Fracture load and phase transformation in monolithic zirconia crowns submitted to hydrothermal or mechanical treatments

2015 ◽  
Author(s):  
Edmara Tatiely Pedroso Bergamo
Keyword(s):  
Phase Transformation ◽  
Fracture Load ◽  
Zirconia Crowns ◽  
Monolithic Zirconia

scholarly journals Fracture Load and Phase Transformation of Monolithic Zirconia Crowns Submitted to Different Aging Protocols

2016 ◽  
Vol 41 (5) ◽  
pp. E118-E130 ◽  
Author(s):  
ETP Bergamo ◽  
WJ da Silva ◽  
PF Cesar ◽  
AA Del Bel Cury
Keyword(s):  
Phase Transformation ◽  
Thermal Fatigue ◽  
Structural Reliability ◽  
Contact Point ◽  
Testing Machine ◽  
Fracture Load ◽  
Hydrothermal Aging ◽  
High Fracture ◽  
Zirconia Crowns ◽  
Monolithic Zirconia

SUMMARY Monolithic zirconia crowns have many favorable properties and may potentially be used to solve dental problems such as chipping. However, monolithic zirconia crown resistance can be affected by its phase transformation when subjected to low temperatures, humidity, and stress. This study evaluated the fracture load and phase transformation of monolithic zirconia crowns submitted to different thermal and mechanical aging tests. Seventy monolithic zirconia crowns were randomly divided into the following five groups: control, no treatment; hydrothermal aging at 122°C, two bar for one hour; thermal fatigue, 104 cycles between 5°C and 55°C, dwell time, 30 seconds; and mechanical fatigue, 106 cycles with a load of 70 N, sliding of 1.5 mm at 1.4 Hz; and combination of mechanical plus thermal fatigue. Fracture load was measured with a universal testing machine. Surface changes and fracture mode and origin were examined with a scanning electron microscope. Monoclinic phase content was evaluated by x-ray diffraction. The fracture load was analyzed using one-way analysis of variance at a level of 5%, and Weibull distribution was performed. No statistically significant differences were observed in the mean fracture load and characteristic fracture load among the groups (p>0.05). The Weibull modulus ranged from 6.2 to 16.6. The failure mode was similar for all groups with the crack origin located at the contact point of the indenter. Phase transformation was shown at different surfaces of the crown in all groups (1.9% to 8.9%). In conclusion, monolithic zirconia crowns possess high fracture load, structural reliability, and low phase transformation.

scholarly journals Effect of Marginal Designs on Fracture Strength of High Translucency Monolithic Zirconia Crowns

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Niwut Juntavee ◽  
Sasiprapa Kornrum
Keyword(s):  
Bearing Capacity ◽  
Testing Machine ◽  
Fracture Load ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Two Factors ◽  
Zirconia Crowns ◽  
Monolithic Zirconia ◽  
Bonferroni Test ◽  
Inclined Planes

Introduction. Monolithic zirconia is able to achieve certain aesthetic, but its durability in resisting fracture has been questioned, as fractures often originate from margins of restoration. This study determined fracture resistance of highly translucent monolithic zirconia crowns with different margin designs in terms of marginal thickness and collar height. Materials and Methods. Zirconia blanks (Ceramill® Zolid HT+) were selected for the fabrication of zirconia crowns according to different designs, including varying margin thicknesses (light chamfer, CL; heavy chamfer, CH) and collar heights (no collar, NC; low collar, LC; high collar, HC), which resulted in CLNC, CLLC, CLHC, CHNC, CHLC, and CHHC groups (15 crowns each). The crowns were seated on a metal die and loaded vertically through round end punch (θ = 10 mm), contacting with inclined planes of cusp in a testing machine with crosshead speed of 0.2 mm/min until fracture. Videos with a rate of 50 frames/second were used to record fracture. Fracture load (N) and durable period (s) were compared for significant differences using ANOVA and Bonferroni test (α = 0.05). Results. The mean ± sd of fracture load (N) and durable time (s) were 3211 ± 778 and 212 ± 47 for CLNC; 3041 ± 1370 and 188 ± 53 for CLLC; 2913 ± 828 and 192 ± 27 for CLHC; 4226 ± 905 and 245 ± 35 for CHNC; 4486 ± 807 and 228 ± 29 for CHLC; and 4376 ± 1043 and 227 ± 37 for CHHC. This indicated that marginal thickness had a significant influence on load-bearing capacity and durable time (p<0.05). No significant impact of collar height was shown, either on load-bearing capacity or durable time (p>0.05). No interaction between two factors was presented (p>0.05). Conclusions. Heavy chamfer margin provided stronger zirconia crown than light chamfer, but both were capable of withstanding fracture load higher than maximum masticatory force. Neither presence nor absence of collar indicated any impact on strength. Fabrication of zirconia crowns with either heavy or light chamfer margin and either presence or absence of collar, with the consideration of emergence profile, should be considered.

scholarly journals Effect of Reduced Occlusal Thickness with Two Margin Designs on Fracture Resistance of Monolithic Zirconia Crowns

