A labial bar is primarily indicated in cases of labial inclination of teeth to provide adequate support and retention for removable prostheses. When teeth are inclined labially, the prosthetic design must prevent tissue impingement and improve stability by incorporating a labial bar. This direct contact helps control vertical and horizontal forces during function. The labial bar also aids in maintaining proper denture extension without interfering with soft tissues. It is less commonly used for situations like shallow vestibule or narrow arch where other design modifications are preferred.

Reference: Prosthodontics, Rosenstiel, 5th Edition.