International Journal of Computerized Dentistry, Pre-Print
Yazigi, Christine / Busch, Reinhard / Kern, Matthias
Seite 1 – 21
Aim: The aim of this paper was to describe a new method to reduce the unwanted reduction of material thickness resulting from overmilling due to the tool diameter compensation correction of common CAD/CAM software.
Materials and methods: Today’s CAD/CAM software (e.g. 3-Shape or Exocad) specifies the same tool diameter compensation for different ceramics. In the case of zirconia ceramics milled in the raw state, this leads to excessive milling of the inner surfaces of crowns. This results in unnecessary large cementation gaps and a restoration that is thinned out from the inside. By manually reducing the preset correction in the digital design process by the volumetric sintering shrinkage factor specified by the manufacturer, excessive thinning of the zirconia can be avoided.
Results: The inner geometry of the restorations changes only slightly after reducing the preset tool diameter compensation correction manually. Consequently, a design of the restoration with the required minimum interocclusal thickness, yet with accurate passive seating and marginal fit is possible without any further interventions.
Conclusions: Understanding the specifics of the subtractive fabrication process as well as the properties of the restorative materials is a key factor in achieving optimal clinical outcomes with all-ceramic restorations fabricated with the CAD/CAM technology. The use of monolithic zirconia combined with a calculated reduction in the preset tool diameter compensation correction might be beneficial in cases with thin or uneven geometry.