Journal of Dental Rehabilitation and Applied Science
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v.33
no.4
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pp.252-259
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2017
Purpose: The purpose of this study was to compare and analyze the wear of a prosthesis for 6 months after restoration with implant-supported fixed dental prosthesis made of either zirconia or gold. Materials and Methods: This study was conducted on patients requiring implant-supported fixed dental prostheses on first or second molar from January, 2015 to January, 2016. A total of 47 prostheses and antagonists were examined. Occlusal surface was recorded by impression of each prosthesis and antagonist 1 week and 6 months after prosthesis delivery. The digital files were created by impression scan. Occlusal shapes of 1 week and 6 months were compared and wear of prostheses and antagonists was analyzed. The Mann-Whitney test was used to analyzed the result data underwent normality test using SPSS (Version 23.0, IBM Corporation) Results: Mann-Whitney test revealed that there was no statistically significant difference in the median amount of mean vertical wear for 6 months in zirconia ($50.84{\mu}m$) and gold ($42.84{\mu}m$) prostheses (P > 0.05). When the opposing teeth were natural, the median amount of mean vertical wear of zirconia and gold prostheses was $47.72{\mu}m$ and $41.97{\mu}m$, respectively, and the median amount of mean vertical wear of enamel was $47.26{\mu}m$ and $44.59{\mu}m$, respectively. Statistical analysis showed no significant difference (P > 0.05). Conclusion: Despite the short study period and the small number of experimental groups, zirconia and gold showed no significant difference in wear during the first 6 months. Opposing natural enamel also showed no significant difference in the wear.
Purpose: The purpose of this study was to compare the fracture behavior of Zironia, glass infiltrated Alumina and PFM full crown system. Materials and methods: Fifteen crowns for each of 3 experimental groups (Zironia, glass infiltrated Alumina and PFM full crown) were made by the conventional method. The crowns mounted on the testing jig were inclined in 30 degrees to the long axis of the tooth and the universal testing machine was used to measure the fracture strength. Results: 1. The mean fracture strengths were $588.3{\pm}49.6MPa$ for zirconia system, $569.1{\pm}61.8MPa$ for PFM system and $551.0{\pm}76.5MPa$ for glass-infiltrated alumina system (P>.05). 2. The mean shear bond strengths were $25.5{\pm}5.6MPa$ for zirconia system, $38.9{\pm}5.0MPa$ for Ni-Cr alloy system and $39.4{\pm}5.1MPa$ for glass-infiltrated alumina system. 3. The chemical bonding was observed at interfaces between PFM or glass-infiltrated alumina and veneering porcelain, however, no chemical bonding was observed at interface between zirconia and veneering porcelain. Conclusion: With the study, the fracture strengths of PFM crown system had a higher fracture strength than conventional zirconia system crown and glass-infiltrated alumina crowns. and than the shear bond strengths glass-infiltrated alumina system had a higher shear bond strength than conventional PFM system and zirconia system.
Journal of Dental Rehabilitation and Applied Science
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v.30
no.1
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pp.16-22
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2014
Purpose: The purpose of this study was to assess the marginal and mesial fitness of zirconia single copings and 3-unit fixed partial dentures (FPDs) manufactured with an identical model. Materials and Methods: An epoxy model in which the maxillary right 2nd premolar is lost and maxillary 1st premolar and 2nd molar are formed as abutments was manufactured and scanned by using a laser scanner. A ten units of zirconia single copings were manufactured for maxillary 1st premolar and 2nd molar, respectively and the same number of 3-unit FPDs were manufactured. For the measurements of fitness, the manufactured silicone replicas were divided into four parts and the fitness were measured by digital microscope at measurement points (P1, P2, P3, P4 and P5) of each plane. The measured gaps were classified into three categories: marginal gap (MG, P1), axial gap (AG, average of P2 and P3), occlusal gap (OG, average of P4 and P5). Results: The ranges of MG, AG and OG for single copings were 18.47 - 40.54 ${\mu}m$, 39.73 - 73.61 ${\mu}m$ and 116.90 - 134.69 ${\mu}m$, respectively. The ranges of MG, AG and OG for 3-unit FPDs were 45.95 - 87.44 ${\mu}m$, 23.78 - 57.00 ${\mu}m$ and 99.89 - 131.06 ${\mu}m$, respectively. Conclusion: The result of the study shows that the MGs for 3-unit FPDs were higher than those of single copings, though they are within the range of clinical acceptance, indicating that the use of more homogeneous zirconia block and modification of sintering processes are needed to ensure the prevention of increase of gap in 3-unit FPDs.
