Thanks for putting up your question on Just Answer.
Teeth turn grey mainly due to two reasons:
1. If there has been some sort of trauma to them, (even though the trauma may have occurred years ago) the pulp
of the tooth slowly dies. Bacteria release substances that slowly make teeth turn grey.
A positive history for trauma and a X ray confirms this diagnosis
. That tooth then needs a root canal
followed by a crown
2. The second common cause for grey teeth if administration of an antibiotic, tetracyclin to the patients pregnant mother, or to the patient when he is less than 6 years of age.
I suggest you visit a dentist
for a proper physical and X rays.
Hope this answers your question. Feel free to contact me again for more information.
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