Materials and methods The experimental protocol will be submitted for approved by the Institutional Human Subjects Ethics committee of Hadassah-Hebrew University School of Dental l Medicine. Informed consent will be obtained from all parents or legal guardians of participating subjects.

Subjects All pediatric patients attending the graduate student pediatric dental clinic of the Department of Pediatric Dentistry at Hadassah Clinic in need of at least two restorative treatment sessions with the use of nitrous oxide will be included. All participants must be in good health (ASA I). Prior to one session subjects will be restricted and have a preprocedural fasting as per the following guidelines: All subjects will be without solids (including milk) for at least 4 hours prior to nitrous oxide administration and without clear liquids 2 hours before treatment. On the alternative session subjects will have no restrictions on their food or liquid intake.

Evaluation

A survey will be given to parents prior to treatment and information regarding the following will be gathered:

Age, previous nitrous oxide experience, history of vomiting or nausea (motion sickness, foods etc), last mea: what and when? The resident administering treatment will record the following: Duration of inhalation administration, percentage of nitrous oxide and flow rate, steady or fluctuating, occurrence of vomiting during or immediately following treatment.

Statistical analysis of data will determine the incidence of vomiting and if any significant differences between the two sessions exist.