Purpose: The purpose of this study was to compare the marginal fit of three-unit zirconia fixed dental prostheses (FDPs) fabricated using CAD/CAM and MAD/MAM system. Materials and methods: Dentiform maxillary central and lateral incisor were prepared for 3-unit FDP and fixed in yellow stone. This model was duplicated to epoxy resin die. On the resin die, fifteen 3-unit FDPs were fabricated. Metal-ceramic group was three-unit metal-ceramic FDPs, $Everest^{(R)}$ group was zirconia three-unit FDPs fabricated using the $Everest^{(R)}$ system (Kavo Dental GmbH, Biberach, Germany) and $Rainbow^{TM}$ group was zirconia three-unit FDPs fabricated using the $Rainbow^{TM}$ system (Dentium Co. Inc., Seoul, South Korea). They were cemented to resin dies with adhesive resin cement. After removing pontics, each retainers were separated and observed under measuring machine (Presize 440C) and analyzed through one-way ANOVA and Duncan test (${\alpha}$ = .05). Results: Mean values and standard deviations of marginal gap dimensions in each group for three-unit FDPs were $78.5{\pm}11.05\;{\mu}m$ for the metal-ceramic group, $59.30{\pm}11.63\;{\mu}m$ for the $Everest^{(R)}$ group and $70.34{\pm}13.98\;{\mu}m$ for the $Rainbow^{TM}$ group. Conclusion: 1. The $Everest^{(R)}$ group in comparison with metal-ceramic group showed better marginal fit, which had significant differences P<.05. 2. The mean marginal gap values between $Everest^{(R)}$ and $Rainbow^{TM}$ group did not showed significant differences (P>.05). 3. The mean marginal gap values between $Rainbow^{TM}$ group and metal-ceramic group did not showed significant differences (P>.05). 4. The mean marginal gaps of each group were within clinically acceptable range ($120\;{\mu}m$).
PURPOSE. The purpose of this study was to assess the effect of resin cement shade on the color of different novel ultratranslucent monolithic zirconia and lithium disilicate veneer materials. MATERIALS AND METHODS. For a total of 40 specimens, flat cylindrical discs with a 9-mm diameter and 0.5-mm thickness were created using CAD/CAM technology. The specimens were divided into five groups according to their material (n = 8) (e.max, Prettau, Aidite, Shofu and Dima) using A1 shade. Resin discs with the same diameter and shade as the specimens served as tooth-colored substructures. Three shades (neutral, light and warm) of resin cement try-in pastes (Variolink Esthetic LC) were used as the luting cement material. The color of each material group was measured before and after cementation using the three cement shades, and the CIE L*a*b* coordinates were obtained with a spectrophotometer. Values for the translucency parameter (TP) and color change delta E (E) before (baseline) and after cementation of each specimen were determined. To compare differences among the material groups within each shade of cement and among various shades of cement within each material, the data were analyzed using one-way ANOVA and post hoc testing. RESULTS. Color coordinates L*, a* and b* significantly changed after the application of try-in pastes relative to baseline values, with a noticeable decrease in lightness (L*) (P < .05). A significant color change (ΔE) was observed in all tested materials after cementation, with ΔE values exceeding 3.3 (P < .05). Although TP changed after cementation for most materials tested, these changes were not statistically significant (P > .05). Shofu and Dima ceramics showed the lowest TP values, while Aidite and Prettau showed the highest TP values. For e.max, translucency decreased after cementation with neutral and warm shades, and it significantly increased after cementation with a light shade. CONCLUSION. The shade of cement significantly altered the final color of the ceramic veneer material to a level above the threshold at which the clinical perception of color change occurred (> 3.3). The TP was not influenced by the cement shade. The translucency levels of the novel ultratranslucent multilayer monolithic zirconia ceramics Aidite and Prettau were higher than that of the lithium disilicate e.max material.
In recent years, precision machining of the dental prosthesis by computer assisted system is becoming pervasive in clinical dentistry. Prosthesis fabricating system that is designed by computer software and made by computer devices is called as a CAD/CAM (Computer-Aided Design/Computer-Aided Manufacturing) system. By the use of dental CAD/CAM system, the improvement of marginal compatibility and mechanical properties in prosthesis can be obtained more effectively, an aesthetic quality by using new materials such as zirconia can be increased. Also, the restoration process can be simple and efficient, the production time can be shortened, the process of manufacture can be standardized, and the mass production is possible. What is clear is that these benefits are theoretically possible, but the dentist or dental technician must understand the CAD/CAM basic principles and limitations for obtaining the maximum advantages of CAD/CAM system. For this reason, this article will be presented about the basic principles of CAD/CAM system and the factors of error that might occur in the CAD/CAM process based on my empirical study.
