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Burkhardt F, Schirmeister CG, Wesemann C, Baur L, Vach K, Nutini M, Licht EH, Metzger MC, Mülhaupt R, Spies BC. Dimensional accuracy and simulation-based optimization of polyolefins and biocopolyesters for extrusion-based additive manufacturing and steam sterilization. J Mech Behav Biomed Mater 2024; 153:106507. [PMID: 38503082 DOI: 10.1016/j.jmbbm.2024.106507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 03/04/2024] [Accepted: 03/12/2024] [Indexed: 03/21/2024]
Abstract
Polyolefins exhibit robust mechanical and chemical properties and can be applied in the medical field, e.g. for the manufacturing of dentures. Despite their wide range of applications, they are rarely used in extrusion-based printing due to their warpage tendency. The aim of this study was to investigate and reduce the warpage of polyolefins compared to commonly used filaments after additive manufacturing (AM) and sterilization using finite element simulation. Three types of filaments were investigated: a medical-grade polypropylene (PP), a glass-fiber reinforced polypropylene (PP-GF), and a biocopolyester (BE) filament, and they were compared to an acrylic resin (AR) for material jetting. Square specimens, standardized samples prone to warpage, and denture bases (n = 10 of each group), as clinically relevant and anatomically shaped reference, were digitized after AM and steam sterilization (134 °C). To determine warpage, the volume underneath the square specimens was calculated, while the deviations of the denture bases from the printing file were measured using root mean square (RMS) values. To reduce the warpage of the PP denture base, a simulation of the printing file based on thermomechanical calculations was performed. Statistical analysis was conducted using the Kruskal-Wallis test, followed by Dunn's test for multiple comparisons. The results showed that PP exhibited the greatest warpage of the square specimens after AM, while PP-GF, BE, and AR showed minimal warpage before sterilization. However, warpage increased for PP-GF, BE and AR during sterilization, whereas PP remained more stable. After AM, denture bases made of PP showed the highest warpage. Through simulation-based optimization, warpage of the PP denture base was successfully reduced by 25%. In contrast to the reference materials, PP demonstrated greater dimensional stability during sterilization, making it a potential alternative for medical applications. Nevertheless, reducing warpage during the cooling process after AM remains necessary, and simulation-based optimization holds promise in addressing this issue.
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Affiliation(s)
- Felix Burkhardt
- Medical Center - University of Freiburg, Center for Dental Medicine, Department of Prosthetic Dentistry, Faculty of Medicine, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany.
| | - Carl G Schirmeister
- Freiburg Materials Research Center FMF and Institute for Macromolecular Chemistry, Albert-Ludwigs-University Freiburg, Stefan-Meier-Str. 21, 79104, Freiburg, Germany; Basell Sales & Marketing B.V., LyondellBasell Industries, Industriepark Höchst, 65926, Frankfurt a.M, Germany
| | - Christian Wesemann
- Medical Center - University of Freiburg, Center for Dental Medicine, Department of Prosthetic Dentistry, Faculty of Medicine, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany
| | - Lukas Baur
- Medical Center - University of Freiburg, Center for Dental Medicine, Department of Prosthetic Dentistry, Faculty of Medicine, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany
| | - Kirstin Vach
- Medical Center - University of Freiburg, Institute for Medical Biometry and Statistics, Faculty of Medicine, University of Freiburg, Stefan-Meier-Str. 26, 79104, Freiburg, Germany
| | - Massimo Nutini
- Basell Poliolefine Italia Srl, LyondellBasell Industries, P. le Privato G. Donegani 12, 44122, Ferrara, Italy
| | - Erik H Licht
- Basell Sales & Marketing B.V., LyondellBasell Industries, Industriepark Höchst, 65926, Frankfurt a.M, Germany
| | - Marc C Metzger
- Medical Center - University of Freiburg, Center of Dental Medicine, Department of Oral and Maxillofacial Surgery, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany
| | - Rolf Mülhaupt
- Freiburg Materials Research Center FMF and Institute for Macromolecular Chemistry, Albert-Ludwigs-University Freiburg, Stefan-Meier-Str. 21, 79104, Freiburg, Germany; Sustainability Center Freiburg, Ecker-Str. 4, 79104, Freiburg, Germany
| | - Benedikt C Spies
- Medical Center - University of Freiburg, Center for Dental Medicine, Department of Prosthetic Dentistry, Faculty of Medicine, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany
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Burkhardt F, Handermann L, Rothlauf S, Gintaute A, Vach K, Spies BC, Lüchtenborg J. Accuracy of additively manufactured and steam sterilized surgical guides by means of continuous liquid interface production, stereolithography, digital light processing, and fused filament fabrication. J Mech Behav Biomed Mater 2024; 152:106418. [PMID: 38295512 DOI: 10.1016/j.jmbbm.2024.106418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 01/16/2024] [Accepted: 01/23/2024] [Indexed: 02/02/2024]
Abstract
