The incisive branch of IAN continues forward in a bony canal or in a plexiform arrangement, giving off branches to the first premolar, canine and incisor teeth, and the associated labial gingiva. The lower central incisor teeth receive a bilateral innervation, fibers probably crossing the midline within the periosteum to re-enter the bone via numerous canals in the labial cortical plate.
Indications of Incisive nerve block:
1. Dental procedures requiring pulpal anaesthesia on mandibular teeth anterior to the mental foramen.
2. When inferior alveolar nerve block isn’t indicated.
3. When six or eight anterior teeth (canine to canine or premolar to premolar) are treated, the incisive nerve block is recommended in place of bilateral inferior alveolar nerve blocks.
The mental nerve passes upward, backward and outward to emerge from the mandible via the mental foramen between and just below the apices of the premolar teeth supplying sensory branches to the chin and lower lip.
Indications of mental nerve block:
When buccal soft tissue anaesthesia is required for procedures on the mandible anterior to the mental foramen, such as
1- Soft tissue biopsies
2- Suturing of soft tissues
Read more on mental nerve(external web site).