Validity of teeth width measurements on conventional versus 3D models

For proper diagnosis of orthodontic problems of a patient, different measurements and analysis should be performed on dental cast. In recent years, due to introduction of paperless offices, 3D reconstruction methods and softwares are available in order to build virtual dental casts and measurements on them. The purpose of the present study was to compare the validity of teeth width measurements on conventional versus 3D models. In this diagnosis study, twenty set-ups of upper and lower casts using artificial teeth corresponding to various malocclusions were created. Impressions were taken of them providing 20 plaster models. The plaster models were scanned by laser surface scanner and the crown widths measured by its software. The gold standard was the teeth width measured by caliper before setting up the teeth. The mesiodistal crown width was also measured on casts as conventional method. The crown width was compared between the three methods by F test, ICC and Dahlberg formula. Coefficient of validity between measurements by 3D scanning and gold standard in overall teeth measurements (premolar to premolar) was 0.914. The mean difference between laser scanning method and gold standard was 1.7 mm and between conventional method and gold was 0.34 mm. In most of the measurements, the difference between mesiodistal crown width belonged to canines. The accuracy of laser surface scanning system was clinically acceptable and in the range of similar studies, but these is not enough for research purposes and it should be improved. In reference to advantages of computerized methods in near future, these methods will be the clinical standard for orthodontic diagnosis.