Hi Karen!

D4261 - osseous surgery (including elevation of a full thickness flap and closure) - one to three contiguous teeth or tooth bounded spaces per quadrant

The code listed above have a direct crosscode we are aware of, so you can either bill the "D" code on the medical claim (many insurers these days will process "D" codes when they are medically necessary services), or you can try the CPT code below and include a narrative report describing the procedure:
41899 - Unlisted procedure, dentoalveolar structures

As for the diagnosis code to use, that will depend on the patient's condition and why they are getting the treatment! Here's a few examples that may be used:

K05.32 - Chronic periodontitis, generalized
K05.31 - Chronic periodontitis, localized
K05.30 - Chronic periodontitis, unspecified
K05.4 - Periodontosis
K05.5 - Other periodontal diseases
K05.6 - Periodontal disease, unspecified
K06.0 - Gingival recession
K05.10 - Chronic gingivitis, plaque induced
K05.11 - Chronic gingivitis, non-plaque induced
K05.20 - Aggressive periodontitis, unspecified
K05.21 - Aggressive periodontitis, localized
K05.22 - Aggressive periodontitis, generalized

Hope this helps, have a great day!