Livia Maria Andaló Tenuta

The importance of fluoride dentifrices to the current dental caries prevalence in Brazil

Similar to that which occurred in most developed countries, dental caries have shown a significant decline in Brazil over the last two decades. Water fluoridation, expansion of preventive programs at schools, and especially, the widespread use of fluoride dentifrice are discussed as factors related to this reduction in caries. Data from epidemiological surveys and historical facts are presented to support the importance of fluoride dentifrices to the current caries prevalence in Brazil.

Effect of Frequency of Sucrose Exposure on Dental Biofilm Composition and Enamel Demineralization in the Presence of Fluoride

It has been suggested that enamel would resist higher frequencies of sucrose exposure if fluoride from water or dentifrice is being used. However, the effect of increasing frequencies of sugar on dental biofilm composition is not well known. Ten volunteers living in a fluoridated area wore palatal appliances bearing human enamel slabs during 14 days. The slabs were exposed to 20% sucrose solution 0 (control), 2, 4, 6, 8 or 10 times/day and the volunteers used fluoride dentifrice 3 times/day. Enamel demineralization was significantly greater than control for sucrose frequencies higher than 6 times/day. However, biofilm mass, total microbiota, total streptococci, lactobacilli counts and insoluble extracellular polysaccharide concentration increased, while Ca, Pi and F concentration in whole biofilm decreased significantly, with frequencies of sucrose exposure lower than 6 times/day. The findings confirm that fluoride can reduce enamel demineralization if sucrose consumption is not higher than 6 times/day, but changes in the biochemical and microbiological composition of the biofilm are observed with lower frequencies of sucrose use.

Effect of Starch and Sucrose on Dental Biofilm Formation and on Root Dentine Demineralization

The cariogenicity of starch alone or in combination with sucrose is controversial and the effect on dentine demineralization and on the dental biofilm formed has not been explored under controlled conditions. A crossover, single-blind study was conducted in four steps of 14 days each, during which 11 volunteers wore palatal appliance containing 10 slabs of root dentine to which the following treatments were applied extraorally: 2% starch gel-like solution (starch group); 10% sucrose solution (sucrose group); a solution containing 2% starch and 10% sucrose (starch + sucrose group), or 2% starch solution followed by 10% sucrose solution (starch → sucrose group). On the 14th day of each phase the biofilms were collected for biochemical and microbiological analyses, and dentine demineralization was assessed by hardness. A higher demineralization was found in dentine exposed to sucrose and starch sucrose combinations than to starch alone (p < 0.01), but the sucrose-containing groups did not differ significantly from each other (p > 0.05). The concentrations of soluble and insoluble extracellular polysaccharides (EPS), and the proportion of insoluble EPS, were lower in the biofilm formed in presence of starch (p < 0.01) than in those formed in the presence of sucrose or sucrose/starch combinations; however, no significant difference was observed among the groups containing sucrose (p > 0.05). RNA was successfully isolated and purified from in situ biofilms and only biofilms formed in response to sucrose and starch/sucrose combinations showed detectable levels of gtfB and gtfC mRNA. The findings suggest that the combination of starch with sucrose may not be more cariogenic to dentine than sucrose alone.

Fluoride: its role in dentistry

In spite of decades of research on fluoride and the recognition of its role as the cornerstone of dental caries reduction in the last fifty years, questions still arise on its use at community, self-applied and professional application levels. Which method of fluoride delivery should be used? How and when should it be used? How can its benefits be maximized and still reduce the risks associated with its use? These are only some of the challenging questions facing us daily. The aim of this paper is to present scientific background to understand the importance of each method of fluoride use considering the current caries epidemiological scenario, and to discuss how individual or combined methods can be used based on the best evidence available.

Low-Fluoride Dentifrice and Caries Lesion Control in Children with Different Caries Experience: A Randomized Clinical Trial

Since there is no consensus on the anticaries effectiveness of low-fluoride (F) dentifrice, this randomized clinical trial evaluated its effect in children at different caries activity status. One hundred and twenty 2- to 4-year-old children, half with and half without active caries lesions, were randomly divided into 2 groups which used 500- or 1,100-µg F/g (NaF) dentifrices during 1 year. Caries progression or regression were evaluated as the number of lesions becoming active/cavities or inactive, respectively. The anticaries effect of the low-F dentifrice was similar to the conventional F dentifrice when used by caries-inactive children. However, in children with active caries lesions the low-F dentifrice was less effective than the 1,100-µg F/g dentifrice in controlling the progression of lesions. The data suggest that the child caries activity may be taken into account to recommend a low-F dentifrice.

