One of the greatest challenges a ceramist faces on a daily basis is that of controlling moisture in the build-up, especially in complex anterior reconstructions. Multiple powder build-ups which attempt to mimic natural incisal esthetics can tax even the most experienced ceramist. The slightest lack of concentration, accidental vibration or even inadequate moisture control may produce undesirable consequences. Subtle, complex effects which have been carefully placed may be instantly lost or blended together. If the build-up falls labially or lingually, the ceramist must grind the effects back to their appropriate labio-lingual position and begin anew.

Begin with the End in Mind

Pressable ceramics offer a much more predictable technology to the ceramist. To insure a complete and ‘stress-free’ pressing, the technician must wax to 80-90% of full-contour. This thickness requirement affords the opportunity to complete a full-contour wax-up with little additional effort, especially if a diagnostic wax-up was created prior to the preparation appointment. Simply lubricate the die and model with an alcohol-free die-lube, and wax inject using a silicone index of the pre-approved master diagnostic model or provisional model. If these tools haven’t been supplied to the technician, one may choose to wax-up to full contour and then fabricate a silicone index from the wax-up.

After pressing, the restoration is carefully divested (fine divesting is accomplished with 50µ aluminum oxide at 15-20 p.s.i. max.) then re-seated on the die using magnification and the proximal contacts are adjusted. At this point, the silicone index is divided labio-lingually into two halves through the incisal edge. The matrix now provides a precise template for the envelope of function, including incisal edge position. This is particularly invaluable for the cut-back of the labial surface, which will subsequently determine how prominent or subtle the incisal effects will appear. If an aggressive cut-back is performed, more space is consequently created and will provide a more diffused or filtered effect. Also, the choice of enamels (more or less translucent) will greatly influence how pronounced or subtle the internal characterizations (mammelons, transparent zones, etc.) appear.

Staining or Layering Ingots? No Longer an Issue

One of the principle advantages of the Authentic® system over other systems is that any ingot may be utilized in the staining technique, the layering technique or a combination of the two. This presents a tremendous opportunity to the technician as he may now select the appropriate ingot based on its opacity level (20, 30, 45 or 70%) and specific esthetic requirements, rather than accommodating the case to the few ingot choices within a particular technique category (i.e. shading or layering.) The critical element of fluorescence, not found in many competing products, is incorporated into all Authentic® ingots, stains and layering materials. Therefore, any combination of techniques (i.e. staining or layering) may be utilized without compromising the esthetics of the case.

Ingot Selection

When selecting an ingot, it is important to pre-determine final thickness of the restoration. A minimum pressable core thickness of 0.8mm is recommended not only for strength issues, but also because its’ respective opacity level and chroma saturation is based upon this thickness as well. The theory behind this rule is that if inadequate or minimal reduction is given, and an ingot of the final shade is selected, then the dentin color (selected ingot shade) will obviously extend into the incisal. Without adequate space for a reasonable incisal cut-back (0.3-0.5mm for enamel application) an unnatural appearance in the incisal and a consequential lowering of the value of the restoration is inevitable.

To compensate for this ‘less than ideal’ reduction situation, as a general rule, the technician should back up 2 ingot shades lighter than the final Vita shade. For example, if the final shade is Vita A2, then an SLA0+ or SLA0++ ingot is selected. If the stump (prepared tooth) is discolored or the shade shift between the pre-treatment shade and the final, requested shade is substantial, an ingot of higher opacity (++) should be chosen. Remember, a ‘+’ ingot is 45% opacified at 0.8mm and will be less opacified (approximately 36%) at 0.6mm. A ‘+ +’ ingot is 70% opacified at 0.8mm and will be less opacified (approximately 52%) at 0.6mm.

Micro-Layering

One of the simplest and most predictable techniques for creating natural-looking restorations is ‘Micro-Layering.’ The effect created is a result of the synergy between ‘Internal Live-Staining’ (direct staining of a reduced dentinal core-Hitoshi Aoshima) and a subsequent minimal, micro-layering of the incisal third and/or occlusal. It consists of the following four easy steps:

Using a Diamond Wheel, the labio-incisal 1/3 is reduced palatally to the desired (labio-lingual) position-use the silicone index to verify this position. Next, using a pencil, the length and definitive outline of the dentinal projections (finger-like structures) is drawn directly on the core material, and then defined using a Silicone wheels, diamond discs & points. Finally, the restoration is lightly abraded using 50µ Aluminum Oxide at 20 p.s.i. and cleaned in an ultra-sonic unit using distilled water.

At this point, depending on the desired effect, the restoration is characterized using Authentic® fluorescent stains; even mammelons may be applied. Several factors must be considered when staining the restorations, including: tooth preparation reduction, the final core thickness, the stumpf color, which ingot was selected and the final tooth shade.

Begin the staining process by applying an even covering of the basic dentin colors, then move on to any special effect stains (i.e. ‘Smoke’). Mammelon effects may be painted on using stains or a mixture of glaze liquid and IODs 1-5 (Intensive Opaceous Dentins).
After characterizing, set the effects by firing on a 2nd Dentin or Stain firing at 740° C. After firing, verify the effects against a black background; soften by removing (grinding away) material, or intensify by adding additional material and firing again.

Having prepared the core material, the technician may begin layering the enamel. Some technicians prefer a ‘Lateral-Segmental’ technique with multiple translucent and transparent enamel powders, while others may apply a mixture of Transparent Opal and Transparent Clear at (2:1). Both techniques have their advantages; however, the later technique has become increasingly more popular because of its simplicity.
Note: If the later technique is chosen, different combinations and ratios of enamels may be selected to produce specific effects with varying degrees of translucency.

If the dentin shade was achieved purely by staining, and no dentin or enamel was applied in the middle and cervical thirds of the tooth, then, at least 2 moderately thick coats of external glaze medium should be applied.

Hint: If the technician knows that only the incisal third will be layered, he may apply a coat of glaze material (extending slightly beyond the ‘stained-only’ area) prior to the layering of the incisal (in a separate firing.) This will allow the ceramist to contour the restoration and then apply glaze only one time. A second option is to simply extend a wash of either the appropriate dentin powder or enamel such as Transparent Opal, over the middle third and cervical areas, thereby facilitating a ‘natural’ self-glaze.

The "Micro-Layering" technique facilitates the technician’s creative abilities by providing a higher degree of predictability in layering. The novice ceramist will produce restorations with natural effects in just a short time, and the experienced ceramist will create characterizations so life-like in his or her restorations, that only heor she will know for certain which is artificial and which is natural. In addition, the technician’s productivity will improve because of an increased ability to precisely place and control color, effects, translucency, value and contour.

Take your restorations to the next level of excellence when you press Authentic® and implement ‘Live-Staining’ and ‘Micro-Layering’ into your technique armamentarium.