• Journal of Technologic Dentistry
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• v.39 no.2
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• pp.75-82
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• 2017

Purpose: This study provided the basic data for selection the zirconia block and CAM by means of marginal fitness observations, flexural strength test and hardness test. Methods: Three dental zirconia blocks(ABCera, NaturaZ, ST98) and two dental milling machines(CAD/CAM MS, DWX-50) were used in this study. Metal abutment(diameter 10 mm, height 5 mm, inclined angle $3^{\circ}$ taper, 1 mm chamfer margin) was fabricated by Ti customized abutment, and then zirconia copings were fabricated for each ten specimens. Silicone replica technique was used to observe the marginal fitness of cross-sections with a stereomicroscope at ${\times}50$ magnification. The dental zirconia blocks was cut into 10 pieces each having a size of $25mm{\times}5mm{\times}1mm$, and fabricated according to the manufacturer's instructions, and flexural strength was measured using a universal testing machine. For hardness test, a micro Vickers hardness tester was used as it was in the flexural strength test. Statistical analysis was performed by one way ANOVA and post-test was performed by Scheffe test. Results: For marginal fitness of bucco-lingual axial, ZU group($59.7{\pm}10.3{\mu}m$) was the lowest, followed by RA, ZA, ZD, RD, RU. For marginal fitness of mesio-distal axial, ZU group($59.3{\pm}10.2{\mu}m$) was the lowest, followed by RA, ZA, RD, ZD, RU. One-way ANOVA showed statistically significant difference between groups(p<0.05). For flexural strength, ABCera block($718.0{\pm}57.2MPa$) was the highest, followed by NaturaZ, ST98. For hardness, ABCera block($1550.3{\pm}19.8Hv$) was the highest, followed by ST98, NaturaZ. There was no significant difference in flexural strength and hardness between blocks(p>0.05). Conclusion: Based on the results of this study, the type of dental zirconia block did influence the marginal fitness, and all dental zirconia blocks are expected to be suitable for clinical application. The highest flexural strength and hardness were ABCera block, and no statistically significant difference was observed.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.5
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• pp.618-630
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• 2000

As Fiber-reinforced composite restorations cannot be made without leaving a marginal gap, luting cements play a pivotal role in sealing the margins as a prevention against margnal leakage. A recently introduced adhesive resin cement system is claimed to adhere chemically, as well as mechanically, to tooth substances, dental alloys and porcelain. But when considering the clinical variation conventional cementation using Zinc Phosphate and Glass-Ionomer can be requested. A vitro study was undertaken to compare microleakage and marginal fitness of Fiber-reinforced composite crowns(Targis/Vectris) depending upon luting cements. Fifty non-carious human premolar teeth were randomly divided into five experimental groups of 10 teeth each and luted with five luting cements. ($Bistite\;II^(R),\;Super-bond^(R),\;Variolink\;II^(R)$), Zinc phosphate and Glass-Ionomer cement) After 24 hours of being luted, all specimens were thermocycled 300 times through water bath of $5^{\circ}C\;and\;55^{\circ}C$ in each bath, then the quality of the marginal fitness was measured by the Digital Microscope and marginal leakage was characterized using Dye Penetration technique and the Digital Microscope The results were as follows : 1. The mean values of marginal fit were Bistite II($46.78{\mu}m$), Variolink II($56.25{\mu}m$), Super-Bond($56.78{\mu}m$), Glass-Ionomer($99.21{\mu}m$), Zinc Phosphate($109.49{\mu}m$) indicated a statistically significant difference at p<0.001. 2. The mean microleakage values of tooth-cement interface, restoration-cement interface were increased in the order of Variolink II, Bistite II, Super-Bond, Glass-Ionomer, Zinc Phosphate 3. Crowns luted with resin cement (Bistite II, Super-Bond, Variolink II, etc) exhibited less marginal gap and marginal leakage than those luted with conventional Glass-Ionomer and Zinc Phosphate cement. 4. The results indicated that all five luting systems yielded comparable and acceptable marginal fit.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.5
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• pp.526-546
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• 2001

