What is the average cost of nitrous oxide use at the dentist?

Varies: I can't answer for every office but we usually charge $50 an hour for it. If it is a long dental procedure with a high cost to it my office will often include it at no charge.

Varies: Some dentists may have a global fee which will include the cost of the nitrous oxide with the fee for the procedure you are having performed, rather than having a separate charge. Other offices may have a separate charge for nitrous oxide. The fee can vary from office to office and from geographic regions.