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Alshahrani AM, Lim CH, Wolff MS, Janal MN, Zhang Y. Current speed sintering and high-speed sintering protocols compromise the translucency but not strength of yttria-stabilized zirconia. Dent Mater 2024; 40:664-673. [PMID: 38378371 PMCID: PMC11015968 DOI: 10.1016/j.dental.2024.02.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Revised: 01/05/2024] [Accepted: 02/12/2024] [Indexed: 02/22/2024]
Abstract
OBJECTIVES To investigate the impacts of speed and high-speed sintering on the densification, microstructure, phase composition, translucency, and flexural strength of yttria-stabilized zirconia (YSZ). METHODS A total of 162 disc-shaped specimens (n = 18) were cold-isostatically pressed from 3YSZ (Zpex), 4YSZ (Zpex 4), and 5YSZ (Zpex Smile) powders (Tosoh Corporation) and sintered according to the following protocols: conventional (control, ∼12 h), speed (∼28 min for 3YSZ; ∼60 min for 4YSZ and 5YSZ), and high-speed (∼18 min) sintering. Dimensions of zirconia specimens after sintering and polishing (1-μm diamond grit finish) were Ø13.75 × 1 mm. Density, microstructure, phase content, translucency parameter, and biaxial flexural strength were evaluated using Archimedes', SEM, XRD, spectrophotometric, and piston-on-3-ball methods, respectively. Data were analyzed with either one-way ANOVA and Tukey's test or Kruskal-Wallis with Dunn's test (α = 0.05). RESULTS For all YSZ compositions, conventional sintering yielded the highest density followed by speed then high-speed sintering. All sintering protocols resulted in similar strength values; however, speed and high-speed sintering protocols afforded significantly lower translucency relative to conventional sintering. XRD analysis revealed similar spectra for YSZs sintered by various protocols. The speed sintered specimens had the smallest grain size whereas the high-speed sintered 5YSZ possessed the largest grain size among all groups. SEM examination of all YSZ compositions revealed that the average pore size was an order of magnitude smaller than the average grain size. SIGNIFICANCE Speed and high-speed sintering of YSZs yield similar strength but diminished density and translucency relative to their conventionally sintered counterparts.
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Affiliation(s)
- Abdulaziz M Alshahrani
- Laboratories for Microstructure Physics & Mechanics of Materials, Department of Preventive and Restorative Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Restorative Dental Sciences, College of Dentistry, King Khalid University, Abha, Saudi Arabia
| | - Chek Hai Lim
- Laboratories for Microstructure Physics & Mechanics of Materials, Department of Preventive and Restorative Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Mark S Wolff
- Morton Amsterdam Dean, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Malvin N Janal
- Department of Epidemiology & Health Promotion, New York University College of Dentistry, New York, NY 10010, USA
| | - Yu Zhang
- Laboratories for Microstructure Physics & Mechanics of Materials, Department of Preventive and Restorative Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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Hajjaj MS, Alamoudi RAA, Babeer WA, Rizg WY, Basalah AA, Alzahrani SJ, Yeslam HE. Flexural strength, flexural modulus and microhardness of milled vs. fused deposition modeling printed Zirconia; effect of conventional vs. speed sintering. BMC Oral Health 2024; 24:38. [PMID: 38185744 PMCID: PMC10771678 DOI: 10.1186/s12903-023-03829-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 12/26/2023] [Indexed: 01/09/2024] Open
Abstract
BACKGROUND Various methods can be used for creating zirconia dental restorations, including 3-dimensional (3D) printing and computer-aided design/ computer-aided manufacturing (CAD/CAM) milling. The fused deposition modeling (FDM) printing method for zirconia presents numerous advantages, albeit research on the mechanical properties of these materials and resultant restorations remains scarce. Such developments are undeniably intriguing and warrant further investigation. The objective of the present study was to evaluate the impact of the sintering firing cycle (Conventional vs. Speed sintering) on the flexural strength, flexural modulus, and Vickers Microhardness of milled vs. FDM printed zirconia. METHODS