Fluoride Intake and Salivary Fluoride Retention after Using High-Fluoride Toothpaste Followed by Post-Brushing Water Rinsing and Conventional (1400-1450 ppm) Fluoride Toothpastes Used without Rinsing

This study aimed to compare the fluoride intake and salivary fluoride levels after brushing with conventional (1400-1450 ppm) fluoride toothpaste containing different fluoride agents: amine fluoride (AmF), sodium fluoride (NaF), sodium monofluorophosphate (SMFP), potassium fluoride (KF), and a high-fluoride (5000 ppm) toothpaste containing NaF. Fourteen volunteers took part in the study. They were instructed to brush and spit without rinsing after using conventional toothpaste or brush and rinse with water after using a high-fluoride toothpaste. Fluoride concentrations were determined using ion-selective fluoride (09-37 type) in the saliva samples before and after procedures. Fluoride intake was estimated based on fluoride recovered after brushing. Additionally, the amount of fluoride present in the oral fluids and lost during the rapid clearance phase after toothbrushing was calculated based on salivary fluoride levels and saliva flow immediately after brushing. Salivary fluoride after using high-fluoride toothpaste was significantly higher than those observed after conventional products. Two hours after brushing, salivary fluoride concentrations did not differ significantly from baseline values (p > 0.05) unless a high-fluoride product was used. Results indicate that by refraining from rinsing after brushing with conventional toothpaste, we cannot obtain fluoride retention in saliva as with high-fluoride toothpaste. Fluoride ingestion was higher after using a high-fluoride product.

Fluoride Intake Through Dental Care Products: A Systematic Review

Fluoride (F) is added to many dental care products as well as in drinking water to prevent dental decay. However, recent data associating exposure to F with some developmental defects with consequences in many organs raise concerns about its daily use for dental care. This systematic review aimed to evaluate the contribution of dental care products with regard to overall F intake through drinking water and diet with measurements of F excretion in urine used as a suitable biomarker. According to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines using keywords related to chronic exposure to F in the human population with measurements of F levels in body fluids, 1,273 papers published between 1995 and 2021 were screened, and 28 papers were finally included for data extraction concerning daily F intake. The contribution of dental care products, essentially by toothbrushing with kinds of toothpaste containing F, was 38% in the mean regardless of the F concentrations in drinking water. There was no correlation between F intake through toothpaste and age, nor with F levels in water ranging from 0.3 to 1.5 mg/L. There was no correlation between F intake and urinary F excretion levels despite an increase in its content in urine within hours following exposure to dental care products (toothpastes, varnishes, or other dental care products). The consequences of exposure to F on health are discussed in the recent context of its suspected toxicity reported in the literature. The conclusions of the review aim to provide objective messages to patients and dental professionals worried about the use of F-containing materials or products to prevent initial caries or hypomineralized enamel lesions, especially for young children.

Chemically Soluble Fluoride in Na2FPO3/CaCO3-Based Toothpaste as an Indicator of Fluoride Bioavailability in Saliva during and after Toothbrushing

The relationship between the concentration of chemically soluble fluoride found in toothpaste and that present in saliva, during and after brushing, was evaluated as an indicator of potentially bioavailable fluoride in toothpaste. Ten adult participants brushed their teeth with the assigned toothpastes: group I: fresh sample of a fluoride toothpaste: Na2FPO3/CaCO3, 1,378 µg F/g of total soluble fluoride (TSF); groups II-IV: aged samples of toothpaste presenting TSF concentrations of 1,160, 900, and 597 µg F/g, respectively; group V: non-F placebo toothpaste. The volunteers brushed their teeth for 1 min with 0.7 g of the toothpaste, all toothbrushing residues (TR) produced were collected, the mouth was rinsed with water, and saliva samples were collected up to 120 min. Total fluoride (TF) and TSF concentrations were determined in TR and in saliva samples using a fluoride ion-selective electrode. TSF concentration (µg F/mL) in TR was determined as an indicator of fluoride bioavailability during toothbrushing and the areas under curves of saliva fluoride concentration versus time (area under the curve, AUC = µg F/mL × min) were calculated as an indicator of fluoride bioavailability after toothbrushing. A significant correlation was found between the TSF concentrations in the toothpastes and the variables TR (r = 0.850; p = 0.0001) and AUC (r = 0.445; p = 0.004). For TF no significant correlation was found for TR (r = -0.099; p = 0.542) and AUC (r = -0.018; p = 0.912). The findings suggest that TSF concentration chemically found in Na2FPO3/CaCO3-based toothpaste could estimate how much fluoride would be bioavailable in saliva when the teeth are brushed.

