Topical anesthesia affects:

Topical anesthesia is designed to provide localized numbness on the mucous membranes, and its effectiveness is typically within a certain depth. It primarily affects the outer layers of the mucous membranes, typically extending to about 2-3 mm. This range allows for the necessary analgesic effect to manage discomfort during procedures that may involve the mucosal tissues.

The outer 1 mm mentioned in another option is less than the usual extent of topical anesthesia's effect. While it may provide some numbing effect, the standard range of 2-3 mm is more accurate for most topical anesthetics used in dental practices, ensuring that there is adequate depth to manage procedures effectively.

Topical anesthetics act primarily on the nerve endings located in the epithelial layer of the mucous membrane, and they do not penetrate deeply enough to affect the nerve root trunk, which is further beneath the surface layers. This characteristic confirms why the option regarding the nerve root trunk is not correct.

By understanding the specific action of topical anesthetics, it becomes clear that the sensation is controlled within a depth that effectively numbs the outer layers of the mucous membrane, making the second option the most accurate representation of topical anesthesia's impact.