Published online Jul 31, 2010.
https://doi.org/10.4047/jkap.2010.48.3.194
Fracture resistance and marginal fidelity of zirconia crown according to the coping design and the cement type
Abstract
Purpose
The purpose was to compare the marginal fidelity and the fracture resistance of the zirconia crowns according to the various coping designs with different thicknesses and cement types.
Material and methods
Zirconia copings were designed and fabricated with various thicknesses using the CAD/CAM system (Everest, KaVo Dental GmbH, Biberach., Germany). Eighty zirconia copings were divided into 4 groups (Group I: even 0.3 mm thickness, Group II: 0.3 mm thickness on the buccal surface and the buccal half of occlusal surface and the 0.6 mm thickness on the lingual surface and the lingual half of occlusal surface, Group III: even 0.6 mm thickness, Group IV: 0.6 mm thickness on the buccal surface and the buccal half of occlusal surface and the 1.0 mm thickness on the lingual surface and the lingual half of occlusal surface) of 20. By using a putty index, zirconia crowns with the same size and contour were fabricated. Each group was divided into two subgroups by type of cement: Cavitec® (Kerr Co, USA) and Panavia-F® (Kuraray Medical Inc, Japan). After the cementation of the crowns with a static load compressor, the marginal fidelity of the zirconia crowns were measured at margins on the buccal, lingual, mesial and distal surfaces, using a microscope of microhardness tester (Matsuzawa, MXT-70, Japan, ×100). The fracture resistance of each crown was measured using a universal testing machine (Z020, Zwick, Germany) at a crosshead speed of 1 mm/min. The results were analyzed statistically by the two-way ANOVA and oneway ANOVA and Duncan's multiple range test at α= .05.
Results
Group I and III showed the smallest marginal fidelity, while group II demonstrated the largest value in Cavitec® subgroup (P < .05). For fracture resistance, group III and IV were significantly higher than group I and II in Cavitec® subgroup (P < .05). The fracture resistances of Panavia-F® subgroup were not significantly different among the groups (P > .05). Panavia-F® subgroup showed significantly higher fracture resistance than Cavitec® subgroup in group I and II (P < .05).
Conclusion
Within the limitation of this study, considering fracture resistance or marginal fidelity and esthetics, a functional ceramic substructure design of the coping with slim visible surface can be used for esthetic purposes, or a thick invisible surface to support the veneering ceramic can be used depending on the priority.
Fig. 1
3D scanned image of stone model using the ISCAN D100® after modification.
Fig. 2
Schematic diagram of lateral and occlusal view of zirconia coping according to the group.
Fig. 3
Assembly designed for measuring the fracture resistance of fabricated zirconia crown on a universal testing machine (A), and a schematic diagram of circled area (B).
Fig. 4
*means significant difference by t-test at α= .05.
Comparison of fracture resistances of zirconia crowns according to the cement type.
Fig. 5
Comparison of failure modes of zircornia crowns with different coping design and cement type. Ic, IIc, IIIc, IVc means group I, II, III, IV in Cavitec® Subgroup, Ip, IIp, IIIp, IVp means group I, II, III, IV in Panavia-F® subgroup.
Table 1
Classification of zirconia coping according to the design of the coping and cement type
Table 2
Marginal fidelity of each surface measurement (µm) (N = 40)
Table 3
Mean of fracture resistances and standard deviation (N)
Table 4
Mean of fracture resistances and standard deviation (N)
Table 5
Result of fracture resistances of zirconia ceramic crown according to the cement type by two-way ANOVA
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