Local anaesthetic is deposited around the nerve proximal to the site that you want to anaesthetise. The
injection site may at some distance from the operative field.
For example, in the inferior alveolar block injection (inaccurately called the mandibular block), local anaesthetic solution is deposited around the inferior alveolar
nerve in the infratemporal space before it enters the intrabony mandibular canal. This way, pulpal
anaesthesia is achieved for all the ipsilateral mandibular teeth. Soft tissue anaesthesia includes the lip, and
buccal tissues of teeth anterior to the second premolar.
This answers the question: why does the dentist inject my throat but my lip goes numb?