Fixed partial dentures (FPDs) are a well-proven treatment measure for a long period in dentistry and the survival rates are documented in a lot of studies. With the introduction of CAD/CAM technology into dental technology, it was one of the first aims to adopt FPDs for the computer-aided process. In the early years, a sufficient material regarding the fracture strength was missing.
The first material for the use in CAD/CAM supported the production of FPDs was VITA In-Ceram. The strength of In-Ceram only allows short spans and the production process was difficult because a glass has to be infiltrated to the milled matrix. The esthetic was poor. The material has to be veneered in every case.
The breakthrough comes with the introduction of zirconium dioxide to the dental CAD/CAM technology. The material is in the pre-sintered stage very easy to mill and after the sintering strong enough to cover nearly every possible indication. But also with this material is a lack of esthetics. It looks white and is more opaque than every tooth substance. So also here the veneering is the standard in the workflow. Veneering is difficult. Especially in anterior cases and it must be done by hand. So it needs time. To solve this problem, the so-called multi-layer technology was developed. The FPDs are designed in the software full-anatomically and is then automatically divided into a framework and a veneering structure. The framework is milled from zirconium dioxide. The veneering structure can be milled from glass ceramics (rapid layering - Vita Zahnfabrik, Germany) or from lithium disilicate (CAD-on, Ivoclar Vivadent, Liechtenstein). The connecting of both parts can be done with organical gluing or with the help of a fusion-ceramic. Also, this workflow is time-consuming and not useful for the so-called in-office treatment with a chairside system like Cerec (Sirona, Germany).
The solution for this cases is the use of full-contoured lithium-disilicate (e.max CAD, Ivoclar Vivadent, Liechtenstein). In a lot of cases, the esthetics are fully sufficient using only staining and glazing of the material. For higher demands a partial veneering is possible. The indication of e.max bridges is very limited. Only three-unit FPDs are possibly located in the anterior and premolar region. The newest trend is the use of esthetically improved zirconium dioxide also for designing full-contoured restorations. The esthetic outcome is not perfect, but acceptable, especially for the lateral regions. Especially in cases with a high functional stress like bruxism the use of improved zirconium dioxide is a good and long-lasting solution. For the future, further development in the material sector can be expected.
