[A method to evaluate the trueness of reconstructed dental models made with photo-curing 3D printing technologies].

Objective: To establish a reference dental model used for trueness evaluation of photo-curing 3D printing technologies, and to establish a multidimensional trueness evaluation method based on the reference dental model, which can yield a comprehensive objective evaluating result.
Methods: A reference dental model was designed in 3ds Max 2018 software based on the statistical analysis results of dental crown and dental arch of Chinese population in previous studies in order to simulate a real dental model. This model was made up of several simple geometrical configurations, which could minimize the manual measurement error. Physical models were fabricated using three types of photo-curing three-dimensional printers using different techniques: Objet30 Pro (PJ), Projet 3510 HD Plus (MJP), and Perfactory DDP (DLP). The models were scanned by a laser-scanning device and the files were exported in a stereolithography file format. In Geomagic Studio 2012, 3D shape deviations (including overall 3D deviation, flatness error, parallelism error and perpendicularity error) were measured by several commands using the data obtained from the scanning. With regard to the feature size of the simulated dental crown and dental arch, linear measurements (including mesiodistal diameter, buccolingual diameter, crown height of each simulated dental crown and feature size of dental arch) were recorded for selected landmarks using a digital caliper. The measurement results of feature sizes were used to analyze the occlusal plane percentage error and the occlusogingival direction percentage error.
Results: For the 3D shape deviation, the results showed that the printed model made by the Objet30 Pro had the lowest overall 3D deviation, the model made by Projet 3510 HD Plus had the best perpendicularity accuracy and the model made by Perfactory DDP had the best flatness accuracy. In terms of the accuracy of the feature size, the model made by the Objet30 Pro was the most accurate in consideration of the results of the occlusal plane percentage error and the occlusogingival direction percentage error.
Conclusion: The reference dental model and the trueness evaluation method using this model is universally applicable in evaluating the trueness of photo-curing three-dimensional printed dental model and can provide a comprehensive objective evaluating result, which can serve as a reference for the clinical use of photo-curing 3D printing technology.