(see Graphic) Stephen Parker has literally seen the light – laser light, that is. In November 1990, he was tapped on the shoulder by a salesman at a trade fair for dental equipment. Parker was impressed with what he was shown, and not long afterwards became one of the first British dentists to replace his drill with a laser. Now he is national publicity officer for the British Association of Laser Dentistry, which he runs from his home in Harrogate in North Yorkshire.FIG-mg18744101.jpg
Like most of the 80-odd members of the association, Parker is a true enthusiast. Virtually all of them use lasers designed in the US by American Dental Laser (ADL) of Michigan, and on sale in Britain for about Pounds Sterling 30 000. The beauty of the technology, according to Parker, is that it allows pain-free drilling. Patients at his private practice are offered an anaesthetic, but ‘the regulars soon gain enough confidence to do without it’. So far, he says, no one has complained of any side effects.
Ironically, if Parker’s practice were in the US, he would not be allowed to use his laser in this way. There, unlike in Britain, all new medical technologies must undergo clinical trials similar to those required for new drugs. Only when a machine has been approved by the US Food and Drug Administration can it be used in general practice. In 1990 the ADL laser was approved for use, but only on soft dental tissues like gums and pulp. Approval for use on the hard tissues, enamel and dentine, could take several years: ADL has only recently received permission to start preliminary clinical trails.
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LOOSE RULINGS
In contrast, Britain has little official regulation on medical lasers. The Department of Health has four codes of practice covering their use, but does not require dentists to be trained to use the new technology, specifying only that all dental lasers be registered with District Health Authorities. Not surprisingly, ADL sees Britain and Germany as its key export markets in Europe, and is keen to maximise sales before other companies start producing lasers that individual dentists can afford.
Chris Lole, the company’s vice-president for strategic planning, estimates that within five years 50 per cent of British dental practice will be privately run. Dentists who use the latest technology find it easier to attract and keep patients. Buying a laser can also be a catalyst to going private because charging for laser treatment is more easily justified than for conventional treatment. Lole makes no bones about it. ‘The market is going to expand quite nicely. The only question is how fast,’ he says. Within a year or so dentists will be able to buy a more powerful 8-watt version, as opposed to the present 3-watt model, for £7000 less. Lole believes this will create a resurgence in interest.
John Frame is less sanguine. Now professor of oral surgery at the school of dentistry at the University of Birmingham, he has been using lasers for surgery in the mouth (on cancers for example) for more than 15 years. He says that there is a good reason why their use in dentistry is still uncommon: ‘People want a painless alternative to the drill’. To be that, a laser would need to cut through all types of tissue – including enamel, the hardest substance in the body – and also desensitise the tooth’s nerves. Frame’s analysis of the requirements match Parker’s. Where the two differ is in their assessment of how well dental lasers meet them.
Two factors determine the effectiveness of a dental laser: its power, which simply measures how quickly energy is transmitted, and the wavelength of its light. Shorter wavelengths mean the individual photons carry more energy. An energetic photon absorbed by an atom in a chemical bond may provide sufficient energy to break the bond at once, without inter-mediate heating. Such lasers are called ‘photoablative’ or ‘excimer’. Photons of light with a longer wavelength cannot provide enough energy to break a stronger bond immediately, but heat it up until the vibration breaks it. These are ‘photo-thermal’ lasers.
Dental lasers like ADL’s are photo-thermal and known as neodymium YAG – the initials stand for yttrium, arsenium and gallium, the crystalline materials used to focus the light beam – and emit infrared light at a wavelength of 1064 nanometres. This easily penetrates soft tissue such as gums and pulp, but drilling through enamel and dentine (the calcified tissue which makes up the bulk of the tooth, around the pulp) requires constant application of a dye that absorbs that wavelength of light and so heats up the surface more quickly. This makes drilling enamel by laser very laborious – at least ten times slower than with a conventional high-speed drill.
PULP THRILLER
The ability to suppress pain is also contentious. Several British researchers believe that the heat from a photothermal laser could damage the sensitive nerve endings in the pulp. Laser proponents claim, however, that because the laser beam is emitted as short pulses (30 per second or more), heat does not build up in the dentine and so the pulp is not affected.
