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Protein-coated dental implants could improve bone regeneration

July 18, 2006

Titanium dental implants coated with proteins that induce bone formation may be a key advancement in treating tooth loss due to gum disease, researchers say.

In laboratory tests, MCG researchers applied a protein onto implants that directs endogenous stem cells to become bone-forming cells. The result was a nearly complete regeneration of lost tissue, says Dr. Ulf Wikesjö, a professor of periodontics in MCG's School of Dentistry.

Loss of teeth and bone is a common and devastating result of gum disease.

Dr. Wikesjö, who came to MCG this year from Temple University in Philadelphia, is researching wound-healing and tissue regeneration with a $1.4 million grant from Nobel Biocare, a leading manufacturer of dental implants and equipment.

Finding the key to improved regeneration is like piecing together a puzzle, Dr. Wikesjö says.

"For the past 20 years, there has been a quest to regenerate tissues around teeth that are lost due to periodontal disease," he says. "I've looked at multiple approaches to achieve regeneration, including bone grafts, root conditioning and membrane devices for directed tissue growth, all resulting in some regeneration. Where we had to look was at the commonalities among these treatments."

Dr. Wikesjö and his colleagues found that any regeneration requires two characteristics: a stable wound and space for the regenerated tissue to grow during the initial stages of healing.

"If these components are in place, regeneration of the tissues around the tooth may occur within a week or two," he says. "After that, it's a matter of the wound maturing - going through the various stages of healing that we're already familiar with."

By experimenting with treatments and discerning their effect on healing bone defects, they found some - including some in use today - that actually hinder tissue regeneration.

"Some biomaterials like hydroxyapatite particles, which are chemically similar to the mineral component of bone, may actually interfere with regeneration," Dr. Wikesjö says. "They may not resorb quickly enough and may block the space for new tissue to grow into."

The experiments helped researchers narrow down possible treatments to the use of proteins that directed stem cells to become bone-forming cells. Those proteins - called bone morpheonetic proteins - have already shown promise as a regeneration therapy for craniofacial reconstruction.

"None of us had any idea at the time how or if those proteins could be useful in treating tooth loss," Dr. Wikesjö says.

To find out, researchers placed the proteins around teeth and implants in animal models.

Around teeth, the bone-forming cells grew into existing bone and eventually morphed into bone themselves. However, the root of the tooth was destroyed by the replacement bone. That process impeded regeneration of other essential tissues around the tooth.

Applying the protein to implants proved more beneficial.

"There was almost complete regeneration," he says. "The generated bone bonded with the implant's surface and, eventually, existing bone in the gums. That allowed for the regeneration of gum tissues."

The next step is clinical trials of an implant coated with the proteins, which Dr. Wikesjö hopes to start this summer.

"There are still things we need to learn. In some cases, the protein may rapidly release from the implant, and other times, there appears to be a more gradual release," Dr. Wikesjö says. "We need to find out what factors cause that. In the end, we may not need to use much protein to make the implant effective. Those are things we're looking at now."

Medical College of Georgia