Table 1 Validity criteria used to score studies

Prospective

Was the study prospective? Was it planned and started prior to the outcome of interest

occurring? Score = 1 or 0

Study Design

The study design hierarchy for this review = cohort > before-after > ecological > cross-

sectional. Scores ranged from 0.25–1, with cohort = 1, cross-sectional = 0.25

Fluoride Measurement

Was the Fluoride level reliably measured? Scores range between 0–1.

Confounding Factors

Were confounding factors addressed (measured)? Scores range between 0–1, with 3 or more

factors measured = 1.

Control for Confounding

Was there adjustment for the possible effect of confounding factors in the analysis or study

design? Scores range between 0–1, with stratification by age and sex = 0.5, other types of

analysis (e.g. regression) = 1.

Blinding

Were those measuring outcomes and exposures blind to the exposure/outcome status of the

person being assessed? Score = 0 or 1

Baseline Survey

Was there a baseline survey at the point of initiation or discontinuation of water fluoridation?

Score = 0 or 1

Follow-Up

Was the study conducted an adequate time after the initiation or discontinuation of water

fluoridation to assess effects (5 years)? Score = 0 or 1