ABSTRACT Objective To test the clinical application of LCM‐printed lithium disilicate veneers. Clinical Considerations A female patient with tooth wear was scanned with intraoral scanner (Prime Scan, Dentsply Sirona). The six non‐prep veneers were designed (DentalCAD, Exocad) and printed from lithium disilicate with an LCM‐printer with the thickness of 0.1–0.2 mm (CeraFab System S65 Medical, Lithoz GmbH). The green parts after printing were cleaned of the excess slurry and debindered in a furnace (Nabertherm, Lilienthal) until 430°C with a dwell time of 5 h to remove all polymeric binder. The resulting parts were sintered in an oven (Programat P510, Ivoclar Vivadent AG) at a temperature of 900°C. The supports were removed with a dental technician handpiece (Perfecta 900, W & H). The final restorations were stained (e‐max Ceram, Ivoclar Vivadent AG) by a master dental technician. Conclusions The six LCM‐printed ultra‐thin non‐prep lithium disilicate veneers were tried‐in on the patient using a try‐in glycerin gel (Ivoclar Vivadent, Schaan, Lichtenstein) and demonstrated excellent fit and esthetics. LCM technology enabled the production of ultra‐thin non‐prep lithium disilicate veneers with layer thicknesses of down to 0.1 mm. Clinical Significance The 3D‐printing of ultra‐thin non‐prep veneers is technically feasible and provides an adequate clinical outcome. Additive manufacturing of ultra‐thin non‐prep lithium disilicate veneers may pose a valid alternative to conventional and subtractive manufacturing.

3D printing is developing rapidly and enables the production of parts manufactured using different materials. These includes zirconium dioxide (ZrO2), which can be of particular interest for bone tissue engineering and implantology. However, highly accurate part-dimensions are a must for these applications, which is why this study addresses geometrical deviations which occur during the printing process and thermal post-processing. Six sets of test geometries with 50 individual features were 3D printed with two different ZrO2 slurries (3 mol% yttria-stabilized ZrO2) and scanned with a profilometer. After debinding and sintering, the profilometer scan was repeated and the deviations and shrinkage factors were determined. A notable difference is observed when the same ceramic is processed using two different slurries. For instance, one used ceramic slurry, LithaCon 210, exhibits shrinkage factors of shrXY=21.2 +/- 3.4% (n=78) and shrZ=23.6 +/- 0.54% (n=24) for protruding structures, while the other ceramic slurry, LithaCon 280, shows shrinkage factors of shrXY=21.7 +/- 3.3% (n=78) and shrZ=24.5 +/- 0.55% (n=24). Geometric deviations differed for intruding (like holes and slots) and protruding (like pillars) geometries, being more pronounced in case of intruding geometries, especially where printing overhangs occur. Although the shrinkage during sintering needs further investigation, these experimental findings are a good starting point to validate and refine simulation models for shrinkage and improve production processes of 3D printed ceramics.

3D printing is developing rapidly and enables the production of parts manufactured using different materials. These includes zirconium dioxide (ZrO2), which can be of particular interest for bone tissue engineering and implantology. However, highly accurate part-dimensions are a must for these applications, which is why this study addresses geometrical deviations which occur during the printing process and thermal post-processing.Six sets of test geometries with 50 individual features were 3D printed with two different ZrO2 slurries (3 mol% yttria-stabilized ZrO2) and scanned with a profilometer. After debinding and sintering, the profilometer scan was repeated and the deviations and shrinkage factors were determined.A notable difference is observed when the same ceramic is processed using two different slurries. For instance, one used ceramic slurry, LithaCon 210, exhibits shrinkage factors of shrXY=21.2±3.4% (n=78) and shrZ=23.6±0.54% (n=24) for protruding structures, while the other ceramic slurry, LithaCon 280, shows shrinkage factors of shrXY=21.7±3.3% (n=78) and shrZ=24.5±0.55% (n=24).Geometric deviations differed for intruding (like holes and slots) and protruding (like pillars) geometries, being more pronounced in case of intruding geometries, especially where printing overhangs occur.Although the shrinkage during sintering needs further investigation, these experimental findings are a good starting point to validate and refine simulation models for shrinkage and improve production processes of 3D printed ceramics.

