Calcium Fluoride Uptake by Human Enamel after Use of Fluoridated Mouthrinses


Luciane Almeida MONTE ALTO
Roberval Almeida CRUZ


School of Dentistry, Estácio de Sá University, Rio de Janeiro, RJ, Brazil

Correspondence: Dra. Marisol Navarro da Rocha, Rua Campinas, n. 42, apto. 101, 20561-250 Grajaú, RJ, Brasil.

Braz Dent J (2001) 12(3): 178-182 ISSN 0103-6440


The aim of this study was to evaluate, using scanning electron microscopy (SEM), the calcium fluoride uptake by human enamel in situ after topical application using three fluoridated mouthrinses: a neutral pH solution (Fluordentâ), an acidulated solution (Fluorgardâ) and a solution associated with chlorhexidine (Duplakâ). Twenty-four samples from 6 third sound human molars were divided into two groups: 5-min treatment and 10-min treatment. In both the 5-min and 10-min treatment samples, those treated with the chlorhexidine-associated solution showed higher formation of CaF2-like material. In the 10-min treatment group, the samples treated with the neutral solution showed higher formation of CaF2. These results indicated that the products used deposited CaF2 on the enamel surface and may be recommended to aid the prevention and control of dental caries.

Key Words: fluoridated mouthrinses, calcium fluoride, caries prevention.


The importance of prevention to improve general oral health has been reported for many years. The use of fluoridated products is considered to be efficient for caries control (1-3). In the past it was believed that the relationship between the use of fluoride by systemic administration (general term used to define ionic forms, ion fluorine or fluoride, ionizable or non-ionic of the element) and the significant reduction of caries was due to its incorporation during enamel formation. Thus, the main objective of the therapy was to promote an increase of incorporation to its structure. Currently there is consensus that this reaction does not confer permanent resistance to caries. Low and constant concentrations of fluoride in the oral cavity are more efficient for disease control (4).
Gerould (5) was one of the first to report the deposit of CaF2 on the surface of human enamel, observed with scanning electron microscopy (SEM), after treatment with fluoridated solutions. Other studies confirmed this finding (6,7). The hypothesis of calcium fluoride uptake by dental enamel acting as a fluoride reservoir for a long period of time has been defended (6), and others have reported that it indirectly induces the solubility reduction of the acid of plaque (3,8).
It is beyond discussion that CaF2 deposited as a result of fluoridated topical application is the basic element in the prevention and control of dental caries. Thus, the products that induce its formation should be largely used (8,9). According to research, the constant presence of fluoride in the oral cavity acts dynamically, performing an important role in the change of dental caries pattern (1,2,4,10).
The CaF2 mechanism of action as a reservoir releases fluoride whenever the pH falls to very low levels. In this way, CaF2 remains adhered to the enamel surface, being released during caries (3,11). CaF2 has a greater impact on the reactions of enamel demineralization and remineralization than the fluoride incorporated in the enamel structure (12).
It is also considered that the main role of fluoride is related to the interference in the progress of incipient caries, acting in enamel and dentin and increasing the remineralization of teeth with the same efficiency in both children and adults. The frequent use of low concentration fluoride compounds by patients has been shown to be very efficient against caries (13). Thus, fluoridated products with low concentration and high frequency, such as toothpaste and mouthrinse, have been used as therapeutic and preventive agents in dentistry aiming to health promotion (14-16).
Mouthrinses have been recommended by the World Health Organization as an alternative method of prevention and treatment of caries, with an impact on Public Health. Their use has led to a decrease in the appearance of caries and can be considered to be simple and inexpensive, besides presenting the advantage of use in school programs, with little work time  necessary and no need for specialized personel for application (4,17).
The efficiency of the use of mouthrinses, in terms of biochemistry, for the control of caries development has been outstanding for acting in a period of up to 4 hours (4). The use of mouthrinses weekly with a neutral 0.2% sodium fluoride solution reduced the prevalence of caries in school-children by 50% (18). It was also concluded that sodium fluoride and phosphate acidulated fluoride solutions were equally effective (2,19).
It has been reported that even with short-period applications, CaF2  is deposited on enamel in situ after treatment with mouthrinses containing 0.2% and 0.05% sodium fluoride (8). The presence of globules of CaF2 after the use of fluoride acidulated compounds for 5 min of treatment has also been reported (4).
The aim of the present study was to examine in situ the CaF2 uptake by human enamel after the use of different fluoridated mouthrinses for 5 and 10 min.


