My culture shows growth of haemophilus parainfluenzae. my gum keeps having recurrent abscess, pus drain. 1/ periodontist and endodontist think it is because there must be crack on my post crow tooth #7. 2/ i think it is i cut into my gum in 2015. ?

Crack: A crack is more likely for a recurring abscess. A cut gum would heal, a crack cannot.

More likely: I would tend to agree with the dental specialists as a fractured root being the culprit. Two suggestions: First -consider a CBCT (3d radiographic image) vs. a conventional 2d x-ray. It usually shows a fractured root when present. Secondly- you can get another opinion to confirm what the first two suggest as the cause of your recurring infection.

Could be: Could be both, bit I'd put my money on the diagnosis made by two Specialists with combined more than 30,000 hours of post-college education and years of practice. They may be wrong, you may be right, but the odds strongly favor their diagnosis. Hope your problem is resolved soon.