Nitrous oxide, more commonly known as laughing gas, is often used as a conscious sedative during a dental visit. The gas is administered with a mixture of oxygen and has a calming effect that helps phobic or anxious patients relax during their dental treatment. Because it is a mild sedative, patients are still conscious and can talk to their dentist during their visit. After treatment, the nitrous is turned off and oxygen is administered for five to 10 minutes to help flush any remaining gas. The effects wear off almost immediately. Nitrous oxide rarely has side effects, although some patients may experience minor nausea and constipation. Your doctor will provide you with pre and post-sedation instructions.