Fluoride Intake Through Dental Care Products: A Systematic Review

Abstract

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.

Keywords: dental products; diet; drinking water; fluoride; toothpaste; urine.

Figure 1

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flowchart for the systematic review. From the 1,273 articles found in PubMed included in the search, 46 studies were included and 28 selected in this review for their analyses. Among the 28 articles, 19 only listed the estimated total daily fluoride intake (TDFI) (Table 1). The other nine articles had information regarding both the TDFI and the daily urinary fluoride excretion (DUFE) (Table 2).

Figure 2

Estimated F intake from diet (water, beverages, and solid foods) (gray bars) and from toothpaste (black bars). F concentration in tap water is represented by the gray line (mg/L). (A) Total daily fluoride intake with dietary and toothpaste inputs (μg/day). (B) The contribution of daily diet (water, beverages, and solid foods) and toothpaste (%) to the estimated F intake in μg/day [based on (A)]. (C) TDFI with dietary and toothpaste inputs (μg/kg bw/day) with reference values of optimal daily F intake [50–70 μg/kg bw/day, the European Food and Safety Authority (EFSA)]. (D) The contribution of daily diet (water, beverages, and solid foods) and toothpaste (%) to the estimated F intake in μg/kg bw/day [based on (C)]. *Diagonal hatched bars represent missing data of daily dietary F intake (DDFI). **Horizontal hatched bars represent missing data of daily F intake from toothpaste. ^#Optimal range of daily F intake reported in the literature.

Figure 3

The contribution of daily toothpaste intake according to mean age (years) of participants in areas with different F concentration in drinking water (mg/L). (A) The contribution of toothpaste to the TDFI (%) in poor fluoridated water (<0.3 mg/L). ¤ Gray arrow indicates the lowest value from Abuhaloob et al. [36]: two toothpaste users among 81 participants. (B) The contribution of toothpaste to the TDFI (%) in low fluoridated water (0.3–0.51 mg/L). ¤ Gray arrow indicates the lowest value from Zohoori and Rugg-Gunn [40]: 3 toothpaste users among 28 in Darab (not the same region presented in Figure 2; Table 3). (C) The contribution of toothpaste to the TDFI (%) in medium fluoridated water (0.52–0.77 mg/L). (D) The contribution of toothpaste to the TDFI (%) in high fluoridated water (>0.77 mg/L). ¤ Gray arrow indicates the lowest values from Abuhaloob et al. [36]: nine toothpaste users among 135 participants.

Figure 4

Estimation of the mean DUFE (μg/day) in relation with the mean TDFI (diet and toothpaste) or only daily F intake from toothpaste in participants aged 1–7 years old and 20–35 years old [the highest dot in (A)]. (A) The mean DUFE (μg/day) in relation with TDFI and daily F intake from toothpaste (μg/day). § Black arrow indicates the lowest value of F intake from toothpaste from Zohoori and Rugg-Gunn [40]: three toothpaste users among 28 in Darab (not the same region presented in Figure 2; Table 3). (B) The mean DUFE (μg/day) in relation with daily F intake from toothpaste (%).