A total of 60 bars (2 × 5 × 27 mm) were fabricated for flexural strength testing, along with 40 discs (12 × 1.5 mm) for Vickers microhardness testing. Half of the specimens underwent conventional sintering, while the other half underwent a speed sintering cycle. The flexural strength and modulus were determined by a three-point bending test in a universal testing machine. The microhardness of the specimens was evaluated using a Vickers microhardness tester. Statistical analysis was performed using a two-way ANOVA test with a post-hoc Tukey test (p < 0.05). RESULTS CAD/CAM milled zirconia had significantly higher flexural strength and modulus than FDM-printed zirconia. The sintering process did not significantly affect the flexural strength or modulus of milled or FDM-printed zirconia. The milled speed sintering group had significantly higher values in the Vickers microhardness test compared to the other groups. CONCLUSIONS The mechanical properties of FDM-printed zirconia specimens were not found to be comparable to those of milled zirconia. Speed sintering cycle may produce milled zirconia restorations with similar flexural strength and modulus to conventional sintering, and even higher Vickers Microhardness values.
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Affiliation(s)
- Maher S Hajjaj
- Department of Restorative Dentistry, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia.
- Advanced Technology Dental Research Laboratory, King Abdulaziz University, P.O. Box 80209, Jeddah, 21589, Saudi Arabia.
| | - Rana A A Alamoudi
- Prosthodontic Master Student, Department of Oral and Maxillofacial Rehabilitation, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Walaa A Babeer
- Department of Oral and Maxillofacial Rehabilitation, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Waleed Y Rizg
- Department of Pharmaceutics, Faculty of Pharmacy, King Abdulaziz University, Jeddah, 21589, Saudi Arabia
- Center of Innovation in Personalized Medicine (CIPM), 3D Bioprinting Unit, King Abdulaziz University, Jeddah, 21589, Saudi Arabia
| | - Ahmad A Basalah
- Mechanical Engineering Department, College of Engineering and Architecture, Umm Al Qura University, Makkah, Saudi Arabia
| | - Saeed J Alzahrani
- Department of Restorative Dentistry, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Hanin E Yeslam
- Department of Restorative Dentistry, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia
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Wallum AJ, Raimondi C, Lien W, Hoopes WL, Vandewalle KS. Effect of Milling Speed on the Properties of Zirconia Restorations. J Clin Exp Dent 2024; 16:e84-e89. [PMID: 38314345 PMCID: PMC10837798 DOI: 10.4317/jced.61231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2023] [Accepted: 12/18/2023] [Indexed: 02/06/2024] Open
Abstract
Background The purpose of this study was to evaluate the effect of milling speed on the surface roughness, marginal gap, marginal gap volume, marginal offset, and fracture load of zirconia restorations. Material and Methods A mandibular molar #30 typodont tooth was digitally scanned and an ideal crown preparation for a zirconia restoration was digitally created. A single master model die of the crown preparation was milled out of a resin material. The master die was scanned, and a final restoration was designed using the bio-copy feature of the typodont tooth. Ten zirconia restorations were milled (CEREC Primemill, Dentsply Sirona) per each of three milling speeds (super-fast, fine, and extra-fine), sintered, and seated on the master die. Surface roughness, marginal gap, marginal gap volume, and marginal offset were measured using a non-contact profilometer. Then, all restorations were cemented to the dies and loaded to failure in a material testing device. Data were analyzed with one-way ANOVA and Tukey's post hoc tests per property (alpha=0.05). Results Super-fast milling speed resulted in restorations with statistically significant greater surface roughness and marginal gap volume compared to fine and extra-fine milling speeds. No significant difference in marginal gap, marginal offset, and fracture load were found based on milling speed. Conclusions Zirconia restorations milled at slower speeds may result in similar or slightly better properties compared to super-fast speed. Key words:Milling speed, properties, zirconia restorations.
