The present study evaluated the records of 27 patients (20 men, 7 wome
n) who were treated under nitrous-oxide (N2O) and oxygen sedation due
to extremely high dental anxiety. Corah's DAS and Kleinknecht's dental
fear survey were completed by the patients. Patients who responded po
sitively to the gas were categorised as N2O+ patients, whereas those w
ho responded negatively were categorised as N2O- patients. A mean DAS
score of 19.3 +/- 1.6 was observed for the entire population. No signi
ficant difference was found between N2O+ patients and N2O- patients in
any DAS item, nor in the total scores (19.4 +/- 1.35 and 18.67 +/- 2.
24 respectively). Only in answer to the question, 'Has fear of dental
work ever caused you to cancel or not appear for an appointment?' were
the scores of N2O- patients significantly higher than of N2O+ patient
s. No differences were found between patients who reported pain as the
source for their dental anxiety and those who did not; between patien
ts with gag reflex and those without, between patients who had never h
ad any dental treatment and those who had, and between patients who re
quired two or three appointments before administration of the gas with
respect to successful treatment under N2O and oxygen sedation. Among
the N2O- group, significantly more patients did not attend for two app
ointments or more. The results suggest that lack of keeping previous d
ental appointments may indicate patients' possible negative response t
o nitrous-oxide and oxygen sedation.