A comparison of bond strength of layered veneering porcelains to zirconia and metal.

STATEMENT OF PROBLEM: High chipping rates of veneering porcelain for zirconia ceramic restorations have been reported in clinical studies. The information on the bonding behavior of veneering porcelain to zirconia frameworks is limited. PURPOSE: This study assessed the relationship between coefficient of thermal expansion (CTE) and shear bond strength of veneering porcelain to zirconia frameworks. MATERIAL AND METHODS: Zirconia ceramics (Katana; ZrO(2)), casting gold alloy (DeguDent U; DEG), and feldspathic porcelain (Cerabien ZR; CZR) were used as the bonding substrates. Five types of porcelain (CZR, Cercon ceramkiss (CER), IPS e.max Ceram (EMX), Vintage ZR (VZR), and VITA VM 9 (VM9)) were fired to ZrO(2) discs (n=8). Feldspathic porcelain (Super Porcelain AAA; AAA) designed for metal ceramic systems was fired to DEG discs. To evaluate the strength of veneering porcelain, CZR was veneered on CZR discs. The porcelain with a strong thermal mismatch for each substrate was applied; AAA and CZR were applied to ZrO(2) and DEG substrates, respectively. Shear bond strength was tested after 24 hours of water storage. Debonded surfaces were examined with an optical microscope and SEM. Data were analyzed with 1- and 2-way ANOVA followed by Dunnett and Tukey multiple comparison tests (α=.05). RESULTS: No significant differences in the mean shear bond strength (MPa) were found between groups ZrO(2)-VZR (24.8), ZrO(2)-CZR (27.0), and ZrO(2)-VM9 (30.9). ZrO(2)-CER (22.0) (P=.017) and -EMX (22.1) (P=.020) groups had significantly lower bond strengths than the ZrO(2)-CZR group. ZrO(2)-CZR, -VM9, -CER, -VZR, and -EMX groups demonstrated cohesive failures in veneering porcelain. There was no significant difference among the groups ZrO(2)-CZR, DEG-AAA, and CZR-CZR. Two-way ANOVA showed that interaction between the 2 factors was significant (P<.001). CONCLUSIONS: Strong discrepancies in CTE between veneering porcelains and zirconia significantly affect their bond strength.

Analysis of prognostic factors in patients with gastric varices after endoscopic treatment.

BACKGROUND: The prognostic factors, including gastric variceal bleeding itself, in patients with gastric varices (GV) after endoscopic treatment remain unclear. The aim of this study was to analyze prognostic factors in patients with GV after endoscopic treatment as well as to evaluate safety and efficacy of our endoscopic treatment. PATIENTS AND METHODS: This study enrolled 115 patients who underwent endoscopic treatment for GV between October 1988 and December 2003 using cyanoacrylate and 5% ethanolamine oleate. Successful hemostasis, recurrence rates, rebleeding rates, survival rates, complications and prognostic factors after the treatment were retrospectively reviewed. RESULTS: Treatment sessions for GV were performed 3.4 +/- 2.5 times. All cases, including 14 emergency cases, were treated successfully. The cumulative recurrence rates at 1, 3 and 5 years after the treatment were 7.0%, 15.6% and 20.0%, respectively, and the cumulative rebleeding rates at 1, 3 and 5 years were 3.5%, 8.7% and 14.8%, respectively. The overall survival rates were 78.3%, 63.7% and 51.5% at 1, 3 and 5 years, respectively. Grade B or C in Child-Pugh classification, emergency or elective cases, and association with hepatocellular carcinoma were identified as significant negative prognostic factors after endoscopic treatment by multivariate analysis. Although several complications were observed, there was no mortality. CONCLUSIONS: Grade B or C in Child-Pugh classification, emergency or elective situation, and association with hepatocellular carcinoma are negative prognostic factors after endoscopic treatment.

Influence of convergence angle and cement space on adaptation of zirconium dioxide ceramic copings.

OBJECTIVE: The purpose of the present study was to evaluate the influence of total convergence angle and cement space on internal and marginal adaptation of posterior zirconium dioxide (zirconia) ceramic copings. MATERIAL AND METHODS: Seventy-two standardized mandibular first molar zirconia copings were fabricated with nine parameters: three different total convergence angles (6 degrees , 12 degrees , and 20 degrees ) with three different computer-fixed cement spaces (10, 30, and 60 microm). Marginal adaptation was assessed to measure vertical discrepancy between the coping and abutment by direct viewing. Internal adaptation was evaluated using the cement replica technique with a laser microscope. The Kruskal-Wallis test and Wilcoxon rank-sum test were performed to test for differences in internal space and marginal discrepancy values (alpha=0.05). RESULTS: The median of mean internal spaces/marginal discrepancies ranged from 54.0/27.4 to 128.1/77.8 microm. Statistically significant differences in the internal spaces were found between groups with 6 degrees and 20 degrees convergence angle, regardless of cement space. The different cement spaces did not have any significant influence on the 12 degrees and 20 degrees convergence angle groups. The 60-microm cement space group exhibited statistically smaller marginal discrepancies than the 10-microm cement space group in all the different convergence angles. CONCLUSIONS: Within the limitations of the present study, the internal spaces of zirconia ceramic copings may decrease as the convergence angles of abutments increase. The computer-fixed cement space might influence the marginal adaptation of zirconia ceramic copings. The internal and marginal adaptation of zirconia ceramic copings obtained was within the range of clinical acceptance.

