Durability of bond between an indirect composite veneering material and zirconium dioxide ceramics

Effects of ceramic microbeads on bonding between a zirconia framework and layered resin composite

This study was conducted to evaluate the effects of ceramic microbeads on the bond strength between resin and zirconia. Microbeads made of zirconia (TZ) and zircon (ZS) were treated with and without hydrofluoric acid (HF). The microbeads were sintered to zirconia disks using intermediate feldspathic porcelains. Two control groups, NB (without microbeads) and AS (without porcelain and microbeads), were also prepared. All specimens were treated with a phosphate primer and veneered with a light-curing resin composite. The 24-h shear bond strengths were determined and analyzed by the Tukey-Kramer test (α=0.05, n=10). The TZ-HF specimen exhibited the highest bond strength, followed by TZ, ZS-HF, ZS, AS, and NB. Scanning electron microscopy observations revealed that the TZ-HF specimen had a complicated debonded surface, and it included microconcavities where the microbeads were detached. Sintering etched zirconia beads onto a zirconia framework with feldspathic porcelains is useful for bonding layered resin composite materials.

Bond strength between a veneering composite resin and zirconia frameworks with attached mechanical retentive devices

The effects of mechanical retentive devices and various surface treatments on the shear bond strength between a veneering composite resin and zirconia was investigated. Zirconia disks were classified into three surface-treatment groups: airborne-particle abrasion, overglazing, and overglazing with white alumina particles of three different grain sizes (50, 70, and 105 μm) attached onto zirconia disks (ZR-50, ZR-70, and ZR-105, respectively). They were further divided into four groups (n=44): unprimed, Clearfil Porcelain Bond Activator (CA), Clearfil Photo Bond (CB), and CA+CB. An indirect composite resin was bonded to zirconia specimens. Shear bond strengths were measured. For the ZR-70 and ZR-105 groups, the CB and CA+CB specimens exhibited higher bond strengths than the other two specimens after thermocycling. The ZR-70 and ZR-105 groups achieved micromechanical interlocking, and priming with a phosphate monomer (MDP) yielded stable bond strengths between the composite resin and zirconia with alumina particles attached as retentive devices.

Optimizing the fitting-surface preparation of zirconia restorations for bonding to dentin

OBJECTIVES

The aim of this study was to identify the relative strengths and weaknesses of different interfaces within the multilayer structure of a zirconia crown restoration when applying different surface pretreatments. These include the influence on shear strengths of different air abrasion protocols, glaze-on techniques, zirconia primers and self-adhesive cements for either the complex structure: zirconia / self adhesive resin composite cement (RCC) / bovine dentin substrate (part 1) or the RCC / zirconia substrate (part 2).

METHODS

In Part 1, zirconia discs, pretreated by either glaze-on techniques or air abrasion using Rocatec™ Soft, were bonded to bovine dentin substrates with different self-adhesive RCCs. In Part 2, steel-cylinders were bonded to zirconia cuboid substrates, pretreated by either different protocols for air-abrasion or a glaze-on-technique, with different self-adhesive RCCs. Shear bond strengths (SBS) were measured for all interfacial combinations.

RESULTS

In part 1, application of air abrasion using Rocatec™ Soft significantly increased the SBS of zirconia to dentin compared to control specimens without pretreatment, while glaze-on techniques did not increase the SBS. Pretreatment of zirconia surfaces with two primers (either Clearfil Ceramic Primer, or Monobond S) showed significantly higher SBS than the controls. Cementations with RelyX Unicem 2 Automix showed significantly higher SBS than with MaxCem Elite. In Part 2, all air abrasion protocols increased the SBS, but there was no significant difference between these protocols. Again the glaze-on technique did not increase SBS. A significant difference between the two RCCs was again observed. When zirconia substrates were air abraded, regardless of which protocol was applied, the highest SBS were obtained by Calibra with P&B active followed by Panavia with or without Clearfil Ceramic Primer Plus. Calibra applied without P&B active exhibited the lowest SBS.

SIGNIFICANCE

Pretreatment of zirconia substrates using air abrasion and/or ceramic primers increased the SBS of the zirconia cement interface. For all tested glaze-on treatments, in our experimental setting no effect was observed.

Influence of coloring liquid immersion on flexural strength, Vickers hardness, and color of zirconia

STATEMENT OF PROBLEM

Zirconia is a widely used restorative material, yet its white color does not meet esthetic requirements and coloring is needed. However, the effects of different durations of coloring have not been thoroughly investigated.

