I have dental pain in my upper left rear molar. the x-ray shows that my tooth is healthy, but i have an enlarged sinus. antibiotics/analgesia provide no relief from pain. what should i do?

Other possibilities : Sometimes dental pain can be tricky and misleading. Please make sure your dentist also checks the lower posterior teeth on the left side because there can be referred pain to the upper. If there does not appear to be any odontogenic origin (dental origin) then see an ENT specialist to rule out a sinus infection.

Decongestant: If teeth is healthy and sure that sinus is reason...A decingestant like sudafed ir a combo Claritin (loratadine) or zyrtec d should help with the sinus...

Sinus issues?: Could be a sinus issue, if you have no medical contraindications , try taking a pure sinus decongestant, with no other additives and see if you get relief. If it doesnt help it may be necessary to get the tooth nerve tested to see if there is an issue brewing.

More tests: Your dentist needs to do other diagnostic tests to determine where is the pain coming from and treat it.

Oral surgeon: Advice from a specialist would be a good idea here. See a board certified oral & maxillofacial surgeon for assessment of this problem.

Different X-Ray: If you think your pain is tooth-related, but nothing shows up on a traditional dental X-ray, then a three-dimensional X-ray would be the next logical step. In dentistry, these are referred to as CBCT or Cone Beam CT. Do NOT get a MEDICAL CT of that area! If the three-dimensional CT doesn't show anything, then it's 99% sure that your problem is not coming from the tooth. In that case, see an ENT.