Which material is best for CAD/CAM milled crowns?
- Jeff Davies
- Nov 15, 2015
- 2 min read
Photo Source: Elsevier, Journal of Prosthetic Dentistry, 2014. (http://www.sciencedirect.com/science/article/pii/S002239131300276X)
There has been a great deal of research on metal-free tooth colored restorations along with developments in indirect prosthetic treatments which have lead to a bit of confusion as to which material if ideal. With so many options available to make a crown, its hard to know which one to trust and select for your patient. There are a variety of CAD/CAM materials, manufacturing systems, etc. So choosing the correct material is crucial for a higher prognosis and longevity of the crown.
Two main groups exist for metal-free, tooth colored, restorations. They are glass ceramic restorations and composite resins. Glass ceramics offer a variety of advantages such as: esthetic appearance, color stability, biocompatibility, and durability. However, some of the negatives that they have are, brittleness, susceptibility to fracture, along with abrasive wear of the opposing natural tooth. The composite resins have the advantages of: low abrasiveness to opposing teeth and low elastic modulus which allows for more absorption of functional stresses through deformation. The disadvantages of composite resin crowns are: wear, deterioration of surface finish, color instability and fracture. Some studies have shown that ceramic restorations tend to wear longer than composite resin crowns, while others have shown that the performance of composite resins have exceeded that of ceramics. Other reports have noted that they are similar. So where do we lie on this situation? So up to now, there is no clear cut consensus saying which restoration material is best. However, a new class of millable resin nanoceramic (RNC) blocks (LAVA Ultimate; 3M ESPE) has been made available to CAD/CAM systems. These blocks aren't true resin or ceramic. RNC combines the two existing groups into one material. However, it is mostly made of ceramic, of which it is 60% of its volume. While being mostly ceramic, it still maintains its flexibility and fracture resistance.
A fatigue resistance research project was preformed by Adriana Carvalho and team, to determine how these three groups would withstand these accelerated fatigue testing. It was noted that, with a simplified cementation process, resin nano ceramic and lithium dislocate crowns demonstrated improved fracture properties over feldspathic glass ceramic crowns. RNC also demonstrated significant practical advantages, such as less mill time, less milling bur usage, no need for firing, polishability, ease of occlusal adjustment, repairability, and friendly wear of antagonistic teeth. Resin nanoceramic should be the material of choice when preforming CAD/CAM milled crowns.
Information for this post was taken from the article mentioned above and is highly recommended to read. Please read to see how the research was preformed and to understand more of the details of the process.
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