EAL

FL: Fluoride Exposure in the US (2010)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine whether coronal dentin of primary teeth can function as a satisfactory indicator of fluoride exposure among children.

Inclusion Criteria:

No specific inclusion criteria were described.

Exclusion Criteria:

Teeth that showed evidence of caries or coronal dentin resorption were not included in the study
Prolonged childhood illness
Vegetarian.

Description of Study Protocol:

Recruitment

A convenience samples of kindergarten (five and six years of age) and fifth grade (10 and 11 years of age) students, respectively, living in four communities in North Carolina in 1995.

Design

Students from four communities were recruited. Two had sub-optimal levels of fluoridation (less than 0.3 and 0.5mg per L). Two fluoridated communities were selected (1mg per L). One fluoridated community was selected because of a high prevalence of fluorosis.
Parents of children in the selected grades were sent questionnaires at enrollment. Those who participated mailed their child's tooth to investigators when it fell out (exfoliation).

Blinding Used

Unclear whether researchers were blinded to child's community or intake status at time of assay. Not reported.

Statistical Analysis

Pearson product moment correlation used to examine bivariate relationships. Ordinary least squares regression was used to build final predictive model. A priori alpha set at 0.05.

Data Collection Summary:

Dependent Variables

Fluoride concentration in coronal dentin (measured using the mean of three assays of slices of the teeth).

Independent Variables

Measures of fluoride intake based on:

Fluoride intake from beverages, toothpaste and fluoride supplement
Place of residence (to determine intake from drinking water based on 1993 CDC water fluoridation census)
Samples of drinking water (where public water was not used)
Models of fluid consumption
Child's body weight
Age at which child began brushing teeth (in conjunction with models of fluoride ingestion during teeth brushing)
Dietary intake
Mother's exposure to fluoride during breastfeeding
Duration of breastfeeding
Use of fluoridated mouth rinse.

Control Variables

Illnesses
Vegetarianism
Race
Sex
Community in which child resides

Description of Actual Data Sample:

Initial N: Primary incisor or molars from 108 children
Attrition (final N): 99 parents completed the questionnaire, leaving a sample of 61 incisors and 38 molars
Age: Kindergarten (five and six years of age) and fifth grade (10 and 11 years of age)
Ethnicity: Coded as white vs. non-white. Sample from non-white subjects, 8% of incisors and 13% of molars
Location: North Carolina, US.

Summary of Results:

Levels of Dentin Fluoride and Explanatory Variables

	Incisors		Molars
	Mean	SD	Mean	SD
Outcome variables
Dentin fluoride concentration, mg per kg	792	402	768	489
Log of dentin fluoride concentration	6.54	0.48	6.49	0.54
Explanatory variables
Water fluoride exposure, mg per kg b.w	83.3	55.6	122	93.1
Toothpaste fluoride exposure, mg per kg b.w	51.2	24.3	67.6	31.8
Supplement fluoride exposure, mg per kg b.w	10.6	20.9	14	32.7
Optimal prenatal fluoride (gte 0.7mg per L)	0.53	0.5	0.4	0.5
School fluoride rinse (ever used)	0.51	0.5	0.63	0.49
Frequent tea consumption	0.22	0.42	0.26	0.45
Frequent soda consumption	0.2	0.4	0.53	0.51
Frequent fish consumption	0.08	0.28	0.05	0.23
Bottle fed	0.8	0.4	0.81	0.39

Bivariate Associations

Lifetime exposure to fluoride from water, toothpaste and supplements were not associated with incisor dentin levels
Only the lifetime exposure from supplements was significantly associated with dentin levels in molars (R=0.593, P<0.01)
With regard to explanatory variables, only place of residency was significantly associated with dentin levels in either incisors or molars.

Multivariate Models

For incisors, only place of residence (between a sub-optimal and an optimally fluoridated city) was a statistically significant predictor and explained only 10.5% of the variance (note that the sample from the sub-optimally fluoridated community consisted of only four children)
For molars, three predictors were significantly associated with dentin level: Supplements fluoride exposure (P≤0.01), place of residence (between optimally fluoridated communities and sub-optimally fluoridated community, again with only four respondents; P≤0.01), and frequent tea consumption (P≤0.01). These variables explained 60.8% of the variance.

Author Conclusion:

Our study found that dentin fluoride regressed on cumulative lifetime fluoride intake estimated from exposures to three primary sources (water, toothpaste and supplements), selected secondary fluoride sources and demographic control variables explained a relatively large percentage of the variance in analytical regression models for molars, but not incisors
This study suggests that a major source of variability in dentin fluoride is the community itself, independent of water fluoridation status.

Funding Source:

Government:

National Institute of Dental and Craniofacial Research, National Institutes of Health

Reviewer Comments:

Comparative design is a strength, but small sample sizes hamper interpretation
Weak reporting of sample selection and inadequate description of group characteristics
Good discussion of the limitations of the study.

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	N/A
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	N/A

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	No
2.	Was the selection of study subjects/patients free from bias?		No
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	No
	2.2.	Were criteria applied equally to all study groups?	No
	2.3.	Were health, demographics, and other characteristics of subjects described?	No
	2.4.	Were the subjects/patients a representative sample of the relevant population?	No
3.	Were study groups comparable?		No
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	No
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	No
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	Yes
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	No
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	Yes
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		No
	4.1.	Were follow-up methods described and the same for all groups?	No
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	No
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	No
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		No
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	No
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	No
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	Yes
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	No
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	Yes
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
7.	Were outcomes clearly defined and the measurements valid and reliable?		Yes
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	Yes
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	N/A
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	Yes
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		Yes
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	Yes
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	Yes
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	N/A
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	Yes
	8.6.	Was clinical significance as well as statistical significance reported?	Yes
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	No
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes