Goward 1982.

Methods	FLUOROSIS STUDY Country of study: England Geographic location: 2 adjacent districts of Leeds with different fluoride levels Year of study: 1979 Year of change in fluoridation status: 1968 Study design: cross sectional
Participants	Inclusion criteria: lifetime residents of study areas (children only); children aged 5 Exclusion criteria: not clear, though children using systemic or topical fluoride supplements were excluded from the study Other sources of fluoride: children using systemic or topical fluoride supplements excluded from the study Social class: not stated Ethnicity: not stated Residential history: lifetime residents Other confounding factors: difference in breast fed vs bottle fed children
Interventions	Group 1: 0.9 ppm (artificial fluoridation) Group 2: < 0.1 ppm (natural fluoridation)
Outcomes	Dental fluorosis (defined by Al‐Alousi) Age at time of measurement: 5 years
Funding	Not stated
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Sampling	Unclear risk	There was insufficient detail reported to determine how selection took place
Confounding	High risk	Did not account for SES
Blinding of outcome assessment (detection bias) All outcomes	High risk	Insufficient information
Incomplete outcome data (attrition bias) All outcomes	Low risk	Data presented for all participants
Selective reporting (reporting bias)	Low risk	Outcome of interest reported
Other bias	High risk	No information on calibration of examiners