scholarly journals Fracture Resistance of CAD/CAM Lithium Disilicate of Endodontically Treated Mandibular Damaged Molars Based on Different Preparation Designs

2019 ◽  
Vol 2019 ◽  
pp. 1-7 ◽  
Author(s):  
Carolina Clausson ◽  
Cristiano Clausson Schroeder ◽  
Paulo Vicenti Goloni ◽  
Flavio Artur Rego Farias ◽  
Leandro Passos ◽  
...  
Keyword(s):  
Fracture Mode ◽  
Fracture Resistance ◽  
Lithium Disilicate ◽  
Fracture Pattern ◽  
Pulp Chamber ◽  
Complete Filling ◽  
Crown Root ◽  
All Ceramic ◽  
Cad Cam ◽  
Ceramic Crowns

The aim of this study was to evaluate the fracture resistance of 2 different types of all-ceramic crown using immediate dentin sealing (IDS), obtained using a CAD/CAM system on molars with different preparations. Forty extracted lower molars were endodontically treated and divided into four groups (n = 10) according to the dental preparation. Group 1 (SP0) was prepared without filling the pulp chamber and crown-root junction was located at the cementoenamel junction (CEJ). Group 2 (SP1) was prepared without filling the pulp chamber and crown-root junction was located 1-mm above the CEJ. Groups 3 and 4 contained a flat preparation surface with no axial wall height. Group 3 (CP0) was made IDS with complete filling of the pulp chamber with composite resin and crown-root junction was located at the CEJ. Group 4 (CP1) was prepared with complete filling of the pulp chamber and crown-root junction was located 1-mm above the CEJ. All groups were restored with CAD/CAM lithium disilicate ceramic crowns. Specimens were subjected to the fracture test and statistically analyzed using analysis of variance (ANOVA). Fracture mode was determined using a stereoscopic microscope, classified as repairable or nonrepairable, and analyzed using Fischer’s exact test. Results indicated that there were no significant differences between the groups in terms of fracture resistance or fracture pattern (p >0.05). Fracture resistance was the lowest in the SP0 group, followed by the SP1 group (1634.38 N) of CP0 (1821.50 N), and it was the highest in the CP1 group. There was a predominance of nonrepairable fractures and there were no significant differences in the fracture resistance and fracture mode of CAD/CAM lithium disilicate molar all-ceramic crowns. Endodontically treated molars teeth might be restored with endocrowns or all-ceramic crowns on flat preparation; however tooth fracture failures that affect reliability of these types of restorations should be considered.

Premolar Axial Wall Height Effect on CAD/CAM Crown Retention

2016 ◽  
Vol 41 (6) ◽  
pp. 666-671 ◽  
Author(s):  
C Gillette ◽  
R Buck ◽  
N DuVall ◽  
S Cushen ◽  
M Wajdowicz ◽  
...  
Keyword(s):  
Computer Aided Design ◽  
Lithium Disilicate ◽  
Resin Cement ◽  
Failure Resistance ◽  
All Ceramic ◽  
Computer Aided ◽  
Cad Cam ◽  
Ceramic Crowns ◽  
Aided Design ◽  
Post Hoc

SUMMARY Objective: To evaluate the significance of reduced axial wall height on retention of adhesively luted, all-ceramic, lithium disilicate premolar computer-aided design/computer-aided manufacturing (CAD/CAM) crowns based on preparations with a near ideal total occlusal convergence of 10°. Methods: Forty-eight recently extracted premolars were randomly divided into four groups (n=12). Each group received all-ceramic CAD/CAM crown preparations featuring axial wall heights of 0, 1, 2, and 3 mm, respectively, all with a 10° total occlusal convergence. Scanned preparations were fitted with lithium disilicate all-ceramic crowns that were luted with a self-etching resin cement. Specimens were tested to failure at a 45° angle to the tooth long axis with failure load converted to megapascals (MPa) based on the measured bonding surface area. Mean data were analyzed using analysis of variance/Tukey's post hoc test (α=0.05). Results: Lithium disilicate crowns adhesively luted on preparations with 0 axial wall height demonstrated significantly less failure resistance compared with the crowns luted on preparations with axial wall heights of 1 to 3 mm. There was no failure stress difference between preparations with 1 to 3 mm axial wall height. Conclusions: Under conditions of this study, adhesively luted lithium disilicate bicuspid crowns with a total occlusal convergence of 10° demonstrated similar failure resistance independent of axial wall height of 1 to 3 mm. This study provides some evidence that adhesion combined with an ideal total occlusal convergence may compensate for reduced axial wall height.

