🔥 E n d o c r o w n 🔥💣
When Where How

• when a posterior tooth has extensive tissue compromising associated with endodontic treatment, mechanisms to help the retention and to improve the stability are necessary for the indirect restoration. 

An alternative to simplify the protocol is the preparation of an endocrown or adhesive endodontic crown. This type of restoration consists of a large ceramic block that fills the pulp chamber and is adhesively cemented to the dental substrate. This technique presents satisfactory long-term clinical results in molars. In premolars, however, due to the unfavorable ratio between the base (area available for adhesion) and the height of the crown, the results are not as positive.

• The preparation is extremely simple, requiring only : 👇🏻
 the pulp chamber to be expulsive or divergent towards the occlusal surface,
 the preparation margins exhibit sharp well defined termination at 90 degrees to the outer surface,
 and that the interior angles are rounder. 
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The diamond points used to achieve these goals are only positioned parallel to the long axis of the tooth and automatically confer the ideal taper to the axial walls of the pulp chamber and always result in rounded internal angles. 

⛔️ An interesting approach in order to improve the mechanical retention of the restoration is “ to ferrule “ the crown, a procedure that consists in the preparation of a shoulder encircling the entire tooth. The ferrule increases the area available for adhesion and causes the restoration to embrace the remnant, resulting in improved stability and improved stress distribution from the occlusal function. It should be clear that 👀 the ferrule is an additional benefit, but not strictly necessary for obtaining a high quality preparation “ optional “.

Thus, in situations where the ferrule is not possible due to a lack of sufficient tooth structure - most modern ceramic systems require 1.5 mm of reduction in the region of termination to obtain suitable strength - or due to the limitations of the restorative system (eg, some CAD/CAM systems are unable to adequately reproduce part of the inner walls when present minimal thickness), one should only delimit the preparation margins 🤷🏻‍♂️.

In this case, the height of the tooth remnant is compatible with the accomplishment of ferrule. Furthermore, the axial distance between the walls of the pulp chamber and the external surface of the tooth includes the necessary reduction to define a shoulder termination without resulting in weak thin walls.

⛔️ It is always crucial to protect the surface of the adjacent tooth during the proximal preparation.

Note the features of the preparation once the initial reduction is concluded

The smoothing of the interior angles is performed initially with fine-grained diamond points, with the same format as the points already used during the preparation. Due to the geometric simplicity of the endocrown type preparations, the smoothing of the internal angles consists of rounding off the occlusal-axial angles. The same diamond points are used in the refinement of the preparation surface, both along the margins and within the axial walls of the chamber. Then the steps are repeated, with a diamond point of equal shape with extra-fine granulation. 
The finishing and polishing are completed through the use of specially shaped abrasive rubbers, similar to the diamond points used for the preparation. 
It should be noted that although in this sequence prior to the cavity preparation it has been chosen to make a filling with adhesive and composite, in the region of canals orifices, alternatively it may be kept exposed guttapercha. But, it is preferable to make the filling to prevent contamination of the root canals in the case of the temporary is dislodged and/or leakage occurs and to block the undercuts in this area.
Finally, the finished preparation presents taper, rounded internal angles and shoulder-end, sharp and well-defined margins with 90 degrees in relation to the external surface. 
An occlusal view of the completed preparation confirms that it fulfilled all the requirements described above. It is Not recommended for the preparation to present sharp angles, since they lead the concentration of stresses and may compromise the mechanical properties of the restoration.
✍🏻 Personally, I’d like to finish such cases the same visit using CEREC ..
The next post will explain how to take impression and commence with cementation procedures.
With regards ..