Six sound third permanent molars extracted for clinical reasons were stored in 2% formaldehyde until use. The teeth were polished with pumice and deionized water for 20 s and subsequently washed with deionized water and dried at room temperature.
Four 9 mm2 enamel fragments of each tooth were obtained from the buccal and lingual surfaces of the middle third of each tooth, totaling 24 samples. These were properly identified and stored in plastic recipients containing deionized water.
Maxillary retainers were made with interproximal clasps for retention and two troughs on the exposed palatal surface to retain the enamel sections (Figure 1). Three fluoridated mouthrinses were used in two groups (A and B): Fluordentâ (0.05% NaF; Johnson & Johnson Indústria e Comércio Ltda., São José dos Campos, SP, Brazil), Fluorgardâ (0.05% FFA; Colgate-Palmolive Ltda., Osasco, SP, Brazil) and Duplakâ (0.05% NaF  and 0.12% chlorhexidine; Herpo Produtos Dentários Ltda., Petrópolis, RJ, Brazil). Both groups also had samples that did not receive any treatment (control). Group A was treated for 5 min and group B was treated for 10 min.
After insertion and gluing of the fragments in the intra-oral device, this was introduced into the oral cavity of a volunteer who rinsed with 10 ml of one of the solutions for 5 or 10 min. The solutions were used individually and on alternate days. After  treatment, the samples were removed, washed with deionized water for 2 min and naturally dried. They were then placed  in metallic bases and prepared for SEM.


Photomicrographs of the repeatedly seen areas in all samples of the same group  were selected. None of the samples of the control group had any deposits on their surface (Figures 2A and 3A). In the samples treated with the fluoridated solutions, there was a variable amount of deposits for both treatments (Figures 2 and 3). The group that was treated with the chlorhexidine-associated solution for 5 and 10 min had the largest quantity of globules on the enamel (Figures 2D and 3D).
Comparing the fluoridated products used in relation to the time of treatment, it seems that the differences were not statistically significant in terms of product vs time, except for the group that was treated with the pH neutral solution.There was larger formation and deposit of CaF2  globules with the 10-min treatment (Figures 2B and 3B). The result obtained with the use of the chlorhexidine-associated solution (Duplakâ;  Figure 4) was surprising. Agglomerated  CaF2-like globules could be observed.


The use of fluoride is an important instrument in preventive programs and health maintenance and its use in the form of fluoride solutions is considered to be an efficient method, because of its ease of use in collective health programs, highly contributing to caries reduction.
The main objective of the use of fluoridated products is its constant presence in the oral cavity, its frequent contact with enamel in low concentrations, that provides the cariostatic effect, by the adsorption of calcium fluoride on its surface and the release of ions during the decay of the plaque pH (1,3,4,10,14,17).
This investigation demonstrates the formation and deposit of CaF2 after the use of commercially available mouthrinses for 5 and 10 min. When the neutral pH fluoridated solution was used, there was greater formation of globules with a longer time of treatment. This confirms that with a longer time of treatment,  the formation of CaF2 will be larger (4). 
There were no significant differences in the deposit of CaF2 between the acidulated compounds and those with a neutral pH. In this study, the largest formation of fluoride was found in the samples treated with Duplakâ, with no differences between the other two products when a shorter time of treatment was used. With the 10-min treatment, the CaF2 globules formation was similar emphasizing the efficacy the neutral pH solution. This solution had the advantage of stability, a tasteful flavor, non-irritating to the gum and no spotting of the teeth.
Since the high frequency of the use of these products in low concentrations is more effective for maintaining constant levels of fluoride in the oral cavity, reducing the solubility of the enamel and promoting the remineralization of incipient lesions, the analysis of results suggests that the tested products can be recommended because there was formation of CaF2 in all cases (14-16). However, careful procedures must be considered when recommending mouthrinses for children less than six years of age because they may swallow a large amount of the solutions. If use is necessary below this age, it would be wise to recommend that the person responsible for the child’s care apply the solution directly to the teeth with cotton.


Navarro M, Monte Alto LA, Cruz RA, Prazeres J. Incremento de CaF2 sobre o esmalte dental humano após utilização de soluções fluoretadas. Braz Dent J 2001;12(3):178-182.

O presente estudo teve como objetivo verificar, através da microscopia eletrônica de varredura (MEV), a formação e retenção de fluoreto de cálcio (CaF2) sobre a superfície do esmalte dental humano in situ após tratamento tópico com diferentes soluções fluoretadas para bochecho disponíveis no mercado, durante 5 e 10 minutos. Foram selecionados três produtos: solução fluoretada em pH neutro (Fluordent), solução fluoretada acidulada (Fluorgard) e uma solução fluoretada associada à clorexidina (Duplak). Cinquenta e seis secções, obtidas de 14 terceiros molares hígidos, foram divididas em dois grupos: grupo A: 5 minutos de tratamento e grupo B: 10 minutos de tratamento. Através da análise dos resultados foi possível observar que as amostras tratadas por 5 min com solução associada à clorexidina demonstraram maior formação do produto semelhante ao CaF2.  No grupo tratado por 10 min, as amostras em pH neutro demonstraram maior incremento de CaF2. De qualquer forma, pôde-se perceber que o produto reacional foi formado e retido em quantidades significantes em todas as situações. Estes resultados demonstraram  que os produtos utilizados neste experimento foram capazes de formar e depositar CaF2 sobre a superfície do esmalte dental, podendo ser recomendados como coadjuvantes na prevenção e no controle da cárie dentária.

Unitermos: soluções fluoretadas, fluoreto de cálcio, prevenção de cárie.


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Accepted May 3, 2001