| 1. |
- Kokubo, Yuji, et al.
(författare)
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Clinical Marginal and Internal Gaps of In-Ceram Crowns Fabricated Using the GN-I System
- 2005
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Ingår i: Journal of Oral Rehabilitation. - : Wiley. - 1365-2842 .- 0305-182X. ; 32:10, s. 753-758
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The marginal and internal gaps of ceramic crowns with alumina copings fabricated using a computer-aided design, computer-aided manufacturing system, were evaluated in vivo using silicone materials. Black and white silicone materials were used to record the marginal and internal gaps of 82 In-Ceram crowns before final cementation. The silicone materials were sectioned bucco-lingually and mesio-distally and viewed under a microscope to measure the thickness of the white silicone layer. Sixteen reference points were measured on each specimen. The mean marginal gaps were compared among the anterior, premolar and molar teeth, and the mean gaps at the reference points within the groups were compared by analysis of variance and the Dunnett T3 test. The mean marginal gap was 66.8 mum. There were no differences in marginal gaps among the three groups. In all the groups, the marginal gaps were the smallest, whereas the occlusal gaps were the largest. The mean marginal gaps of the In-Ceram crowns with the alumina copings fabricated using the GN-I system were within the range of clinically acceptable values.
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| 2. |
- Kokubo, Yuji, et al.
(författare)
-
Clinical Marginal and Internal Gaps of Procera AllCeram Crowns
- 2005
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Ingår i: Journal of Oral Rehabilitation. - : Wiley. - 1365-2842 .- 0305-182X. ; 32:7, s. 526-530
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This study evaluated the marginal and internal gaps of Procera AllCeram crowns in vivo using silicone materials. Ninety Procera AllCeram crowns were evaluated before final cementation. White and black silicone materials were used to record the marginal and internal fit; then the crowns were sectioned bucco-lingually and mesio-distally to measure the thickness of the silicone layer using a microscope. Sixteen reference points were measured on each specimen. Mean marginal gaps among anterior, premolar and molar teeth, and mean gaps at the reference points within the groups were compared by analysis of variance and Dunnett T3 test. The mean values at the margins were the smallest in all tooth groups, whereas those at the rounded slope of the chamfer were the largest. There were significant differences (P < 0.001) in the mean gaps at the four reference points (margin, rounded slope of the chamfer, axial wall and occlusal surface) in each group, except for the molar teeth. The mean marginal gaps of the Procera AllCeram crowns were within the range of clinical acceptance.
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| 3. |
- Kokubo, Yuji, et al.
(författare)
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Clinical marginal gap of porcelain fused to electro-formed gold coping crowns
- 2006
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Ingår i: European Journal of Prosthodontics and Restorative Dentistry. - 0965-7452. ; 14:2, s. 85-89
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Tidskriftsartikel (refereegranskat)abstract
- This study evaluated the marginal and internal gaps of Auro Galvano Crowns (AGC) in vivo. One hundred AGC crowns were examined using white and black silicone materials; the thickness of the silicone layer was measured at 16 reference points using a microscope. The mean marginal gaps among anterior, premolar and molar teeth, and the mean gaps within the groups were compared by analysis of variance and Dunnett T3 test. The results showed that at the margins, there were no significant differences among the four measuring points within each group, and there were no significant differences in the mean marginal gaps among the three groups. The mean marginal gaps in all groups were within the limits of clinical acceptability.
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| 4. |
- Kokubo, Yuji, et al.
(författare)
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The effect of core framework designs on the fracture loads of all-ceramic fixed partial dentures on posterior implants
- 2007
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Ingår i: Journal of Oral Rehabilitation. - : Wiley. - 1365-2842 .- 0305-182X. ; 34:7, s. 503-507
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Tidskriftsartikel (refereegranskat)abstract
- This study evaluated the fracture loads of three-unit all-ceramic bridges on implants; the core frameworks of the bridges were made of zirconium oxide. Three core framework designs were fabricated according to the design of the bars between the retainers: (i) straight, (ii) curved in the occlusal direction, or (iii) curved in the gingival direction. A static load was applied at the centre of the pontic, and the mean initial crack and final fracture loads were measured and compared. The core framework curved in the occlusal direction had the highest final fracture loads; there were significant differences (P < 0.05) in the mean final fracture load, whereas initial fracture load, which fractured of veneered porcelain, did not show significant differences among three designs. The all-ceramic bridges on the implants made with Procera zirconium core frameworks had high final fracture load. The core framework design that curved in the occlusal direction helped the framework withstand the occlusal load, which results in reliable prostheses, especially in the molar region.
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| 5. |
- Tsumita, Mitsuyoshi, et al.
(författare)
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Effect of framework shape on the fracture strength of implant-supported all-ceramic fixed partial dentures in the molar region
- 2008
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Ingår i: Journal of Prosthodontics. - 1059-941X .- 1532-849X. ; 17:4, s. 274-285
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: The aim of the present study was to clarify the effects of the shape of the zirconium framework of implant-supported, all-ceramic fixed partial dentures (FPDs) on the fracture strength and fracture mode. MATERIALS AND METHODS: This study consisted of mechanical strength testing and 3D finite element analysis (FEA). The three framework shapes used in this study were: (1) conventional shape (control); (2) convex shape: 1.0-mm curve in the direction of the occlusal surface; and (3) concave shape: 1.0-mm curve in the direction of the gingival surface. Five frameworks were made for each condition (total: 15). A load (N) was applied until the FPD fractured. For FEA, a 3D model consisting of cortical bone, cancellous bone, implant bodies, and superstructure was constructed. RESULTS: The results of the mechanical strength test showed that fracture load was 916.0 +/- 150.1 N for the conventional shape, 1690.5 +/- 205.3 N for the convex shape, and 1515.5 +/- 137.0 N for the concave shape. The mean final fracture load for the FPDs with frameworks was the highest for the convex shape; however, a critical crack in the veneer porcelain (736.5 +/- 145.2 N) was confirmed during loading for the convex shape. Stress distribution maps for all conditions showed that tensile stress was generated at the veneer porcelain on the gingival side of the mesial and distal connectors of the pontic; however, there were differences in the maximum value and stress distribution within the framework. CONCLUSION: The shape of the framework, particularly the shape of the pontic-connector interface, affects the stress distribution, fracture strength, and fracture mode of all-ceramic FPDs, and stress concentration inside a framework may induce cracking of layering porcelain.
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