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Pressed ceramic systems : 


These are probably the most widely used all-ceramic systems worldwide due to the lost-wax technique that has been mastered and is loved by dental technicians everywhere, the inexpensive laboratory technology, and the versatility of the current systems, which are able to fabricate all types of ceramic restorations (from the smallest veneer to posterior bridges).

The most famous example of pressed ceramic is the IPS Empress system (Ivoclar Vivadent), which was introduced more than 20 years ago.

♨️ All the systems that press the ceramic use the same laboratory technology:
- On the plaster model, patterns are made from wax either to the full size of the restoration or to a reduced dimension – called a core.
- The sprue is then attached and the wax pattern is invested in refractory material.
- The wax is eliminated from the mold, after which the ceramic is heated at a high temperature and injected/infused into the obtained mold.


♨️ Steps in fabricating a pressed ceramic restoration through the IPS Empress system :

1️⃣ The teeth are prepared following the general rules for all-ceramic restorations and the impression is taken with polyvinyl siloxanes (PVSs) or polyethers.

2️⃣ Specific models in the laboratory are poured, with and without removable dies and an alveolar model.

3️⃣ The wax pattern is fabricated on the cast in two different sizes:
** as a core (undersized) with 0.2 to 0.5 mm space left for the final layering for individualization.
** as the final restoration, in accordance with the real size and morphology of the restored tooth. Only the surface colorations and the glaze are applied.

4️⃣ The wax pattern is immersed in a special phosphate-based investment material, thus producing the refractory mold. The mold is inserted into a special furnace for the pre-heating and heating treatment.

5️⃣ In the special injection furnace, the mold and the ceramic ingots are introduced. These are available in five degrees of translucency: high translucency (HT), low translucency (LT), medium opacity (MO), high opacity (HO), and the value and opal special shades. These various options for translucency have improved the final esthetic results considerably.

6️⃣ The ceramic ingots are heated then pressed into the mold under pressure.

7️⃣ After pressing, the ceramic piece is removed from the investment material, resulting in:
** A restoration reproducing the final form and morphology, where the characterization is obtained only by external painting.
This technique was mainly used in the first generation of these materials and is still used in posterior teeth, inlays, onlays, and single crowns.
** A coping of “ undersized “ proportions, over which the e.max Ceram is layered.
This technique is mainly used in the esthetic area, for veneers, crowns, and bridges in the anterior area.








♨️ The space for final esthetic layering is obtained through the " cut-back " technique applied at one of two different stages in the technological process:
✅ Option 1 :
A full-size pattern of the ceramic crown is made in wax; it is invested and the ceramic is pressed; thereafter space is cut back from the pressed crown. 👀check the case below 👇🏻


✅ Option 2 :
The wax pattern is made in the final form and shape of the crown; the cut-back technique is done at this stage, thus investing an undersized pattern; it is then pressed, the result being an undersized restoration, on top of which the feldspar ceramic is layered. 
   
⛔️ If the first Empress generations were indicated only for inlays, onlays, veneers, and crowns, the last generation – e.max Press – have almost generalized applications. They can be used for mini-veneers, occlusal veneers, table-tops, inlays, onlays, anterior and posterior crowns, and three-unit bridges in both the anterior and posterior areas (except for the molar area). These ceramics are good for over-pressing on galvano-formed crowns or prefabricated metal abutments, single implants in the anterior and posterior area, three-unit bridges up to the second premolar, or telescopic crowns.
⛔️ This system is not meant for bridges in the posterior area, long-span bridges, subgingival margins of the preparation, extended edentulous spaces, bruxism, cantilever bridges, and Maryland bridges.
For long-span bridges in the premolar/molar area, the only ceramic that is
resistant enough is zirconium dioxide, but even here the glass-ceramic e.max Press finds its applications, because these ingots can be pressed over zirconia frameworks for superior esthetics.

To be continued ,,, “ Lab techniques “
Stay blessed 😇 💐