kadonye wrote:If fluoride in water causes brown teeth, why does it happen that some people using the same water will not get their teeth discoloured?
these must be 'dentally discordant couples'
Am not a guru but the little I know is that lifestyle/diet can also play a huge part.
eg drinks that can stain your 'fangs' are coffee, while smoking plays a huge part in teeth discolouration as well.
@guka, that does not explain why some engines merely hum?