Objective: To design a patient-specific subperiosteal implant for a severely atrophic maxillary ridge using yttriastabilized additively manufactured zirconia (3YSZ) and evaluate its material properties by applying topology optimization (TO) to replace bulk material with a lattice structure. Materials: A contrast-based segmented skull model from anonymized computed tomography data of a patient was used for the initial anatomical design of the implant for the atrophic maxillary ridge. The implant underwent finite element analysis (FEA) and TO under different occlusal load-bearing conditions. The resulting implant designs, in bulk material and lattice, were evaluated via in-silico tensile tests and 3D printed. Results: The workflow produced two patient-specific subperiosteal designs: a) an anatomically precise bulk implant, b) a TO lattice implant. In-silico tensile tests revealed that the Young's modulus of yttria-stabilized zirconia is 205 GPa for the bulk material and 83.3 GPa for the lattice. Maximum principal stresses in the implant were 61.14 MPa in bulk material and 278.63 MPa in lattice, both tolerable, indicating the redesigned implant can withstand occlusal forces of 125-250 N per abutment. Furthermore, TO achieved a 13.10 % mass reduction and 208.71 % increased surface area, suggesting improved osteointegration potential. Significance: The study demonstrates the planning and optimization of ceramic implant topology. A further iteration of the implant was successfully implanted in a patient-named use case, employing the same fabrication process and parameters.

Objective The study aims to evaluate the wear surface using 3D surface roughness and other material characterization of zirconia fabricated using photopolymerization based Lithography-based Ceramic Manufacturing (LCM). Method LCM technology was used to fabricate zirconia specimens of size 10 × 10 × 2mm 3 . Scanning Electron Microscope, 3D–profilometer, X-ray Diffraction, and hardness test characterized the samples before and after wear and Coefficient of friction (COF) was monitored. Result The COF was around 0.7 and did not differ much between the horizontally and vertically printed specimens. However, the surface roughness after wear for horizontally printed specimen was 0.567 ± 0.139 μm, while that for vertically printed specimen was 0.379 ± 0.080 μm. The reduced valley depth and the dale void volume were low for the vertically printed zirconia specimen, indicating lesser voids and low fluid retention. In addition, it was observed that the hardness value of the vertically printed sample was better. The scanning electron microscopic images and 3D surface profiles of the zirconia specimens depicted the surface topography and revealed the wear track. Conclusion The study shows that zirconia fabricated using LCM technology possesses surface roughness of about 0.5 μm with no machining scars that are usually associated with CAD/CAM dentistry and also indicating agreement with clinically acceptable values for minimal surface roughness of dental restorations. Dental restorations using LCM fabricated zirconia redues the requirement of post-processing work flow that is part of CAD/CAM dentistry.

Background: ceramic veneers, crowns, and other types of restorations are often made using either the press heating technique or the subtractive method. The advent of lithography-based ceramic manufacturing (LCM) allows for the manufacturing of such restorations in an additive way. Methods: this concept paper describes the first clinical experience in the application of LCM lithium disilicate restorations in vivo for the manufacturing of classic veneers for a patient with severe tooth wear. The applied restorations were analyzed in terms of their marginal fit in metrology software (Geomagic Control X, 3D Systems). Furthermore, the feasibility of 3D printing of non-prep veneers with a 0.1 mm thickness was tested. Results: the classic LCM lithium disilicate veneers were tried in the mouth cavity and demonstrated adequate esthetics and a sufficient marginal fit of 100 µm. Furthermore, the non-prep veneers with a 0.1 mm thickness could be successfully printed using LCM technology and also demonstrated an adequate fit on the model in vitro. Conclusions: the described technical approach of lithium disilicate 3D printing with LCM technology may pose a valid alternative to subtractive and analog manufacturing and be a game-changing option with the use of additive chairside ceramic fabrication.