scholarly journals The Tooth as a Basis for Biomimetic Design

2000 ◽  
Author(s):  
Van P. Thompson ◽  
Stephen Kao ◽  
Ivory Kirkpatrick
Keyword(s):  
High Cycle Fatigue ◽  
Critical Role ◽  
Contact Loads ◽  
All Ceramic ◽  
Cad Cam ◽  
Molar Teeth ◽  
Natural Teeth ◽  
Wide Transition ◽  
Ceramic Crowns ◽  
Improved Performance

Abstract Teeth are uniquely capable of withstanding high forces (>200 N) with small contact area (< 0.5 mm2) and a high number of fatigue cycles (> 107) with little evidence of damage. Yet the tooth is comprised of an outer very brittle, anisotropic, highly crystalline enamel layer supported by an inner soft, but tough dentin. These structures are joined by a small (appoximately 30 microns wide) transition zone called the dento-enamel junction (DEJ). The DEJ plays a critical role in transfer of stress across the layers of the tooth. How the enamel-dentin complex (EDC) comprised of these layers and the DEJ is able to withstand the high contact loads and high cycle fatigue is not well understood. An understanding of the interplay of the various components would serve as the basis for design of dental ceramic or resin based composite crowns capable of service lives approaching those on natural teeth. Current all ceramic crowns have high failure rates (1–5% per yr) on molar teeth and improved performance is required before CAD-CAM restorations can be successful.

scholarly journals Effect of Incisal Porcelain Veneering Thickness on the Fracture Resistance of CAD/CAM Zirconia All-Ceramic Anterior Crowns

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Noha Badran ◽  
Sanaa Abdel Kader ◽  
Fayza Alabbassy
Keyword(s):  
Fracture Resistance ◽  
Testing Machine ◽  
Mode Iii ◽  
Nickel Chromium ◽  
Significant Difference ◽  
All Ceramic ◽  
Metal Ceramic ◽  
Cad Cam ◽  
Ceramic Crown

Statement of Problem. In some clinical situations, the vertical length of either a prepared tooth or an implant abutment is short, while the occlusal clearance to be restored by a porcelain crown is large. Incisal thickness of the veneering porcelain should be considered to prevent mechanical failure of the crown. Purpose. The aim of this study is to evaluate the effect of two different incisal veneering porcelain thickness on the fracture resistance of the anterior all-ceramic CAD/CAM zirconia crown system as compared with the conventionally used metal ceramic crown system. Method. CAD/CAM zirconia all-ceramic and metal ceramic crowns were fabricated on the prepared dies with standardized dimensions and designs using standardized methods according to the manufacturer’s instructions. All crowns were then adhesively luted with resin-based cement (Multilink cement system), subjected to thermal cycling and cyclic loading, and were loaded until fracture using the universal testing machine to indicate the fracture resistance for each crown material in each veneering thickness. Results. Statistical analysis was carried out, and the results showed that the fracture resistance of the nickel-chromium metal ceramic group was significantly higher than that of the CAD/CAM zirconia all-ceramic group. Also, the fracture resistance of crowns with 1.5 mm incisal veneering thickness was significantly higher than those with 3 mm incisal veneering thickness in both groups. Furthermore, there was no significant difference in the fracture mode of the two groups where 50% of the total specimens demonstrated Mode II (veneer chipping), while 35% demonstrated Mode I (visible crack) and only 15% demonstrated Mode III (bulk fracture). Conclusion. High failure load values were demonstrated by the specimens in this study, which suggest sufficient strength of both incisal veneering thickness in both crown systems to withstand clinical applications; however, the fracture patterns still underline the requirement of a core design that support a consistent thickness of the veneering ceramic, and it is recommended to conduct long-term prospective clinical studies to confirm findings reported in the present study.

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