A bone suggests permanence, in contrast to the flesh, muscle and sinew that once encased it.
Yet this impression may be misleading.
Like other tissue, bones can be fragile. They can wither and die, causing major health problems.
Most noticeable is the jawbone, with its primary function of holding teeth in place. When teeth are lost, the portion of jawbone that held them recedes, weakened from disuse.
In dentistry this is a major problem because even the best-made dentures eventually become loose and ill-fitting as the jawbone shrinks and changes the shape of the mouth. The skin around the mouth and jaw becomes slack and wrinkled, causing the dentures to hurt and click.
One approach to correct this problem has been dental implants of titanium that are anchored directly into the remaining bone to give dental replacements a solid footing and to keep the jawbone viable. Unfortunately, implants cannot be used if a patient has lost so much jawbone that there is nothing in which to anchor an implant.
Another technique is to graft bone or artificial materials, often made from ceramics or other substances, to receded bone as filler to build up the bone to normal levels.
For years dental researchers have been looking for improved synthetic materials with which to do this. Indications are that these years of experimentation and study are yielding results that can benefit patients.
At the annual midwinter meeting of the Chicago Dental Society in the Hilton Hotel starting Sunday, a new approach to the problem of jawbone recession will be presented. It involves a material that its backers claim can stimulate withered bone tissue to regrow, not only halting the process of bone recession but also reversing it.
If the new material, a composite of plastics coated with calcium, is able to function as its developers expect, it could open a new era for bone replacement not only in dentistry but also throughout the body.
While some experts are skeptical that the new material can deliver all the benefits claimed by its developers, they acknowledge that dentistry is entering a new era in which synthetic bone or replacement bone for many patients may become a reality.
Dr. Arthur Ashman, a Manhattan dentist who helped invent the new plastic bone-replacement material, which he calls HTR polymer, for hard-tissue replacement, has been working on bone replacement for two decades. Dr. Paul Bruins, a chemical engineer, is a coinventor of HTR with Ashman.
The purpose of HTR, said Ashman, who will demonstrate it at the dental meeting, is to provide a scaffolding onto which bone can grow and thrive. It can be used to build up bone already lost or to prevent a patient from losing jawbone when a tooth is pulled.
When a single tooth is removed, Ashman said, the dentist can take granules of HTR, mix them with water and insert them into the hole left by the tooth. Jawbone will grow in and around the HTR and eventually will provide a level surface of bone filling the cavity left by the missing tooth, he said.
When gum disease has resulted in a receding gum line, loss of bone and loose teeth, dentists can cut away the gum, clean out plaque, then fill in the area around the roots of the teeth with HTR. This will stimulate bone growth and provide the teeth with solid support again, Ashman said.
Besides its granular form, HTR may be molded to fit the jaw line. These molds can come with implants installed, then placed over the receded bone. Once gum tissue is put back into place to cover the HTR mold and several months pass, bone cells in the jaw that grow into the lattice of HTR material should provide a solid graft, he said.
Then artificial teeth can be screwed onto the implant supports imbedded in the graft, Ashman said.
The key to HTR success, Ashman said, is that the plastic materials are hydrophilic. That is, they attract water.
”When you put HTR into the mouth, blood clots are attracted to it and absorbed by it,” Ashman said. ”They anchor it. HTR stays where you put it. It doesn`t migrate.”
Calcium coating of the plastic gives the HTR material a negative electrical charge, Ashman said, and this helps to stimulate bone growth and to repel bacteria, which also often are negatively charged.
A representative of United States Surgical Corp., of Norwich, Conn., which markets HTR, contended that this plastic material is superior to its ceramic competitors as a bone-replacement filler. The company and Ashman both said that using HTR is simple enough that general dentists can provide these services with some training.
The use of HTR has been concentrated among dentists in the East, but corporate officials said that after demonstrations in Chicago, they hope dentists across the country will become familiar with HTR and offer it to patients it could help.
”Getting bone to regrow and fill in gaps has long been the goal of periodontists,” said Dr. Virginia K. Murray, a New York City periodontist who has treated about 75 patients with HTR.
”We`ve tried fillers made from ceramics, plaster of Paris, human bone, animal bone and all kinds of combinations,” she said. ”Nothing seems to work as consistently, to be as predictable in its outcome, as HTR. I`ve been very happy using it.”
Dentists and patients hate to initiate any procedure unless they have confidence that it will provide at least some benefits, Murray said.
Murray first used HTR 3 1/2 years ago with a young woman who suffered the loss of bone supporting two front teeth to such an extent that saving the teeth appeared impossible, Murray said. The bone loss was caused by severe periodontal disease.
”She just didn`t want her two front teeth extracted,” Murray said, ”so we tried HTR, which I considered very experimental at the time.”
The area around the roots of the teeth was exposed and cleaned, and HTR was deposited. Eventually, bone regrew around the roots, and the teeth are doing well today, Murray said.
In fact, the patient, who has moved from New York to Chicago, is undergoing orthodontic treatment to realign her teeth. The procedure would be impossible, Murray said, if the woman`s teeth were not rooted firmly and her mouth were unhealthy.
Patients generally experience less pain and almost no infection with HTR treatment, she said. In almost all cases, they have at least some benefit from HTR, she said.
Whether HTR or any other synthetic bone substitute can stimulate natural bone growth has not been proved, said Dr. P.L. Fan, associate secretary for the American Dental Association`s Council on Dental Materials, Instruments and Equipment.
”The jury is still out on whether any material actually stimulates bone growth,” Fan said.
The dental association has found that some synthetic materials are safe and effective in building up ridges or maintaining them in the jaw line, he said. These materials are synthetic imitation of human bone.
HTR has not been submitted for evaluation by the dental association, so the dental-materials council has not made any judgment on the product, Fan said.
Dr. Robert Brackett, who practices dentistry in Park Ridge and Downers Grove, has used several kinds of bone substitute to treat periodontal patients.
”I`m not 100 percent satisfied with any of these products,” Brackett said, ”and that`s why I keep looking and trying new products.”
But after three months of using HTR, he said, his initial impressions are good.
”The research indicates it can stimulate bone growth, and I haven`t had any initial failures clinically,” Brackett said. ”More research is needed, and I`ll have to have a much longer clinical experience with HTR before a true assessment can be made.”
Brackett said he hopes other dentists who also have tried other methods with less than satisfactory results will give this newest one a chance.
”We tend to get conservative and to stick with old and proven methods,” he said. ”But we owe it to our patients to try these new materials and to keep current on developments that can improve the quality of care we can offer.”
