Entodontist wants to do hot water test to know which tooth is troubling me & then decide if my tooth # 30?

or 31 needs refilling or root canal. How will I know which one is required ? I just have pain on& off near those teeth. Biting does not hurt. X ray only shows little darker near the tooth. This is what I was told. I feel root canal is not necessary. Existing filling is old like 15 + years. I don't have dental insurance . Please answer. What question do I need to ask dental doctor? Thanks so much.
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root canal is done only when your nerve is exposed to the mouth. It will cause you sever pain due to any thermal change, cold or hot. If you do not have pain due to cold or hot, you just need a filling.
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