Maintenance phase of PDL therapy starts after:

Maintenance (phase IV therapy)—periodontal procedures during the maintenance phase include evaluation of oral hygiene status, presence or absence of local factors, condition of the periodontium (pocket depths, attachment levels, mobility, furcation involvements, mucogingival issues and occlusion) and other pathologic changes. This phase should begin after the completion of phase II therapy. This phase may also be called supportive periodontal therapy.