Dental community warms up to lasers

The dental market has been a tough nut for lasers to crack.

The dental market has been a tough nut for lasers to crack. For more than a decade, each new US Food and Drug Administration (FDA) clearance and product introduction has been met with much enthusiasm. But all too often this initial excitement has ended in disappointment, as products fail to perform as promised and manufacturers struggle with the fallout.

But 1999 could be the exception. Soft-tissue lasers are finally becoming more widely accepted by the dental community; for some applications, such as the treatment of periodontal disease and removal and reshaping of diseased gum tissue, they are even becoming the preferred modality. And with two hard-tissue lasers (Premier and BioLase) now commercially available and another (Continuum Biomedical) on the verge of FDA clearance, the potential for the laser to replace the drill for caries removal, cavity preparation, and other hard-tissue applications continues to expand.

According to the American Dental Association, more than 60 million soft-tissue procedures and 170 million hard-tissue procedures-primarily cavity preparation and decay removal-are conducted annually, and many of these are prime candidates for laser procedures. But, as noted in a recent report from Frost & Sullivan, New Technologies in the US Dental Treatment Market, the total number of dental lasers being used in the USA today remains relatively low (about 4000 in 1998), and only 3% of all practicing dentists in the USA (about 143,000) own a dental laser. In 1998, this translated into revenues of $19.6 million; but Frost & Sullivan projects 21% average annual growth in the dental-laser market over the next several years, with revenues reaching $76 million in 2005. And that does not take into account the 260,000 or so active dentists outside the USA who are also potential customers.

No single technology or application is expected to account for this growth; rather, continued interest in and familiarity with soft-tissue lasers, broader acceptance and availability of hard-tissue and tooth-whitening lasers, and emerging optical-diagnostic applications will together create more broad-based opportunities for lasers in the dental field and lead to greater market penetration. In addition, patient demand for laser-based dental procedures is expected to increase steadily over the next five years due to increasing awareness of "painless" dentistry and the growing number of laser-based applications and benefits supported by clinical studies and adopted by the dental community.

Diagnostic frontier
One of the most exciting potential growth areas for lasers in dentistry is diagnostics. According to Dr. John Featherstone, a researcher at the University of California (UC), San Francisco, and chair of the "Lasers in Dentistry" segment of the Biomedical Optics symposium (SPIE Photonics West, Jan. 23-29, 1999, San Jose, CA), using optical methods to enhance the early detection of dental decay has become a "hot" topic. Because decay often begins as a tiny area of demineralization on the outside of the tooth that can quickly turn into a large lesion inside the tooth, it is often discovered too late to prevent the kind of decay that leads to cavities.

Currently, clinical detection of caries relies primarily on visual examination, hand-held explorers, and conventional radiographs, all of which are inadequate when examining biting surfaces, where most dental decay occurs. In fact, according to Featherstone, dentists often have to explore by drilling with a dental bur. But new methods developed for the management of tooth decay work best if lesions can be detected at an early stage and chemical rather than physical intervention can take place, thereby preserving the natural tooth structure and helping the saliva to heal, or remineralize, the areas of early decay.

"The standard in the [dental] industry has for many years been `take out the knife and cut`," says Dr. Harvey Wigdor at Ravenswood Hospital Medical Center (Chicago, IL). "But we now have a more medical model. New antimicrobial agents are available to treat many conditions, and this provides us with an opportunity to treat lesions earlier. The issue is, how do we diagnose it earlier?"

That is where several optical approaches, including fluorescence spectroscopy and optical coherence tomography (OCT), come in. These methods, which exploit the differences between healthy and decayed enamel and dentin, show great promise for the early detection of carious lesions. The goal is to be able to leapfrog standard x-rays in identifying caries in their infancy and then apply conventional treatments such as fluoride to circumvent more serious decay and prevent the formation of cavities.

For example, because healthy and decaying dentin fluoresce differently when illuminated with low-level laser energy, researchers are studying laser fluorescence as a method for early caries detection. At the BiOS meeting, Dr. Raimond Hibst and colleagues at the University of Ulm Dental School (Germany) reported on their research involving a 630-nm diode-laser system used in conjunction with detectors to capture and create a value of the fluorescence as it relates to the decayed dentin.

