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White smile

Tooth paste with less fluoride and a low pH reduces the incidence of fluorosis in children

MIGUEL BOYAYANNew dentifrice formulation in the form of a gel guarantees less fluoride on the tooth brushMIGUEL BOYAYAN

The pleasant taste of toothpastes hides a danger for children between 11 months and 7 years old. If swallowed in excess toothpaste causes fluorosis, an illness that leaves whitish or opaque stains on teeth that are forming and in the most serious cases causes porosity that can more easily lead to fractures and the absorption of colorants from food. The villain of the piece is the volume of fluoride in tooth paste, although it plays an opposite and important role in protecting teeth against decay, another ill than can cause infection and destroy teeth.

Reducing the fluoride in toothpaste to avoid fluorosis in children – this problem does not affect adults – would seem to be the obvious solution, but it does not resolve the problem of tooth decay. “There’s no evidence that, by reducing the fluoride, the effect against decay remains the same”, says dentist, Marília Afonso Rabelo Buzalaf, a professor in the Department of Biological Sciences at the Bauru School of Odontology of the University of São Paulo (USP). She is coordinating a series of scientific studies that have resulted in a dentifrice with less fluoride and a modified composition. In the first tests the dentifrice, which is a fluid gel, that is applied in drops to the brush, proved effective both against fluorosis, the incidence of which is around 30% in Brazil, as well as in preventing tooth decay. Professor Marília remimds us that up to 2 years old the children, who are constantly monitored by a dentist, should use toothpaste that has no fluoride.

The idea of making a tooth paste with low levels of fluoride started being developed in 2004. “In the formulation we compensated for the reduction in fluoride concentration by reducing the pH, making the product more acidic”, says Marília. The dental gel won the main prize in the first Olympiad of the USP Innovation Agency in 2008, the results of which were known in November. “We won first place in the health area and first in the Olympiad”, says Marília. In addition to a trophy, a notebook and R$ 5000, professor Marília’s group also won a Chevrolet Prisma automobile.

The objective of the strategy to reduce the pH used in preparing the new toothpaste to 4.5, compared with the 7,0 used in  dental creams on the market, is to increase the power for producing calcium fluoride on the teeth, a substance that functions as a deposit of calcium and fluoride in the mouth. By causing the surface layer of the tooth, formed from hydroxyapatite, to dissolve slightly calcium is released and bonds with the fluoride of the toothpaste forming calcium fluoride. This fluoride is adsorbed (a process in which the molecules of one substance are fixed to the surface of another) on to the dental enamel, acting as a reservoir of protective ions (calcium and fluoride), which will be released when the bacteria of the plaque produce acids. “The lower pH increases the formation of calcium fluoride”, explains Marília. The strategies of the researchers from USP already exist in a different way in other products. “There are toothpastes with little fluoride, others that have a low pH (not in Brazil) and others that are liquid. We combined all of them into a single product and tested it in a random clinical study (by sample) for 20 months.”

The clinical trials, with funding from FAPESP, started in 2006 in São José dos Campos, where PhD student, Fabiano Vieira Vilhena, who did the tests on the use of the dentifrice, lives. With collaboration from the city’s Department of Education, he managed to have the new gel distributed to children over 4 years old studying in the city’s public schools. The 1400 families that took part received supplies of dentifrice and tooth-brushes for 20 months. The families did not know if the product was the one from the study or something similar. Four groups were formed. Three used liquids, one of which had a formulation that was the brainchild of the researchers and that had 550 parts per 1,000,000 (ppm) of fluoride and pH of 4.5. Another had 1110 ppm of fluoride and pH of 4.5 and the third had 1100 ppm of fluoride and pH of 7.0 (neutral). The fourth group received a commercial product in the form of a cream with 1100 ppm of fluoride and pH of 7.0.

We measured the progression of the index of decayed dental surfaces, lost to decay or filled, called Ceos, and we saw that all the products were effective against decay and fluorosis. “Our formulation protects children as effectively as do those with 1100 ppm of fluoride”, says Marília. In another study, with a sub-sample of 20 children from each group that had participated in the previous study, analyses of the bacterial plaque of the nails were carried out. The plaque was analyzed because it is a store of fluoride ions that can be made available to the teeth and nails because it is a biomarker of the ingestion of fluoride. The result is that lower pH doubled the amount of fluoride incorporated into the plaque. Furthermore, the liquid formulations when applied to the brush in drops led to the use of less dentifrice, which was reflected in lower levels of fluoride in the nails. So, this was an additional advantage; the substance was not swallowed and it did not get into the blood stream. “Liquid dentifrice is more fluid and manages to incorporate better with the plaque”, says Marília. According to the researchers this happens because of the consistency of the dentifrice, which facilitates the circulation of fluoride in the enamel channels of the teeth.

Dosage test
Smaller children commonly swallow toothpaste, because when they are rinsing they are unable to spit it all out. This is also due to too much toothpaste being used. Another study carried out in Bariri, close to Bauru, measured the dose of liquid dentifrice compared with the toothpaste that children put on their brushes. The researchers measured the quantity of liquid in drops, which on average was 0.14 grams, while cream reaches a concentration of 0.50 grams, on average. “With the greater amount it is easier to swallow the toothpaste.” The next study, which should be carried out over the next few months, will be to compare the use of the new dentifrice in towns with and without fluoridated water. “In São José dos Campos there is fluoride in the water and the effectiveness of our product may have been helped by the fluoridation of the water.”

In addition to the advantages in terms of children’s health the new dentifrice may also be of benefit to the parent’s pockets. “Our formulation makes the product cheaper, meaning it can be sold for R$ 1 for a 120 gram tube”, says Marília. The USP Innovation Agency is preparing a public licensing notice for interested companies. In addition to Marília and Fabiano the name of professor Alberto Carlos Delbem, from the Araçatuba School of Odontology of the Paulista State University (Unesp) also appears on the patent.

The project
Clinical study of the effect of a new formulation for a liquid dentifrice with a reduced pH and low concentration of fluoride for preventing the appearance of new decay (nº 05/03975-6); Modality Regular Research Awards; Coordinator Marília Afonso Rabelo Buzalaf – USP; Investment R$ 96,281.47 (FAPESP)