Effect of Microleakage and Fluoride on Enamel-Dentine Demineralization around Restorations

There is no consensus about an association between microleakage and secondary caries, especially considering the presence of fluoride (F) at the tooth/restoration interface. Thus, a randomized, double-blind, crossover study was carried out to evaluate in situ the effect of microleakage on caries around enamel-dentine restorations in the presence of F from dental materials or dentifrice, either alone or in combination. In 4 phases of 14 days each, 14 volunteers wore palatal devices containing dental slabs restored with composite resin (CR) or resin-modified glass ionomer cement (GI). Restorations were made without leakage (L–), following the recommended adhesive procedures, or with leakage (L+), in the absence of adhesive procedures. Plaque-like biofilm (PLB) was left to accumulate on the restored slabs, which were exposed extraorally to a 20% sucrose solution 10×/day. The volunteers used a non-F (NF) or an F (FD) dentifrice 3×/day, depending on the experimental phase. No differences were found between L+ or L– restorations (p > 0.05). Higher demineralization in both enamel and dentine around CR restorations was observed under NF (p < 0.05). F concentration was higher in the fluid of PLB exposed to FD or formed onto GI restoration (p < 0.05). These results suggest that while microleakage does not affect caries development, GI or FD may maintain increased F levels in the PLB, thereby decreasing caries progression.

Effect of starch on the cariogenic potential of sucrose

Since in vitro and animal studies suggest that the combination of starch with sucrose may be more cariogenic than sucrose alone, the study assessed in situ the effects of this association applied in vitro on the acidogenicity, biochemical and microbiological composition of dental biofilm, as well as on enamel demineralization. During two phases of 14 d each, fifteen volunteers wore palatal appliances containing blocks of human deciduous enamel, which were extra-orally submitted to four groups of treatments: water (negative control, T1); 2 % starch (T2); 10 % sucrose (T3); and 2 % starch+10 % sucrose (T4). The solutions were dripped onto the blocks eight times per day. The biofilm formed on the blocks was analysed with regard to amylase activity, acidogenicity, and biochemical and microbiological composition. Demineralization was determined on enamel by cross-sectional microhardness. The greatest mineral loss was observed for the association starch+sucrose (P<0.05). Also, this association resulted in the highest lactobacillus count in the biofilm formed (P<0.05). In conclusion, the findings suggest that a small amount of added starch increases the cariogenic potential of sucrose.

Initial Erosion Models

Initial dental erosion – the very first tooth surface changes caused by short-term acidic exposures before any tissue loss is observed – has been studied using in vitro and in situ/in vivo protocols. This paper describes the events that should be considered when modelling initial erosion, the available protocols and their strengths and limitations. In vitro initial erosion models can provide relevant information about the erosive outcome. However, the published studies vary considerably regarding the erosive parameters used, and few of these studies have been validated. On the other hand, relevant in situ/in vivo studies are available that have studied the effect of salivary pellicle and preventive treatments on initial erosion, as well as the changes in salivary pH following exposure to acid solutions. Guidelines for good methodology in modelling initial erosion are proposed.

Ca, Pi, and F in the Fluid of Biofilm Formed under Sucrose

Calcium (Ca), inorganic phosphorus (Pi), and fluoride (F) concentrations are low in the whole plaque biofilm formed under exposure to sucrose. It was hypothesized that this would be reflected in the biofilm fluid, where these low values should greatly influence the de/remineralization process. Dental biofilms were formed in situ over enamel blocks mounted in palatal appliances and exposed 8 times/day to distilled water, glucose+fructose, or sucrose solutions for 14 days. While Ca, Pi, and F concentrations in the whole biofilms were significantly lower in the glucose+fructose and sucrose groups, no effect on biofilm fluid was observed, even after a cariogenic challenge. An increase in whole biofilm mineral ions was observed 24 hrs after the carbohydrate treatments were suspended, but this effect was also not observed in the fluid. These results suggest that there is a homeostatic mechanism that maintains biofilm fluid mineral ion concentration, regardless of its total concentration in the whole biofilm.

Available fluoride in toothpastes used by Brazilian children

Toothpastes should have a minimum concentration of 1000 ppm of fluoride (F) to control caries and also the active F agent must be chemically free (soluble) in the formulation. Thus, the aim of this study was to evaluate the concentration of soluble F in dentifrices used by 206 Brazilian children. The concentrations of total fluoride (TF), total soluble fluoride (TSF) and fluoride ion were determined. From these analyses, the concentrations of F as sodium monofluorophosphate (MFP) and % of insoluble F were calculated. F was analyzed with an ion specific electrode in duplicates. The majority of dentifrices used (96%) contained F and in 84% of them, TF concentration was according to that declared by the manufacturers. In the F-toothpastes, 78% showed TSF concentration ≥ 1000 ppm, varying from 422.3 to 1432.3 ppm F (mean ± SD of 1017.6 ± 239.4). These findings suggest that most dentifrices used by Brazilian children present available fluoride concentration for caries control.