Dental chairs do not go down that low , a knee on the torso would make it virtually impossible to get into the mouth and see what you are doing. It would make it physically impossible to take a tooth out , impossible to see what you are doing and would cause a lot damage to patients torso. A fully grown adults weight on one knee on your chest would cause significant damage and very few dentists would have the flexibility , balance or physique to be able to do it!
To take a tooth out you push, rather than pull a tooth. Both arms should be straight with one hand around gum and one on instrument to remove tooth. You do not pull a tooth until the last second when it is loose.
Bruising and swelling can be seen , particularly when removing lower wisdom teeth under general anaesthetic , around neck and down into chest area. This is because a general anaesthetic or sedation is used when a tooth is very difficult to get out and often requires extensive bone removal . The swelling and bruising goes downwards and stops where the muscles insert into the chest in some cases.
For any other surgical proceedure involving the face and bone removal you would not be surprised to have extensive bruising and swelling , eg nasal surgery , the bruising often spreads to the eyes and up into hairline and around the ears although none of these areas are involved in the surgery.
The nerve supply to the face is enormously complicated and peoples reaction to various drugs varies enormously as well, eg people with Ehler Danlos and hypermobility problems can be difficult to numb up . Add to this when someone is very nervous, in pain, tired and stressed the nerve gateways get overloaded and pressure starts to be perceived as pain.
very, very occasionally a tooth can have a "hot pulp" or other problem that means it is difficult to numb up. There are a variety of ways this can be over come but pain relief can be challenging in an environment that has five times as many nerve endings as the rest of your body .
A couple of end points
if you feel pain agree a signal with your dentist to stop. They can try different anaesthetics , give longer for them to take or , in extremis , refer you for sedation. However in most places unless you pay privately this will take months to come through even if you are in pain.
Sometimes going away , coming back after an anti inflammatory or even just time (in the case of "hot pulp" ) is enough to get you nice and numb .
sometimes a sedative approach is necessary but this will almost always involve a long wait unless private.
Antibiotics are never a first line approach , the first approach for a dental infection is to drain it , either through the tooth or by taking it out. Apart from anything else antibiotics cannot penetrate into a good collection of pus .
Rather like child birth , some people relish giving their horror stories . It is easy to think this is the norm when the reality is dentists take out teeth every day from the very young (the youngest I have done whilst awake with just an injection is a 3 year old) to the very old , from fit and healthy to very poorly and the vast majority of these extractions are painless and routine. However every person and every tooth is different and although you will feel pressure and hear a crunchy noise it should be possible to take a tooth out on anyone with no pain , but everyone may need a different approach.
In the end dentistry is unique in that dentists do microsurgery on one of the most sensitive parts of the body on a conscious patient . You need to have trust the dentist will do their best , you need to agree control ie hand signal to stop and what to do if things become uncomfortable .