This study aimed to evaluate construct validity and face validity of a new training device for practicing
indirect vision in dental work. The study was undertaken at Faculty of Dentistry, Thammasat University. Forty-two
participants were divided into three groups (n=14 in each group) as novices (second-year students), competences
(sixth-year students) and experts (dental practitioners). All participants completed four drawing exercises, which
were attached on the training device, with indirect vision using mouth mirror. Construct validity was evaluated
by comparing time spent and errors in each exercise among the three groups. To assess face validity, expert and
competence groups completed a 5-point rating scale questionnaire concerning various aspects of training realism
and usefulness in learning indirect vision skill. The rating scale ranges from 5=strongly agree to 1 strongly disagree.
The results showed that experts performed significantly fewer errors than novices in most exercises (p<0.05).
However, there was no statistically significant difference in mean time spent among the three groups. Most of the
participants rated high scores on helpfulness of the training device for learning indirect vision, and its realism in
comparison with performing mirror-inverted movement in clinical situation. In conclusion, the face validity of the
training device could be established. The training device was able to differentiate the level of indirect vision skill in
dental practice, which demonstrated construct validity of this new device. Overall, the findings of the study support
that this device has a potential for training indirect vision skill in pre-clinical dental students.