Statement of problem. Whether additively produced zirconia could overcome problems with conventional computer-aided design and computer-aided manufacture (CAD-CAM) such as milling inaccuracies and provide accurate occlusal veneers is unclear. Purpose. The purpose of this in vitro study was to compare the marginal and internal fit of 3D -printed zirconia occlusal veneers with CAD-CAMefabricated zirconia or heat-pressed lithium disilicate ceramic (LS2) restorations on molars. Material and methods. The occlusal enamel in 60 extracted human molars was removed, with the preparation extending into dentin. Occlusal veneers at a thickness of 0.5 mm were designed and manufactured according to their group allocation: 3DP, 3D-printed zirconia; CAM, milled zirconia; and HPR, heat-pressed LS2. The prepared teeth and restorations were scanned and superimposed, and the marginal and internal adaptation were measured 2-and 3-dimensionally; the production accuracy (trueness) was also measured. The comparisons of the group medians were performed with nonparametric methods and a pairwise group comparison (a=.05). Results. Three-dimensionally printed zirconia revealed median outcomes of 95 gm (margin), 252 gm (cusp), 305 gm (fossa), and 184 gm (3D internal adaptation). CAM showed median values of 65 gm (margin), 128 gm (cusp), 203 gm (fossa), and 120 gm (3D internal adaptation). The respective values for the group HPR were 118 gm (margin), 251 gm (cusp), 409 gm (fossa), and 180 gm (3D internal adaptation). Significant differences (P<.001) between CAM and 3DP (cusp, fossa, 3D internal adaptation) and between CAM and HPR (all regions) were found, with the former group showing higher accuracies. The trueness showed median discrepancies of 26 gm (3DP), 13 gm (CAM), and 29 gm (HPR) with significant differences (P<.001) for the comparisons 3DP-CAM and CAM-HPR. Conclusions. Three-dimensionally printed zirconia occlusal veneers produced by means of lithography-based ceramic manufacturing exhibit a marginal adaptation (95 gm) and a production accuracy (26 gm) similar to those of conventional methods. (J Prosthet Dent 2022;128:709-15)

Objectives. The load-bearing capacity of ultra-thin occlusal veneers made of 3D-printed zirconia were compared to the ones obtained by fabricating these reconstructions by CAD/CAM milling zirconia or heat-pressing lithium- disilicate. Methods. On 60 extracted human molars, the occlusal enamel was removed and extended into dentin. Occlusal veneers of 0.5 mm thickness were digitally designed. The specimens were divided into 3 groups (n = 20 each) differing in the restorative material and the fabrication technique of the occlusal veneer. (1) 3DP: 3D-printed zirconia (Lithoz); (2): CAM: milled zirconia (Ceramill Zolid FX); (3) HPR: heat-pressed lithium disilicate (IPS e.max Press). After conditioning procedures, the restorations were adhesively bonded onto the conditioned tooth. Thereafter, all specimens were aged in a chewing simulator by exposure to cyclic fatigue and temperature variations. Subsequently the specimens were statically loaded and the load which was necessary to decrease the maximum load by 20% and initiate a crack (F-initial) and the load which was needed to fracture the specimen (F-max) were measured. Differences between the groups were compared applying the Kruskal-Wallis (KW) test and the Wilcoxon-Mann-Whitney-Test (WMW: p < 0.05). Results. The median F-initial values for the groups 3DP, CAM and HPR were 1'650 N, 1'250 N and 500 N. The differences between all three groups were statistically significant (KW: p < 0.0001). The median F max values amounted to 2'026 N for the group 3DP, 1'500 N for the group CAM and 1'555 N for the group HPR. Significant differences were found between 3DP and CAM (WMW: p = 0.0238). (C) 2020 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

Bone regeneration requires porous and mechanically stable scaffolds to support tissue integration and angiogenesis, which is essential for bone tissue regeneration. With the advent of additive manufacturing processes, production of complex porous architectures has become feasible. However, a balance has to be sorted between the porous architecture and mechanical stability, which facilitates bone regeneration for load bearing applications. The current study evaluates the use of high resolution digital light processing (DLP) -based additive manufacturing to produce complex but mechanical stable scaffolds based on β-tricalcium phosphate (β-TCP) for bone regeneration. Four different geometries: a rectilinear Grid, a hexagonal Kagome, a Schwarz primitive, and a hollow Schwarz architecture are designed with 400 μm pores and 75 or 50 vol% porosity. However, after initial screening for design stability and mechanical properties, only the rectilinear Grid structure, and the hexagonal Kagome structure are found to be reproducible and showed higher mechanical properties. Micro computed tomography (μ-CT) analysis shows <2 vol% error in porosity and <6% relative deviation of average pore sizes for the Grid structures. At 50 vol% porosity, this architecture also has the highest compressive strength of 44.7 MPa (Weibull modulus is 5.28), while bulk specimens reach 235 ± 37 MPa. To evaluate suitability of 3D scaffolds produced by DLP methods for bone regeneration, scaffolds were cultured with murine preosteoblastic MC3T3-E1 cells. Short term study showed cell growth over 14 d, with more than two-fold increase of alkaline phosphatase (ALP) activity compared to cells on 2D tissue culture plastic. Collagen deposition was increased by a factor of 1.5–2 when compared to the 2D controls. This confirms retention of biocompatible and osteo-inductive properties of β-TCP following the DLP process. This study has implications for designing of the high resolution porous scaffolds for bone regenerative applications and contributes to understanding of DLP based additive manufacturing process for medical applications.

