When would it be appropriate to anaesthetize only the anterior superior alveolar nerve?

Anaesthetizing only the anterior superior alveolar nerve is particularly appropriate when performing a filling on the maxillary anterior teeth. This nerve supplies sensation to the incisors and canines in the upper jaw, so targeting it allows for adequate pain control specifically for procedures on these teeth without the need to anesthetize the entire area.

In contrast, during an extraction or periodontal surgery, a more extensive area of anaesthesia is usually necessary to ensure complete pain relief due to the nature and location of the procedures. Crown preparations typically require a similar broader anaesthetic approach since they can involve working closely with adjacent structures, including those supplied by other nerves. Therefore, the specific anaesthesia of just the anterior superior alveolar nerve is most relevant and useful when dealing with restorative work such as fillings on the anterior teeth.