Effect of cooling rate on shear bond strength of veneering porcelain to a zirconia ceramic material.

The purpose of the present study was to evaluate the effect of cooling rates after firing procedures of veneering porcelain on shear bond strength between veneering porcelain and a zirconium dioxide (zirconia; ZrO2) ceramic material. A total of 48 ZrO2 disks were divided equally into three groups. Two veneering porcelains that are recommended for ZrO2 material - Cerabien ZR (CZR), IPS e.max Ceram (EMX) - and one that is recommended for metal ceramics - Super Porcelain AAA (AAA) were assessed. Each group was then further divided into two subgroups (n = 8) according to cooling time (0 or 4 min) after porcelain firing. Specimens were fabricated by veneering the porcelain on the ZrO2 disks, after which shear bond testing was conducted. Bond strength differed significantly by cooling time in ZrO2-AAA (P < 0.001) and ZrO2-EMX (P = 0.001) specimens. There was no significant difference in shear bond strength with respect to cooling time in ZrO2-CZR specimens (P = 0.382). The duration of cooling from firing temperature to room temperature may affect the shear bond strength of veneering porcelain to a zirconia material depending on porcelain material used.

Shear bond strength between an indirect composite veneering material and zirconia ceramics after thermocycling.

The present study evaluated the shear bond strength between an indirect composite material and zirconium dioxide (zirconia) ceramics after thermocycling. A total of 80 zirconia (Katana) discs were divided into five groups and primed with one of following agents: All Bond 2 Primer B (ABB), Alloy Primer (ALP), AZ Primer (AZP), Estenia Opaque Primer (EOP), and Porcelain Liner M Liquid A (PLA). An indirect composite material (Estenia C&B) was then bonded to the primed zirconia. One-half of the specimens (n = 8) in each group were stored in distilled water at 37 degrees C for 24 h, and the remaining eight specimens were thermocycled 5,000 times before shear bond strength testing. Mean bond strengths before thermocycling varied from 10.1 to 15.6 MPa; bond strengths after thermocycling ranged from 4.3 to 17.6 MPa. The ALP group had the highest strengths after thermocycling; there were no significant differences among the PLA, AZP, and EOP groups. The bond strength values for PLA, AZP, EOP, and ALP did not decrease with thermocycling. The application of an acidic functional monomer containing carboxylic anhydride (4-META), phosphonic acid (6-MHPA), or phosphate monomer (MDP) provided durable bond strength between Estenia C&B indirect composite and Katana zirconia.

Influence of priming agents on the short-term bond strength of an indirect composite veneering material to zirconium dioxide ceramic.

OBJECTIVE: Indirect composites are promising alternatives as veneering materials for zirconium dioxide (zirconia) ceramic frameworks. This study evaluated the effects of priming agents and a high-flow bonding agent on the short-term bond of an indirect composite material to a zirconia framework material. METHOD AND MATERIALS: Indirect composite (Estenia C and B) was bonded to particle-abraded zirconia samples (Katana, n = 144) using no (control) or 1 of 8 priming agents: All Bond 2 Primer B (ABB), Alloy Primer (ALP), Clearfil Ceramic Primer (CCP), Clearfil Photo Bond (CPB), Clearfil Photo Bond with Clearfil Porcelain Bond Activator (CPB+Activator), Estenia Opaque Primer (EOP), Porcelain Liner M Liquid A (PLA), and V-Primer (VPR) with or without a high-flow bonding agent (Estenia C and B Opaque). Shear bond strength was tested after 24-hour wet storage. Data were analyzed with Levene test for equality of variance, Dunnett T3 multiple comparison, and Mann-Whitney U test (P = .05). RESULTS: Mean bond strengths without the high-flow bonding agent application varied from 0.1 to 13.6 MPa, whereas bond strengths with bonding agent application ranged from 0.1 to 24.2 MPa. CPB+Activator (containing phosphate MDP and silane) and CPB (containing MDP) revealed the significantly highest bond strength among the 9 groups without high-flow bonding agent application (P < .05). Application of the high-flow bonding agent significantly increased bond strengths (P < .001). CONCLUSION: Primers containing either the functional phosphate monomer MDP or an MDP-silane combination provide superior resin bonds of Estenia C and B composite to Katana zirconia. An intermediate high-flow bonding agent further improves the bond between these materials.