Radical induced cationic frontal polymerization (FP) is a technique that allows the curing of huge epoxy parts (e.g., rotors of generators and construction composites), as well as parts with < 1 mm, within minutes instead of hours to days using only a fraction of the energy. Even harsh environmental conditions, like being submerged in water, cannot stop the FP

Within this review, the current needs of the dental industry will be discussed with special focus on additive manufacturing (3D printing) of dental restorations. Up to now, subtractive manufacturing methods are state of the art for production of monolithic restorations. Here, the challenges and opportunities currently existing for 3D printing of crowns and bridges will be evaluated. Over the last 10 years, the LCM technology has evolved to the state of the art 3D printing technique for dense and precise ceramics. A case study will present here the full digital workflow from acquiring the data of the patient to manufacturing the final restoration. It can be shown that with the LCM technology, it is possible to manufacture highly accurate parts with exceptional good surface quality. Furthermore, it can be shown that established techniques for staining and glazing conventionally manufactured restorations are also perfectly suitable for parts manufactured by means of the LCM technology. Particularly attractive restorations and outstanding reproduction of the sharp-edged crown margins are possible, together with the exact reproduction of the occlusal surfaces with sharp and natural replication of the fissures.

Cationic photopolymerization is a powerful method for UV-curing of epoxy, vinyl ether and oxetane monomers. Little attention has been paid to it over the last few decades compared to the corresponding free radical applications due to unsuitable and inefficient photo-acid generators (PAGs) used for photoinitiation. We introduce a novel type of PAG based on the tetrakis(perfluoro-t-butyloxy) aluminate anion. In facile preparations, diphenyliodonium and triarylsulfonium salts were synthesized, followed by characterization of absorbance and thermal stability. Comparative photo-differential scanning calorimetry (photo-DSC) studies with common onium salt PAGs showed the advantageous reactivity of the novel alkoxyaluminate-based cationic photoinitiators. The novel diphenyliodonium PAG was also examined in photosensitization studies for potential use in higher wavelength applications.

ABSTRACTRadical induced cationic frontal polymerization (RICFP) is an extremely powerful and elegant alternative curing technique that allows cationic bulk curing of epoxy resins with very little energy consumption, as well as curing in compartments that are not readily accessible. We recently introduced a bisphenol‐A diglycidylether (BADGE) based system that allows the bubble‐free photocuring of this widely used epoxy resin. In this article, we describe the high storage stability and possibilities to influence the curing speed via the initiator concentrations of different formulations. These properties allow the adjustment of the frontal polymerization to ones need. We also show that the (thermo)mechanical and electrical properties of frontal cured epoxy polymers compares favorably with those of state of the art material. Finally, different strategies to overcome the challenges on producing epoxy resin based mica composites via RICFP are presented. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3751–3759

Novel modifications of the synthetic polymer poly(vinyl alcohol) (PVA) were developed for application in the field of biomedical engineering. PVA was modified with allyl succinic anhydride, norbornene anhydride as well as with c-thiobutyrolactone to produce macromers with reactive ene and thiol groups, respectively. Cytotoxicity studies have shown that the material exhibits almost no cell-toxicity, when used in concentrations of 1 and 0.1 wt % for 24 h. The obtained macromers were photocrosslinked via thiol-ene chemistry. Storage stability of the macromer mixtures with different concentrations of pyrogallol as stabilizer were investigated. Photorheometry was employed to optimize mixtures concerning reactivity based on their thiol-to-ene ratio, photoinitiator concentration, and macromer content. The crosslinked hydrogels were studied concerning their swellability. To form hydrogels with cellular structure two-photon-polymerization (2PP) was employed. Processing windows for 2PP of selected mixtures were determined. (C) 2016 Wiley Periodicals, Inc.

Die Erfindung betrifft ein Verfahren zur radikalisch induzierten kationischen Frontalpolymerisation von kationisch polymerisierbaren Monomeren mittels einer Kombination aus zumindest einem kationischen Polymerisationsinitiator und zumindest einem Aktivator fur den zumindest einen Initiator, das dadurch gekennzeichnetist, dassals Aktivator Benzpinakol eingesetzt wird.

