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Dentistry

Light in the arches

Researches in the country are making headway with laser techniques and equipment in dental treatment

Characterized as a concentrated beam of light, the laser, amongst its various other uses, is more and more turning into safe and sure equipment for use in dentistry. From the removal of caries to root canal treatment, it is attracting attention from researchers and dentists all over the world. In Brazil, it is no different. At least three institutions the School of Dentistry of the University of São Paulo (Fousp), the Institute of Nuclear Energy and Research (Ipen) and the Physics Institute of USP in São Carlos – have presented in the last few years, in an independent fashion or in partnership, a bulky scientific and technological production, associating the use of the laser with dental treatment.

The contributions lie in the creation of new procedures and protocols (processes for applying the techniques) and in the development of new equipment that is now at the disposal of Brazilian dentists. Amongst the innovations, for example, there is a technique that allows the removal of caries without damaging the tooth’s healthy tissue, a procedure that can be carried out without anesthesia in 80% of the cases, because the use of the laser does not usually cause pain.

The Brazilian researchers have also developed techniques for diagnosing the structure and vitality of the tooth using a laser, besides creating a new protocol for the treatment of oral mucositis, which is ulceration in the mucous membrane of the mouth common in patients submitted to high doses of chemotherapy and to radiotherapy. “We do a job of prospecting, looking for new techniques and applications for the laser in denstistry”, says physicist Vanderlei Salvador Bagnato, from IF-USP, the coordinator of the Optics and Photonics Research Center (Cepof) in São Carlos, a multidisciplinary and multi-institutional center belonging to FAPESP’s group of Research, Innovation and Diffusion Centers (Cepids).

Ipen and Fousp are also taking part in Cepof. Bagnato explains that the laser can replace, in many cases, the instrumentation used by dentists, because it has similar properties. “In dental treatment, the two kinds of instrumentation are used”, says Bagnato. “The first serves for cutting and trimming. They are the drills and the files. The other is the bactericidal products, which kill microorganisms. The laser, in turn, is nothing but a beam of light, with a great concentration of energy, suitable for cutting and trimming.

And it is a bactericidal agent as well, because of its high temperatures.””The laser can be used in various areas of odontology, and it is a very safe procedure. But those who think that it has come to replace the traditional equipment are mistaken. It is a partner in dental treatments”, explains Professor Carlos de Paula Eduardo, from Fousp. According to the researcher, the new technology brings several benefits for patients. Besides not causing pain in most cases, the laser does a selective removal of the decayed tissue, because the beam of light acts exclusively on the caries, preserving the side areas that are healthy – something that the high-speed drill does not do. In prevention, the laser, associated with fluorine, increases the resistance of the tooth to caries.

Another great advantage, perhaps the greatest of them, is that it reduces microbial infections in dental treatment – precisely one of the areas of research at Fousp, in conjunction with Aachen University, in Germany. By means of a process denominated ablation of carious tissues, the laser causes microexplosions in the dentine (a layer right below the enamel of the tooth) affected by bacteria, removing the caries and reducing by up to 99.6% the population of microorganisms. The same benefit occurs in root canal treatment and in periodontal treatment, those that involve the gums.

In September 2002, the researches were given a push with the inauguration of the new installations of the Experimental Laboratory for the Laser in Odontology (Lelo) at Fousp. The building, with its 400 square meters, is equipped with 25 lasers, which are worth roughly US$ 800,000. “The laboratory’s objective is to do research, to teach, and to provide clinical treatment, establishing a bridge with companies from the sector, and taking benefits to the community”, explains Carlos Eduardo, Lelo’s founder and director.

The center is prepared, in the near future, to receive between 100 and 150 patients a day; the funds for building the laboratory, of around R$ 1 million, came from USP and the Foundation for the Scientific and Technological Development of Odontology (Fundecto). Several companies in the business, like Kavo, Dabi Atlante and Gnatus, have donated equipment, either definitively or as a loan for carrying out the researches. Regarded as one of the most advanced centers in the area in the world, Lelo can count on over 50 researchers, between professors and postgraduate students, and it receives students from all over Brazil and from other countries. In June last year, for example, a group of ten Italian researchers spent a week at the laboratory, learning how to use the new technology. The second group is scheduled to arrive in February, and the third in July.

