Nitrous Oxide:

You can request Nitrous oxide sedation before a procedure if you are very anxious or apprehensive about getting anesthetic or the sound of the "drill".
Local anesthetic is given to numb the tooth and/or area that is being treated. This prevents the patient from feeling any pain during the procedure.
If a patient is extremely anxious and needs more than local anesthetic, nitrous oxide can be used. Nitrous oxide is a gas that’s combined with oxygen to produce a calming effect when inhaled. When the dental procedure is over, the patient is placed on oxygen only for a few minutes until the nitrous has wore off.