Ockerse 1941.

Methods	FLUOROSIS STUDY Country of study: South Africa Geographic location: Upington, Kenhardt and Pofadder Year of study: 1939 Year of change in fluoridation status: NA Study design: cross‐sectional
Participants	Inclusion criteria: children attending schools in study areas; children aged 6‐17 years Exclusion criteria: none stated Other sources of fluoride: not stated Social class: not stated Ethnicity: not stated Residential history: participants were born and lived up to the age of 8 in the study areas Other confounding factors: sStudy areas at same altitude, same climate, similar countryside and vegetation, differences in drinking water composition discussed
Interventions	All natural fluoridation Group 1: 2.46 ppm (average) Group 2: 6.8 ppm Group 3: 0.38 ppm
Outcomes	Mottled enamel; caries data also evaluated within the study but excluded from review due to study design Age at assessment: 6‐17 years
Funding	Not stated
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Sampling	High risk	Areas thought to be most affected by caries and mottling were selected and visited. Selection of 'at risk' population is likely to have introduced bias
Confounding	High risk	Did not 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	Low risk	Data presented for all participants
Selective reporting (reporting bias)	High risk	Caries data reporting may have been a post‐hoc decision
Other bias	High risk	Data were collected on age of commencement of tooth brushing but not reported. There was no mention of examiner training or calibration