Abstract
Background: Currently available adequate intake (AI) and tolerable upper intake levels (UL)for fluoride assume that 100% of ingested fluoride is available for utilization by the human
body, which is often not the case due to a variety of factors. It has been suggested that these
values must be modified and improved by incorporating fluoride bioavailability levels alongside
total fluoride intake. However, such modification has not yet been possible due to the lack of
relevant data on fluoride bioavailability/bio-accessibility.
Main aims: The main aims of this project were to a) measure fluoride bio-accessibility in the
most commonly consumed food/meals by participants of the Iowa Fluoride Study (IFS) during
the first three years of their life, and b) to examine the association between fluoride bioaccessibility
and the occurrence of dental fluorosis on permanent teeth.
Methods: In Study I, 3-day food diaries gathered through the IFS were analysed to identify
commonly consumed dietary sources of children during the first three years of their life, as this
period was highlighted as the most critical for dental fluorosis development on permanent
teeth. To measure fluoride bio-accessibility, Study II subjected food/meal samples identified
in Study I to standardized static in vitro digestion and fluoride determination methods. Study
III utilized data gathered in previous studies to develop predictive models examining the
association between fluoride bio-accessibility and the occurrence of dental fluorosis on
permanent teeth using logistic regression.
Results: In Study I, 103 food/meal samples were identified as the most commonly consumed
by participants of the IFS during the first three years of their life. The list comprised 67 meal
samples and 36 individual food items. Study II revealed fluoride bio-accessibility (%) below
100% for the majority of food/meal samples. For individual food samples, the mean (SD)
fluoride bio-accessibility was 44.7 (37.5)%. Meal samples were grouped according to the
mixing agent, and the mean (SD) fluoride bio-accessibilities for meals that included juice,
carbonated drinks, tap water, and milk were 79 (21.9)%, 64.3 (20.7)%, 40.2 (20.9)%, and 71.5
(17.1)%, respectively. For the rest of the meals, the mean (SD) fluoride bio-accessibility was
50.8 (55.9)%. Study III found total daily fluoride intake (TDFI) to be a statistically significant
predictor of dental fluorosis development when the whole IFS dataset was observed. When
dietary datasets were analysed, models of varying predictive capacity were created. Dynamic
fluctuations in mean total daily dietary fluoride intake (TDDFI) and bio-accessible dietary
fluoride intake (BADFI) (μg F/kg bw/d) were observed with a notable decrease in mean TDDFI
but an increase in BADFI at 12 months of age. Such findings potentially explain conflicting
results over the ‘window of maximum sensitivity’ for dental fluorosis development on
permanent teeth.
Conclusions: Bio-accessible fluoride intake cannot serve as a sole parameter for dental
fluorosis development, as both TDFI and TDDFI have repeatedly emerged as significant
predictors of dental fluorosis development. However, the fluoride bio-accessibility of the
majority of samples was below 100%, indicating that the amount of absorbed and bodyretained
fluoride is lower than the total fluoride intake. Such discrepancy leads to inaccuracies
in recommended fluoride intake values. Therefore, bio-accessible fluoride should be used as
an addition to total fluoride intake as a helpful parameter for refinement of currently available
dietary reference values. Finally, considering the variability in TDDFI and BADFI at 12 months
of age, further studies on fluoride bio-accessibility could help establish a consensus on the
most critical age and fluoride intake levels associated with dental fluorosis on permanent teeth.
| Date of Award | 28 Jul 2023 |
|---|---|
| Original language | English |
| Awarding Institution |
|
| Supervisor | Vida Zohoori (Supervisor), Ralph Marsland Duckworth (Supervisor), Claudio Angione (Supervisor) & Steven Levy (Supervisor) |