The Effect of Different Occlusal Preparation Designs on the Fracture Resistance of two All–Ceramic Crowns Restoring Endodontically Treated Teeth
Mostafa Ahmed Mahmoud Khalaf;
Abstract
This study was designed to evaluate the effect of different occlusal preparation designs on the fracture resistance of two All - Ceramic crowns restoring endodontically treated teeth
Thirtynatural sound lower first molars of the same size were endodontically treated then prepared with the same criteria except for the occlusal surface using CNC machine.
Flat occlusal preparation was performed on ten samples, another ten samples were prepared with occlusal plane in two planes and the last ten samples were prepared with anatomical occlusal design.
Thirty full contour crowns were designed on the scanned abutments, using inLab 3D software (V4.2.5), and then were milled using translucent zirconia blocks and lithium disilicate blocks, 5 crowns of each material for every occlusal preparation design .
The translucent zirconia crowns were milled with an oversize of approximately 25% to compensate for the later sintering shrinkage. The crowns were sintered in high temperature furnace to have maximum density. While the lithium disilicate crowns were adjusted in the pre-crystallized state and then were glazed and crystallized.
The crowns were then seated and cemented. All crowns in all groups were cemented with self-adhesive resin cement . During cementation static finger pressure was applied then the specimens were axially loaded with a 5kg load using a specially designed device.
After cementation, the specimens were screwed to an attachment which was screwed to the base of the machine. The specimens were then loaded vertically on their occlusal surfaces. The loading piston was centered along the long axis of the specimens. The specimens were then loaded in the universal testing machine under a thrust speed of 0.5mm/min.
Two-Way ANOVA test was used to examine the effect of the different occlusal preparation designs on the fracture resistance of monolithic lithium disilicate crowns and translucent zirconia crowns. Strain gauges were adhered to the cervical thirds (1mm above the crown margin) of the buccal surfaces of each crown.
The results revealed that the fracture resistance of translucent zirconia crowns was significantly higher than that for lithium disilicate crowns regardless the type of occlusal preparation design. While in e.max crowns the flat occlusal preparation designs showed the highest fracture resistance followed by occlusal preparation in two planes and the flat occlusal preparation design.
In case of zirconia crowns the flat occlusal preparation design showed significantly the lowest fracture resistance than the other types of occlusal preparation designs. Anatomical occlusal preparation design showed the highest fracture resistance in all groups.
Thirtynatural sound lower first molars of the same size were endodontically treated then prepared with the same criteria except for the occlusal surface using CNC machine.
Flat occlusal preparation was performed on ten samples, another ten samples were prepared with occlusal plane in two planes and the last ten samples were prepared with anatomical occlusal design.
Thirty full contour crowns were designed on the scanned abutments, using inLab 3D software (V4.2.5), and then were milled using translucent zirconia blocks and lithium disilicate blocks, 5 crowns of each material for every occlusal preparation design .
The translucent zirconia crowns were milled with an oversize of approximately 25% to compensate for the later sintering shrinkage. The crowns were sintered in high temperature furnace to have maximum density. While the lithium disilicate crowns were adjusted in the pre-crystallized state and then were glazed and crystallized.
The crowns were then seated and cemented. All crowns in all groups were cemented with self-adhesive resin cement . During cementation static finger pressure was applied then the specimens were axially loaded with a 5kg load using a specially designed device.
After cementation, the specimens were screwed to an attachment which was screwed to the base of the machine. The specimens were then loaded vertically on their occlusal surfaces. The loading piston was centered along the long axis of the specimens. The specimens were then loaded in the universal testing machine under a thrust speed of 0.5mm/min.
Two-Way ANOVA test was used to examine the effect of the different occlusal preparation designs on the fracture resistance of monolithic lithium disilicate crowns and translucent zirconia crowns. Strain gauges were adhered to the cervical thirds (1mm above the crown margin) of the buccal surfaces of each crown.
The results revealed that the fracture resistance of translucent zirconia crowns was significantly higher than that for lithium disilicate crowns regardless the type of occlusal preparation design. While in e.max crowns the flat occlusal preparation designs showed the highest fracture resistance followed by occlusal preparation in two planes and the flat occlusal preparation design.
In case of zirconia crowns the flat occlusal preparation design showed significantly the lowest fracture resistance than the other types of occlusal preparation designs. Anatomical occlusal preparation design showed the highest fracture resistance in all groups.
Other data
| Title | The Effect of Different Occlusal Preparation Designs on the Fracture Resistance of two All–Ceramic Crowns Restoring Endodontically Treated Teeth | Other Titles | تأثير تصميمات تحضير سطح الإطباق المختلفة على مقاومة الكسر لنوعان من التيجان الخزفية المعوضة لأسنان معالجة لبيًا | Authors | Mostafa Ahmed Mahmoud Khalaf | Issue Date | 2015 |
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