The researchers from Lelo also have an eye-catching academic production. “In the last ten years, we have produced 130 theses and dissertations, of which 75 came from the professionalizing master’s degree course, and 55 from postgraduate studies”, Carlos Eduardo says. Scientific production is not falling behind. 115 complete works have now been published in international scientific magazines and newspapers and 55 in Brazilian periodicals (for example, Laser Surgery and Medicine , and theJournal Clinical Laser and Surgery). They are important investigations , such as, for example, the series of works that is investigating in what way the laser can act towards reducing the presence of microorganisms in dental treatments.

All this technological knowledge generated in these centers has been passed on to business. Brazil currently boasts a dozen laser manufacturers focused on odontology. Some of them, like MMOptics, DMC and Condortek, are installed in São Carlos and have received a transfer of the technology produced at USP and Ipen. “Our business is to develop optical and electronic systems and to make prototypes, which afterwards can be passed on to private enterprise”, says Bagnato. “Some time ago, we created a prototype of a laser device that would simultaneously control time, power, and the area hit by the beam of light. MMOptics was interested in it, and from this prototype produced a model called BDP.” From then on, the company started to innovate, and nowadays is one of the leaders of the sector.

Invisible elements
Several kinds of laser can be employed in the treatments, the most common of which are those with argon, carbon dioxide (CO2 ), erbium-YAG (Er:YAG) and neodymium-YAG (Nd:YAG). The argon laser operate by using as its active medium an ampoule of argon gas that emits light in the ultraviolet ranges of blue and green, while the CO2 laser has a an ampoule of carbon dioxide for an active medium. ts light is emitted in the infrared range and it is very much used in the practice of vaporization, a situation in which a biological tissue, soft or hard, is converted into steam by the energy absorbed from the beam of light.

Then there are the Er:YAG and Nd:YAG lasers, which are formed, respectively, using the chemical elements erbium and neodymium, and YAG is the designation for a synthetic crystal constituted of yttrium oxide and aluminum. With the exception the argon laser beam, visible to the human eye, the others are invisible. In this case, the equipment emits a beam of red light, called a guide light, which serves to indicate the exact place that the laser beam should hit. These lasers vary according to the form in which they are produced, and they are classified as high or low power, according to the concentration of energy in the beam of light. While the high power lasers make it possible even to cut through steel plate, the low power ones are used for biostimulation.

With them, the dentist is capable of interfering in the cellular metabolism, by exciting the molecules and speeding up such reactions as cicatrization, analgesia and reducing inflammation”, says Bagnato. This is a very well delimited chemical reaction, and not one to be mixed up with chromotherapy. “When one works with light, the frontier between the real and the esoteric becomes very narrow.”

According to Professor Bagnato, the noblest applications of laser in dentistry are brought about with high power lasers. They can be used in curative or esthetic treatments, such as the removal of caries, replacing restorations, or dental whitening. It was with one of these kinds of equipment – an Er:YAG -, inside Cepof, that it proved possible to develop a new technique for removing old restorations with the total preservation of the healthy part of the tooth. This research, without precedent, was presented last year at international congresses, and has now been accepted for publication in the American magazine, Laser in Surgery and Medicine. “Up until then, there was no technique using laser for removing old resins from teeth”, Bagnato explains.

The laser is also an effective instrument for root canal treatment. “We have now done several clinical and non-clinical jobs using, in the main, the Nd:YAG laser. Besides vaporizing the tissue present in the root canal, it brought about a sealing of theso-called dentinal tubules (tiny structures present in the dentine, a layer below the enamel of the tooth), preserving the integrity of the internal part of the treated tooth”, the researcher claims.

Another application of this new technology is the periodontal treatments in which control is exercised over infections that involve the tooth and the gum. “In one of our studies, we managed to prove the bactericidal action of the iodine laser, by means of a far less aggressive treatment than the traditional curettage and scraping.” Low-power lasers are also used in pre-surgery as an analgesic, and in the postoperative period for regenerating the tissues. Some researches also point to their effectiveness in controlling pain.