Different printing technologies can be used for prosthetically oriented implant placement, however the influence of different printing orientations and steam sterilization remains unclear. In particular, no data is available for the novel technology Continuous Liquid Interface Production. The objective was to evaluate the dimensional accuracy of surgical guides manufactured with different printing techniques in vertical and horizontal printing orientation before and after steam sterilization. A total of 80 surgical guides were manufactured by means of continuous liquid interface production (CLIP; material: Keyguide, Keyprint), digital light processing (DLP; material: Luxaprint Ortho, DMG), stereolithography (SLA; Surgical guide, Formlabs), and fused filament fabrication (FFF; material: Clear Base Support, Arfona) in vertical and horizontal printing orientation (n = 10 per subgroup). Spheres were included in the design to determine the coordinates of 17 reference points. Each specimen was digitized with a laboratory scanner after additive manufacturing (AM) and after steam sterilization (134 °C). To determine the accuracy, root mean square values (RMS) were calculated and coordinates of the reference points were recorded. Based on the measured coordinates, deviations of the reference points and relevant distances were calculated. Paired t-tests and one-way ANOVA were applied for statistical analysis (significance p < 0.05). After AM, all printing technologies showed comparable high accuracy, with an increased deviation in z-axis when printed horizontally. After sterilization, FFF printed surgical guides showed distinct warpage. The other subgroups showed no significant differences regarding the RMS of the corpus after steam sterilization (p > 0.05). Regarding reference points and distances, CLIP showed larger deviations compared to SLA in both printing orientations after steam sterilization, while DLP manufactured guides were the most dimensionally stable. In conclusion, the different printing technologies and orientations had little effect on the manufacturing accuracy of the surgical guides before sterilization. However, after sterilization, FFF surgical guides exhibited significant deformation making their clinical use impossible. CLIP showed larger deformations due to steam sterilization than the other photopolymerizing techniques, however, discrepancies may be considered within the range of clinical acceptance. The influence on the implant position remains to be evaluated.
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Affiliation(s)
- Felix Burkhardt
- Medical Center - University of Freiburg, Center for Dental Medicine, Department of Prosthetic Dentistry, Faculty of Medicine, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany.
| | - Leon Handermann
- Medical Center - University of Freiburg, Center for Dental Medicine, Department of Prosthetic Dentistry, Faculty of Medicine, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany
| | - Severin Rothlauf
- Medical Center - University of Freiburg, Center for Dental Medicine, Department of Prosthetic Dentistry, Faculty of Medicine, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany
| | - Aiste Gintaute
- Medical Center - University of Freiburg, Center for Dental Medicine, Department of Prosthetic Dentistry, Faculty of Medicine, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany
| | - Kirstin Vach
- Medical Center - University of Freiburg, Institute of Medical Biometry and Statistics, Faculty of Medicine, University of Freiburg, Stefan-Meier-Str. 26, 79104, Freiburg, Germany
| | - Benedikt C Spies
- Medical Center - University of Freiburg, Center for Dental Medicine, Department of Prosthetic Dentistry, Faculty of Medicine, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany
| | - Jörg Lüchtenborg
- Medical Center - University of Freiburg, Center for Dental Medicine, Department of Prosthetic Dentistry, Faculty of Medicine, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany
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Tailoring the composition of biocopolyester blends for dimensionally accurate extrusion-based printing, annealing and steam sterilization. Sci Rep 2022; 12:20341. [PMID: 36434090 PMCID: PMC9700831 DOI: 10.1038/s41598-022-24991-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 11/23/2022] [Indexed: 11/27/2022] Open
Abstract
Fused filament fabrication (FFF) represents a straightforward additive manufacturing technique applied in the medical sector for personalized patient treatment. However, frequently processed biopolymers lack sufficient thermal stability to be used as auxiliary devices such as surgical guides. The aim of this study was to evaluate the dimensional accuracy of experimental biocopolyester blends with improved thermal characteristics after printing, annealing and sterilization. A total of 160 square specimens and 40 surgical guides for oral implant placement were printed. One subgroup of each material (n = 10) underwent thermal annealing before both subgroups were subjected to steam sterilization (134 °C; 5 min). Specimens were digitized and the deviation from the original file was calculated. The thermal behavior was analyzed using differential scanning calorimetry and thermogravimetric analysis. A one-way ANOVA and t-tests were applied for statistical analyses (p < 0.05). All biocopolyester blends showed warpage during steam sterilization. However, the material modification with mineral fillers (21-32 wt%) and nucleating agents in combination with thermal annealing showed a significantly reduced warpage of printed square specimens. Geometry of the printing object seemed to affect dimensional accuracy, as printed surgical guides showed less distortion between the groups. In summary, biocopolyesters did benefit from fillers and annealing to improve their dimensional stability.