Systemic Effects (Risks) of Water Fluoridation

Abstract Since the 1950s, the benefits and risks of fluoridated water use have been debated worldwide. In the past, it was considered that the systemically ingested fluoride would exert its primary preventive effect after being incorporated into the enamel as fluorapatite, making the enamel more resistant to the caries process; however, it is now recognized that the main effect of water fluoridation is local and post eruptive. On the other hand, irrespective of the caries decline reported worldwide, the anticaries benefit of water fluoridation continues to be observed even in developed countries. Regarding the risks, water fluoridation is considered an acceptable community-based method for fluoride delivery, because the risk of developing dental fluorosis lesions due to the ingestion of fluoride during the enamel formation period has been deemed acceptable when contrasted to the anticaries benefits of fluoride. However, the use of fluoride in water to control caries has created a controversy due to data associating water fluoridation as the cause of some systemic diseases. Therefore, the aim of this descriptive review was to discuss the systemic effects (risks) of water fluoridation use.

Gastrointestinal Absorption and Renal Excretion of Fluoride After Ingestion of a High-Fluoride Dentifrice

This study aimed to evaluate the gastrointestinal absorption and renal excretion of fluoride after the ingestion of high-fluoride dentifrice. Twelve volunteers participated in this in vivo, crossover, and blinded study. In three experimental phases, the volunteers were randomly assigned to one of three treatment groups, who ingested either the following: distilled and deionized water (control), conventional dentifrice (1100 μg/g), or high-fluoride dentifrice (5000 μg/g). Both dentifrices contained fluoride in the form of NaF/SiO₂. To determine the rate of fluoride absorption, non-stimulated saliva was collected for up to 120 min after ingestion and the area under the curve of the salivary fluoride concentration was plotted as a function of time and the maximum concentration determined. All urine produced during the 24 h before and after ingestion was collected, and urinary excretion was calculated from the difference between the urinary fluoride concentrations in the two periods. A specific ion electrode coupled to an ion analyzer was used to measure fluoride concentrations. Statistical analysis was performed by ANOVA followed by Tukey's test with p set at 5%. All measured parameters were highest after the ingestion of the dentifrice with 5000 μg/g (p < 0.001), confirming that this has an increased level of bioavailable fluoride compared with the conventional dentifrice. The high-fluoride dentifrice increases the concentration of salivary fluoride, which may explain its greater anticaries effect. However, it poses a potential risk of causing dental fluorosis and so should not be used by children.

Does flavoured dentifrice increase fluoride intake compared with regular toothpaste in children? A systematic review and meta-analysis

BACKGROUND

Toothpaste manufacturers encourage through aggressive marketing strategies the overconsumption of fluoridated dentifrices. There are conflicting results regarding fluoride intake from toothpastes in children.

AIM

The aim of this systematic review and meta-analysis was to determine whether dentifrice flavour increases fluoride ingestion by children.

DESIGN

We included clinical trials on children that evaluated the use of flavoured dentifrice - FD vs regular dentifrice - RD to identify the fluoride intake. An electronic search was performed in PubMed, Web of Science, Scopus, The Cochrane Library, LILACS/BBO, and grey literature followed by manual search. The methodological quality of the studies was assessed using the Cochrane Collaboration common scheme for bias and ROBINS-I tool. Data were analysed in subgroups such as low (G1) and ordinary (G2) fluoride concentrations of dentifrices. We carried out heterogeneity and sensitive analyses.

