Developments in Guided Tissue Regeneration
Could Help Spur Laser Use in Dentistry
Chris Chinnock
At the recent conference on Lasers in Surgery and Medicine held in Toronto, early results were
presented that hold the promise for improved periodontal care through the use of lasers. So far,
extensive animal studies, and data on 60 patients has been compiled. Detailed analysis of the
human studies, along with minute cell structure (histological) animal data should be available this summer. If results are as expected, the new procedure could become readily implemented by
dentists and periodontitis. The new procedure, called laser-assisted guided tissue regeneration.
is significant because it could lead to better patient outcomes.
Traditional (GTR) is Effective but Costly In guided tissue regeneration (GTR), the dentist seeks to grow new periodontal ligament onto teeth that have lost this attachment due to periodontal disease. Since teeth with poor root attachment also show bone loss too, it can lead to tooth loss if left untreated. Consequently, GTR has been a subject of intense interest.
In the last five years, predictable methods for guided tissue regeneration have been established.
The conventional approach relies on the use of a barrier, or membrane, to inhibit the growth of
the unwanted epithelial, or surface-layer cells. This membrane is typically a Gore-Tex material
which is placed between the tooth and the covering skin known as the flap. The Gore-Tex
membrane must be removed 30-40 days after surgery. In the last six months, new absorbable
membranes have been introduced which eliminate the need for a second surgery to remove the
membrane.
Once periodontal surgery is completed, four cell types begin to compete for attachment to the
treated root surface of the tooth. Epithelial cells, which reside on the outside of the flap, will
grow down the inside of the flap and try to attach themselves to the root surface. Connective
tissue grows from the inside of the flap, while periodontal ligament and bone grow up the root
surface from the bottom. The preferred tissues In this race are the periodontal ligament and bone, since they duplicate the natural support of the tooth. The problem is, epithelial cells will win this race every time unless somehow blocked from reaching the root surface. The membranes used in GTR effectively blocks both the epithelial cells and connective tissue from reaching the root surface, thereby allowing the 30 days necessary for the periodontal ligament to gain the advantage "Technically, it is a difficult procedure to perform with a long learning curve. Success rates are very much dependent upon the nature of the underlying defect and the experience of the periodontist", according to Dr. Jeffrey Rossmann, DDS, MS, of the University of Texas, Houston Health Science Center. In addition, the use of the membrane adds $300 to $500 to the procedure, which often precludes treatment of many root surfaces which may need it. Laser-Assisted GTR may be as Effective but with Less Cost A new, laser-based approach being developed by Dr. Rossmann uses a C02 laser to retard the growth of the epithelial cells on the outside of the flap. Running the laser in a superpulse mode, a layer of epithelial cells is ablated in a painless and bloodless procedure that takes only seconds to complete. The technique causes a minimum of thermal damage to underlying tissue. Since the epithelial cells grow back to the point where they might begin down growth in about 10 days, Dr. Rossmann re-ablates the flap three or four times over the first month. This helps insure that the epithelial cells are excluded from the healing wound, allowing periodontal ligament to connect.
The technique is not a direct replacement for conventional GTR since it only inhibits growth of
the epithelial cells. A membrane is still necessary to retard grow of the connective tissue. But
use of the laser for this aspect is being tested in preliminary trials.
In early work, Dr. Rossmann used monkeys and dogs to develop the technique. With dogs, he
compared laser-assisted GTR to conventional GTR. Preliminary results suggest that the laser-
assisted GTR procedure can increase treatment effectiveness both with and without the use of a
Gore-Tex membrane. Detailed histological analysis will determine the exact composition of the
root surface attachments.
In collaboration to this work, Dr. Michael Israel, DDS of Waterbury, CT, has been performing
laser-assisted GTR, without Gore-Tex membranes in hut77an subjects in his private practice. With 60 patients completed so far, in what Dr. Rossmann termed, "pre-clinical trials", preliminary results are again encouraging. The results of both studies will be published this summer.
Comments by another dentist following Dr. Rossmann's presentation in Toronto, suggested that
he was obtaining similar de-epithelialization results in human patients using the new Nd:YAG
contact tips. His technique does not involve cutting away the flap material, but is used to treat
infected periodontal pockets around the root of the tooth.