Journal of Dental Rehabilitation and Applied Science
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v.36
no.1
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pp.41-47
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2020
Purpose: The purpose of this study was to evaluate the flexural strength and reliability of highly translucent colored zirconia for all ceramic restoration. Materials and Methods: Bar-shaped specimens (25 × 4 × 2.5 mm) were prepared from highly translucent monolithic zirconia. Three experimental groups were set up according to color (shade A0, A1, and A3). For each group, 20 specimens were prepared. Flexural strength was determined using a 3-point flexural test and results were analyzed with one-way ANOVA test. Weibull statistical analysis provided 2 parameter estimates: Weibull modulus and characteristic strength. X-ray diffraction (XRD) analysis was performed. Results: There was statistically significant difference between uncolored (Shade A0) and colored (shade A1 and A3) (P < 0.05), but there was no difference between colored groups (P > 0.05). The uncolored group had higher reliability compared with colored study groups. On x-ray diffraction analysis of each group, typical peaks of tetragonal phase appeared in all groups. Conclusion: Within the limitations of this in vitro study, coloring highly translucent zirconia had significant effect on flexural strength and reliability. Therefore, clinicians should be careful when using highly translucent colored zirconia to prevent breakage of veneering ceramic and enhance aesthetics.
Journal of the Korean Academy of Esthetic Dentistry
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v.22
no.1
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pp.30-46
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2013
Porcelain fused to metal crown has been used mostly over the last 50 years for restorations in dentistry. However, the patients' awareness of aesthetic aspect, biocompatibility and the problems such as an allergy to metals led to the growing interest in the 'metal free restoration'. In particular, the price of the precious metals that have been mainly used to date has risen drastically, which made them impossible to play their role as oral restorative materials anymore, and in addition, the PFM restoration has intrinsic problems of chipping and fracture. Therefore, the CAD/CAM has been drawing more attention than ever due to the popular needs for the material that is more aesthetic and stronger for restoration of the molar implant. Considerations in carrying out the full zirconia restoration are as follows: 1) strength, 2) combination work, 3) light penetrability, 4) treatment of cracks, 5) the color reproducibility of the block, 6) the abrasivity of antagonistic tooth, 7) low temperature degradation. In this presentation, the color reproducibility of the block will be discussed. One of the biggest reasons for avoiding the full zirconia restoration is that it is difficult to reproduce the natural color compared to the conventional PFM restoration. Thus, many clinicians show reluctance due to the exposure of the ugly block when the coloring on the surface is removed after occlusal adjustment. From the experience of using blocks by Zirkonzahn for more than 4 years, it is considered that these problems can be addressed to some degrees. Accordingly, how to make restorations that are well in harmony with surrounding prosthesis or natural teeth will be discussed.
Journal of Dental Rehabilitation and Applied Science
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v.26
no.3
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pp.253-264
/
2010
The purpose of this study is to know whether Yttrium-stabilized-tetragonal -zirconia-polycrystal(Y-TZP ceramic) gets enough shear bond strength for clinical uses by applying veneering composite resin through surface treatment on it and finally to compare it with the case of applying veneering porcelain. LavaTM zirconia frameworks(3M ESPE, Seefeld, Germany) were prepared. Group P was manufactured with LavaTM Ceram(3M ESPE, Seefeld, Germany) in cylindrical shape which has 4mm diameter, 5mm height. Group ZSR disposed sandblasting and applied silane, bonding agent and after that indirect composite resin was applied. Group ZRR got tribochemical coating by RocatecTM system(3M ESPE. Seefeld, Germany) and treated silane. Finally Group ZPR took the same treatment and applied LavaTM Ceram in the size of 0.3-0.5mm height. After burning out, sandblasting, HF and silane was applied. And then, indirect composite resin was applied. 1000 cycle thermocycling was performed in $5-55^{\circ}C$ and shear bond strength was measured. There were no significant differences between combining veneering porcelain to Y-TZP ceramic group and combining veneering resin to Y-TZP ceramic group in the aspect of shear bond strength (p>.05).
Journal of Dental Rehabilitation and Applied Science
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v.25
no.2
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pp.95-107
/
2009
The purpose of this research was to examine the fitness of zirconia cores that were made by different sintering methods; generic electricity furnace and microwave furnace. Firstly, 12 cores for each group were made by using each different sintering process and attached them to a metal die with silicon. The internal and marginal gap of sintered zirconia was measured by using Skyscan 1076 micro-CT, then it was reorganized by CT-An software. To each samples, we extracted B-L image, M-D image of cutting side, and cross-sectional side of tooth long axis and calculated the mean value of marginal, axial, and occlusal gap each side. Results: 1. The mean marginal gap of sintered zirconia was $36.20{\mu}m$ for EVE, $47.67{\mu}m$ for LAV, $52.47{\mu}m$ for DEN, and $54.63{\mu}m$ for CER. 2. For the axial wall, the research showed the largest value of $63.49{\mu}m$ for EVE, but there were no statistical significance. 3. In related to the occlusal internal measurement, DEN showed the smallest value ($77.06{\mu}m$), EVE and CER showed significantly high value. From this study, it is suggested that CAD/CAM zirconia core which was made in the process of microwave sintering has clinically acceptable values in marginal and internal gap.
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