section three:

• XII. Core Reduction and Cut Back
• XIII. Staining Technique
• xIV. Low Fusing Ceramic Calibration
• XV. Layering Procedure

Xii.    core reduction and cut back

• Using clean diamond discs, diamond impregnated silicon/rubber wheels and ceramic stones (MICROSTAR, carefully reduce labial, lingual and inter-proximal surfaces to the respective degree of full-anatomical contour desired.



VIP: Remember, we must observe the same minimum thickness
requirement as for all-ceramic restorations (0.8mm) and maintain a majority thickness ratio of at least 60% pressable core, to no more than 40% ceramic overlay material. Failing to observe this rule will result in fracturing and the potential failure of the restoration !


• Reducing the pressable ceramic material to less than 0.8mm is contra-indicated, and is an inherently risky compromise. Keep in mind that all manufacturers of leucite-reinforced pressable ceramic base their respective strength studies on a minimum core thickness of 0.8mm.
• Prior to staining or layering, the surface of the pressable forms should be abraded lightly with 50 micron aluminum oxide @ 20 psi. They should also be cleaned thoroughly in an ultra-sonic unit using distilled water.

XIII. staining technique

1. Mix stain thoroughly to a creamy consistency using an agate spatula or glass rod.
2. Do not wet the restoration surface with glaze liquid prior to staining.
   Wetting the surface will inhibit precise placement of characterizing stains, and the stains may puddle-up or move.
3. Apply stain evenly-if a significant amount of staining is required to achieve the shade, two stain firings may be necessary.
4. Apply incisal effects carefully and sparingly- remember, "less is better."
5. Fire stains on a stain/glaze firing.
6. After characterizing, apply glaze material, preferably in 2 applications.
7. For best results, mix glaze powder with glaze liquid to a cold "honey-like" consistency, or use Authentic® Paste Glaze pre-mixed.
8. The first coat should be applied in a relatively thick coat. Do not wet restoration with glaze liquid prior to the application of glaze as this will dilute the mixture and cause inconsistent coverage (puddling).
9. The first coat will penetrate the surface, and the second application will seal the stain in and provide a smooth, homogenous surface. After firing, use diamond polishing paste, or silicon wheels to achieve a natural surface luster.

RESOURCES:
Authentic® Pressing Parameters Guide
Authentic® Firing Parameters Guide

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xiv.   low fusing ceramic calibration

Because most ceramic furnaces fluctuate in the lower fusing range (800 °C,) it is imperative that test tabs be fired using Transparent Clear ceramic to determine the correct high temperature specific to your furnace which fully vitrifies the ceramic.

To perform this test, the technician must follow these four easy steps:

1. Create tabs of Transparent Clear about 8mm square and approximately 0.5mm thick.
2. Replicate 1st dentin firing conditions. Place ceramic tab on an ultra-thin piece of fiber-tray or platinum foil, on top of a firing peg (Master Ceramist® Micro Color coded w/ metal pins) then place on top of a honeycomb tray at the same height position in the furnace as a crown would be fired.
3. Work with one variable (high temperature) only. Keep all other parameters constant, including hold time.
4. Verify that the tab is fully vitrified, with no partially fired particles. Additionally, the print on the cap of a bottle of Authentic® should be readable through the tab. The surface gloss should be relatively high, while still maintaining the edges of the tab.

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Xv.   layering Procedure

1. Use the appropriate intensive opaceous dentin (IOD), dentin, enamels and transparent enamels to complete the anatomical build-up.
2. Because of the 4 micron average particle size, a minimal amount of shrinkage will take place, and consequently very little condensing is required (generally one gentle tap to bring the moisture to the surface).
3. Additionally, overbuilding is not necessary because of aforementioned ceramic particle attributes.
4. Verify correct maturation of 1st dentin firing as per previously mentioned ceramic calibration technique.
5. In most cases, a minimal, "micro layering" technique is all that’s necessary to achieve a beautiful esthetic result.
   See Authentic® pressable ceramic manual.