Local anaesthesia is what made modern dentistry bearable. It is worth understanding how it works, because knowing what happens greatly reduces tension.
What the anaesthetic does
It does not «put the tooth to sleep»: it temporarily blocks signal transmission along the nerve fibres of that area. The nerve is there and works, but for a time it does not carry the painful stimulus to the brain. This is why you stay fully awake and cooperative: it is a local block, not sedation.
Why you still feel pressure
This is the most common misunderstanding. The fibres carrying pain and those carrying pressure and vibration are different, and the anaesthetic acts mainly on the former. Feeling that «something is moving» is normal and does not mean the anaesthetic is not working. Feeling pain is another matter: raise your hand and we top it up.
Why it sometimes «doesn't take»
It happens, and there are concrete explanations:
- acute inflammation — an abscess or pulpitis makes the environment acidic and reduces the anaesthetic's effectiveness. This is why a very painful tooth is harder to anaesthetise, and sometimes a supplementary technique is needed;
- anatomical variability — nerve pathways are not identical in everyone;
- high anxiety — it lowers the perception threshold and makes everything more intense.
In these cases we do not persist with the same technique: we change approach.
How long it lasts
Numbness outlasts the appointment, generally by a couple of hours, sometimes longer with techniques involving the lower arch. It is expected and temporary.
Precautions afterwards
- Do not eat until sensation returns, especially hot food: you would not feel a burn.
- Watch your lip and tongue: biting them without noticing is the most common minor mishap, especially in children. Keep an eye on little ones.
- The tingling as sensation returns is normal.
What to tell us beforehand
Always: medication you take, known allergies, heart conditions, pregnancy. If you have had a reaction to anaesthesia in the past — even just palpitations or feeling unwell — tell us: many sensations reported as «allergy» have other causes, and knowing them lets us choose better.
If anxiety is the problem
When fear is the real obstacle, local anaesthesia can be combined with conscious sedation, whose suitability is assessed at the visit. Discussing it beforehand is always better than discovering it in the chair.
Sources
- Italian Ministry of Health — Dental health — safety and appropriateness of dental care.
- FDI World Dental Federation — international reference on clinical dental practice.