The ideal thickness of the palatal surface of a maxillary complete denture should be 2 mm to ensure a balance between strength and patient comfort. A thickness of 2 mm provides adequate rigidity to resist fracture under masticatory forces while maintaining a comfortable bulk that does not interfere with tongue space or speech. Thinner than 2 mm increases the risk of denture fracture, whereas thicker than 2 mm may cause discomfort and impaired phonetics. Thus, 2 mm is considered optimal for functional durability and patient acceptance.

Reference: Prosthodontics, Sharry J. Berstein, 3rd Edition.