Both sides are frustrated by the lack of information. ‘A lot of claims have been made, but few are well founded,’ says Ronald Strang, of the University of Glasgow Dental Hospital and School. He and his colleagues were concerned enough to seek Scottish Office funding for a comprehensive study – which began a year ago – into the performance of neodymium YAG lasers.
The investigations include both clinical trials and laboratory tests intended to answer such questions as whether the laser can really desensitise nerves in the pulp, what effects it has on teeth, gums and oral bacteria, and how well tooth filling materials bond with the laser-treated surface. The first results are now coming through. Controlled tests with 22 patients suggest that a neodymium YAG laser can partly desensitise nerve endings in the pulp. But this result has generated more questions than it has answered. ‘I can’t imagine how it would desensitise the tooth enough to allow drilling,’ says Strang. Consequently, researchers are trying to devise another experiment to test the results of the first.
Meanwhile, the debate continues. Gavin Pearson, who heads the department of biomedical science at the Eastman Dental Hospital in London, decided to conduct his own research into the effects of photothermal lasers. He concluded that they do not ‘cut’ through hard tooth tissue at all, but that the chemical bonds between tooth molecules vibrate until the tissue melts. His electron microscopic inspection of teeth treated with neo-dymium YAG lasers revealed irregular cuts and crater-like holes, leading him to fear that fillings made on top of such an unstable base may not last.
This evidence does not deter Parker. He argues that the quality of treatment with a laser is highly dependent on the skill of the user. And he points out that when dentine suffers prolonged exposure to laser light, it becomes dehydrated and chars and the treated surface is weakened. He argues that this effect is compounded in laboratory experiments with extracted teeth, because they are already less elastic and more dehydrated than teeth rooted in the mouth. Having performed around 5000 laser dental procedures in the past 18 months, he is convinced that fillings in laser-drilled teeth are just as sound as those in conventionally-drilled ones.
Those using the ADL laser have previously been overwhelmingly positive about its ability to replace drills and be used without anaesthetic. Only recently has a more critical approach emerged. At a meeting organised by the British Association of Laser Dentistry in Edinburgh last autumn, many speakers talked of limitations in the technology. Parker insists that this does not mean that support is slipping, just that dentists are learning more about laser dentistry.
Their criticism certainly affected some. Jim Fotheringham, a dentist from Penrith in Cumbria, attended the conference, having already invested in a day-long laser dentistry training course. Before handing over Pounds Sterling 30 000 for a neodymium YAG laser, he sought assurance from his peers. But he found the opposite. ‘Hearing those speakers was the last straw,’ he recalls. ‘The laser was just too limited in its uses . . . I decided to spend the money on a new set of (conventional) drills instead.’
A consensus does, however, seem to be emerging. This is best summed up by Parker, who says: ‘I use the neodymium YAG laser more and more on soft tissue work, where I believe it has no equal.’ Enthusiasts and sceptics alike are convinced that new dental lasers will offer greater flexibility, and that as a dental tool their future is assured. Even Pearson agrees. He predicts that before long they will revolutionise dentistry. If he is right, the filling of the future will consist of a tiny hole made in the side of a tooth by an excimer laser powerful enough to cut through enamel. This ‘keyhole’ dentistry will be followed by treatment with another laser to kill any bacteria causing decay inside the tooth. No tissue need be removed and the intrusion will be barely visible. Excimer lasers for dentistry are already available – but at £60 000 each, they are only being bought and used by dental hospitals and research laboratories.
But prices will come down, meaning that more and more dentists will face the problem of when to buy into the new technology and which laser to choose. So who will they turn to for independent information and advice?
Unfortunately, the answer seems to be no one. With about 16 000 members – almost 90 per cent of all Britain’s general dental practitioners – the British Dental Association might seem the obvious arbiter. But the BDA has no plans to offer advice; neither will it be running an accreditation service for lasers in the foreseeable future.
Dentists deciding whether or not to buy the new technology must therefore rely primarily on the assessments of fellow practitioners who already have a laser. Until the full results from the Glasgow study are available, private dental patients are, effectively, paying to let dentist test lasers.