Thesis
Sintering effect on zirconia manufactured by suspension enclosed projection stereolithography
University of Iowa
Master of Science (MS), University of Iowa
Spring 2023
DOI: 10.25820/etd.007147
Abstract
Objectives: To evaluate the suitability of using zirconia dental materials with a novel 3D printing process named suspension enclosed projection stereolithography (SEPS); and to investigate the effect of sintering time and temperature on the flexural strength and density of zirconia produced by SEPS.
Methods: Ceramic suspensions (slurries) were prepared using zirconia powders (Tosoh) and 3D printing resins, with varying percentages depending on the type of zirconia used. The 3Y (60wt%) slurries had a zirconia to resin ratio of 60:40 and used ANYCUBIC white 405nm UV resin and Formlabs Clear Resin at 20% each, while the 5Y (70wt%) slurries had a ratio of 70:30 and used the same resins at 15% each. The slurries were prepared with 1.5% Solsperse 20000 dispersant and 0.5% isopropyl alcohol, and were ball milled and degassed. 40 bar specimens (36.2mm x 4.9mm x 1.5mm) of each material were fabricated via SEPS manufacturing (Curing Time – 45 seconds/layer. 0.062mm layer thickness, 28 layers) and post-cured under UV light for 10min. Specimens were debinded at 600°C for 180min. Slurry viscosity was also measured. Samples were categorized into 4 groups (n=10 per group): A:1450°C for 120min, B:1530°C for 120min, C:1530°C for 30min, and D:1530°C for 10min, with a heating rate of 8°C/min using a Ceramill Therm 3 sintering furnace. Sintered specimens were measured with a digital micrometer. Flexural strength was tested in three-point bending at crosshead speed of 1 mm/min. Density was measured by the Archimedes method (n=10) and phase composition was determined by X-Ray diffraction.
Results: The viscosities of the 5Y and 3Y slurries at a shear rate of 1/100 were measured to be 2897.9 Pa·s and 2185.4 Pa·s, respectively One-way Welch ANOVA showed that there was no significant difference in mean flexural strength among 3Y groups (p=0.362), however there was a significant difference in mean flexural strength between 5Y sintered at 1450°C & 120min compared to 5Y sintered at 1530°C & 120min. Pairwise Welch t-tests with Holm adjustment revealed significant difference (p=0.002) between the Kruskal-Wallis followed by Dunn’s test indicated a significant difference for density between 3Y groups B and D (p=0.0326), but no significant differences between 5Y groups. 3Y samples sintered at 1450°C for 120 minutes showed significantly higher shrinkage in height compared to 3Y at 1530°C for 120 minutes. X-ray diffraction data confirmed the presence of predominantly tetragonal phase in both materials.
Conclusion: Zirconia printed via SEPS manufacturing can be sintered at a higher temperature with shorter dwell times compared to manufacturer recommendations for milled zirconia materials. X-ray diffraction and density data confirmed that different settings can be used to fully sinter 3D printed zirconia for potential dental applications.
Details
- Title: Subtitle
- Sintering effect on zirconia manufactured by suspension enclosed projection stereolithography
- Creators
- Amit Unnadkat
- Contributors
- Erica Teixeira (Advisor)Xuan Song (Committee Member)Akimasa Tsujimoto (Committee Member)Thiago Porto (Committee Member)
- Resource Type
- Thesis
- Degree Awarded
- Master of Science (MS), University of Iowa
- Degree in
- Oral Science
- Date degree season
- Spring 2023
- DOI
- 10.25820/etd.007147
- Publisher
- University of Iowa
- Number of pages
- xi, 89 pages
- Copyright
- Copyright 2023 Amit Unnadkat
- Language
- English
- Date submitted
- 04/24/2023
- Date approved
- 06/30/2023
- Description illustrations
- Illustrations, tables, graphs, charts
- Description bibliographic
- Includes bibliographical references (pages 59-66).
- Public Abstract (ETD)
A new method for 3D printing dental materials was recently developed at the University of Iowa, called suspension enclosed projection stereolithography (SEPS). This study aimed to investigate the effect of sintering time and temperature on the flexural strength and density of zirconia produced by SEPS, and to evaluate its suitability for use in dental applications.
To create the zirconia material, ceramic suspensions were prepared using zirconia powders and 3D printing resins, with varying percentages depending on the type of zirconia used. The slurries were then ball-milled and degassed before being fabricated via SEPS manufacturing. The resulting specimens were sintered at different temperatures and times and tested for flexural strength and density.
The study found that the 3D printed zirconia could be sintered at higher temperatures with shorter dwell times compared to traditional milled zirconia materials. This is significant because it suggests that the 3D printing method can produce stronger materials with less processing time. Additionally, X-ray diffraction and density data confirmed that different sintering settings can be used to fully sinter 3D printed zirconia for potential dental applications.
In summary, this study demonstrates the potential of SEPS for creating zirconia dental materials and highlights the importance of optimizing the sintering process for 3D printed materials. The findings from this study have important implications for the future of dental manufacturing and may ultimately lead to more durable and longer-lasting dental restorations.
- Academic Unit
- Oral Pathology, Radiology and Medicine
- Record Identifier
- 9984425198402771
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