Nitrous oxide, sometimes called “laughing gas,” is one option your dentist may offer to help make you more comfortable during certain procedures. It is not intended to put you to sleep. You will be able to hear and respond to any requests or directions the dentist may have. Your dentist will ask you to breathe normally through your nose, and within a few short minutes you should start to feel the effects of the nitrous oxide. You may feel light-headed or a tingling in your arms and legs. Some people say their arms and legs feel heavy. Ultimately, you should feel calm and comfortable. The effects of the gas wear off soon after the mask is removed.