• The Journal of Advanced Prosthodontics
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• v.5 no.4
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• pp.485-493
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• 2013

PURPOSE. To evaluate the effects of surface treatments on shear bond strength (SBS) between microwave and conventionally sintered zirconia core/veneers. MATERIALS AND METHODS. 96 disc shaped Noritake Alliance zirconia specimens were fabricated using YenaDent CAM unit and were divided in 2 groups with respect to microwave or conventional methods (n=48/group). Surface roughness (Ra) evaluation was made with a profilometer on randomly selected microwave (n=10) and conventionally sintered (n=10) cores. Specimens were then assessed into 4 subgroups according to surface treatments applied (n=12/group). Groups for microwave (M) and conventionally (C) sintered core specimens were as follows; $M_C$,$C_C$: untreated (control group), $M_1,C_1:Al_2O_3$ sandblasting, $M_2,C_2$:liner, $M_3,C_3:Al_2O_3$ sandblasting followed by liner. Veneer ceramic was fired on zirconia cores and specimens were thermocycled (6000 cycles between $5^{\circ}-55^{\circ}C$). All specimens were subjected to SBS test using a universal testing machine at 0.5 mm/min, failure were evaluated under an optical microscope. Data were statistically analyzed using Shapiro Wilk, Levene, Post-hoc Tukey HSD and Student's t tests, Two-Way-Variance- Analysis and One-Way-Variance-Analysis (${\alpha}$=.05). RESULTS. Conventionally sintered specimens ($1.06{\pm}0.32{\mu}m$) showed rougher surfaces compared to microwave sintered ones ($0.76{\pm}0.32{\mu}m$)(P=.046), however, no correlation was found between SBS and surface roughness (r=-0.109, P=.658). The statistical comparison of the shear bond strengths of $C_3$ and $C_1$ group (P=.015); $C_C$ and $M_C$ group (P=.004) and $C_3$ and $M_3$ group presented statistically higher (P=.005) values. While adhesive failure was not seen in any of the groups, cohesive and combined patterns were seen in all groups. CONCLUSION. Based on the results of this in-vitro study, $Al_2O_{3-}$ sandblasting followed by liner application on conventionally sintered zirconia cores may be preferred to enhance bond strength.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.2
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• pp.151-157
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• 2010

Purpose: The purposes of this study was to evaluates shear bond strength between zirconia core and veneer-ceramic in order to examine the clinical practice of colored zirconia block fabricated by infiltration method into the metal chloride solution. Material and methods: CNU block and $Everest{(R)}$ ZS blank were used. VITA In-$Ceram{(R)}$2000 YZ Coloring liquid (LL1) and 3 aqueous metal chloride solutions containing chromium and molybdenum ingredients were used. 40 zirconia specimens were prepared into cuboid shape ($5{\times}5{\times}10 mm$). All specimens were divided into 5 groups by infiltrating into the coloring liquids. After that, porcelain was build up into the shape of $5{\times}5{\times}4mm^3$, followed by sintering. The maximum loading and shear bond strength was measured. Failure patterns and failure sites were examined. Results: 1. There were no statistical differences in shear bond strength between zirconia blocks (P > .05). 2. There were no statistically significant differences in shear bond strength between non-colored and colored zirconia blocks, while shear bond strength of non-colored zirconia blocks is higher than that of colored specimen (P > .05). 3. In the comparison with shear bond strength among colored zirconia blocks, there were no statistical differences according to kinds of coloring liquid (P > .05). 4. Mixed failure patterns were mainly observed in the failure between zirconia and veneering ceramic. The veneering ceramic failure of all specimens was observed in either interface of zirconia or veneering ceramic. Conclusion: Shear bond strength between colored zirconia and veneering ceramic shows lower tendency than non-colored zirconia, but there was clinically allowable value.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.4
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• pp.416-423
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• 2009

