Szpunar 1988.

Methods	FLUOROSIS STUDY Country of study: USA Geographic location: Hudson, Redford, Richmond (F); Cadillac (non‐F), Michigan Year of study: not stated Year of change in fluoridation status: not stated Study design: cross‐sectional
Participants	Inclusion criteria: lifetime residents of study areas; children aged 6‐12 years Exclusion criteria: none stated Other sources of fluoride: use of fluoride supplements; dental attendance; time interval since last dental visit; age began brushing (parent & child); age at start of F rinsing; feeding method in 1st year of life. Social class: not stated Ethnicity: not stated Residential history: lifetime residents Other confounding factors: not stated
Interventions	Group 1: 1.2 ppm (artificial fluoridation) Group 2: 1.0 ppm (artificial fluoridation) Group 3: 0.8 ppm (artificial fluoridation) Group 4: 0.0 ppm (natural fluoridation)
Outcomes	Dental fluorosis (TSIF); caries data also evaluated in the study but not included in the review due to study design Age at assessment: 6‐12 years
Funding	NIH National Research Service Award
Notes	Data extracted from Szpunar 1988 differs from that presented in CRD review
Risk of bias
Bias	Authors' judgement	Support for judgement
Sampling	Unclear risk	Classroom teachers distributed and collected permission slips
Confounding	High risk	Did not appear to account for the use of fluoride from other sources or SES
Blinding of outcome assessment (detection bias) All outcomes	High risk	Insufficient information
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Data collected for 1103 participants but only lifetime resident data (n = 556) presented
Selective reporting (reporting bias)	Low risk	Relevant fluorosis outcome data
Other bias	Low risk	No other apparent risk of bias