Production of high-quality temporary crowns and bridges by stereolithography

Abstract

Introduction: Temporary crowns and bridges are the main elements in the treatment with fixed partial dentures. They are usually manufactured from methacrylate polymers and composites by heat-curing or CAD/CAM milling. Additive technologies (ATs) offer a number of advantages in the production of temporary dental restorations. However, there is a lack of information about the application of AT for manufacturing of provisional prostheses due to the multiple variants and complexity of their design as well as the wide variety of the 3D printing processes. Aim: The aim of the present paper was to establish the peculiarities in the production of high-quality temporary crowns and bridges by stereolithography (SLA) with digital light projection (DLP). Materials and Methods: Two groups of samples - cubic (5 mm x 5 mm x 5 mm) and four-part dental bridges (1-st premolar to 2-nd molar) were printed with different layer thickness - 35 µm and 50 µm from NextDent C+B polymer using RapidShape D30 . Results and Discussion: It was established that for effective production of temporary crowns and bridges with high dimensional accuracy and surface smoothness, it is necessary to take into account the peculiarities of the 3D printing process and to make corrections still at the stage of virtual model generation. Individual corrections of the dimensions along the separate axes of the virtual model have to be done with correction coefficients, depending on the construction type - crown or bridge. In order to obtain high smoothness, the construction should be positioned with the vertical axes of the teeth parallel to the printing direction (Z-axis). The number of the supports has to be increased (≥4 per tooth) for reduction of the deformations during 3D printing and final photopolymerization. Conclusion: The findings in the present study could be very helpful in the development of proper construction design and technological process for improving the quality of temporary restorations.