The National Institutes of Health announced it will award $2.8 million this year for six research projects to pursue a longer-lasting dental composite, the white, currently resin-based fillings that are a mainstay of dentistry.
The six projects, each funded for five years, will allow a select group of scientists around the country to work independently toward the common goal of doubling the service life of dental composites. In the U. S., dentists currently place more than 122 million dental composites per year. But they fail on average in less than eight years and must be replaced, often with another dental composite.
“The time is right scientifically to develop the next-generation dental composite,” said Martha Somerman, D.D.S., Ph.D., director of NIH’s National Institute of Dental and Craniofacial Research (NIDCR), which supports the research. “There have been major advances over the past decade in chemistry, microbiology, imaging, and several other potentially important research areas. Let’s get the right people talking to each other and see if it’s possible to double the service life of tomorrow’s dental composite.”
The first dental composite was developed during the early 1960s to answer dentistry’s need for an esthetically pleasing, tooth-colored filling. The new material was packaged into tubes as a sticky paste composed of thousands of individual molecules, or monomers, of methacrylate and a reinforcing filler of white silica powder. Methacrylate is a derivate of the organic compound methacrylic acid and a common constituent of polymer plastics.
Dentists loaded the paste into the cavity and pulsed a light source. The light energy triggered a chemical chain reaction in which the methacrylate monomers interconnected like links in a necklace and formed strong, durable, adhesive polymers that hardened inside the tooth.
Over the past half century, researchers have made numerous improvements to the filler material and added additional compounds to enhance the depth and degree of the monomer-to-polymer conversion. But the majority of today’s dental composites still employ the original methacrylate monomer, known as Bis-GMA.
A concern is this monomer, when polymerized, may work together with certain microorganisms in the mouth to cause a recurrence of decay in the repaired tooth. An estimated 600 to 800 distinct microorganisms that inhabit the mouth have learned to colonize for a competitive advantage over its microbial rivals.
“Bacteria have learned to colonize virtually every organic and inorganic surface on our planet,” said James Drummond, D.D.S, Ph.D., director of NIDCR’s Dental and Biomaterials Program. “But little is known about how oral bacteria interact with a dental composite. It is critical to determine whether and to what extent oral bacteria might contribute to the aging, mechanical fatigue, and ultimately the failure of composite fillings.”
To explore the issue further, each of the five research projects will team for one of the first times material scientists, polymer chemists, and microbiologists. Another possible area of study will be to characterize whether the natural enzymes in saliva also play a role in degrading restorative dental materials.
The six grants include:
- Principal Investigators: Christopher N. Bowman, Ph.D.,
Christopher J. Kloxin, Ph.D., and Jeffrey Stansbury, Ph.D., University
of Colorado, Boulder
Title: Cu-catalyzed azide-alkyne reactions for novel dental composite materials
- Principal Investigator: Christopher N. Bowman, Ph.D., University of Colorado
Title: Dental composite materials based on photoinitiated thiol-vinyl sulfone reactions
- Principal Investigator: H. Ralph Rawls, Ph.D., University of Texas Health Science Center, San Antonio
Title: Oxarane-acrylate system to double the clinical service life of restorative resins
- Principal Investigator: Jirun Sun, Ph.D., American Dental Association, Gaithersburg, Md.
Title: Novel dental resin composites with improved service life
- Principal Investigators: Carmen S. Pfeifer, D.D.S.,
Ph.D., and Jack Ferracane, Ph.D., Oregon Health and Science University,
Title: Tertiary methacrylamides and thiourethane additives as novel dental composites
- Principal Investigators: Brian H. Clarkson, Ph.D., and
Timothy F. Scott, Ph.D., University of Michigan School of Dentistry,
Title: The design, development and evaluation of a nano/micro filled novel smart dental composite