The potential for using lasers does not stop there. “They can also be employed for prevention and diagnosis, showing where there are incipient caries”, explains Denise Zezell, the coordinator of the Lasers in Life Science Laboratory, of the Lasers and Applications Center (CLA), a unit of Ipen. The cavity is often beneath the enamel of the tooth and is not picked up by the X-ray.

The laser detects these incipient infiltration with greater sensitivity than the conventional equipment. The technology may also help to make diagnoses of pulp vitality by ultrasound techniques, another technique developed at Ipen. “In this case, the laser hits the microvessels of the pulp of the tooth, and brings information about the speed of displacement of the blood, showing whether the region is healthy or not”, explains physicist Nílson Dias Vieira Júnior, who runs the CLA. This diagnosis, made with a low power laser, reveals possible cases of necrosis caused by the traction from orthodontic appliances.

Another field of application is the treatment of labial herpes, a viral disease that causes blisters on the lips. Inside the mouth, the laser can also eliminate mucositis, an ailment that is common in patients with Aids or under treatment for cancer. TV presenter Ana Maria Braga resorted to the laser to treat this problem when she underwent chemotherapy about a year and a half ago. “Researches carried out at Ipen and Lelo, and with the support of the Syrio-Lebanese Hospital, in São Paulo, and of the Alfredo Abraão Cancer Hospital, in Campo Grande, in Mato Grosso do Sul, showed that the preventive use of the low power laser reduces in a significant way the appearance of mucositis”, says the researcher from Ipen.

Recent history
The first studies about the use of the laser in dentistry arose at the end of the 1960’s, with English physicist Theodor Maiman, and later in Russia and in Hungary. In 1990, the technique began to be studied in Brazil. The pioneers were professors from Fousp, who were sent that year to an interchange program at Kyushu University, in Fukuoka, Japan, one of the main centers for research in this area. Two years later, USP entered into a partnership with Ipen, which already had good experience in the development of lasers. The agreement aimed at developing new protocols for using lasers in dental treatments. Amongst other things, these procedures involve technical specifications such as power, time and exposure, type of equipment and regulation of the laser beam.

In 1995, Lelo was created at Fousp, and at the end of the decade, the professionalizing master’s degree course in lasers in dentistry appeared, run by Ipen and USP in partnership. Since then, 80 professionals have now been formed by the course, which is now on its fifth intake and is recognized by the Coordination for Perfecting Higher Level Personnel (Capes). Contributions to this rapid academic success came in the form of the purchase, with funds from FAPESP, of an erbium laser, worth US$ 70,000, and of an argon laser, which cost US$ 12,000, apparatuses that were installed at Lelo.

In spite of all the advantages offered by the new technology, there are still few professionals using laser equipment in their practices. Of the 170,000 dentists in Brazil, it is estimated that only some 100 to 200 are using high-power lasers. “This occurs for the fact that lasers are a new technology. And every novelty meets some kind of resistance”, explains Carlos de Paula Eduardo, from Lelo.

The researcher, though, makes a point of stressing the safety of the procedures. “Provided that you know the parameters and have mastered the techniques correctly, lasers are very safe.” Another reason for the limited use of the laser is the high cost of the equipment. High-power apparatuses cost around US$ 60,000. With time, though, when the technique is more disseminated, the tendency is for this amount to fall and for the use of lasers in odontology to be able to spread all over the country.

The Project
Lasers in Odontology
Coordinators
Vanderlei Bagnato – Optics and Photonics Research Center (Cepof) in São Carlos
Carlos de Paula Eduardo – Experimental Laboratory for the Laser in Odontology (Lelo) of the School of Odontology of the University of São Paulo (Fousp)
Nílson Dias Vieira Júnior – Institute of Nuclear Energy and Research (Ipen)
Investment
R$ 150,000 per annum (Cepof), R$ 1 million (construction of Lelo), US$ 82,000.00 (Regular Grant Line from FAPESP to Fousp) and R$ 300,000 per annum (Ipen)

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