Titratable acidity of beverages influences salivary pH recovery

A low pH and a high titratable acidity of juices and cola-based beverages are relevant factors that contribute to dental erosion, but the relative importance of these properties to maintain salivary pH at demineralizing levels for long periods of time after drinking is unknown. In this crossover study conductedin vivo, orange juice, a cola-based soft drink, and a 10% sucrose solution (negative control) were tested. These drinks differ in terms of their pH (3.5 ± 0.04, 2.5 ± 0.05, and 5.9 ± 0.1, respectively) and titratable acidity (3.17 ± 0.06, 0.57 ± 0.04 and < 0.005 mmols OH- to reach pH 5.5, respectively). Eight volunteers with a normal salivary flow rate and buffering capacity kept 15 mL of each beverage in their mouth for 10 s, expectorated it, and their saliva was collected after 15, 30, 45, 60, 90, and 120 s. The salivary pH, determined using a mini pH electrode, returned to the baseline value at 30 s after expectoration of the cola-based soft drink, but only at 90 s after expectoration of the orange juice. The salivary pH increased to greater than 5.5 at 15 s after expectoration of the cola drink and at 30 s after expectoration of the orange juice. These findings suggest that the titratable acidity of a beverage influences salivary pH values after drinking acidic beverages more than the beverage pH.

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.

Não 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 tempo.