What makes teeth strong?
Taking a closer look at a gene critical to tooth formation, researchers from the University of Southern California School of Dentistry discovered that the gene expresses a protein that is split into two proteins that have opposite functions.
The two proteins - dentin sialoprotein (DSP) and dentin phosphoprotein (DPP) - derive from the gene dentin sialophosphoprotein, which plays an important role in the formation of substances that cover the tooth, enamel and the softer dentin.
"We were able to dissect this gene into two different proteins and look at them individually," said Dr. Michael Paine of the USC dental school.
Dr. Paine and his team conducted animal studies in which either DSP or DPP were over-expressed in forming enamel during tooth development. Their conclusion is that over-expression of DSP increased the hardness of enamel and its rate of formation. Over-expression of DPP created pitted enamel more prone to fracture and wear.
Dr. Paine believes that DSP could have the potential to become a protective agent in dental care. Normally, DSP is only expressed in dentin and a very thin layer of enamel where it meets the dentin. This thin layer of enamel also appears to be considerably harder than the bulk enamel on the teeth.
If the protein DSP could be incorporated into the entire layer of enamel, "it might act in a similar way to fluoride in water," said Dr. Paine, by making teeth harder and more resistant to decay.
While the other protein, DPP, appears to weaken enamel, it's necessary for proper tooth formation.
"All the data suggest that it [DPP] is one of the few proteins that seems to be involved with the very early stages of mineralization," Dr. Paine said.
The fine balance between DSP and DPP highlights the delicacy of the critical dentin-enamel junction, where the softer dentin is joined securely to the outer, ceramic-like enamel covering.
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