Event Abstract Back to Event Poly(vinyl alcohol) based hydrogels for 3D biomaterial constructs Stefan Baudis1, Daniel Bomze1, Markus Lunzer1, 2, Jürgen Stampfl2, Aleksandr Ovsianikov2 and Robert Liska1 1 Vienna University of Technology, Institute of Applied Synthetic Chemistry, Austria 2 Vienna University of Technology, Institute of Materials Science and Technology, Austria Introduction: Poly(vinyl alcohol) (PVA) is a water soluble, odorless, tasteless, white and non-toxic polymer widely used in industry, e.g., as additive to food and cosmetic products. These properties, taken together with the sheer endless possibilities for chemical modification of the free secondary hydroxyl groups makes it especially interesting for the design of hydrogels for biomedical applications. In this paper, a modular system is created, combining ene-functionalized with thiol-functionalized PVA to thiol-ene based photo-curable hydrogel formulations [1] which can be processed by laser microfabrication. Materials and Methods: Differently functionalized PVAs were synthesized by acid catalyzed ring-opening addition of according heterocycles to free hydroxyl groups. PVA-allyl (PVA-A) was obtained from allylsuccinic anhydride, PVA-norbornene (PVA-N) from cis-5-norbornene-endo-2,3-dicarboxylic anhydride, and PVA-thiol (PVA-T) from g‑thiobutyrolactone. Cytocompatibility of the macromeres was assessed by metabolic assay. In order to elucidate structure-properties relationships PVA-A, PVA-N, and PVA-T with different degree of substitution (DS) were photo-crosslinked while monitored with rheology. Dithiothreitol (DTT) was taken as low molecular weight reference thiol. The slope of the storage modulus from these photorheometric curves was taken as a measure for the reactivity whereas the final storage modulus as reference value for the crosslink density. Additionally, the swellability of ready-cured hydrogels was determined. Arbitrary structures of an optimized PVA-based hydrogel formulation were manufactured by two-photon microfabrication [2]. Results: PVA-A, PVA-N, and PVA-T were obtained with each two different DS by adjusting stoichiometry. It was found that all PVA modifications have a comparable good cytocompatibility, which generally decreased with macromere content and DS. In order to investigate an optimal thiol to ene ratio PVA-A and PVA-N were combined with different amounts of DTT in photorheologic measurements. The found optimum of 60 mol% thiol was confirmed in formulations with PVA-T. These measurements also showed that the photoreactivity and crosslink density of formulations with 15 wt% macromer with PVA-N as ene-component were higher compared to similar formulations with PVA-A. This was also confirmed by the higher swellability of hydrogels composed of PVA-A. Optimized formulations could be processed by two-photon lithography (Figure 1). Discussion: The photoreactivity and cytocompatibility of the PVA based hydrogel precursors as well as the mechanical properties of the final hydrogels is highly influenced by the introduced reactive groups and their ratio. However, with the found optimal formulations the microfabrication of 3D hydrogel constructs was enabled. The wider processing window of PVA-N compared to PVA-A was also found as a manifestation of the higher photoreactivity of norbornene compared to allyl groups. Conclusion: Both macromere thiol-ene systems are suitable to be processed by laser microfabrication based on two-photon lithography. However, PVA-A combined with PVA-T emphasized to be the system with higher cytocompatibility and should therefore be considered as basis for biocompatible 3D hydrogel while PVA-N/PVA-T has a higher photoreactivity and thus can be fabricated with higher laser scanning speeds. Austrian research funding association (FFG, project number 849787); European Research Council (Starting Grant-307701, A.O.)References:[1] Torgersen, J.; Qin, X.-H.; Li, Z.; Ovsianikov, A.; Liska, R.; Stampfl, J. Adv. Funct. Mater. 2013, 23, (36), 4542-4554[2] Hoyle, C. E.; Lowe, A. B.; Bowman, C. N. Chem. Soc. Rev. 2010, 39, (4), 1355-1387. Keywords: microstructure, material design, Rapid prototyping, 3D scaffold Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016. Presentation Type: Poster Topic: Three-dimensional fabrication Citation: Baudis S, Bomze D, Lunzer M, Stampfl J, Ovsianikov A and Liska R (2016). Poly(vinyl alcohol) based hydrogels for 3D biomaterial constructs. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.02453 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Mar 2016; Published Online: 30 Mar 2016. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Stefan Baudis Daniel Bomze Markus Lunzer Jürgen Stampfl Aleksandr Ovsianikov Robert Liska Google Stefan Baudis Daniel Bomze Markus Lunzer Jürgen Stampfl Aleksandr Ovsianikov Robert Liska Google Scholar Stefan Baudis Daniel Bomze Markus Lunzer Jürgen Stampfl Aleksandr Ovsianikov Robert Liska PubMed Stefan Baudis Daniel Bomze Markus Lunzer Jürgen Stampfl Aleksandr Ovsianikov Robert Liska Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.