This approach has already been incorporated into at least one commercial product currently sold only outside the USA. The Diagnodent from KaVo (Biberach, Germany) uses a diode laser to provide fluorescence measurements in fissure areas of the tooth and thereby improves diagnoses of fissue caries. According to KaVo, when the incident light meets a change in tooth substance, it stimulates fluorescent light of a different wavelength that is then translated through the handpiece into an acoustic signal. The wavelength is then evaluated by an appropriate electronic system in the Diagnodent control unit.

Rather than relying on tissue fluorescence, researchers from Lawrence Livermore National Laboratory (LLNL; Livermore, CA) in conjunction with researchers from UC San Francisco are using OCT to image demineralization of dental enamel and improve the detection, characterization, and monitoring of early caries. The laboratory`s noninvasive polarization-sensitive OCT (PS-OCT) system discriminates between normal and carious regions by measuring the state of polarization of the back-scattered 1310-nm laser energy, which is affected by the state of demineralization of the enamel.

The PS-OCT system is based on a polarization-sensitive Michelson white-light interferometer. Circularly polarized low-coherence light is focused on biological tissue, and high-resolution cross-sectional imaging and birefringence characterization of the tissue are obtained by measuring the backscattered light intensity and polarization as a function of axial depth and transverse location in the tissue.

The system`s ability to detect carious lesions was initially tested on bovine enamel blocks containing artificially generated caries, then on naturally occurring caries in extracted human teeth. In both cases, the LLNL researchers demonstrated successful noninvasive detection and imaging of carious lesions with nonionizing radiation (see figure on p. 115). High-resolution cross-sectional images show the ability of the system to clearly discriminate between the normal and carious regions, and regions that appeared to be demineralized in the PS-OCT images were verified using histological thin sections examined under polarized light. Further studies are now under way.

Soft tissue takes off
Currently, soft-tissue lasers-which have been commercially available to dentists for more than a decade-still comprise the bulk of laser sales in the dental market. Several types of lasers-including CO2, Nd:YAG, argon, diode, holmium, and erbium-are sold for soft-tissue (periodontal) applications. These applications include gigivectomy, gingivoplasty, and biopsies (CO2); oral surgery (Nd:YAG, diode, and erbium); and composite curing and tooth whitening (argon). Advantages of the laser in the treatment of periodontal disease include less bleeding both during and after surgery, less postoperative discomfort, and less infection due to the elimination of micro-organisms by the laser during surgery. Some studies have even shown successful sterilization of root canals when a laser is used to perform the procedure.

While CO2 lasers were the first in this market, of those dentists who use lasers, Nd:YAG and diode lasers have become the preferred laser types. American Dental Technologies (Troy, MI), which introduced its Nd:YAG laser technology to this market in the late 1980s, claims to hold the bulk of the market share in soft-tissue lasers; in addition, the company owns several key patents related to the use of Nd:YAG and erbium lasers for both soft- and hard-tissue dental applications. However, the Aurora diode-laser system from Premier Laser (Irvine, CA), which gained FDA clearance in 1997 (and additional clearance for treating children in 1998), is beginning to make inroads in this market, and dentists appear to prefer its compactness and portability.

BioLase (Irvine, CA) also now has an FDA-approved diode laser and expects to find a market for this product in soft-tissue surgery and bacteria reduction.

Luxar (Bothell, WA), a subsidiary of ESC Medical (Yokneam, Israel), claims to be doing a fair business with its compact CO2 laser system in the dental market. Argus Photonics (Jupiter, FL) is also developing a CO2 laser for soft- and hard-tissue dental applications that the company plans to sell for less than $30,000 once FDA clearance is obtained. Most of these products range from $10,000 (CO2) to $25,000 (diode and Nd:YAG lasers).

Hard tissue heats up
Despite what appears to be an expanding market for soft-tissue lasers, hard-tissue laser applications and sales continue to represent the Holy Grail for most dental-laser manufacturers. As noted in a recent report on the medical-laser market by BlueStone Capital, if only 1% of the US dentist population purchased a laser each year at an average selling price of $40,000, sales of hard-tissue lasers alone would reach $50 million to $60 million annually. Further, over the next three to five years, if 10%-15% of practicing US dentists purchased a hard-tissue laser, the potential market would be $500 million to $900 million.

