This can cause serious lung damage. Eating is usually not allowed from six hours before surgery but in some cases clear fluid may be taken up to two hours before hand. During the operation, it is often necessary to pass a tube into the throat to permit normal breathing. The instrument used to pass this tube into the gullet can easily damage loose teeth and crowns, so the anaesthetist will ask if you have any so that extra care can be taken to avoid them. The same problem applies to dentures, which are removed to prevent them interfering with breathing.
Anaesthetics are almost entirely safe, but every operation carries a very slight risk.
A recent survey in the UK showed that death due to anaesthesia occurred in about five in every million anaesthetics given. People who are in poor health run a higher risk than those who are fit and well. This can be discussed with the anaesthetist. While waiting for their operation, patients are given medicine known as a 'premed' to make them them feel slightly drowsy and stop them becoming anxious. They might not even remember going to the operating theatre or being put to sleep.