Luc Rutten and Patrick Rutten explore the use of digital workflow and interdisciplinary planning to improve the quality of implant treatment.
Zirconium dioxide is one of the highest performance ceramics in dental technology. This material has excellent mechanical properties combined with coloured options and semi-translucency. The coefficient of thermal expansion (CTE) is around 10.5, which is ideal when the veneering ceramic (VM9, Vita Zahnfabrik) has a somewhat lower CTE (approximately 9.0).
Uncoloured zirconia copings have a white colour and the light transmittance property is 48%, which is enough to become a natural appearance of the restoration. Coloured zirconia is favourable for the shade of the end result, especially when there is a lack of veneering space.
Before veneering, a thermal treatment is recommended to reverse potential phase transformation. It is sufficient to fire the copings at 1,050°C for a holding time of 15 minutes. Effect Liner (VM9, Vita Zahnfabrik) was used as a wash bake layer, both for its bonding capacity and its fluorescence properties. This melting layer was fired at an extremely high temperature (970°C to 980°C) to ensure a strong mechanical bond between the zirconia and the layering ceramic (Tholey, Swain and Thiel, 2009; Tholey et al, 2010).
Individual stratification
We start the main first firing with an effect chroma colour interdentally and build-up the shape with some basic dentine. A cutback at the incisal third and a mixture of enamel and some translucency will be applied. The individualisation of the incisal edge is created with a warmer and more opaque fluorescent ceramic material, a mixture of Window and Interno 2 and Interno 4 (Vita Zahnfabrik) (Rutten and Rutten, 2006).
The correction firing can be done with translucent and enamel powders irregularly and finally controlled to check the contact areas and line angles (Figure 1). The clinician will check function, shape, colour, fit and gingiva support. The bisque situation can now be tried in.
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