Comparison of Measurements on Conventional Plaster Model and Computer-Aided Digital Dental Models

Objective: The objective of the present study was to examine the veracity and precision of measurements obtained from plaster models and digital models of subjects presenting with different malocclusion patterns. Methods: A total of 68 orthodontic patients, who had requested treatment were randomly selected and included in the study and classified as Class I (n=20), Class II (n=20) and Class III (n=18). The first group underwent an alginate impression procedure, which involved taking measurements from both the upper and lower jaws. Subsequently, plaster models were created through the casting of these impressions. In the second group, digital models were created by digitizing the patients’ upper and lower jaws with an intraoral scanner. In the third group, the plaster models were digitized via a camera, thus creating a digital model record. A series of measurements was taken on both the digital and plaster models. These included intercanine width, intermolar width, overjet, overbite, mesiodistal dimensions of the teeth, as well as the Bolton, Hayes-Nance and midline shift analyses. The reliability of the measurements taken on the plaster models with electronic calipers and on the digital models with 3Shape Ortho Analyzer software was then evaluated. Results: The results of the analyses revealed no statistically significant differences between the groups (p>0.05). Statistically significant differences were observed between Class II and Class III malocclusions in Group 1 in terms of mandibular intermolar distance measurements, and between Class I malocclusion, Class II and Class III malocclusions in Group 3 in terms of Bolton 12 teeth measurements (p < 0.05). Conclusion: The measurements derived from plaster models, digital models obtained directly with an intraoral camera and digital models generated through the scanning of the plaster models, and demonstrated comparable reliability. In orthodontics, digital models represent an acceptable alternative to plaster models for the purpose of taking measurements.