Periodontal treatment, both surgical and non-surgical, including root-planing; deep scaling, irrigation of periodontal pockets, subgingival curettage is always Band 2, regardless of the number of visits that the treatment would require.
As with any Band 2 claim, an examination and an assessment of the patient's oral health and completion of the planned treatment (that the patient is willing to undergo) is a requirement. Further guidance can be found on the British Society of Periodontology website.
The number of visits required is left to a performer's own clinical judgement, on a case-by-case basis.