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Dental restoration

Remedial shine

Dental pins with nanoparticles emit light and enable tooth recovery

075_Resina_194Tiago CirilloA transparent, fiberglass dental pin is already available on the market. This pin reduces the time – from 5 minutes to no more than 30 seconds – it takes for the resin and cement used for dental restoration and cavities to harden (cure). This new product is the result of a partnership between the Multidisciplinary Center for the Development of Ceramic Materials (CMDMC), one of the Research, Innovation and Diffusion Centers (Cepid) funded by FAPESP, and the Angelus company, based in the city of Londrina, State of Parana. This partnership has also produced intelligent anti-microbe packaging for these pins.

The knowledge that enabled the development of this dental product was based on the doctoral thesis of researcher Valdemir dos Santos, whose advisor was professor Elson Longo, coordinator of CMDMC, which is located in the Biochemical Sciences Institute at the Araraquara campus of São Paulo State University (Unesp). During his research work, Santos used microwaves innovatively to synthesize calcium molybdate, from calcium chloride and sodium molybdate, which have photoluminescent properties. When they are exposed to blue light (from a lamp or LED, emitted by a rod used by dentists) coming from a wavelength of 460 to 490 nanometers, the particles of this material in the pin emit light (they are photoluminescent) and function somewhat like a LED,” explains Longo. “This cures the cement or resin used in dental treatment.”

The use of pins in endodontics has been a standard procedure for quite some time. Endodontics is the specialty that prevents and heals dental pulp diseases, such as dental caries. The standard treatment is to remove the infected tissue and substitute it with material such as cement or resin. After the damaged tissue is removed, the tooth can become fragile, and the solution is to use pins to keep it firmly in place. Various kinds of pins are available on the market. The most commonly used ones are made of metal (zirconium, stainless, steel, or titanium). These pins, however, have some drawbacks, such as mechanical properties that differ from those of the tooth, which causes significant changes in the mechanical behavior. These pins, subject to corrosion and oxidation, also transmit heat.

Non-metallic pins, made of carbon or fiberglass, have recently appeared on the market. Their behavior is more similar to that of the dental structure. Their mechanical properties are compatible with those of teeth, which lowers the risk of root failure or fractures. In addition, they adhere better and their elasticity is very similar to that of dentine, the tissue that forms the tooth and is coated with enamel. The non-metallic pins are also more resistant to corrosion and can be easily removed.

The pins developed by Angelus consist of fiberglass (80%) and epoxy resin (20%) doped with calcium molybdate particles. They are approximately 2 centimeters long with a diameter of 1.4 millimeters at their thickest portion. “In spite of their rigid and compact structure, these fiberglass pins are translucent; 12% of the light goes through them, which is enough to cause the polymerization of the materials,” Longo explains. The hardening process is quicker because, unlike opaque pins, the light reaches the tooth’s deepest parts, which cannot be reached otherwise. This is useful for the dentist to be sure that his work was successfully concluded.”

In addition to the photoluminescent pins, which have resulted in a patent, the partnership between Angelus and professor Longo produced another innovative product: intelligent packaging. This partnership began eight years ago, when the professor was teaching at the Federal University of São Carlos (UFSCar). The packaging is in the shape of a small five-centimeter tube, made of polypropylene (98.5% ) and anti-microbe agents (1.5%). Longo explains that the bacteria and fungi need molybdenum for their metabolism. “This element is part of the enzymes’ catalyst mechanism, a fundamental process for digesting the food they eat; as such, it plays a major role in metal biochemistry (the name given to the metabolism of beings that feed on metals) of these microorganisms,” he says. “This is why the microorganisms will go anywhere for food to ensure their survival.”

This characteristic was used against the microorganisms. To this end, the researchers used sodium molybdate, calcium molybdate and silver nanoparticles, mixed with molten polypropylene. The plastic is injected into a mold and solidifies, thus forming the packaging, as particles of the molybdate and silver concentrate at some random points that attract bacteria and fungi. In fact, this is a trap. “Not only does the molybdate attract the microorganisms but they also align the light emitted by the material to a specific wave length that activates the complex at the base of the silver and eliminates the fungi and the bacteria,” Longo explains. “This is why the packaging is said to be intelligent.”

According to Cesar Bellinati, R&D manager Angelus, the packaging is not sold separately. “It is only used to package the photoluminescent pins,” he says. This is a special feature of our product.” Ever since the product’s launch in 2010, the company has sold 25 thousand five-pin sets packaged in the intelligent tube, resulting in revenues of US$ 1 million.

Founded in 1994, Angelus is currently one of the leaders of the Latin American dental pin and dental products market. According to Bellinati, the company – which employs 65 people and whose sales last year came to R$ 12 million – aims at finding scientific and technology-based solutions for dentistry. “This is why we have a close relationship with the academic, technical, and scientific sectors,” he says.

The Project
Multidisciplinary Center for the Development of Ceramic Materials (CMDMC) (nº 98/14324-0); Modality Center of Research, Innovation and Dissemination (Cepid); Coordinator Elson Longo – Unesp; Investment R$ 1 million a year for all of the CMDMC projects (FAPESP)

Scientific article
LONGO, V.M. et al. Hierarchical assembly of CaMoO4 nano-octahedrons and their photoluminescence properties. Journal of Physical Chemistry C. v. 115, n. 13, p. 5.207-19, Apr. 2011.