Fiber-reinforced composite(FRC) was developed as a structural component for dental appliances such as prosthodontic framework. FRC provides the potential for fabrication of a metal-free, excellent esthetic prostheses. It has demonstrated success as a result of its simple fabrication, natural colour, and marginal integrity, and fracture resistance of veneering composite resin and the FRC material. Although it has lots of merits, clinical and objective data are insufficient. The purpose of this study was to evaluate the fracture strength and the marginal fitness of fiber reinforced composite bridge in the posterior region for clinical application. Sixteen bridges of each group. $Targis/Vectris^{(R)}$, $Sculpture-Fibrekor^{(R)}$, and In-Ceram, were fabricated. All specimens were cemented with Panavia 21 to the master dies. Strength evaluation was accomplished by a universal testing machine (Instron). The marginal fitness was measured by using the stereoscope (${\times}50$). The results were as follows. : 1. The fracture strength according to the materials was significantly decreased in order In-Ceram($238.81{\pm}82$), Targis Vectris($176.25{\pm}18.93$), Sculpture-Fibrekor($120.35{\pm}20.08$) bridges. 2. FRC resin bridges were not completely fractured, while In-Ceram bridges were completely fractured in the pontic joint. 3. The marginal accuracy was significantly decreased in order Targis/Vectris ($60.71{\mu}m$), Sculpture-Fibrekor($73.10{\mu}m$) In-ceram Bridge ($83.81{\mu}m$). 4. The fitness of occlusal sites had a lower value than the marginal sites(P<0.001), and the marginal gaps of inner site of the pontic were greater than that of outer sites of the pontic. Fiber reinforced composite bridges are new, esthetic prosthesis and can be clinically used in anterior regions and short span bridges. However, caution must be exercised when extrapolating laboratory data to the clinical situation because there are no long term clinical data regarding the overall success of the FRC.

• The Journal of Korean Academy of Prosthodontics
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• v.20 no.1
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• pp.75-81
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• 1982

The purpose of this study was to compare the marginal fitness between Ni-Cr alloy and type III gold alloy, according to two finishing line, chamfer and shoulder. As experimental materials, author selected type III gold alloy and Ni-Cr alloy (Hicrown) which were popularly used in Korea for the full cast crown. Author prepared the wax patterns with milled stainless steel die and ring. The wax patterns were invested, burnouted, and casted. The maginal discrepancy was measured with scanning electron microscope. Author obtained the following results from this study. 1. The maginal fitness of Type III gold alloy was not significantly different from that of Ni-Cr alloy (Hi-crown). 2. There is no significant difference between chamfer and shoulder in case of Type III gold alloy. 3. The maginal fitness of chamfer type is significantly superior to that of shoulder type in the Ni-Cr alloy (Hi-Crown).

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.3
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• pp.262-268
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• 2002

Statement of problem. In-Ceram system is one of the all-ceramic crowns that can be used in anterior 3 unit fixed partial dentures and posterior single crowns. The alumina core used in In-Ceram system is manufactured using slip-casting technique. The slip-casting technique is difficult and technique sensitive. To improve this problem, tape-casting method was introduced into dentistry. There were no studies to examine the effect of margin design on the margin fitness of all-ceramic crowns fabricated from alumina tape. Purpose. The purpose of this study was to compare the marginal fitness of glass infiltrated alumina core fabricated from aqueous-based alumina tape according to different margin types ($90^{\circ},\;110^{\circ},\;135^{\circ}$ shoulder margin). Material and method. Three upper central resin incisors were prepared with $90^{\circ},\;110^{\circ}$, and $135^{\circ}$ shoulder margins for all-ceramic crowns, respectively. The resin teeth were duplicated and master die and special plaster die were made as usual. After alumina cores were fabricated from aqueous-based alumina tape, cores were cemented to each 15 epoxy dies replicated from three resin teeth with resin cement. These cemented cores were embedded in epoxy resin. Specimens were cut mesiodistally and buccolingually. Marginal gap and discrepancy were measured under microscope. Results. The marginal gap and discrepancy of $90^{\circ}$ marginal angle was $75.1{\mu}m,\;86.6{\mu}m,\;110^{\circ}$ marginal angle was $41.5{\mu}m,\;50.7{\mu}m$ and $135^{\circ}$ marginal angle was $51.7{\mu}m,\;54.2{\mu}m$, respectively. The smallest value was seen in 110 (angle, which was statistically significant compared to that of $90^{\circ}$ angle (p<0.05). Conclusion. Marginal fitness of alumina cores made of alumina tape with $110^{\circ}$ shoulder margin was best and others were clinically acceptable.

