How is an infected tooth with root in sinus diagnosed?

Ongoing sinusitis for 4 plus years on left side. Dentist said it isn’t dental related as there are no abscesses at the roots. I have a bunch of riots that are well in my sinus cavity, so I don’t see how an abscess would be possible. I have tooth tightness/mild pain on the infected side. How is an infected tooth diagnosed when the root is in the sinus? I have less sensitivity to the ‘cold test’ on one tooth, but still feel something, so have been told it is fine.

Ongoing sinusitis for 4 plus years on left side. Dentist said it isn’t dental related as there are no abscesses at the roots. I have a bunch of riots that are well in my sinus cavity, so I don’t see how an abscess would be possible. I have tooth tightness/mild pain on the infected side. How is an infected tooth diagnosed when the root is in the sinus? I have less sensitivity to the ‘cold test’ on one tooth, but still feel something, so have been told it is fine.