Statement of problem: The degree of light attenuation at the time of cementation of the PLV restoration depends on characteristics such as thickness, opacity and shade of the restorations, which interfere with light transmittance and, as a result, may decrease the total energy reaching the luting cement. Purpose: The purpose of this study was to compare the degree of conversion of light-cured resin cements measuring by FT-IR in regard to different thickness, light devices and curing time. Material and methods: In the control group, a clear slide glass (1.0 mm) was positioned between the light cured resin cement and light source. The specimens of ceramics were made with IPS Empress Esthetic. The ceramics were fabricated with varying thicknesses-0.5, 1.0, 1.5 mm with shade ETC1. Rely $X^{TM}$ Veneer with shade A3, light-cured resin cement, was used. Light-activation was conducted through the ceramic using a quartz tungsten halogen curing unit, a light emitting diode curing unit and a plasma arc curing unit. The degree of conversion of the light-cured resin cement was evaluated using FT-IR and OMNIC. One-way ANOVA and Tukey HSD test were used for statistical analysis ($\alpha$< .05). Results: The degree of conversion (DC) of photopolymerization using QTH and LED was higher than results of using PAC in the control group. After polymerization using QTH and LED, the DC results from the different ceramic thickness- 0.5 mm, 1.0 mm, 1.5 mm- did not show a significant difference when compared with those of control group. However, the DC for polymerization using PAC in the 1.5mm ceramic group showed significantly lower DC than those of the control group and 0.5 mm ceramic group (P<.05). At 80s and 160s, the DC of light-cured resin cement beneath 1.0 mm ceramic using LED was significantly higher than at 20s (P<.05). Conclusion: Within the limitation of this study, when adhering PLV to porcelain with a thickness between 0.5-1.5 mm, the use of PAC curing units were not considered however, light cured resin cements were effective when cured for over 40 seconds with QTH or LED curing units. Also, when curing the light cured resin cements with LED, the degree of polymerization was not proportional with the curing time. Curing exceeding a certain curing time, did not significantly affect the degree of polymerization.

• Journal of Technologic Dentistry
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• v.33 no.4
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• pp.299-306
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• 2011

Purpose: This study aimed to investigate the shear bond strength by manufacturing the veneering porcelain on the IPS e.max $ZirCAD^{(R)}$ zirconia core, using the layering technique and heat-pressing technique, and to evaluate the clinical stability by comparing to the conventional metal ceramic system. Methods: The Schmitz-Schulmeyer test method was used to evaluate the core-veneer shear bond strength of zirconia core ceramic(IPS e.max $ZirCAD^{(R)}$) and their manufacture recommended two veneering ceramic systems(IPS e.max $ceram^{(R)}$, IPS e. max $ZirPress^{(R)}$). A metal ceramic system(Bellabond $plus^{(R)}$, VITA $VM13^{(R)}$) was used as a control group for the two all ceramic system test groups. The maximum loading and shear bond strength was measured. The average shear strength(MPa) was analyzed with the one-way ANOVA and the Tukey's test(${\alpha}$=.05). The fracture specimens were examined using Microscope to determine the failure pattern. Results: The mean shear bond strengths(SD) in MPa were MBSB control 43.62(2.13); ZBSB 18.65(1.76); ZPSB 18.89(1.54). The shear strengths of the zirconia cores were not significantly different(P>.05). Microscope examination showed that zirconia specimens presented mixed failure, and base metal alloy specimens showed adhesive failure. Conclusion: There was no siginificant different between the layering technique and the heat pressing technique in the veneering methods on the zirconia cores. None of the zirconia core and veneering ceramics could attain the high bond strength values of the metal ceramic combination.

• Journal of dental hygiene science
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• v.14 no.1
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• pp.29-34
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• 2014

The purpose of this study was to evaluate the influence of low temperature degradation (LTD) on the bonding strength of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). The push-shear bond test method was used to investigate the core-veneer bonding strength of industrially manufactured Y-TZP core ceramic and manufacturer recommended veneering ceramic. Four groups from ceramic-zirconia specimens (n=28; n=7 per group) were assigned into four experimental aging conditions, namely storage in an autoclave at $134^{\circ}C$ for 0, 3, 5, 10 hours. Bonding strength was obtained using a universal testing machine with crosshead speed 0.5 mm/min. Data were statistically analyzed using one-way ANOVA and Tukey's test (${\alpha}=0.05$). In bonding strength test, the group which was treated with LTD showed lower bonding strength than no treated group. The ceramic-zirconia bonding strength was affected by LTD (p<0.05). Digital microscope examination of the fracture surface showed mixed failures with adhesive and cohesive types in LTD with treated Y-TZP groups.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.2
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• pp.199-205
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• 2009