• 대한치과보철학회:학술대회논문집
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• 2001.11a
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• pp.64-64
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• 2001

• Journal of Technologic Dentistry
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• v.14 no.1
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• pp.45-54
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• 1992

The purpose of this study was to observe the change of marginal distortion related to heat treatment and surface treatment in. Thirty copings were made on the self-curing resin dies and twenty coping among them were treated by heat and surface grinding. All copings were adapted on the respective dies and then were invested into the plastic boxes with tray resin. Both copiong and die invested in tray resin were cut through labio-lingually by a separating disc. This cross-cutting surface was ground and polished. Specimens were mounted on a light microscope and photographed. Marginal discrepancies were measured on photographes by a scale. The obtained results could be summarized in the followings : 1. In all metal copings, the distortion of cervical margin was shown after heat treatment and surface treatment. 2. There were no statistically significant differences in marginal fitness between shoulder and deep chamfer. 3. There were no statistically significant differences in marginal fitness between labial margin and lingual margin in one die. 4. In case of the copings which were not treated with preheating and were treated with surface grinding, the marginal distortion shows a tendency to increase.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.1
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• pp.120-132
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• 1998

This stusy was to investigate the marginal fitness of porcelain-fused-to- metal crown after succesive firing cycle. Main variables were the degree of marginal curvature of labiocervical margin and the type of alloy. The exaggerated marginal curvature(EMC) was created by additional reduction at the faciocervical wall of the normallized marginal curvature (NMC)-typed ivorine tooth by using milling machine. The difference in the shape was the mid facial margin was placed 2mm apical to cemento- enamel junction in labial surface. Three types of alloy were high noble, noble, and base metal alloy. Test specimens were divided into 8 groups and each group had 8 specimens. Sixty four ceramometal crowns were made totally. Measurement stages were following degassing, opaquing. body porcelain firing, and glazing, and measuring sites were 4. (midmesial, midfacial, middistal, and midlingual). Digital, travelling measuring microscope (0.5 um precision, Olympus. Japan) was used under ${\times}250$ magnification. Within the limitation of this investigation, it was concluded as belows: 1. The pattern of marginal distortion was varied. Degassing stage was not a specific, causative stage that induce most of total marginal distortion during whole procedure fabricating a ceramometal crown. Body firing stage induced discrepancy relatively more than other firing stages. 2. The specimens that were Ni-based alloy and had EMC were distorted persistently following successive fabricating procedures. But marginal openings were decreased after glazing. 3. The release of metal grinding-induced stress was presumed as a cause that induce marginal distortion. 4. The amount of discrepancies of the labial and lingual margins were greater than that of the mesial and distal margin in the specimen that had EMC. 5. Silver-plated die was not enough to resist abrasion during repeated seating of metal copings on the die-holding device.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.4
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• pp.406-415
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• 2009

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 $\times$ 100. 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.

• The Journal of Advanced Prosthodontics
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• v.12 no.4
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• pp.233-238
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• 2020

PURPOSE. This study aims to compare the marginal fitness of two types of implant-supported fixed dental prosthesis, i.e., cementless fixation (CL.F) system and cement-retained type. MATERIALS AND METHODS. In each group, ten specimens were assessed. Each specimen comprised implant lab analog, titanium abutment fabricated with a 2-degree tapered axial wall, and zirconia crown. The crown of the CL.F system was retained by frictional force between abutment and relined composite resin. In the cement-retained type, zinc oxide eugenol cement was used to set crown and abutment. All specimens were sterilized with ethylene oxide, immersed in Prevotella intermedia culture in a 50 mL tube, and incubated with rotation. After 48 h, the specimens were washed thoroughly before separating the crown and abutment. The bacteria that penetrated into the crown-abutment interface were collected by washing with 500 µL of sterile saline. The bacterial cell number was quantified using the agar plate count technique. The BacTiter-Glo Microbial Cell Viability Assay Kit was used to measure bacterial adenosine triphosphate (ATP)-bioluminescence, which reflects the bacterial viability. The t-test was performed, and the significance level was set at 5%. RESULTS. The number of penetrating bacterial cells assessed by colony-forming units was approximately 33% lower in the CL.F system than in the cement-retained type (P<.05). ATP-bioluminescence was approximately 41% lower in the CL.F system than in the cement-retained type (P<.05). CONCLUSION. The CL.F system is more resistant to bacterial penetration into the abutment-crown interface than the cement-retained type, thereby indicating a precise marginal fit.