Insoluble Naf in Duraphat® may prolong fluoride reactivity of varnish retained on dental surfaces

There is no consensus about the clinical recommendation of the time that Duraphat® varnish should be maintained on enamel surfaces without suffering mechanical disturbance by the patient. Considering the importance of calcium fluoride (CaF2)-like reservoirs on the anticaries effect of professional fluoride application, an in vitro study was designed to test the reactivity of Duraphat® varnish with enamel forming these reservoirs as a function of time. Since most fluoride in Duraphat® varnish is insoluble to react and form products on enamel, the relative contribution of the varnish soluble and insoluble fluoride fractions to the reactivity was also evaluated. For this, whole-varnish, containing soluble and insoluble fluoride (total fluoride concentration of 23699±384 μg F/g), or centrifuged varnish, containing only soluble fluoride (fluoride concentration of 258±97 μg F/g), were applied in a standardized manner on enamel slabs (n=8/varnish group/time), which were immersed in continuously renewed artificial saliva for up to 36 h. CaF2-like reservoirs formed on enamel by varnish application were extracted using 1 M KOH and fluoride concentration was measured with ion specific electrode. The results were expressed as μg F/cm2 of enamel area. Whole varnish formed significantly higher fluoride concentration on enamel than centrifuged varnish, reaching maximum concentration at 24 h (22.0±4.5 μg F/cm2). Centrifuged varnish reached maximum concentration at 6 h (3.20±0.81 μg F/ cm2). In conclusion, a longer varnish retention time than the usually recommended could improve the anticaries effect of Duraphat® varnish, allowing that NaF particles, initially insoluble in the varnish matrix, prolong the reactivity with enamel.There is no consensus about the clinical recommendation of the time that Duraphat® varnish should be maintained on enamel surfaces without suffering mechanical disturbance by the patient. Considering the importance of calcium fluoride (CaF2)-like reservoirs on the anticaries effect of professional fluoride application, an in vitro study was designed to test the reactivity of Duraphat® varnish with enamel forming these reservoirs as a function of time. Since most fluoride in Duraphat® varnish is insoluble to react and form products on enamel, the relative contribution of the varnish soluble and insoluble fluoride fractions to the reactivity was also evaluated. For this, whole-varnish, containing soluble and insoluble fluoride (total fluoride concentration of 23699±384 μg F/g), or centrifuged varnish, containing only soluble fluoride (fluoride concentration of 258±97 μg F/g), were applied in a standardized manner on enamel slabs (n=8/varnish group/time), which were immersed in continuously renewed artificial saliva for up to 36 h. CaF2-like reservoirs formed on enamel by varnish application were extracted using 1 M KOH and fluoride concentration was measured with ion specific electrode. The results were expressed as μg F/cm2 of enamel area. Whole varnish formed significantly higher fluoride concentration on enamel than centrifuged varnish, reaching maximum concentration at 24 h (22.0±4.5 μg F/cm2). Centrifuged varnish reached maximum concentration at 6 h (3.20±0.81 μg F/ cm2). In conclusion, a longer varnish retention time than the usually recommended could improve the anticaries effect of Duraphat® varnish, allowing that NaF particles, initially insoluble in the varnish matrix, prolong the reactivity with enamel252160164Marinho, V.C., Higgins, J.P., Logan, S., Sheiham, A., Fluoride varnishes for preventing dental caries in children and adolescents (2002) Cochrane Database Syst Rev, pp. CD002279Marinho, V.C., Higgins, J.P., Logan, S., Sheiham, A., Fluoride gels for preventing dental caries in children and adolescents (2002) Cochrane Database Syst Rev, pp. CD002280Ten Cate, J.M., Review on fluoride, with special emphasis on calcium fluoride mechanisms in caries prevention (1997) Eur J Oral Sci, 105, pp. 461-465Tenuta, L.M., Cerezetti, R.V., Del Bel Cury, A.A., Tabchoury, C.P., Cury, J.A., Fluoride release from CaF2 and enamel demineralization (2008) J Dent Res, 87, pp. 1032-1036Villena, R.S., Tenuta, L.M., Cury, J.A., Effect of APF gel application time on enamel demineralization and fluoride uptake in situ (2009) Braz Dent J, 20, pp. 37-41Calvo, A.F., Tabchoury, C.P., Del Bel Cury, A.A., Tenuta, L.M., da Silva, W.J., Cury, J.A., Effect of acidulated phosphate fluoride gel