الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
 |  | from | 101 |  |  |
| | | from | 101 | | |
Abstract
Pressed lithium disilicate ceramics are widely used in the fabrication of dental restorations using the lost wax techniques. The lost wax technique involves contouring restorations to desired patterns. The patterns are sprued and invested, followed by burnout to create a mold within the investment, into which molten ingots are heat pressed. The patterns, either wax or resin, can be fabricated conventionally through laboratory manipulation and precise shaping or digitally through milling castable pattern materials. Ideally, pattern materials should burn out leaving residue-free molds for pressing. It has been claimed that some waxes may leave ash or carbon residue, possibly affecting the pressed restorations. The aim of this study was to evaluate the color of a pressed lithium disilicate glass-ceramic, IPS e.max Press, fabricated from wax or resin patterns that are fabricated by using conventional and milling techniques. Fifty-six pattern discs were divided into 4 groups (n=14) based on the pattern material and fabrication technique: conventional wax pattern group, conventional resin pattern group, milled wax pattern group, and milled resin pattern group. For comparison and evaluation of results, reference discs were fabricated, where a mold was created without the use of any pattern material. Lithium disilicate discs were fabricated by using the lost wax technique. The color parameters were measured with a spectrophotometer (VITA Easyshade® Advance) over a black background. The color difference (ΔE00) values were calculated and compared with perceptibility (ΔE00=0.8) and acceptability (ΔE00=1.8) thresholds to evaluate the color differences.
70
The results revealed that there was a significant difference in the color of IPS e.max Press ceramic fabricated from wax and resin pattern materials using conventional and milling techniques. In relation to the reference, the highest ΔE00 (2.06 ± 0.22) was that of the conventional resin group, which was beyond the clinical acceptability threshold. There was no significant difference in the ΔE00 values between the reference and the milled wax (1.48 ± 0.13) and milled resin (1.51 ± 0.15) groups, which were both clinically perceptible yet acceptable. The lowest ΔE00 was that of the conventional wax group (0.76 ± 0.04), which was clinically imperceptible.