How can you differentiate between fluorosis and caries?

Differentiate: Fluorosis is characterized by deep brown or black hard stains that cannot be polished away with a dental cleaning. Caries can be brown or black however it is sticky and there is an associated 'stick'/hole in the tooth as the bacteria dissolve the enamel.

Differentiate: Fluorosis is characterized by deep brown or black hard stains that cannot be polished away with a dental cleaning. Caries can be brown or black , is 'sticky' and is associated with a hole as the bacteria dissolve the enamel.