita company]. Both ceramic materials were fused [3mm in diameter and 2mm in thickness] according to manufacture instruction. They were examined by scanning electron microscope [SEM] at different magnification. For shear bond strength testing, ten cylindrical metal specimens [35mm in length and 4.5mm in diameter] were prepared five for each ceramic material. The ceramic materials were applied in dimension 8mm in height and 1mm in thickness, all specimens were subjected to shear bond strength testing in a universal testing machine. Data were collected, tabulated and statistically analyzed using Student t test
Results: SE micrographs revealed that the two tested materials composed of two phases, grayish white leucite crystals in dark gray vitreous glassy phase. The scanning electron micrographs of Leucite-Egypt ceramic were characterized by the presence of microcracks as well as the presence of the two crys-tallographic forms, tetragonal form and metastable cubic form. No statistically significant differences were found between the mean shear bond strength values of the two tested materials. Further studies are recommended to investigate the strength properties of Leucite-Egypt by different rate of cooling