Purpose: The purpose of this research was to evaluate the shear bond strength between zirconia core and veneer ceramic after surface treatment. Material and methods: Zirconia cores(N=40, n=10, $10mm{\times}10mm{\times}3mm$) were fabricated according to the manufacturers' instructions and ultrasonically cleaned. The veneering ceramics(thickness 3 mm) were built and fired onto the zirconia core materials. Four groups of specimens with different surface treatment were prepared. Group I: without any pre-treatment, Group II: treated with sandblasting, Group III: treated with liner, Group IV: treated with sandblasting and liner. The shear bond strength was tested in a universal testing machine. Data were compared with an ANOVA and $Scheff{\acute{e}}$ post hoc test(P=.05). Results: The shear bond strength of group VI was significantly higher than the other groups. Conclusion: Both mechanically and chemically treated simultaneously on zirconia core surface influenced the shear bond strength between the core and veneering ceramic in all-ceramic systems.

• The Journal of Advanced Prosthodontics
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• v.5 no.3
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• pp.262-269
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• 2013

PURPOSE. Perceived color of ceramics changes by the spectral power distribution of ambient light. This study aimed to quantify the amount of shifts in color and color coordinates of clinically simulated seven all-ceramics due to the switch of three ambient light sources using a human vision simulating spectroradiometer. MATERIALS AND METHODS. CIE color coordinates, such as $L^*$, $a^*$ and $b^*$, of ceramic specimens were measured under three light sources, which simulate the CIE standard illuminant D65 (daylight), A (incandescent lamp), and F9 (fluorescent lamp). Shifts in color and color coordinate by the switch of lights were determined. Influence of the switched light (D65 to A, or D65 to F9), shade of veneer ceramics (A2 or A3), and brand of ceramics on the shifts was analyzed by a three-way ANOVA. RESULTS. Shifts in color and color coordinates were influenced by three factors (P<.05). Color shifts by the switch to A were in the range of 5.9 to 7.7 ${\Delta}E{^*}_{ab}$ units, and those by the switch to F9 were 7.7 to 10.2; all of which were unacceptable (${\Delta}E{^*}_{ab}$ > 5.5). When switched to A, CIE $a^*$ increased (${\Delta}a^*$: 5.6 to 7.6), however, CIE $b^*$ increased (${\Delta}b^*$: 4.9 to 7.8) when switched to F9. CONCLUSION. Clinically simulated ceramics demonstrated clinically unacceptable color shifts according to the switches in ambient lights based on spectroradiometric readings. Therefore, shade matching and compatibility evaluation should be performed considering ambient lighting conditions and should be done under most relevant lighting condition.

• The Journal of Advanced Prosthodontics
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• v.7 no.5
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• pp.358-367
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• 2015

PURPOSE. The aim of this study was to evaluate the biaxial flexural strength (BFS) of one zirconia-based ceramic used with various veneering ceramics. MATERIALS AND METHODS. Zirconia core material (Katana) and five veneering ceramics (Cerabien ZR; CZR, Lava Ceram; LV, Cercon Ceram Kiss; CC, IPS e.max Ceram; EM and VITA VM9; VT) were selected. Using the powder/liquid layering technique, bilayered disk specimens (diameter: 12.50 mm, thickness: 1.50 mm) were prepared to follow ISO standard 6872:2008 into five groups according to veneering ceramics as follows; Katana zirconia veneering with CZR (K/CZR), Katana zirconia veneering with LV (K/LV), Katana zirconia veneering with CC (K/CC), Katana zirconia veneering with EM (K/EM) and Katana zirconia veneering with VT (K/VT). After 20,000 thermocycling, load tests were conducted using a universal testing machine (Instron). The BFS were calculated and analyzed with one-way ANOVA and Tukey HSD (${\alpha}$=0.05). The Weibull analysis was performed for reliability of strength. The mode of fracture and fractured surface were observed by SEM. RESULTS. It showed that K/CC had significantly the highest BFS, followed by K/LV. BFS of K/CZR, K/EM and K/VT were not significantly different from each other, but were significantly lower than the other two groups. Weibull distribution reported the same trend of reliability as the BFS results. CONCLUSION. From the result of this study, the BFS of the bilayered zirconia/veneer composite did not only depend on the Young's modulus value of the materials. Further studies regarding interfacial strength and sintering factors are necessary to achieve the optimal strength.

