Researchers at the New York University College of Dentistry have received a pair of 5-year grants from the National Institute of Dental and Craniofacial Research totaling nearly $3.7 million to develop resilient and aesthetically pleasing materials for restorative dentistry.
“Teeth play a critically important role in our lives, and their loss has both health and social implications,” said Yu Zhang, PhD, associate professor or biomaterials and leader of the projects.
“While function and aesthetics can be restored with dental crowns and fixed dental prostheses, there are still limitations on the materials used in terms of their durability and how natural they look,” Zhang said.
One grant will focus on the development of zirconia-based ceramics that are both strong and translucent. Both factors are important for ceramic restorative materials, as strength prevents damage like fracturing, while translucency helps materials look more natural and like enamel.
However, these properties often are mutually exclusive in restorative materials. Porcelain-based and glass-ceramic materials have higher translucency but lower strength, making them susceptible to premature failure. Zirconia-based ceramics are stronger and tougher but have poor translucency.
Using the first $1.8 million grant, Zhang will work toward creating aesthetic, strong, and abrasion-resistant materials by developing a new form of nanocrystalline yttria-stabilized tetragonal zirconia polycrystals using novel processing methodologies.
The research aims to extend clinical indications for zirconia to aesthetics and has applications for minimally invasive treatments. Improved zirconia-based materials can preserve tooth structure and prolong the lifetime of dental prostheses and crowns, reducing money and time spent.
The second $1.8 million grant will focus on improving the fracture resistance of porcelain-veneered dental prostheses, including crowns and bridges, which usually are constructed by applying an aesthetic porcelain veneer that makes them look more natural to a strong core.
Ceramic core materials, such as zirconia and lithium disilicate, are currently favored for their ease of fabrication and for their strength. While porcelain chipping and fractures are observed in all types of veneered dental prostheses, they are particularly prevalent in porcelain-veneered zirconia.
The high chipping and fracture rate of porcelain-veneered zirconia is due predominantly to residual stresses introduced by the high-temperature veneering process. However, researchers have lacked a comprehensive understanding of key material, design, and processing parameters that govern these residual stresses.
Zhang will aim to fill in this knowledge grant and improve the fracture resistance of porcelain-veneered prostheses. He aims to do this through both reducing residual tensile stresses in conjunction with designing a veneer/core interface that is continuously graded rather than 2 separate layers.
By developing a model to design continuously graded veneer/core interfaces, described as a viscoeleastic graded finite element method, the researchers can design the next generation of fracture-resistant porcelain-veneered ceramic prostheses. They also will use clinically relevant fracture mechanics test methods to validate their finite element model predictions.
“This research aims to advance the understanding of how stress profiles in all-ceramic prostheses can be tailored for better fracture resistance,” Zhang said. “Ultimately, such knowledge will bring us closer to a solution of a pervasive clinical problem—chipping, delamination, and fracture of porcelain-veneered prostheses—leading to reduced issues and cost of replacement.”