To determine the impact of build orientation, increased layer thickness, and dental crowding on the trueness of three-dimensional (3D)–printed models, and to evaluate how these parameters affect the fit of thermoformed appliances.

Materials and Methods

Ninety-six dental models were printed horizontally and vertically on the building platform using different 3D-printing technologies: (1) a stereolithography (SLA) printer with layer thicknesses of 160 μm and 300 μm and (2) a digital light processing (DLP) printer with layer thicknesses of 100 μm and 200 μm. Each printed model was digitalized and superimposed on the corresponding source file using 3D rendering software, and deviations were quantified by the root mean square values. Subsequently, a total of 32 thermoformed appliances were fabricated on top of the most accurate 3D-printed models, and their fit was evaluated by digital superimposition and inspection by three blinded orthodontists. Paired t-tests were used to analyze the data.


Significant differences (P < .05) between printing technologies used were identified for models printed horizontally, with the SLA system achieving better trueness, especially in crowded dentitions. No significant differences between technology were found when models were printed vertically. The highest values of deviation were recorded in appliances fabricated on top of DLP-printed models. The results of the qualitative evaluation indicated that appliances fabricated on top of SLA models outperformed the DLP-modeled appliances.


Three-dimensional printing with increased layer height seems to produce accurate working models for orthodontic applications.

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Author notes


Private practice, Long Island, NY, USA.


Private practice, Butler, Penn, USA.


Postgraduate student, Division of Orthodontics, Columbia University, New York, NY, USA.


Associate Director of Biostatistics, Vertex Pharmaceuticals, Boston, Mass, USA.


Associate Professor and Chair, Department of Orthodontics and Dentofacial Orthopedics, University of Pittsburgh, Pittsburgh, Penn, USA.