Comparison of 3-dimensional dental models from different sources: Diagnostic accuracy and surface registration analysis Sercan Akyalcin, a David J. Dyer, b Jeryl D. English, c and Cagla Sar d Houston, Tex, Okinawa, Japan, and Ankara, Turkey Introduction: The aim of this study was to assess the diagnostic accuracy and surface matching characteristics of 3-dimensional digital dental models obtained from various sources. Methods: Three sets of maxillary and mandibular digital models of 30 subjects were included in this study. Three-dimensional stereolithography model files were obtained from a 3-dimensional laser desktop scanner (Ortho-Insight 3D; Motionview Software, Hixson, Tenn), the emodel system (GeoDigm, Chanhassen, Minn), and cone-beam computerized tomography. Arch-length discrepancy measurements were made on the 3-dimensional digital models and compared with direct caliper measurements. Additionally, stereolithography files from the 3 digital model systems were paired and superimposed using a best-fit algorithm. Average linear differences between the stereolithography shells were computed together with surface correlation amounts at various tolerance levels. Data were evaluated using intraclass correlation coefficients and the Tukey mean difference test. Results: Although all 3 digital model groups displayed good correlation with caliper measurements, the virtual scan models had the highest correlation with the manual method (ICC . 0.95). The Tukey mean difference test showed no consistent bias of one approach vs the others compared with caliper measurements; random errors were detected in all the comparisons. For the estimation of arch-length discrepancy, the mean bias of the scanned virtual models in comparison with caliper measurements (0.24 6 0.67 mm) was smaller than the mean biases of the emodels and the models generated from cone-beam computed tomography. Additionally, the best surface overlap correlation was observed between the virtual scanned models and the emodels. The mean linear distances between the stereolithography shells of these 2 model systems were 0.14 and 0.13 mm for the maxillary and mandibular arches, respectively. Conclusions: All 3 digital model systems can provide diagnostic information similar to caliper measurements, with varying degrees of agreement limits. The scanned virtual models had the least mean bias. A strong surface match correlation was observed between the virtual scanned models and the emodels, indicating that these could be used interchangeably. (Am J Orthod Dentofacial Orthop 2013;144:831-7) P laster models have been the gold standard in dental diagnosis and treatment procedures for many years. However, they require rigorous archiving and massive physical storage space. 1,2 Moreover, plaster models are not practical in the long term because of breakage and degradation issues associated with them. 2 Accordingly, digital models made a rapid introduction into clinical practice in the late 1990s, and their clinical use has escalated since then. 3 There have been numerous efforts to investigate the diagnostic accuracy and measurement sensitivity of dig- ital models compared with plaster models. 4-11 It was reported that information obtained from digital models is interchangeable with direct caliper measurements made on conventional plaster models. According to these reports, 2-point linear measurements such as intermolar and intercanine width, 6,10 tooth size, 9 tooth height, 10 overjet, and overbite 5,6,9 always show near-excellent agreement between conventional models and the analog alternatives. However, some other a Assistant professor, Department of Orthodontics, School of Dentistry, The University of Texas Health Science Center at Houston, Houston, Tex. b Orthodontist, United States Navy, Okinawa, Japan. c Chair and program director, Department of Orthodontics, School of Dentistry, The University of Texas Health Science Center at Houston, Houston, Tex. d Assistant professor, Department of Orthodontics, School of Dentistry, Baskent University, Ankara, Turkey. All authors have completed and submitted the ICMJE Form for Disclosure of Po- tential Conflicts of Interest, and none were reported. Address correspondence to: Sercan Akyalcin, 7500 Cambridge St, Suite 5130, Houston, TX 77054; e-mail, Sercan.Akyalcin@uth.tmc.edu. Submitted, June 2013; revised and accepted, August 2013. 0889-5406/$36.00 Copyright Ó 2013 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2013.08.014 831 ORIGINAL ARTICLE