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Affiliation(s)
- Adam J Wallum
- DMD, MS. Maj, USAF, DC. Director, Restorative Dentistry Advanced Education in General Dentistry Residency. AF Postgraduate Dental School. 1615 Truemper St Joint Base San Antonio - Lackland, TX, USA 78236. Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Christopher Raimondi
- DDS, MS, MS. Lt Col, USAF, DC. Co-Director of Dental Materials Research. USAF Dental Research and Consultation Service. 3650 Chambers Pass, Bldg 3610. Joint Base San Antonio - Fort Sam Houston, TX, USA 78234. Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Wen Lien
- DMD, MS, MS. Col (ret), USAF, DC. Former Director of Dental Materials Research. USAF Dental Research and Consultation Service. 3650 Chambers Pass, Bldg 3610. Joint Base San Antonio - Fort Sam Houston, TX, USA, 78234. Uniformed Services University of the Health Sciences, Bethesda, MD, 20814, USA
| | - Wyeth L Hoopes
- DDS, MS. Lt Col, USAF, DC. Program Director. Advanced Education in General Dentistry Residency. 4102 Pinion Drive. US Air Force Academy, CO, USA 80840. Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Kraig S Vandewalle
- DDS, MS. Col (ret), USAF, DC. Air Force Consultant in Dental Research. Advanced Education in General Dentistry Residency. AF Postgraduate Dental School. 1615 Truemper St. Joint Base San Antonio - Lackland, TX, USA 78236. Uniformed Services University of the Health Sciences, Bethesda, MD, USA
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Lee S, Choi G, Choi J, Kim Y, Kim HK. Effect of high-speed sintering on the marginal and internal fit of CAD/CAM-fabricated monolithic zirconia crowns. Sci Rep 2023; 13:17215. [PMID: 37821643 PMCID: PMC10567905 DOI: 10.1038/s41598-023-44587-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 10/10/2023] [Indexed: 10/13/2023] Open
Abstract
This study compared the marginal and internal fit of zirconia crowns fabricated using conventional and high-speed induction sintering. A typodont mandibular right first molar was prepared and 60 zirconia crowns were fabricated: 30 crowns using conventional sintering and 30 crowns using high-speed sintering. We presented a new evaluation methodology to measure the marginal and internal fit of restorations through digital scanning, aligning the two datasets, and measuring the distance between two arbitrary point sets of the datasets. For the marginal fit, we calculated the maximum values of the shortest distances between the marginal line of the prepared tooth and that of the crown. The calculated values ranged from 359 to 444 μm, with smaller values for the high-speed sintered crowns (P < 0.05). For the internal fit, we employed mesh sampling and computed the geodesic distances between the prepared tooth surface and the crown intaglio surface. The measured values ranged from 177 to 229 μm with smaller values for the high-speed sintered crowns, but no significant difference was found (P > 0.05). Based on our results, the high-speed sintering method can be considered a promising option for single-visit zirconia treatment in dental practice.
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Affiliation(s)
- Seulgi Lee
- Department of Dental Public Health, Graduate School of Clinical Dentistry, Ajou University, Suwon, Republic of Korea
| | | | | | | | - Hee-Kyung Kim
- Department of Prosthodontics, Institute of Oral Health Science, Ajou University School of Medicine, Suwon, Republic of Korea.
