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NO. It is not likely to be something serious.
"Shadows" at the top (apex) of a tooth's root is almost invariably an abscess. Ocasionally it may be a cyst.
What has your dentist recommended?
Dr. John BDS PhD
I can only repeat my previous answer, this is nothing to concern yourself with.
At worse, this is a cyst that may need removal. It will not be cancer. Cancer does not present like this.
Please stop worrying about this, it is a routine dental problem.
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Good luck and my very best wishes,