Yes, this helps. Thank you!

Hello Forum, I'm a parent of a child who's survived 3 bouts with Leukemia. He's had multiple rounds of chemo and radiation and a bone marrow transplant that led to advanced, non-restorable dental caries and failing dentition. I have a letter from an implant specialist stating he needs all on four dual arch. Specifically, "Four maxillary dental implants with immediate fixed prosthesis and four mandibular dental implants with immediate fixed prosthesis."
I'm trying to get this covered by our health insurance which normally does not cover this procedure. (BCBS Illinois, PPO) I've made significant progress and I have a letter from the periodontist stating the procedure is medically necessary. The insurance company is now asking for a diagnosis code and/or a CPT code. My question is, does anyone know what codes are applicable for this situation? Although my implant office is trying to help us, they don't know what codes to use or how to navigate health insurance vs. dental. I'm assuming I'll have to pay upfront and then try to collect reimbursement from the insurance co. if I can get them to cover the procedure. Any help or advice is deeply appreciated!