2020 ◽  
Vol 14 (02) ◽  
pp. 245-249
Author(s):  
Haider Hasan Jasim ◽  
Meelad Basil Findakly ◽  
Nada Ali Mahdi ◽  
Mustafa Tariq Mutar
Keyword(s):  
Fracture Resistance ◽  
Testing Machine ◽  
Three Dimensional ◽  
Fracture Load ◽  
Anova Test ◽  
Optical Scanner ◽  
Nickel Chromium ◽  
Significant Difference ◽  
Zirconia Crowns ◽  
Monolithic Zirconia

Abstract Objectives The aim of this study was to compare the effects of two margin designs (shoulderless and slight chamfer) with two occlusal thicknesses on fracture resistance and failure mode of the monolithic zirconia crowns. Materials and Methods Forty nickel–chromium dies were duplicated from the previous two prepared teeth using a three-dimensional optical scanner. Nickel–chromium supporting dies were divided into two main groups (n = 20) according to the type of margin design: group A, slight chamfer margin design and group B, shoulderless margin design. These groups were further divided into two subgroups according to the occlusal thicknesses (0.5 and 1 mm). The digital imaging of each die was done using a three-dimensional optical scanner, then zirconia blocks were milled by 5-axis machine. The crowns were cleaned by alcohol, air dried, and cemented by resin cement. Next, the crowns were subjected to 500 hot and cold cycles (30 seconds for each cycle). The samples were subjected to a static load until failure using an electronic universal testing machine and fracture resistance was recorded in Newton (N). Statistical Analysis Data were analyzed using the test of normality (Shapiro–Wilk test) and two-way analysis of variance (ANOVA) test. Results  The highest mean fracture load was recorded by the shoulderless (1 mm occlusal thickness) subgroup (3,992.5 N), followed by shoulderless (0.5 mm occlusal thickness) subgroup (3,244.4 N), and the slight chamfer (1 mm occlusal thickness) subgroup (2,811 N). The lowest mean of fracture load was recorded by slight chamfer (0.5 mm occlusal thickness) subgroup (1,632.9 N). The two-way ANOVA test revealed a significant difference between the four subgroups. Regarding the fracture mode, the slight chamfer subgroups showed a severe fracture of the restoration while the shoulderless subgroups showed a fracture through the midline of the restoration. Conclusion Within the limitation of the comparative study, shoulderless margin design has a more favorable outcome than a slight chamfer design in all thicknesses. Although the restoration with reduced occlusal thickness has lower fracture resistance than 1 mm occlusal thickness, the 0.5 mm restorations still can tolerate occlusal forces.

scholarly journals Effect of occlusal groove on abutment, crown thickness, and cement-type on fracture load of monolithic zirconia crowns

2018 ◽  
Vol 37 (5) ◽  
pp. 843-850 ◽  
Author(s):  
Yu TSUYUKI ◽  
Toru SATO ◽  
Syuntaro NOMOTO ◽  
Mamoru YOTSUYA ◽  
Teruyoshi KOSHIHARA ◽  
...  
Keyword(s):  
Fracture Load ◽  
Cement Type ◽  
Zirconia Crowns ◽  
Monolithic Zirconia

scholarly journals Fracture Strength of Monolithic Zirconia Crowns with Modified Vertical Preparation: A Comparative In Vitro Study

2021 ◽  
Author(s):  
Marwah Ismael Abdulazeez ◽  
Manhal A. Majeed
Keyword(s):  
Fracture Strength ◽  
In Vitro Study ◽  
Fracture Load ◽  
Significant Difference ◽  
Zirconia Crowns ◽  
Group A ◽  
Monolithic Zirconia ◽  
Bonferroni Test ◽  
Group B

Abstract Objective The aim of this study was to evaluate the influence of different marginal designs (deep chamfer, vertical, and modified vertical with reverse shoulder) on the fracture strength and failure modes of monolithic zirconia crowns. Materials and Methods Thirty sound human maxillary first premolar teeth with comparable size were used in this study. The teeth were divided randomly into three groups according to the preparation design (n = 10): (1) group A: teeth prepared with a deep chamfer finish line; (2) group B: teeth prepared with vertical preparation; and (3) group C: teeth prepared with modified vertical preparation, where a reverse shoulder of 1 mm was placed on the buccal surface at the junction of middle and occlusal thirds. All samples were scanned by using an intraoral scanner (CEREC Omnicam, Sirona, Germany), and then the crowns were designed by using Sirona InLab 20.0 software and milled with a 5-axis machine. Each crown was then cemented on its respective tooth with self-adhesive resin cement by using a custom-made cementation device. A single load to failure test was used to assess the fracture load of each crown by using a computerized universal testing machine that automatically recorded the fracture load of each sample in Newton (N). Statistical Analysis The data were analyzed statistically by using one-way analysis of variance test and Bonferroni test at a level of significance of 0.05. Results The highest mean of fracture load was recorded by chamfer (2,969.8 N), which followed by modified vertical (2,899.3 N) and the lowest mean of fracture load was recorded by vertical (2,717.9 N). One-way ANOVA test revealed a significant difference among the three groups. Bonferroni test showed a significant difference between group A and group B, while a nonsignificant difference was revealed between group C with group A and group B. Conclusion Within the limitations of this in vitro study, the mean values of fracture strength of monolithic zirconia crowns of all groups were higher than the maximum occlusal forces in the premolar region. The modification of the vertical preparation with a reverse shoulder placed at the buccal surface improved the fracture strength up to the point that it was statistically nonsignificant with the chamfer group.

