Hong 1990.

Methods	FLUOROSIS STUDY Country of study: Taiwan Geographic location: Chung‐hsing New village (F) and Tsao‐tun (non‐F) Year of study: not stated Year of change in fluoridation status: 1978 Study design: cross sectional
Participants	Inclusion criteria: children aged 6‐15 years: resident in village since initiation of fluoridation Exclusion criteria: children who migrated from other areas during study period Other sources of fluoride: not stated Social class: 2 communities alike in social and living customs Ethnicity: not stated Residential history: resident since fluoride initiation Other confounding factors: 2 areas have virtually identical climates, only 3 km apart
Interventions	Group 1: 0.6 ppm (artificial fluoridation) Group 2: 0.08 ppm (natural fluoridation)
Outcomes	Dental fluorosis (Dean's Index) Age at assessment: 6‐15 years
Funding	Not stated
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Sampling	Unclear risk	The participating sample consisted of children from 6‐15 years in the study areas. No other information was provided on sample selection
Confounding	High risk	Did not account for the use of other fluoride sources
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 was fully reported on and balanced across groups
Other bias	Low risk	No other apparent bias