D4266 is Guided Tissue Regeneration – Resorbable Barrier, Per Site, typically used in areas where natural teeth still exists. —Sometimes placed over area of root surface following a periodontal surgery to enhance healing. D7956 Guided tissue regeneration, edentulous area - resorbable barrier, per site, is the code likely to be used in areas of an edentulous space/missing tooth. Sometimes recommended by your dentist for bone regeneration in the area of missing tooth, where the provider is prepping for an implant. If your dental office utilized the incorrect code, insurance may deny that the code used is for natural teeth only and the tooth was already extracted. If your insurance had reprocess the claim with the correct code D7956 and paid, your dentist should receive that payment and refund you the difference after deductible and coinsurance balance have been paid. You can contact your dentist’s office and let them know you had spoken with your insurance and they have corrected the treatment code and paid.