application time on enamel demineralization of deciduous and permanent teeth (2012) Caries Res, 46, pp. 31-37Retief, D.H., Sorvas, P.G., Bradley, E.L., Taylor, R.E., Walker, A.R., In vitro fluoride uptake, distribution and retention by human enamel after 1- and 24-hour application of various topical fluoride agents (1980) J Dent Res, 59, pp. 573-582Bruun, C., Givskov, H., Formation of CaF2 on sound enamel and in carieslike enamel lesions after different forms of fluoride applications in vitro (1991) Caries Res, 25, pp. 96-100Du, M., Cheng, N., Tai, B., Jiang, H., Li, J., Bian, Z., Randomized controlled trial on fluoride varnish application for treatment of white spot lesion after fixed orthodontic treatment (2012) Clin Oral Investig, 16, pp. 463-468Weintraub, J.A., Ramos-Gomez, F., Jue, B., Shain, S., Hoover, C.I., Featherstone, J.D., Fluoride varnish efficacy in preventing early childhood caries (2006) J Dent Res, 85, pp. 172-176Arruda, A.O., Senthamarai Kannan, R., Inglehart, M.R., Rezende, C.T., Sohn, W., Effect of 5% fluoride varnish application on caries among school children in rural Brazil: A randomized controlled trial (2012) Community Dent Oral Epidemiol, 40, pp. 267-276Skold-Larsson, K., Modeer, T., Twetman, S., Fluoride concentration in plaque in adolescents after topical application of different fluoride varnishes (2000) Clin Oral Investig, 4, pp. 31-34Ten Cate, J.M., Duijsters, P.P., Alternating demineralization and remineralization of artificial enamel lesions (1982) Caries Res, 16, pp. 201-210Retief, D.H., Bradley, E.L., Holbrook, M., Switzer, P., Enamel fluoride uptake, distribution and retention from topical fluoride agents (1983) Caries Res, 17, pp. 44-51Caslavska, V., Moreno, E.C., Brudevold, F., Determination of the calcium fluoride formed from in vitro exposure of human enamel to fluoride solutions (1975) Arch Oral Biol, 20, pp. 333-339Ritwik, P., Aubel, J.D., Xu, X., Fan, Y., Hagan, J., Evaluation of short-term fluoride release from fluoride varnishes (2012) J Clin Pediatr Dent, 36, pp. 275-278Arends, J., Nelson, D.G., Dijkman, A., Jongebloed, W.L., Effect of various fluorides on enamel structure and chemistry (1984) Cariology Today, pp. 245-258. , Guggenheim (Editor). Zürich: KargerAttin, T., Lennon, A.M., Yakin, M., Becker, K., Buchalla, W., Attin, R., Deposition of fluoride on enamel surfaces released from varnishes is limited to vicinity of fluoridation site (2007) Clin Oral Investig, 11, pp. 83-88Tenuta, L.M., Cury, J.A., Laboratory and human studies to estimate anticaries efficacy of fluoride toothpastes (2013) Monogr Oral Sci, 23, pp. 108-124Miller, E.K., Vann Jr., W.F., The use of fluoride varnish in children: A critical review with treatment recommendations (2008) J Clin Pediatr Dent, 32, pp. 259-264Não há consenso sobre a recomendação clínica do tempo que o verniz Duraphat® deve ser mantido nas superfícies de esmalte sem ter perturbação mecânica pelo paciente. Considerando a importância dos reservatórios tipo fluoreto de cálcio (“CaF2”) no efeito anticárie da aplicação profissional de fluoreto, um estudo in vitro foi delineado para testar a reatividade do verniz Duraphat® com o esmalte na formação desses reservatórios em função do tempo. Como a maioria do fluoreto no verniz Duraphat® é insolúvel para reagir e formar produtos no esmalte, também se avaliou a contribuição relativa das frações solúvel e insolúvel do verniz na reatividade. Assim, verniz total, contendo fluoreto solúvel e insolúvel (concentração total de 23699±384 µg F/g), ou verniz centrifugado, contendo somente o fluoreto solúvel (concentração de 258±97 µg F/g), foram aplicados de maneira padronizada sobre blocos de esmalte (n =8/grupo de verniz/tempo), os quais foram imersos em saliva artificial com renovação continua por até 36 h. Os reservatórios tipo “CaF2” formados no esmalte pela aplicação do verniz foram extraídos com KOH 1 M e a concentração de F foi medida utilizando um eletrodo específico. Os resultados foram expressos como µg F/cm2. O verniz total formou significativamente maior concentração de fluoreto no esmalte que o verniz centrifugado, atingindo concentrações máximas após 24 h (22,0±4,5 µg F/cm2 de área de esmalte). O verniz centrifugado apresentou a máxima formação após 6 h (3,20 ± 0,81 µg F/cm2). Em conclusão, um tempo maior de retenção do que habitualmente recomendado poderia melhorar o efeito anticárie do verniz Duraphat®, pois partículas de NaF, inicialmente insolúveis na matriz do mesmo, possibilitam uma reatividade prolongada do verniz com o esmalte em função do temp