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Burkhardt F, Spies BC, Wesemann C, Schirmeister CG, Licht EH, Beuer F, Steinberg T, Pieralli S. Cytotoxicity of polymers intended for the extrusion-based additive manufacturing of surgical guides. Sci Rep 2022; 12:7391. [PMID: 35513701 PMCID: PMC9072356 DOI: 10.1038/s41598-022-11426-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 04/19/2022] [Indexed: 11/09/2022] Open
Abstract
Extrusion-based printing enables simplified and economic manufacturing of surgical guides for oral implant placement. Therefore, the cytotoxicity of a biocopolyester (BE) and a polypropylene (PP), intended for the fused filament fabrication of surgical guides was evaluated. For comparison, a medically certified resin based on methacrylic esters (ME) was printed by stereolithography (n = 18 each group). Human gingival keratinocytes (HGK) were exposed to eluates of the tested materials and an impedance measurement and a tetrazolium assay (MTT) were performed. Modulations in gene expression were analyzed by quantitative PCR. One-way ANOVA with post-hoc Tukey tests were applied. None of the materials exceeded the threshold for cytotoxicity (< 70% viability in MTT) according to ISO 10993-5:2009. The impedance-based cell indices for PP and BE, reflecting cell proliferation, showed little deviations from the control, while ME caused a reduction of up to 45% after 72 h. PCR analysis after 72 h revealed only marginal modulations caused by BE while PP induced a down-regulation of genes encoding for inflammation and apoptosis (p < 0.05). In contrast, the 72 h ME eluate caused an up-regulation of these genes (p < 0.01). All evaluated materials can be considered biocompatible in vitro for short-term application. However, long-term contact to ME might induce (pro-)apoptotic/(pro-)inflammatory responses in HGK.
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Affiliation(s)
- Felix Burkhardt
- Department of Prosthetic Dentistry, Faculty of Medicine, Medical Center, Center for Dental Medicine, University of Freiburg, Hugstetter Straße 55, 79106, Freiburg, Germany.
| | - Benedikt C Spies
- Department of Prosthetic Dentistry, Faculty of Medicine, Medical Center, Center for Dental Medicine, University of Freiburg, Hugstetter Straße 55, 79106, Freiburg, Germany
| | - Christian Wesemann
- Department of Prosthetic Dentistry, Faculty of Medicine, Medical Center, Center for Dental Medicine, University of Freiburg, Hugstetter Straße 55, 79106, Freiburg, Germany.,Department of Prosthodontics, Geriatric Dentistry and Craniomandibular Disorders, Charité -Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität Zu Berlin and Berlin Institute of Health, Assmanshauser Str. 4-6, 14197, Berlin, Germany
| | - Carl G Schirmeister
- Freiburg Materials Research Center FMF and Institute for Macromolecular Chemistry, Albert-Ludwigs-University Freiburg, Stefan-Meier-Str. 21, 79104, Freiburg, Germany.,Basell Sales & Marketing B.V., LyondellBasell Industries, Industriepark Höchst, 65926, Frankfurt, Germany
| | - Erik H Licht
- Basell Sales & Marketing B.V., LyondellBasell Industries, Industriepark Höchst, 65926, Frankfurt, Germany
| | - Florian Beuer
- Department of Prosthodontics, Geriatric Dentistry and Craniomandibular Disorders, Charité -Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität Zu Berlin and Berlin Institute of Health, Assmanshauser Str. 4-6, 14197, Berlin, Germany
| | - Thorsten Steinberg
- Division of Oral Biotechnology, Faculty of Medicine, Medical Center, Center for Dental Medicine, University of Freiburg, Hugstetter Straße 55, 79106, Freiburg, Germany
| | - Stefano Pieralli
- Department of Prosthetic Dentistry, Faculty of Medicine, Medical Center, Center for Dental Medicine, University of Freiburg, Hugstetter Straße 55, 79106, Freiburg, Germany
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Three-Dimensional Modeling and 3D Printing of Biocompatible Orthodontic Power-Arm Design with Clinical Application. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11209693] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Three-dimensional (3D) printing with biocompatible resins offers new competition to its opposition—subtractive manufacturing, which currently dominates in dentistry. Removing dental material layer-by-layer with lathes, mills or grinders faces its limits when it comes to the fabrication of detailed complex structures. The aim of this original research was to design, materialize and clinically evaluate a functional and resilient shape of the orthodontic power-arm by means of biocompatible 3D printing. To improve power-arm resiliency, we have employed finite element modelling and analyzed stress distribution to improve the original design of the power-arm. After 3D printing, we have also evaluated both designs clinically. This multidisciplinary approach is described in this paper as a feasible workflow that might inspire application other individualized biomechanical appliances in orthodontics. The design is a biocompatible power-arm, a miniature device bonded to a tooth surface, translating significant bio-mechanical force vectors to move a tooth in the bone. Its design must be also resilient and fully individualized to patient oral anatomy. Clinical evaluation of the debonding rate in 50 randomized clinical applications for each power-arm-variant showed significantly less debonding incidents in the improved power-arm design (two failures = 4%) than in the original variant (nine failures = 18%).
