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Surface of dental implant will promote healing (7/13/98)

Better and easier dental implantation is the goal of ongoing research by David L. Cochran, DDS, PhD, professor and chairman of the department of periodontics at The University of Texas Health Science Center at San Antonio.

If you were going to have a dental implant to support the root system of an extracted tooth, it would be an endosseous-type implant, meaning the dentist would anchor a small, round post made from titanium directly into your jaw bone. There are two techniques used in dental implants – the submerged approach and the non-submerged approach.

In the submerged approach, developed in Sweden, the implant is inserted into the bone under the gum line. The tissue is sutured over it and allowed to heal. In three or four months in an additional surgical procedure, the oral surgeon will open the surgical site and place a crown on top of the implant to complete the procedure.

In the non-submerged approach, developed in Switzerland and called the Swiss approach, the implant extends above the gum line, eliminating the need for a second surgery. Both techniques require three or four months for the patient to completely heal before the crown can be attached to the implant.

Dr. Cochran and his colleagues have been able to show that slightly more bone loss occurs with the submerged-type implant than with the non-submerged type. They also have discovered that the implant’s surface is a contributing factor in the time it takes the implant site to heal.

"Our researchers have collaborated with Dr. Barbara Boyan’s group in the department of orthopaedics to determine how cells attach themselves to an implant," says Dr. Cochran. "By using acid to sandblast the surface of the implant material, we have developed a rougher surface. Bone cells seem to like the result.

"This new surface allows the cells to get a good grip on the implant and the bone attaches more quickly," Dr. Cochran continues. "When the rougher surfaced implant is used, the body heals in six weeks as opposed to three months with the smoother implant, cutting recovery time in half. We also have developed a tighter bond between the bone and implant surfaces."

Oral implants must integrate with the bone, the connective tissue and the gums. Some early researchers considered the Swedish (submerged) approach more successful in preventing plaque and subsequent inflammation from forming around the implant. Later, no significant differences were found on either hard or soft tissue between the two approaches, and it was decided that both the submerged and non-submerged techniques could be clinically successful.

"We are also doing trials with bone morphogenic protein (BMP)," Dr. Cochran says. Stephen E. Harris, PhD, associate professor/research, in the laboratory of Gregory R. Mundy, MD, in the department of medicine, is removing protein from crushed bone.

"We’ve been working with Dr. Mundy, implanting BMP into bone at the extraction site," Dr. Cochran adds. "We now acquire our BMP from Genetics Institute, which manufactures the protein in a combination of forms.

"We’ve already completed our first FDA clinical trails with BMP," he continues. "We extracted a tooth and then inserted the BMP into the extraction socket to see if the bone would grow back. Later, we inserted an implant."

Dr. Cochran is working with a group of former colleagues at Harvard University. "The Harvard group has six patients and we have six. We’ve been able to show that the BMP used in extraction sockets works well and is safe to use," he says.

Dr. Cochran and his colleagues also are experimenting with growing bone in the sinus area to form a bridge for dental implants. "As we grow older, our sinuses enlarge. There’s a window of opportunity where it’s possible for oral surgeons and periodontists to do bone grafting at this site," Dr. Cockran says. "The added bone permits implants that would not be possible otherwise.

"Do higher doses of BMP stimulate the bone to grow faster?" he asks. "That’s what we are trying to determine now. After four months a CAT scan is done to evaluate the amount of bone that has been replaced in the patient’s sinus area. In the future, BMP also will be used for spinal fusion and broken bones.

"This is exciting research because we are able to transfer technology – we began in the research laboratory, continued our work in animal trials and we are currently in the midst of human clinical trials," the researcher concludes.

Dr. Cochran, who received his DDS and PhD in biochemistry from the Medical College of Virginia and was trained in periodontology at the Harvard School of Dental Medicine, has won awards for his research at both the national and international levels.

Contact: Jan Elkins, (210) 567-2570