Influence of CAD/CAM Fabrication and Sintering Procedures on the Fracture Load of Full-Contour Monolithic Zirconia Crowns as a Function of Material Thickness

2020 ◽  
Vol 45 (2) ◽  
pp. 219-226 ◽  
Author(s):  
M Zimmermann ◽  
A Ender ◽  
A Mehl
Keyword(s):  
Computer Aided Design ◽  
Mean Value ◽  
Fracture Load ◽  
Significance Level ◽  
Material Thickness ◽  
Computer Aided ◽  
Cad Cam ◽  
Zirconia Crowns ◽  
Monolithic Zirconia

Summary Objective: The purpose of this in vitro study was to analyze the effect of computer-aided design/computer-aided manufacturing (CAD/CAM) fabrication and sintering procedures on the fracture load of monolithic zirconia crowns with different material thicknesses adhesively seated to methacrylate dies fabricated with stereolithography technology. Method: Monolithic zirconia crowns were fabricated from inCoris TZI C material with a chairside CAD/CAM system (CEREC MCXL) comprising three material thicknesses (0.5/1.0/1.5 mm, n=8 each). Two CAD/CAM fabrication procedures (milling, MI; grinding, GR), two chairside sintering procedures (superspeed, SS; speedfire sintering, SF), and one labside sintering procedure (classic, CL) were evaluated. In total, 144 crowns were fabricated. Restorations were adhesively seated to methacrylate dies fabricated with SLA technology. Thermomechanical cycling (TCML) was performed before fracture testing. Loading forces until fracture were registered and statistically analyzed with one-way analysis of variance (ANOVA), post hoc Scheffé test, and three-way ANOVA (α=0.05). Results: Test groups showed statistically significant differences (p&lt;0.05). The highest mean value was found for 1.5-mm crowns of group GR_SF with 3678.6 ± 363.9 N. The lowest mean value was found for group 0.5-mm crowns of group MI_SF with 382.4 ± 30.7 N. There was a significant three-way interaction effect between thickness, sintering, and processing [F(4,126)=9.542; p&lt;0.001; three-way ANOVA, significance level α=0.05]. Conclusions: CAD/CAM fabrication and sintering procedures influence the maximum loading force of monolithic zirconia crowns with different material thicknesses. A material thickness of 0.5 mm should be considered as a critical thickness for monolithic zirconia crown restorations.

scholarly journals Quantitative analysis on the wear of monolithic zirconia crowns on antagonist teeth

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Zhenyu Tang ◽  
Xinyi Zhao ◽  
Hui Wang
Keyword(s):  
Epoxy Resin ◽  
Tetragonal Zirconia ◽  
Fatigue Wear ◽  
Posterior Teeth ◽  
Contact Points ◽  
Significant Difference ◽  
Zirconia Crowns ◽  
Natural Teeth ◽  
Monolithic Zirconia

Abstract Background The present study aimed to quantitate the wear of the highly transparent Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) ceramic monolithic zirconia crown on the enamel in vivo and discuss the prone position of the wear and the underlying mechanism. Methods A total of 43 patients with 43 posterior teeth were selected for full zirconia crown restoration and examined immediately, at 6 months, and at 1 year after restoration. During the follow-up visit, the fine impression of the patients’ monolithic zirconia crowns, the antagonist teeth, the corresponding contralateral natural teeth, the super plaster cast, and epoxy resin model was ontained. The model of epoxy resin was observed under a stereo microscope, and the microstructure parts were observed under a scanning electron microscope. Results After 1 year, the mean depth and volume of wearing of the monolithic zirconia crown were the smallest (all P < 0.01), while those of the antagonist teeth were significantly larger than those of the natural teeth (P < 0.0001), and no significant difference was found among the natural teeth (P = 0.3473, P = 0.6996). The amount of wear after one year was remarkably higher than that at 6 months (P < 0.0001). The microscopic observation revealed the tendency of wearing of the monolithic zirconia crown on the antagonist teeth at the protruding early contact points. Electron micrographs of tooth scars showed that the wearing mechanism of the monolithic zirconia crown on natural teeth was mainly abrasive and fatigue wear. Conclusions Although the self-wearing is insignificant, the monolithic zirconia crown can cause wear of the antagonist teeth via occlusal or early contact significantly; the amount of wearing is higher than that of natural teeth and increases over time. The wearing mechanism is mainly abrasive and fatigue wear.

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