Thesis
Evaluation of fracture resistance of bonded and luted zirconia crowns with varying occlusal thicknesses after the endodontic access preparation
University of Iowa
Master of Science (MS), University of Iowa
Spring 2023
DOI: 10.25820/etd.007248
Abstract
Objective: Endodontic access preparation after crown cementation potentially affects the resistance of all-ceramic crowns. This study evaluated the effect of crown occlusal thickness, cement type, and endodontic access on the fracture resistance of full-contour zirconia crowns (Cercon HT, Dentsply Sirona) containing 3 mol% yttria (3Y).Methods: One hundred and twenty extracted molars were prepared, scanned and a crown was designed in 3 Shape CAD software with different occlusal thicknesses of 1.0 mm, 1.5mm, and 2.0 mm. Crowns were milled (Ceramill motion 2, Amann Girrbach) and sintered in the furnace (Lab Profire, Dentsply Sirona) using the manufacturer’s recommended sintering cycle. Crowns were cemented using, either a Resin-Modified Glass Ionomer cement (RelyX Luting Plus) or a resin cement (PanaviaV5), then submitted to thermocycling test (5,000 cycles, 5-55°C). An endodontic access was prepared under the microscope on half of the specimens (n=60). The endodontic accesses were restored with resin composite (Filtek Supreme Ultra, 3M ESPE). All samples underwent a fracture resistance test. Fracture load was measured as the maximum load until fracture in Newton (N).
Results: Predicting clinical performance of zirconia crowns and thickness selection is important for long term results. Larger occlusal thicknesses require more fracture force with a p-value of 0.006. Furthermore, when the occlusal thickness increased from 1mm to 2mm thickness, the force at fracture increased by 1582.75 N. and the p-value was <0.001. When the tooth changed from not having an endodontic access to having an endodontic access, the interaction of the force at fracture was decreased by 1264.50 N with a statistical significant p-value of 0.017. Catastrophic failure by force and cement type showed a relationship between force and cement type. Catastrophic failure with Panavia was higher than with Rely X Luting by proportions of mode of fracture IV. Furthermore, the teeth luted with Panavia, showed odds of catastrophic failure by 195% compared to Rely X cement with a significant p-value = 0.032. The higher catastrophic failure with Panavia signifies that Panvaia better withstood the force. Results demonstrate a rejected null hypotheses. T-tests against null hypotheses of no effect indicate significant main effects of the thickness and endodontic access. Increased occlusal thickness increases fracture force and presence of endodontic access decreased fracture force.
Conclusion: Design and selection of occlusal thickness influence the strength of zirconia crowns. After endodontic treatment, the zirconia material potentially suffers long-term drawbacks by potentially yielding clinically relevant fractures and failure.
Details
- Title: Subtitle
- Evaluation of fracture resistance of bonded and luted zirconia crowns with varying occlusal thicknesses after the endodontic access preparation
- Creators
- Maria Teresa Rosas Diaz
- Contributors
- Terry Lindquist (Advisor)Erica Teixeira (Advisor)Tarek El Kerdani (Committee Member)Manuel M Gómez (Committee Member)Erliang E Zeng (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.007248
- Publisher
- University of Iowa
- Number of pages
- xi, 83 pages
- Copyright
- Copyright 2023 Maria Teresa Rosas Diaz
- Language
- English
- Date submitted
- 04/24/2023
- Date approved
- 06/30/2023
- Description illustrations
- color illustrations
- Description bibliographic
- Includes bibliographical references (pages 78-83).
- Public Abstract (ETD)
Objective: Approximately 15% of natural teeth receiving full zirconia crown coverage present pulp vitality changes and root canal complications. Endodontic access produce residual stress during access preparation due to poor heat conduction of zirconia and cracking susceptibility. Alterations during endodontic access opening in all-ceramic crowns have shown edge chipping around access openings and radial crack formation. . This study evaluated the effect of crown occlusal thickness, cement type, and endodontic access on the fracture resistance of full-contour zirconia crowns (Cercon HT, Dentsply Sirona) containing 3 mol% yttria (3Y).
Methods: 120 extracted molars were prepared, scanned and designed in 3D Shape CAD software with different occlusal thicknesses of 1.0 mm, 1.5 mm and 2.0 mm. Crowns were wet milled using zirconia containing 3 mol% yttria (3Y Ceramill) then cemented using Resin Modified Glass Ionomer (Relyx) and Resin-based (Panavia). Thermo-cycling test (5,000 cycles, 5°C-55°C) confirmed lifecycle aging. The endodontic accesses were restored with resin composite (Filtek Supreme Ultra, 3M ESPE). All samples were tested in Universal testing machine. Fracture load was measured at the maximum load until catastrophic fracture; calculated in Newtons (N).
Results: Predicting clinical performance of zirconia crowns and thickness selection is important for long term results. Larger occlusal thicknesses required more fracture force with a p-value of 0.006. When the tooth changed from not having an endodontic access to having an endodontic access, the interaction of the force at fracture was decreased by 1264.50 N with a statistical significant p-value of 0.017.
Conclusion: Design and selection of occlusal thickness influence the strength of zirconia crowns. After endodontic treatment, the zirconia material potentially suffers long-term drawbacks by potentially yielding clinically relevant fractures and failure.
- Academic Unit
- Oral Pathology, Radiology and Medicine
- Record Identifier
- 9984424790502771
Metrics
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