But for these numbers to be achieved, several barriers must be overcome. The two commercially available hard-tissue lasers (both erbium based), which sell for around $40,000, are competing against the conventional high-speed hand drill, which sells for $600-$800, and air-abrasion systems, which spray a stream of minute aluminum oxide particles at high velocity through a dental handpiece to remove enamel, dentin, decay, and restorative materials. Although air-abrasion systems are

more expensive than hand drills ($4000-$16,000) and do not always cut as quickly or efficiently as lasers, they currently hold a strong market share-in large part because of their modest price. In addition, some dentists feel that, while the erbium laser works well when treating small areas, it is not very efficient with larger areas that need restoration, such as between teeth or for crown preparation.

The first commercial hard-tissue laser, the Centauri Er:YAG laser from Premier, may have had a leg up in terms of market entry, but the product has been plagued by anecdotal reports of fiber problems. Premier has also been struggling with a series of legal and financial problems, including a dispute with its distributor that eventually forced Premier to restate its financial results for third- and fourth-quarter 1998 and led to a series of shareholder lawsuits. The company is now in the process of settling those lawsuits out of court for

$4.6 million in cash and 2.25 million shares of stock. In addition, Premier has reduced the price of all Centauri lasers in stock from $44,950 to $24,950 in an effort to clear out what the company says is excess inventory resulting from its dispute with former distributor Henry Schein.

Even with Premier`s problems and what appears to be some residual backlash against lasers in the dental market, the promise of painless dentistry continues to attract patients, manufacturers, and even dentists to this technology. The latest newcomer is BioLase, which gained FDA clearance for its Er,Ch:YSGG laser (the Millennium) and hydrokinetic approach to hard-tissue applications last October. But the Millennium, which sells for $37,000-$45,000, is more than just a hard-tissue laser; according to BioLase, dentists using the Millennium report that they can quickly cut dentin and enamel without anesthesia and also perform numerous soft-tissue procedures with speed and precision. The company has received several patents for this technology and also holds patents covering the use of Nd:YAG lasers in combination with air or water cooling for hard-tissue dental and medical procedures.

A third laser company-Continuum Biomedical (Dublin, CA)-is likely to enter the market this year with an erbium hard-tissue laser that could give both Premier and BioLase a run for their money. According to anecdotal reports, the ConBio laser is as efficient as the Centauri (which some dentists feel is more efficient than the Millennium) but lacks the fiber and delivery-system problems. Other wavelengths are also in the offing-researchers at LLNL report good hard-tissue results using an ultrashort-pulse Ti:sapphire laser, and new CO2 lasers are being developed by at least two commercial entities.

The brighter side
One area in which dental lasers are still trying to prove their mettle is tooth whitening. While laser tooth whitening is an attractive alternative for many consumers compared to at-home bleaching trays and tooth-whitening toothpastes, each procedure costs $500-$800. At this price, BlueStone Capital estimates that if only 3% of the 79 million baby boomers in the USA decide to have a laser whitening treatment, the market could reach $1.2 billion to $1.9 billion. But that "if" is a big one because it depends on the ability to sell consumers on the idea that, while more expensive, laser tooth whitening is superior to other methods.

At least two US companies-Premier and BriteSmile (formerly Ion Laser Technology; Philadelphia, PA)-are currently pursuing this market. Premier was the first to gain FDA clearance for its argon laser for tooth whitening back in 1996. According to Premier, the laser is used in combination with various bleaching reagents to achieve an average of three shades of whitening in about one hour.

BriteSmile is taking a more aggressive, consumer-oriented approach targeted at individuals the company calls "image investors." BriteSmile recently opened the first of five planned teeth-whitening retail centers in California. Outside of California, BriteSmile plans to open retail centers in Denver, CO; Louisville, KY; and Raleigh, NC, before the end of this year.

According to BriteSmile, by applying its proprietary whitening gel to the teeth and exposing them to a noncoherent light source, optimum natural whiteness can be achieved in less than two hours. While this procedure originally involved the use of both an argon and CO2 laser, the company has developed a proprietary blue-light source that eliminates the need for either laser. This approach also reduces the price of the BriteSmile tooth-whitening system.

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