Is laughing gas safe for a child's dental work at age 4 years?

If experienced.: Yes if the dentist is well trained/credentialed for the administration to kids. Monitoring vital signs are important. Check with the experiences of other patients/parents.

Yes: So long as the provider is trained properly and feels comfortable with providing it, the nitrous can be a successful way to calm a child but not needed if the child is already compliant.

Probably: Barring any respiratory issues, nitrous oxide is a great adjunct on apprehensive 4 (and 40) year olds. Since the use of the nitrous is completely reversible at the end of the visit, it is very convenient for a pain free experience. In my experience, some children can be treated without local anesthesia while on nitrous depending on the severity of the treatment that needs to be completed.