New Digital Protocol for Standardization of Endocrown Preparation.

Objectives: One of the most important variables that should be standardized is the cavity preparation of the tested samples in the in vitro studies, the purpose of this study is to produce an accurate technique for standardization of cavity preparation by using CAD\CAM.
Methods: : ten selected non carious recently extracted for orthodontic treatment plane purposes of upper premolars had been used in this study.
All extracted teeth received endodontic treatment by the same operator, then immersed in auto polymerizing resin at the level of 2mm below of the cement enamel junction.
First, we design the standard cavity preparation parameters through 3D Design software (Rhinoceros 3D; Robert McNeel & Associates, North America, USA) as follow: (Buccolingual width 4mm , Miseodistal width 3mm, Total depth 4mm, Degree of convergence 20 degree).
Then, we send the cavity design as an STL file to the milling software ((hyperDENT®, Follow-me, Technology Group, Munich, Germany) in order to select job procedures needed to produce our predetermined cavity design.
At the last, to hold the tested samples within the milling machine we designed a special holder
Results: By using this technique, we had the ability to use CAD/CAM system to perform a standard intracoronal cavity preparations for total 10 upper extracted premolars which resemble perfectly our digital designed cavity preparations.
This study will give us opportunity to use this technique to standardize any cavity design accurately.
Conclusions: through using 3d designing software we could design any cavity preparation for any cavity preparation either intracoronal or extra coronal, full coverage or partial coverage and send it accurately to the milling software ( hyperDENT®, Follow-me, Technology Group, Munich, Germany) which give us the opportunity to select the job procedures from simulation process that will produce this specific cavity preparation in all specimens , in order to standardize the position of the cavity within the specimen , we can use the special designed holder to determine the central position within the specimen at which the cavity preparation will be obtained.