Aim: The aim'of the present study was to investigate whether the same orthodontic information can be obtained from study models or photographs of study models in order to assess the Index of Orthodontic Treatment Need (IOTN). The study also aimed to assess inter- and intra-examiner reliability in the assessment of orthodontic treatment need.
Sample: Thirty sets of start and finish study models, demonstrating a range of malocclusions, were non-randomly obtained from patients treated at the University of Manchester Dental Hospital. The start models demonstrated a range of malocclusions (according to The British Standard Institute Incisor Classification 1983) of varying complexity.
Method: Six photographic views of each set of study models were taken against a dark background. Millimetric distances were determined by using dividers to measure photographic distances and actual distances in millimeters from a ruler embedded in the image. Four examiners assessed the study models and photographs of the models in a random order and the Aesthetic and Dental Health components of the IOTN were recorded.
Results: There were no statistically significant differences in the IOTN scores from photographs of study models compared with IOTN scoresrom study models of the same patient.
Conclusion: The IOTN scores derived from photographs of study models are valid and reliable measures of malocclusion.