In periodontal instrumentation, angulation is crucial for effective scaling and root planing. The angulation refers to the relationship between the face of the instrument's blade and the surface of the tooth being treated. Proper angulation allows for optimal removal of calculus and plaque. The other options refer to different relationships that are not specifically defined as "angulation" in the context of periodontal instruments.

Finger-on-finger rest is used for scaling in the maxillary posterior region.

A tight grasp by the operator on the explorer will prevent tactile sensitivity.

A periodontal abscess primarily affects the periodontal tissues and does not typically alter the health of the pulp, which means the tooth may still respond to pulp vitality tests.