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Cho MH, Seol HJ. Effect of High-Speed Sintering on the Optical Properties, Microstructure, and Phase Distribution of Multilayered Zirconia Stabilized with 5 mol% Yttria. MATERIALS (BASEL, SWITZERLAND) 2023; 16:5570. [PMID: 37629861 PMCID: PMC10456241 DOI: 10.3390/ma16165570] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2023] [Revised: 07/28/2023] [Accepted: 08/03/2023] [Indexed: 08/27/2023]
Abstract
As dental 5 mol% yttria-stabilized (5Y-) zirconia demand high esthetics, it is necessary to clarify how the optical properties are affected by high-speed sintering, which is not yet fully understood. Our study aimed to investigate the effect of high-speed sintering on the translucency and opalescence parameters (TP and OP, respectively), as well as their related microstructure and phase distribution, using two types of multilayered 5Y-zirconia. Multilayered 5Y-zirconia (Cercon xt ML, Lava Esthetic) were cut layer-by-layer, followed by conventional and high-speed sintering. The TP and OP values were subsequently obtained using a spectrophotometer, and field emission scanning electron microscopy images were used to analyze the average grain size. The phase fractions were analyzed using X-ray diffraction. Regardless of the zirconia type, the TP was slightly lowered by high-speed sintering in all the layers except the dentin layer (DL) for Lava Esthetic (p < 0.05). The OP decreased by high-speed sintering in the DL for Cercon xt ML and in all the layers for Lava Esthetic (p < 0.05). The decrease in translucency after high-speed sintering was attributed to a decrease in the yttria-rich t'-phase with low tetragonality, along with an increase in the yttria-lean t-phase with high tetragonality.
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Affiliation(s)
- Mi-Hyang Cho
- Department of Dental Lab, Wonkwang Health Science University, Iksan-si 54538, Republic of Korea;
| | - Hyo-Joung Seol
- Department of Dental Materials, Dental and Life Science Institute, School of Dentistry, Pusan National University, Yangsan-si 50612, Republic of Korea
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El-Farag SAA, Elerian FA, Elsherbiny AA, Abbas MH. Impact of different CAD/CAM materials on internal and marginal adaptations and fracture resistance of endocrown restorations with: 3D finite element analysis. BMC Oral Health 2023; 23:421. [PMID: 37357307 DOI: 10.1186/s12903-023-03114-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Accepted: 06/06/2023] [Indexed: 06/27/2023] Open
Abstract
PURPOSE To assess and compare the impact of various computers aided design/manufacturing (CAD/CAM) materials on internal and marginal discrepancies, fracture resistance and failure probability of Endocrown restorations with 3D Finite Element analysis. MATERIAL AND METHODS Forty devitalized human maxillary first molars were collected. After endodontic treatment, they classified into 4 groups (n = 10) based on the materials used for endocrown fabrication. Group V (Vita-Enamic), Group N (Nacera Hybrid), Group T (Translucent Prettau Zirconia) and Group P (Pekkton ivory). All samples were exposed to artificial aging method simulating one year of clinical service. Silicone replica technique and stereomicroscope (25X) utilized to evaluate the marginal and internal gaps of endocrowns at different areas. Fracture resistance test used for cemented specimens followed by qualitative investigation utilizing Stereomicroscopy. Four models representing four endocrown systems used for restoration of severely-damaged endodontically treated upper first molar were generated for finite element analysis (FEA). Axially and centrally static occlusal compressive load was applied. Modified Von Mises and maximum principal stress values on the remaining tooth structure, cement lines and restorative materials were assessed independently. Resulted data were statistically analyzed at P-value ≤ 0.05. RESULTS In the current study, the highest mean values of internal and marginal discrepancies (μm) among studied groups were reported for Zirconia group (100.300 and 102.650) respectively, while the lowest mean value of internal discrepancy (μm) was observed for Nacera group (69.275) and the lowest mean value of marginal discrepancy (μm) was observed for PEKK group (78.4750). Regarding internal discrepancy, Vita-Enamic and PEKK groups did not exhibit any statistically significant differences (P = 0.293), however zirconia and the other tested groups exhibited statistically significant differences in the mean values of the marginal gap region (p 0.05).On the other hand, PEKK group showed the highest mean value of fracture resistance (1845.20 N) and the lowest value was observed for Vita-Enamic group (946.50 N). Regarding to stress distributions through 3D FEA, and according to modified von Mises (mvM) analysis, the greatest possible stress values were noticed in PEKK model in relation to tooth structure, cement line, and flowable composite as the following: (93.1, 64.5, 58.4 MPa) respectively, while Zirconia revealed lower maximum stress values (11.4, 13.6, 11.6 MPa) respectively. CONCLUSIONS Statistically excellent marginal and internal fit was observed for PEKK in relation to other used endocrown materials. Also, PEKK material explained fracture resistance comparable to zirconia value while the lowest value was detected for Vita Enamic material.