Dentists Have Been Slow to Accept Lasers
Lasers were first introduced to dentists in about 1990. After an initial burst of activity, sales
slowed. The uses and benefits of the laser had been oversold, and dentists became cautious.
But the benefits of soft tissue applications for the laser are well recognized by some dentists.
In many cases, the laser is an improvement over the scalpel. An often cited example is a
frenectomy. This procedure cuts the muscular tissue that connects to the lip between the two
front teeth. According to Dr. Robert Pick, DDS, MS, Associate Clinical Professor of
Periodontics at Northwestern University School of Dentistry, "With the laser, the procedure takes 15 seconds. In addition, there is no swelling, no bleeding, no sutures, and no scar. In 99% of the patients, there is also no pain." Procedure Could Boost Laser Use C02 and Nd:YAG have FDA approval for soft tissue applications. Although no ruling from the FDA has been forthcoming on laser assisted GTR, it is considered a soft tissue procedure. If the
results of the laser assisted GTR studies prove effective, it will add another application to the
growing list of soft tissue procedures that dentists can perform. Dr. Pick, who was also the
chairman for the dentistry session at the recent conference on Lasers in Surgery and Medicine,
characterized Dr. Rossmann's laser assisted GTR results as, "Very exciting."
But other factors will influence dentists' decision to buy and use lasers. For example, no laser
today has FDA approval for use on hard tissue, such as teeth. This is believed to be the "killer
app", that dentists are waiting for. Progress is being made in this area, with Er:YAG system
being introduced overseas because of the lack of FDA approval.
In addition, many dentists are now on a buying spree for another high-tech tool, the intraoral
camera. Essentially an oral endoscope, the tool allows the dentist to conduct a video tour of the
patient's mouth. The enhanced patient education sells procedures, which is why dentists are
buying them. As they move through this purchase cycle, they may look at lasers again.
But the economic benefits of using a laser, which cost from $10K to over $30K, must be there
for conservative dentists to consider their merits. Flap surgery and GTR are a regular
occurrence in most periodontal practices, and the laser can improve outcome results and patient
trauma. An inexpensive laser treatment could also allow many more teeth to be treated, which
is cost prohibitive with today's protocols. Since many of these procedures are covered by
insurance, the insurance companies need to also become convinced of the laser's benefits.
Dr. Rossmann comments that he, "Hesitates to say it is a proven enough technique to be
recommended in practices right now." But results to be published this summer make this an
exciting new application to watch.
2 Medical Laser Report - May 1994
Erbium Laser Advances Toward Hard-Tissue Applications
Premier Laser S-stems (Irvine, CA) thinks it has a winner on its hands The company's Er:YAG laser system is apparently? making excellent progress toward become the first laser approved to
market by the FDA for hard-tissue applications in dentistry. The laser shows promise for removing and treating carious lesions (cavities) and other defects and in preparing tooth surfaces for more advanced restorations--all with little or no pain and no anesthesia. Data from FDA-approved clinical trials an human patients are due to be released this summer. At the recent meeting of the American Society for Laser Medicine and Surgery, results of early clinical studies of the Er:YAG laser for use on teeth were presented. Dr. James Pelagalli of the Cleveland Oral Clinic discussed preliminary results from 46 procedure. although 200 patients have been treated so far in US sites. These studies follow FDA guidelines, and Premier reportedly plans a submittal of the data soon. " 'The significant result is that, after a series of animal studies and now with the human studies. we have demonstrated the safety and efficacy of the erbium laser for hard-tissue applications, stated Dr. Pelagalli. "We have had good response using the laser to remove enamel and carious lesions, to etch the surface of the enamel, and to seal pits and fissures. Perhaps most importantly,. the patients I have worked on have had no need for anesthesia. There is no pain during the procedure, afterwards, or a month later Only teeth with shallow or moderate depth caries were considered for laser treatment in this study.
Premier is being very cautious about disclosing details about its erbium laser system. However,
the company will say that it believes that it has developed the first fiberoptic delivery system for
Er:YAG lasers-an improvement over articulated arms because almost every portion of the mouth
can now be accessed. Contact tips and other unspecified delivery mechanisms are also available.
As Dr. Pelagalli says, "We have reached a milestone. This is the first practical tooth cutter.''
--Chris Chinnock
Now Technical Marketing Services (Westport, CT )