University of Kansas researchers synthesize a novel material
By the time a typical American reaches adulthood, at least one cavity has developed in a tooth, and every year, dentists fill millions of cavities.
Unfortunately for most people, dental restorations don’t last a lifetime. And every time a filling is replaced, the dentist must remove the old filling. Repeating this process whittles down the tooth until the remaining tooth structure is insufficient to hold a filling in place.
The lifespan of a dental restoration depends on many factors, including the ability of the restoration material to hold up in the harsh environment of the mouth. For tooth-colored composite fillings, the dental restoration may wear out in about seven to ten years.
“The composite-tooth interface is characteristically identified as the weak link in the composite restoration,” explained Paulette Spencer, Ackers Distinguished Professor in the Department of Mechanical Engineering and Director of the Bioengineering Research Center at the University of Kansas School of Engineering.
Spencer and her research team are designing and creating new dental restoration materials that will function better and last longer than those currently used for composite restorations. Members of her team (pictured below) represent a diverse spectrum of disciplines, including chemistry, polymer chemistry, civil engineering, bioengineering, materials science, mechanical engineering, pharmaceutical sciences, structural biology, chemical engineering, and clinical sciences.
In the October 2014 issue of the Journal of Biomedical Materials Research Part B: Applied Biomaterials, the NIDCR-supported researchers reported that they synthesized a novel material that may be able to survive the wet environment of the mouth longer than the materials already used by dentists.
Etch, Prime, and Bond
To repair a tooth that has decay, the dentist first removes the decay. Then—just as a housepainter sands the wall before applying primer and paint—the dentist removes mineral from the tooth core (dentin) beneath the tooth enamel. Next, the dentist uses a liquid material that flows into the cavity and fills the voids in the dentin. After that, a special curing light transforms the liquid into a solid filling, and the filling is bonded to the tooth.
The liquid solidifies because the curing light makes microscopic chains within the liquid stick together (a process called polymerization). Because the chains have become permanently cross-linked, they no longer flow freely in a liquid state.
To create a new dental restoration material that is superior to products already used by dentists, Spencer’s team modifies the chemistry and then tests how the new material functions in the research lab. By adding a carboxylic acid group to the material, they made it easier to mix with water. By adding a vinyl group, they improved mechanical performance. The name of their colorless liquid creation is BMPMOB, which stands for 4-((1,3-Bis(methacryloyloxy) propan-2-yl)oxy)-2-methylene-4-oxobutanoic acid.
The results of their lab tests suggested that BMPMOB offers better mechanical properties and better water compatibility than BisGMA, the material used most often by dentists in clinical practice. Because BMPMOB is less likely than BisGMA to break down in the moist environment of the mouth, using BMPMOB in an adhesive formulation “should lead to a restoration that is more resistant to premature degradation,” Spencer said.
The University of Kansas research team will continue to modify and optimize BMPMOB as well as synthesize new dental restoration materials. “We will continue our efforts to optimize the adhesive formulation,” Spencer said. “Our research is directed towards the development of durable, multifunctional adhesives.”
- Song L, Ye Q, Ge X, Misra A, Laurence JS, Berrie CL, Spencer P. Synthesis and evaluation of novel dental monomer with branched carboxyl acid group. J Biomed Mater Res B Appl Biomater. 2014 Oct;102(7):1473-84. doi: 10.1002/jbm.b.33126. Epub 2014 Mar 5. NIH Grant R01DE014392