Nitrous oxide is perhaps the safest sedative for use in the dental environment. It helps to alleviate fears and to eliminate a strong gag reflex.
It may smell/taste like a faint sweet aroma and your child experiences relaxation but remains conscious. Some kids may also report feelings of giddiness or tingliness of their arms and legs.

If your child is worried about the sounds or sensations associated with dental procedures then this may be a good option to consider.

It can also be used in combination with other oral sedative medications to enhance the sedative effects.