After a cavity has been prepared, it is necessary to cover it with filling material so as to preserve the prepared tooth. Also caries is irreversible, so once occured it requires treatment.
If the cavity is left unfilled than the area being close to nerves will become sensitive and may require RCT. So, its better to get the tooth filled once the caries part is removed. It won't hurt.
For more info on Dental Caries you can read our article...http://www.identalhub.com/articlecategory-dental-caries-7.aspx
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