USC University of Southern California

USCSD Researchers Use Tooth Enamel Protein to Remineralize Enamel in the Lab

Tooth enamel has remarkable resistance to wear and tear that isn’t quite matched by materials currently used for dental repair and restoration, but researchers at the USC School of Dentistry’s Center for Craniofacial Molecular Biology have taken a promising step toward one day recreating natural enamel on tooth surfaces.

Associate Professor Janet Oldak , along with researchers Yuwei Fan and Zhi Sun, published the study, “Controlled remineralization of enamel in the presence of amelogenin and fluoride,” in the Nov 8 issue of Biomaterials.

For the study, third molars (“wisdom teeth”) extracted from patients at the USC School of Dentistry were sliced and etched with acid to remove debris , dissolve minerals and model tooth decay. The slices were then placed in a biomimetic solution containing fluoride and calcium phosphate, ions needed to form hydroxyapatite, the mineral component of tooth enamel.

By adding amelogenin, an extracellular protein found in developing tooth enamel, and varying its concentration within the solution, Oldak and her team found the optimal concentrations for the formation of organized hydroxyapatite crystal layers. Scanning electron microscope images of the tooth samples revealed progressively more elegant bundles of the nano-rods attached to the etched enamel surface.

The goal of reconstructing enamel on teeth surface is an especially unique challenge, as enamel mineralization is an extracellular process that can’t simply be bioengineered with specialized cell lines or other common biological approaches. This is because the development of enamel-making cells is intimately related to the development of underlying dentin tissue, Oldak said.

“In our lab it’s more about the chemistry than the cell biology,” she said.

While the structure of tooth enamel is much more complex than the hydroxyapatite layers synthesized during the project, Oldak hopes that one day, full enamel remineralization will be possible. Synthetic enamel would be a very attractive option compared to amalgam or composite for patients looking to repair tooth decay or damage and regain the original strength of their teeth, she said.

“This is one of the primary steps towards the development and design of novel biomaterial for future application in reparative and restorative dentistry,” Oldak said.

The study is available online at http://dx.doi.org/10.1016/j.biomaterials.2008.10.019.