RESULTS

For G1, the fluoride intake from RD was significantly higher than from FD [standardised mean difference = -2.57 (-3.26, -1.89), P < 0.00001]. For G2, the fluoride ingestion from RD was significantly higher than from FD [mean difference = -0.00 (-0.00, -0.00), P = 0.02].

CONCLUSIONS

There is evidence to support the null hypothesis that flavouring from dentifrice does not increase fluoride intake in young children.

Stability of chemically available fluoride in Chilean toothpastes

BACKGROUND

Storage time may reduce the amount of soluble fluoride (F) in toothpastes. Although we previously studied the type and concentration of F in fresh samples of commercial Chilean toothpastes, their stability was not determined.

AIM

To evaluate the stability of soluble F in Chilean toothpastes after 1 year of storage.

DESIGN

All the toothpastes (n = 30) previously used were re-analyzed after 1 year of storage time at room temperature (±22°C). Total F (TF = soluble F + insoluble F) and total soluble F (TSF = F ion + MFP ion) were assessed using an ion-specific electrode, through a validated methodology. Data were expressed in ppm of F (mg F/kg).

RESULTS

Mean (±SD; n = 30) TF and TSF concentrations after storage were 1049 ± 427 and 987 ± 411 ppm F, respectively. Five toothpastes showed between 30% and 50% of insoluble F, four of them formulated with MFP/calcium-based abrasive. In two products, there was a reduction in TSF below the evidence-based anticaries effectiveness threshold of 1000 ppm F.

CONCLUSIONS

Although most of the toothpastes tested kept their original TSF content after 1 year of storage, some products evidenced an important reduction, which may compromise their anticaries efficacy. Reductions in TSF may be explained by an incorrect F salt-abrasive formulation.

Is severe early childhood caries predictive of caries and fluorosis in permanent teeth? Ten-year follow-up

Abstract Introduction Severe early childhood caries is defined as the presence of any sign of decay in children younger than three years. Objective This retrospective longitudinal observational study investigated caries and fluorosis in children with S-ECC from a city with fluoridated water. Material and method We included children under the age of three years who followed a maternal and child dental care program between the years of 1997 and 2003. The children were divided into 2 groups: group 1 (S-ECC) and group 2 (no caries). Guardians were contacted by telephone or mail. Caregivers completed questionnaire on socio-demographic and behavioral variables. The clinical dental examinations were performed in a dental clinic to assess caries experience and dental fluorosis. Multiple linear regression was used to determine factors associated with DMFT, and multivariate analysis by multiple logistic regression was used to determine the possible independent factors associated with the occurrence of fluorosis. Result The sample consisted of 126 patients aged 8-12 years, of whom 52.4% were male. The presence of S-ECC increased the DMFT by an average of 0.84 (p = 0.02). Both the frequency of tooth brushing and the use of standard toothpaste were protective factors from the development of caries in the permanent dentition (p <0.05). Parents who reported that their children refused to brush their teeth had 70% less chance of developing fluorosis (p = 0.02). Conclusion The presence of S-ECC was a risk factor for the development of caries in the permanent dentition, but not for the development of fluorosis.

