Methods: The sample comprised of twenty consecutive study models from the Discipline of Orthodontics, University of Queensland. Tooth width measurements were performed using three different methods. The methods involved: 1.Digital calipers to record the mesiodistal widths directly; 2.Taking digital photos of the models and measuring each tooth width using a computer program; and 3.Taking impressions which were CT scanned to produce 3D digital models from which tooth widths were measured. The 3D digital models were measured using the DigiModel software. Measurements were replicated three times for each method. A paired Student's t-test was performed to compare the measurements obtained by the two new methods to those obtained by the calipers.
Results: There was a statistically significant difference in the measurement of tooth widths between DigiModel and the calipers (p=0.02), and the digital photos and the calipers (p=0.0007). DigiModel had a lower width estimate while the digital photos had a higher width estimate. However these discrepancies were judged not clinically significant. When used to determine anterior and overall Bolton's tooth size ratios, the accuracy of DigiModel and the digital photos was also clinically acceptable. The average reliability scores were 98% for the digital calipers, 98% for DigiModel, and 99% for the digital photos.
Conclusions: The validity of DigiModel and digital photos in measuring tooth widths and performing a Bolton's tooth size analysis is clinically acceptable. In addition, the reliability of both methods is excellent.