# Accuracy Comparison among 3D-Printing Technologies to Produce Dental Models  
[PERSON]  
1 Department of Stomatology, School of Dentistry, University of Sao Paulo, Sao Paulo 05508-000, Brazil 1, [PERSON] 1, [PERSON]  
1 Department of Stomatology, School of Dentistry, University of Sao Paulo, Sao Paulo 05508-000, Brazil 1, [PERSON]  
1 Department of Stomatology, School of Dentistry, University of Sao Paulo, Sao Paulo 05508-000, Brazil 1, [PERSON]  
2 Department of Dental Prosthesis, Simple Dental Center, Sao Paulo 01332-000, Brazil 2, [PERSON]  
1 Department of Stomatology, School of Dentistry, University of Sao Paulo, Sao Paulo 05508-000, Brazil 1, [PERSON]  
3 Department of Dental Surgery, Faculty of Dental Surgery, University of Malta, MSD 2080 Misida, Malta 3, [PERSON]  
1 Department of Stomatology, School of Dentistry, University of Sao Paulo, Sao Paulo 05508-000, Brazil 1, and [PERSON]
is described to lead to minimal material waste and to produce dental casts with highly detailed and clinically acceptable geometries [3]. The group of additive manufacturing devices that use vat polymerization 3D-printing include different printing technologies, such as stereolithography (SLA) and digital light processing (DLP), which are among the most commonly used in dentistry. Basically, SLA and DLP printers use the same process for printing, but they differ in the procedure in that light is delivered to cure the 3D-printed object. SLA is the oldest and has been one of the most commonly used method in general 3D-printing. This type of 3D printer projects an ultraviolet (UV) laser beam that rapidly moves into a reservoir filled with light-cured liquid resin to build by drawing the details of each layer of the object. The first cured layer is attached to the printing bed (building platform), rather than to the resin reservoir. Once the first layer is completed, the building platform rises slightly in order to form consecutive new layers on top of the previous ones. This process repeats continuously until the object is fully manufactured. DLP, in turn, is an alternative method to deliver light during 3D-printing. Instead of using a laser beam to scan each layer at a time, the DLP printer projects a silhouette of the entire first layer simultaneously and cures it with light. This enables a relatively faster printing procedure, as compared to SLA [3,4]. Although milling has been widely used to fabricate definitive prostheses with a series of materials such as zirconia and lithium disilicate, there are some drawbacks inherent to the process, such as inability to reproduce fine details and relatively higher cost if compared with 3D-printing. The advantages of the latter include the production of desired objects with a minimum amount of material, low waste of the material, and the ability to create multiple products at a time [4]. Nonetheless, 3D-printed models also present a unique set of limitations (e.g., resolution of the optical scanner, quality of the light-cured resin, etc.). The accuracy of the resultant models depends on several factors related either to CAD or CAM, in which errors may occur. This includes the parameters involved in the manufacturing and postprocessing procedures, as it does the data acquisition and image processing of the oral hard and soft tissues [5]. However, recent articles have described 3D-printing as clinically acceptable to produce dental devices such as crowns, surgical guides, and dental casts, with clinical results comparable to the respective milled and conventionally produced devices [1,4]. A recent article found similar accuracy results between 3D-printed models using specific technologies and conventional stone casts [3]. Accurate impressions, as well as conventional or 3D-printing procedures, are prerequisites to manufacture satisfactory dental casts. These, in turn, can be used in the fabrication or adjustment of definitive prostheses or restorations with adequate fit.