Tissue conditioning material is indicated when:
Correction of ill-fitting dentures

Areas of denture causing trauma to the tissues (causing inflammation of oral mucosa) are trimmed and polished.
Generally rough areas on fitting surface are smoothed or relined with tissue conditioner.

Ref: Textbook of prosthodontics V Rangarajan Ed. 2nd
Tissue symptoms are related to diabetes
Mucosa is inﬂamed due to ill ﬁtting dentures
Mandibular tori is present
Large maxillary tori is present