• The Journal of Advanced Prosthodontics
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• v.12 no.4
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• pp.181-188
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• 2020

PURPOSE. The effect of core design on the fracture resistance of zirconia-lithium disilicate (LS2) bilayered crowns for anterior teeth is evaluated by comparing with that of metal-ceramic crowns. MATERIALS AND METHODS. Forty customized titanium abutments for maxillary central incisor were prepared. Each group of 10 units was constructed using the same veneer form of designs A and B, which covered labial surface to approximately one third of the incisal and cervical palatal surface, respectively. LS2 pressed-on-zirconia (POZ) and porcelain-fused-to-metal (PFM) crowns were divided into "POZ_A," "POZ_B," "PFM_A," and "PFM_B" groups, and 6000 thermal cycles (5/55 ℃) were performed after 24 h storage in distilled water at 37 ℃. All specimens were prepared using a single type of self-adhesive resin cement. The fracture resistance was measured using a universal testing machine. Failure mode and elemental analyses of the bonding interface were performed. The data were analyzed using Welch's t-test and the Games-Howell exact test. RESULTS. The PFM_B (1376. 8 ± 93.3 N) group demonstrated significantly higher fracture strength than the PFM_A (915.8 ± 206.3 N) and POZ_B (963.8 ± 316.2 N) groups (P<.05). There was no statistically significant difference in fracture resistance between the POZ_A (1184.4 ± 319.6 N) and POZ_B groups (P>.05). Regardless of the design differences of the zirconia cores, fractures involving cores occurred in all specimens of the POZ groups. CONCLUSION. The bilayered anterior POZ crowns showed different fracture resistance and fracture pattern according to the core design compared to PFM.

• Journal of Technologic Dentistry
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• v.35 no.2
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• pp.137-142
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• 2013

Purpose: This study was to observe the surface and interfacial characteristic of Zirconia by surface treatment. And it was observed the roughness and contact angle according to processing, and the interfacial properties by surface treatment on zirconia. Methods: The oxide formation and ion diffusion between core and veneer ceramic were determined by the X-ray Dot Mapping of EPMA(Electron probe micro analyzer). The roughness was measured by 3D Digital microscope and the contact angle according to processing of zirconia was observed using distilled water on the surface. Results: The surface roughness of the specimens Z04, Z12, Z15 was measured $0.67({\pm}0.03){\mu}m$, $0.50({\pm}0.12){\mu}m$, $0.35({\pm}0.09){\mu}m$, respectively. As results of contact angle test, Z04, Z12, Z15 of specimen group without binder treatment was measured $46.79({\pm}3.17)^{\circ}$, $57.47({\pm}4.83)^{\circ}$, $56.19({\pm}2.66)^{\circ}$, respectively. but, L04, L12, L15 of specimen group without binder treatment was measured $63.84({\pm}2.20)^{\circ}$, $66.08({\pm}0.16)^{\circ}$, $65.10({\pm}1.01)^{\circ}$, respectively. Average contact angle of L15 was measured $65.10({\pm}1.01)^{\circ}$. In X-ray Dot Mapping results, thickness of binder including Al element was measured that each of L04, L12, L15 were $20{\mu}m$, $15{\mu}m$, $10{\mu}m$. Conclusion: The more rough surface increases the wettability, but the sintered exclusive binder decreases the wettability.