الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Bonded porcelain veneers can provide successful esthetic and functional long-term service for the patients. Porcelain laminate veneers offer more extensive applications when they are used cautiously and the results achieved have been gratifying for the dentist and the patient alike. It has become increasingly apparent that conservation of tooth structure is a major factor in determining the long-term prognosis of any restorative procedure.
This clinical study was reviewed to evaluate the effect of two preparation designs and two different ceramic materials fabricated by two different techniques on both color and marginal accuracy of porcelain laminate veneers.
Thirty two porcelain laminate veneer units for maxillary anterior teeth were divided into two equal main groups according to the tooth preparation design; feather edge preparation design and butt joint preparation design. Each main group was further divided into two equal subgroups according to the technique of fabrication: subgroup A, n=16 were fabricated by build up technique of feldspathic porcelain. And subgroup B, n=16 were fabricated by heat pressing technique of lithium disilicate ceramic.
For each PLV unit included in this clinical study, color reproduction was assessed and marginal accuracy of both gingival and incisal margins were measured.
All teeth were prepared to accommodate laminate veneers of standard thickness. The PLVs were fabricated according to the manufacturer’s instructions. Then the laminate veneers were surface treated and silanated. The enamel of the prepared surfaces of all teeth was acid etched and bonded. Each laminate was luted to its corresponding prepared tooth with light cure composite resin cement.
The color reproduction was assessed using intra-oral VITA Easy shade spectrophotometer; Results and color information were displayed on the screen of the device.
The marginal accuracy measurement was done using the digital microscope (Scope Capture Digital Microscope, Guangdong, China). The images were captured by magnification X25, and transferred to an IBM personal computer equipped with the Image-tool software (Image J 1.43U, National Institute of Health, USA). Within the Image J software, all limits, sizes, frames and measured parameters are expressed in pixels. The mean marginal gap discrepancies for the individual PLV were not only calculated as a whole, but also categorized according to margin location in order to discover which margin had minimum/maximum gap. Then all results were collected and tabulated for further analysis.
The data were analyzed by Mixed ANOVA to assess the effect of the preparation design, the fabrication technique, and the margin location over the marginal accuracy of the PLVs followed by simple main effect with Bonferrioni correction. And Two- way ANOVA to assess the effect of the fabrication technique and the preparation design over the color reproduction (∆E) of the PLVs.
The results of the marginal accuracy revealed that the gingival margins showed better marginal accuracy in comparison to the incisal margins. At the incisal margin: no influence of the preparation design was found on the marginal accuracy, however, the fabrication technique showed significant effect; where the build up technique showed less marginal gap than the heat pressing technique incisally.
In color reproduction results, both preparation designs: (feather edge & butt joint) and both fabrication techniques (build up & heat pressing) showed clinically accepted color reproduction (∆E < 3.7).