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Affiliation(s)
- Shaimaa Ahmed Abo El-Farag
- Fixed Prosthodontics Department, Faculty of Dentistry, Mansoura University and Horus University (HUE), Mansoura, Egypt
| | - Fatma Abdallah Elerian
- Production and Mechanical Design Department, Faculty of Engineering, Mansoura University, Mansoura, 35516, Egypt
| | - Abdallah Ahmed Elsherbiny
- Production and Mechanical Design Department, Faculty of Engineering, Mansoura University, Mansoura, 35516, Egypt
| | - Mahy Hassouna Abbas
- Fixed Prosthodontics Department, Faculty of Dentistry, Mansoura University and Delta University for Science and Technology, Mansoura, Egypt.
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Alshahrani AM, Lim CH, Kim J, Zhang Y. Transient thermal stresses developed during speed sintering of 3 mol% yttria-stabilized tetragonal zirconia polycrystals. Dent Mater 2023; 39:522-528. [PMID: 37045719 PMCID: PMC10168597 DOI: 10.1016/j.dental.2023.04.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 04/05/2023] [Indexed: 04/14/2023]
Abstract
OBJECTIVES To investigate transient thermal stresses that developed in 3Y-TZP green compacts during speed sintering. METHODS A total of 312 disc-shaped green compacts (Ø17.1 ×1, 1.5, 2, 2.5, 3 mm) were cold-isostatically pressed from 3Y-TZP powder (Zpex, Tosoh Corp.) for speed sintering studies as well as compositional analysis and biaxial flexural strength measurements (both at room temperature and following heating at 90 °C/min to 500 °C). Flexural strength was determined using the piston-on-3-ball method. Phase assemblies were analyzed using the X-ray diffraction method. Effects of heating/cooling rates on transient stresses were investigated by conducting definitive sintering studies to determine the threshold for fracture. Finite element analysis (FEA) was used to validate the experimental findings using measured thermomechanical properties. RESULTS The bulk and relative density of the green compact were 2.95 ± 0.03 g/cm3 and 48.52% ± 0.45%. The flexural strength was drastically decreased from 10.3 ± 0.4 MPa to 1.09 ± 0.07 MPa following heating at 90 °C/min to 500 °C. The monoclinic and tetragonal contents were 54.9% and 45.1%, respectively. The threshold for fracture was located at 500 °C during the first heating stage with a 90 °C/min heating rate in specimens of 2.5 mm thickness or greater. No fractures occurred in the second heating stage and cooling phase. The FEA estimated that the principal transient tensile stress was ∼1.14 MPa at 500 °C during the heating phase, which exceeded the corresponding flexural strength (1.09 ± 0.07 MPa). SIGNIFICANCE Advanced FEA methods are an accurate and efficient tool to analyze the history of transient stresses during sintering of ceramic dental restorations.
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Affiliation(s)
- Abdulaziz M Alshahrani
- Department of Preventive and Restorative Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Department of Restorative Dental Sciences, College of Dentistry, King Khalid University, Abha, Saudi Arabia
| | - Chek Hai Lim
- Department of Preventive and Restorative Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Jeongho Kim
- Department of Civil and Environmental Engineering, University of Connecticut, 261 Glenbrook Rd, U-3037, Storrs, CT 06269, USA
| | - Yu Zhang
- Department of Preventive and Restorative Sciences, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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