Dental Anaesthetic: Pre-Empting Problem Patients

Local anaesthetic is an essential tool when performing an array of dental treatments, namely any which would otherwise cause pain or discomfort for the patient. In the majority of cases, dental anaesthetic works without a hitch and you can successfully go ahead with the treatment.

Occasionally, however, certain patients can experience problems where the anaesthetic either doesn't work or causes an unexpected reaction. It's helpful to be able to spot where you might run into a problem, what you can do about it. Here are some of the cases where anaesthetic sometimes doesn't work as it should, to help you better treat your patients.

Dental infections

Quite often, the presence of an infection is the very reason you'll need to anaesthetise a patient. Unfortunately, infections can sometimes cause the anaesthetic to become ineffective.

The reason behind this is that dental infections can slightly change the acidity of the affected area, which prevents the anaesthetic working as it should. In most cases, applying a higher dose of anaesthetic is enough to deal with the problem, but use your judgement.

Anxious patients

Many people are nervous when visiting a dentist, which can cause all sorts of problems. One of the most difficult, however, is that a highly anxious state can stop anaesthetic from working properly. In some patients, it can even make it appear that they're having an adverse reaction.

It's tricky to deal with this, but there are many calming techniques that can help. In extreme cases, a general anaesthetic might be a better option.


You should always discuss allergies with patients before using anaesthetic, but those who haven't had it before might not know they're allergic. It's usually epinephrine that people have a reaction to, and anaesthetics are available without it. However, they're not as effective, so higher doses might be needed.

Some medical conditions

Heart conditions can limit your choice of anaesthetics to those without epinephrine. You should consult with your patient beforehand to make sure you have something suitable.

Some rare genetic conditions, such as Ehlers-Danlos Syndrome, can cause resistance to anaesthetic. While this isn't yet fully understood, different techniques or types of anaesthetic might help, plus a large dose of caution.

Unexplained resistance

There are still some people, for reasons unknown, for whom anaesthetic simply doesn't work – or works poorly. Depending on their medical history, these people might not even be aware of the problem until the treatment begins.

If a patient informs you that anaesthetic doesn't work on them, varying the technique could help, as could a different type of anaesthetic. On some occasions, simply trying on another day makes all the difference. If all else fails, a general anaesthetic might be necessary for particularly uncomfortable treatments.