Introduction: The type of the preparation junction is determined by a number of factors that need to be taken in consideration with CAD/CAM Fixed Prosthodontics: the material of which the construction will be made; the type and condition of the retainer teeth, of their periodontium and the occlusion; the design software, the CAM setting and the type of drills; the working protocol; the type of the cement and the method of cementation. Purpose: The aim of this publication is to describe the optimal preparation junctions for all-ceramic crown and bridge restorations made by CAM 5 - S 2 Impression, VHF. Materials and methods: Suitable are chamfer and shoulder preparation junction with rounded inner angle (width 1 - 1, 5 mm). Trimming of 1.5 – 2 mm dental tissues is necessary on the occlusal surface. The homothetic reduction of teeth is optimal. Results and discussion: The width depends on the size and vitality of the tooth. In stained teeth and those built with metal pins the removal of more tissues provides a greater volume needed to disguise the dark color. Vestibular preparation under the level of the gingiva is preferable to ensure optimal aesthetics. Preparation junction is determined also by the CAD/CAM technology - the type of drills and protocol of impression taking (classical or digital). The creation of a working model with TRIOS, 3Shape intraoral scanner is greatly facilitated by preparation junctions made above the gingival margin. Conclusion: Knowledge about the criteria for selection the preparation junctions is essential for fabrication accurate and aesthetic CAD/CAM restorations.

Medical University Plovdiv Bulgaria

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