About: http://webisa.webdatacommons.org/133367385

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	Extrinsic stains, which develop on the outside of the tooth structure, are caused by substances such as tobacco, coffee, tea, red wine, certain drugs, chromogenic bacteria, and metallic materials.
http://www.w3.org/ns/prov#wasQuotedFrom	dentalaegis.com