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Nold J, Metzger MC, Schwarz S, Wesemann C, Wemken G, Pieralli S, Kernen F, Weingart J, Schirmeister CG, Schumann S, Schlager S, Spies BC. Air seal performance of personalized and statistically shaped 3D-printed face masks compared with market-available surgical and FFP2 masks. Sci Rep 2021; 11:19347. [PMID: 34588584 PMCID: PMC8481495 DOI: 10.1038/s41598-021-98963-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2021] [Accepted: 08/23/2021] [Indexed: 11/09/2022] Open
Abstract
The ongoing COVID-19 pandemic has revealed alarming shortages of personal protective equipment for frontline healthcare professionals and the general public. Therefore, a 3D-printable mask frame was developed, and its air seal performance was evaluated and compared. Personalized masks (PM) based on individual face scans (n = 8) and a statistically shaped mask (SSM) based on a standardized facial soft tissue shape computed from 190 face scans were designed. Subsequently, the masks were additively manufactured, and in a second step, the PM and SSM were compared to surgical masks (SM) and FFP2 masks (FFP2) in terms of air seal performance. 3D-printed face models allowed for air leakage evaluation by measuring the pressure inside the mask in sealed and unsealed conditions during a breathing simulation. The PM demonstrated the lowest leak flow (p < 0.01) of inspired or expired unfiltered air of approximately 10.4 ± 16.4%, whereas the SM showed the highest (p < 0.01) leakage with 84.9 ± 7.7%. The FFP2 and SSM had similar values of 34.9 ± 18.5% leakage (p > 0.68). The developed framework allows for the time- and resource-efficient, on-demand, and in-house production of masks. For the best seal performance, an individually personalized mask design might be recommended.
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Affiliation(s)
- Julian Nold
- Department of Prosthetic Dentistry, Center for Dental Medicine, Faculty of Medicine, Medical Center, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany
| | - Marc C Metzger
- Department of Oral and Maxillofacial Surgery, Center for Dental Medicine, Faculty of Medicine, Medical Center, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany
| | - Steffen Schwarz
- Department of Oral and Maxillofacial Surgery, Center for Dental Medicine, Faculty of Medicine, Medical Center, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany
| | - Christian Wesemann
- Department of Prosthetic Dentistry, Center for Dental Medicine, Faculty of Medicine, Medical Center, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany
| | - Gregor Wemken
- Department of Prosthetic Dentistry, Center for Dental Medicine, Faculty of Medicine, Medical Center, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany
| | - Stefano Pieralli
- Department of Prosthetic Dentistry, Center for Dental Medicine, Faculty of Medicine, Medical Center, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany.,Department of Oral and Maxillofacial Surgery, Center for Dental Medicine, Faculty of Medicine, Medical Center, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany
| | - Florian Kernen
- Department of Oral and Maxillofacial Surgery, Center for Dental Medicine, Faculty of Medicine, Medical Center, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany
| | - Julia Weingart
- Department of Oral and Maxillofacial Surgery, Center for Dental Medicine, Faculty of Medicine, Medical Center, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany
| | - Carl G Schirmeister
- Institute for Macromolecular Chemistry, Freiburg Materials Research Center, University of Freiburg, Stefan-Meier-Str. 21, 79104, Freiburg, Germany.,Basell Sales & Marketing B.V., LyondellBasell Industries, Industriepark Höchst, 65926, Frankfurt am Main, Germany
| | - Stefan Schumann
- Department of Anesthesiology and Critical Care, Faculty of Medicine, Medical Center, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany
| | - Stefan Schlager
- Department of Biological Anthropology, Medical Center, University of Freiburg, Hebelstraße 29, 79106, Freiburg, Germany
| | - Benedikt C Spies
- Department of Prosthetic Dentistry, Center for Dental Medicine, Faculty of Medicine, Medical Center, University of Freiburg, Hugstetter Str. 55, 79106, Freiburg, Germany.
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