J Korean Acad Prosthodont.  2009 Oct;47(4):406-415. 10.4047/jkap.2009.47.4.406.

Fracture load and marginal fitness of zirconia ceramic coping by design and coloration

• Shin MR
• Kim MJ
• Oh SC

• KMID: 2195589
• DOI: http://doi.org/10.4047/jkap.2009.47.4.406

Abstract

PURPOSE
The purpose of this study was to compare the marginal fitness and fracture load of the zirconia copings according to the design with different thickness and coloration. MATERIAL AND METHODS: The evaluation was based on 80 zirconia copings. Zirconia copings were fabricated in design with different thicknesses using CAD/CAM system (Everset, KAVO dental GmbH, Biberach, Germany). The designs of copings were divided into four groups. The first group consisted of copings with uniform thickness of 0.3 mm. The thickness in the second group was 0.3 mm on the buccal surface and 0.6 mm on the lingual surface. The third group consisted of coping with uniform thickness of 0.6 mm. The thickness in the fourth group was 0.6 mm on the buccal surface and 1mm on the lingual surface. Each group consisted of 10 colored and 10 uncolored copings. Half of the copings (40) processed with a milling system according to the specific design were sent to be given a color (A3) through saturation in special dye by a manufacturing company. Just after sintering, the marginal discrepancies of copings were measured on the buccal, lingual, mesial and distal surfaces of metal die, under a Video Microscope System (sv-35, Sometech, Seoul, Korea) at a magnification of x100. It was remeasured after the adjusting of the inner surface. Next, all copings were luted to the metal dies using reinforced cement {GC FujiCEM (GC Corp. Tokyo, Japan)} and mounted on the testing jig in a Universal Testing Machine (Instron 4467, Norwood, MA, USA). The results were analyzed statistically using the one-way ANOVA test.
RESULTS
The obtained results were as follow: 1. The measured value of marginal discrepancy right after sintering was the greatest in the contraction of the buccal area in all groups, except for group I2. 2. There was no significant difference of marginal fitness among the groups in the colored zirconia group (P<.05). 3. When the marginal fitness among the groups in the uncolored zirconia group was considered, group II2 had the smallest marginal discrepancy. 4. When the colored and uncolored groups with the same design were compared, there was a significant difference between I1 and II1 groups. In group 2, 3, and 4, the uncolored zirconia had the greatest marginal fitness (P<.05). 5. After adjustment of inner surface, there was no significant difference in the marginal fitness in all groups when color and design of the zirconia coping were compared. 6. The fracture load of CAD/CAM zirconia copings showed significant difference in group 1, 2, 3, and 4. I4 and II4 had the strongest fracture load. 7. When groups with different color and same design were compared, all colored groups showed greater fracture load (P>.05), with no significance. CONCLUSION: There was difference in the marginal fitness according to the design and coloration of zirconia copings right after sintering, but it was decided that the copings may well be used clinically if the inner surface are adjusted. The copings should be thick enough for the reinforcement of fracture strength. But considering the esthetics of the visible surfaces (labial and buccal surface), the thickness of copings may be a little thin, without giving any significant effect on the fracture strength. This type of design may be considered when giving priority to preservation of tooth or esthetics.

Keyword

Zirconia ceramic copings; Design; Coloration; CAD/CAM; Marginal fitness; Fracture strength

MeSH Terms

Ceramics
Collodion
Contracts
Esthetics
Glass Ionomer Cements
Reinforcement (Psychology)
Tokyo
Tooth
Zirconium
Ceramics
Collodion
Glass Ionomer Cements
Zirconium

Figure

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  Fig. 1. Schematic view of tooth preparation.

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  Fig. 2. Schematic view of zirconia coping by design.

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  Fig. 3. Measuring points for marginal discrepancy.

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  Fig. 4. Measurement of the marginal discrepancy using the video microscope system just after sintering (× 100).

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  Fig. 5. Measurement of the marginal discrepancy using the video microscope system after internal adjusting and sintering (× 100).

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  Fig. 6. Schematic view of the test specimen on the universal testing machine.

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  Fig. 7. Comparison of fracture strengths of zirconia coping with different color & designs.

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  Fig. 8. Comparison of marginal discrepancy of zirconia core with different designs just after sintering without any adjustment.

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  Fig. 9. Comparison of marginal discrepancy of zirconia coping with different color just after sintering.

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