CAD/CAM zirconia ceramic dental crowns and manufacturing
- May 30, 2018 -
There is a long history of dental biomaterial use in routine dental practice.
There are two main methods for the application of dental biomaterials. Firstly, raw dental biomaterials are transplanted into living tissue, such as tooth and bone and secondly, dental devices such as crown and bridge restorations and dentures are fabricated from dental materials to restore dental morphology and oral function.
Crown and bridge restorations are commonly used by general practitioners after operative and endodontic treatments. Since mechanical durability and intimate fit to abutments are mandatory for crown and bridge restorations, metallic restorations and metallic frameworks covered by glass or resin composites have become popular.
We are currently in a new era of routinely providing all‐ceramic restorations because of newly available materials such as highly sintered glass, polycrystalline alumina and zirconia based ceramic materials, and adhesive monomers.
The application of CAD/CAM is currently limited to laboratory processing. For example, even if the zirconia framework is fabricated using a CAD/CAM process in the machining centre, final restorations are completed by veneering conventional porcelain using conventional manual dental technology by dental technicians.
Besides the tools for fabrication of restorations, computer technology is now available for communication tools with patients, examination and diagnosis, treatment planning and guided surgery in all fields of dentistry. Digital dentistry is becoming a keyword for the future of dentistry.
Porcelain has been used in dentistry for 100 years. Aesthetics is its major advantage, but brittleness for load bearing restorations its weakest point. Therefore, porcelain fused to metal restorations has been the first choice to meet both restoration aesthetics and durability requirements.
Currently, prefabricated reinforced ceramic blocks are available for milling using a CAD/CAM device. Mechanical properties of leucite‐reinforced glass ceramics are equal or superior to those of tooth enamel. Glass ceramic crowns can be automatically fabricated without any sensitive manual labour using a CAD/CAM process.
CAD/CAM ceramic crowns are clinically useful because of their easy manipulation without technically sensitive build‐up processes. They are user‐friendly because finishing work such as conventional staining, add‐ons and glazing techniques are available. They are also promising because of their excellent fit and aesthetics, strong durability with adhesive resin cements and quick fabrication.
Zirconia is available for fabricating frameworks of bridge restorations instead of metal bonded restorations because of its higher fracture toughness. There are two types of zirconia blocks currently available for distinct CAD/CAM applications. The first application is the use of fully sintered dense blocks for direct machining using a dental CAD/CAM system with a grinding machine. The second application is the use of partially sintered blocks and green blocks for CAD/CAM fabrication followed by post‐sintering to obtain a final product with sufficient strength.
The application of CAD/CAM technology in dentistry provides an innovative, state‐of‐the‐art dental service to patients and is also beneficial for general practitioners. Conventional laboratory technology and dental technician skills remain important because dental restoration and prostheses are not just industrial products but medical devices that need to function in the body.