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.

Effect of printing layer thickness on the trueness of 3-unit interim fixed partial dentures

“…8 Another study, which investigated the influence of layer thickness on the trueness of interim FPDs also achieved the best results when using a small layer thickness. 17 However, in this study, 17 the trueness of the 35-mm-layer thickness group was higher than that of the 50-mm-layer thickness group, whereas in the present study, no difference was seen between the 20-and 50-mm-layer thickness groups.…”

“…15,16 Currently methacrylate polymers and composite resins are typically used for interim restorations. 17 Polymethyl methacrylate (PMMA) is the leading alternative among these materials because of its low cost, ease of fabrication, and reliability. 15 However, polymerization shrinkage, marginal discrepancies, and that the polymerization reaction of this material is exothermic are problems associated with the direct use of PMMA.…”

“…15 It is also possible to manufacture these restorations by using either SM or AM, 6,16,18,19 and compared with the conventional method, these CAD-CAM technologies lead to more rapid production with a final product that has higher precision and adaptation. 17 The accuracy of a printed object can be affected by the technology and software program used, laser speed, laser intensity, printing orientation, number of layers, printing angle, layer thickness, and postprocessing methods. 7,10,11,18,20 Printing orientation has been the main subject of interest of previous studies on 3Dprinted interim materials.…”

“…23 Studies on the effects of layer thickness on the accuracy of 3D-printed interim restorations are sparse. 14,17 Dikova1 17 did not compare 3D-printed and milled interim fixed partial dentures (FPDs), while Park et al 14 focused on the marginal fit and internal gaps of interim FPDs. Therefore, the purpose of this in vitro study was to evaluate the effect of printing layer thickness on the trueness of 3-unit PMMA interim FPDs and to compare them with milled PMMA interim FPDs.…”

An Interdisciplinary Study Regarding the Characteristics of Dental Resins Used for Temporary Bridges

“…Different types of materials are prone to produce effects which can affect the final product in terms of shrinkage by polymerization. Volumetric and surface changes of resins that are used for interim fixed prosthesis can influence the elements of the prosthetic area, with negative consequences on the final therapeutic solution [21][22][23] Digital systems that are used to build temporary bridges, such as computer-aided design/computer-aided manufacturing (CAD/CAM) milling and 3D-printing, greatly reduce workflow and can be used in both direct and indirect technologies [24].…”