Risk Assessment Study of Fluoride Salts: Probability-Impact Matrix of Renal and Hepatic Toxicity Markers

The present risk assessment study of fluoride salts was conducted by oral administration of three different doses of sodium and potassium fluorides (NaF, KF) and zinc fluoride tetrahydrate (ZnF2 •4H2O) to male Wistar rats. The rats were divided into control and nine experimental groups, to which oral injections of 0.5 mL distilled water and 0.5 mL of fluoride solutions, respectively, were given. The dosage of fluoride compounds was adjusted to contain 2.1 mg (low-dose group, LG), 4.3 mg (mid-dose group, MG), and 5.4 mg fluoride per 200 g rat body weight (high-dose group, HG) corresponding to 5, 10, and 12.5 % of LD50 values for NaF. The 24-h urine volume, N-acetyl-β-D-glucosaminidase (NAG) and creatinine clearance (Ccr) were measured as markers of possible acute renal impact. The levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were determined in serum samples as markers of acute hepatic impact. The levels of serum and urinary fluoride were determined to evaluate fluoride bioavailability. The results reveal that higher doses of NaF, KF, and ZnF2 induced renal damage as indicated by higher urinary NAG (p < 0.05 with ≥90th percentile of control). High doses of ZnF2 also induced a significant Ccr decrease (p < 0.05 with ≤10th percentile of control). Low doses of NaF and mid-doses of ZnF2 induced polyuria (p < 0.05 with ≥90th percentile of control) while medium doses of NaF and low doses of KF also induced liver damage, as indicated by a high level of AST (p < 0.05 with ≥90th percentile of control). These findings suggest that oral administration of fluoride is a potential, dose-dependent risk factor of renal tubular damage.

Vigilância epidemiológica da fluorose dentária em município de clima tropical com água de abastecimento público fluoretada

Resumo O objetivo deste estudo foi avaliar a prevalência e a severidade de fluorose dentária em escolares de 11 a 14 anos de idade em Teresina (PI) Brasil, município de clima tropical com água de abastecimento público fluoretada. Estudo do tipo observacional transversal no qual foram avaliadas 571 crianças distribuídas nas redes pública e particular de ensino. A coleta de dados foi realizada nas unidades escolares, após recolhimento do Termo de Consentimento Livre e Esclarecido (TCLE) e questionário respondido pelos pais referentes às condições socioeconômicas e demográficas e aos hábitos de higiene bucal. O exame dentário foi realizado por um cirurgião-dentista calibrado. O índice aplicado foi o Thylstrup e Fejerskov (TF). A prevalência de fluorose foi de 77,9%, e apenas 12,5% das crianças acometidas apresentaram TF ≥ 3, grau com comprometimento estético. Os pré-molares foram os dentes mais afetados pela fluorose. Dentre os escolares com maior severidade de fluorose, 98,6% dos pertenciam à classe social mais baixa (>B2), 91,5% nasceram e sempre moraram em Teresina, 94,4% consumiam água de abastecimento fluoretada, 76% usaram dentifrício infantil e 64% as mães relataram que engoliam dentifrício. A prevalência de fluorose foi elevada, mas com baixa severidade, em indivíduos expostos à fluoretação desde o nascimento.

Estimated fluoride doses from toothpastes should be based on total soluble fluoride

The fluoride dose ingested by young children may be overestimated if based on levels of total fluoride (TF) rather than levels of bioavailable fluoride (total soluble fluoride—TSF) in toothpaste. The aim of the present study was to compare doses of fluoride intake based on TF and TSF. Fluoride intake in 158 Brazilian children aged three and four years was determined after tooth brushing with their usual toothpaste (either family toothpaste (n = 80) or children’s toothpaste (n = 78)). The estimated dose (mg F/day/Kg of body weight) of TF or TSF ingested was calculated from the chemical analysis of the toothpastes. Although the ingested dose of TF from the family toothpastes was higher than that from the children’s toothpastes (0.074 ± 0.007 and 0.039 ± 0.003 mg F/day/Kg, respectively; p < 0.05), no difference between types of toothpaste was found regarding the ingested dose based on TSF (0.039 ± 0.005 and 0.039 ± 0.005 mg F/day/Kg, respectively; p > 0.05). The fluoride dose ingested by children from toothpastes may be overestimated if based on the TF of the product. This finding suggests that the ingested dose should be calculated based on TSF. Dose of TSF ingested by children is similar whether family or children’s toothpaste is used.