PURPOSE

The purpose of this in vitro study was to evaluate the effects of coloring liquid immersion of different durations on the flexural strength, Vickers hardness, and color of zirconia.

MATERIAL AND METHODS

Fifty bar-shaped and 60 disk-shaped zirconia specimens were milled from nonshaded (Copran Zri) and preshaded (Copran Zri Precoloured Medium) disks by using a computer-aided design and computer-aided manufacturing (CAD-CAM) system. Preshaded specimens were assigned to the group PS and received no further immersion. Nonshaded specimens were divided into 4 subgroups as per immersion time in coloring liquid (Copran Color A2 Shade): control (C; no immersion), G45 (45 seconds of immersion), G90 (90 seconds of immersion), and G135 (135 seconds of immersion). Bar-shaped specimens were subjected to a 3-point flexural strength test by using a universal testing machine (Lloyd LRX), following the International Organization for Standardization (ISO) 6872:2015 specification. Color coordinates of disk-shaped specimens were measured with a spectrophotometer (VITA Easyshade Advance 4.0) over a gray background. Color differences were calculated by using both CIE76 and CIEDE2000 formulas, followed by a comparison of obtained values with perceptibility (CIE76: 3.7, CIEDE2000: 0.8) and acceptability (CIE76: 6.8, CIEDE2000: 1.8) thresholds of each formula. Subsequently, Vickers hardness measurements were conducted. The data were statistically analyzed by using the Shapiro-Wilk test, 1-way ANOVA, and the Tukey HSD test (α=.05).

RESULTS

Immersing zirconia specimens in coloring liquid decreased the flexural strength and hardness values, as group C presented the highest values for both parameters. In addition, prolonged duration had a negative effect on mechanical properties. The flexural strength of groups PS and G45 (P=.993) and groups G90 and G135 (P=.999) was statistically similar. For Vickers hardness, group G135 presented the lowest values with the difference between groups G90 and G135 being statistically similar (P=.061). Color differences among groups varied from 2.49 to 27.33 for ΔE∗, whereas ΔE₀₀ values ranged from 0.58 to 8.26. Compared with group C, ΔE∗ values of all shaded specimens exceeded the acceptability threshold of 6.8. The color difference between each group was higher than the acceptability threshold values of both ΔE∗ and ΔE₀₀ except for groups G45 and PS.

CONCLUSIONS

Colored zirconia specimens had lower flexural strength and Vickers hardness values than nonshaded specimens, regardless of the immersion time or coloring technique.

Bond strength of CAD/CAM-manufactured composite resin and ceramic veneers to a zirconia framework

This study investigated bond strength of CAD/CAM-manufactured composite resin and ceramic veneers to a zirconia framework and analyzed the effect of treatments of veneer surfaces. A CAD/CAM resin-based (AVE) composite or lithium disilicate ceramic (IEC) block was used as the veneer material. AVE and IEC specimens were assigned to receive one of three surface treatments (n = 22): no surface treatment, acid-etching with 9.5% hydrofluoric acid gel, and airborne-particle abrasion with alumina particles. Zirconia disks and AVE or IEC specimens in each group were bonded with a resin-based luting agent, and shear bond strength of the specimens was measured at 0 and 20,000 thermocycles. Significant differences were assessed by the Steel-Dwass test for multiple comparisons and Mann-Whitney U-test (α = 0.05). As compared with other surface treatments, bond strengths were significantly higher at 0 and 20,000 thermocycles in the airborne-particle abraded AVE and acid-etched IEC specimens. Airborne-particle abrasion of the surface of AVE specimens increased bond strength between AVE veneers and zirconia frameworks, while hydrofluoric acid treatment enhanced bond strength between IEC veneers and zirconia frameworks.

In vitro comparison of fracture load of implant-supported, zirconia-based, porcelain- and composite-layered restorations after artificial aging

This study evaluated fracture load of single-tooth, implant-supported, zirconia-based, porcelain- and indirect composite-layered restorations after artificial aging. Forty-four zirconia-based molar restorations were fabricated on implant abutments and divided into four groups, namely, zirconia-based all-ceramic restorations (ZAC group) and three types of zirconia-based composite-layered restorations (ZIC-P, ZIC-E, and ZIC groups). Before layering an indirect composite material, the zirconia copings in the ZIC-P and ZIC-E groups were primed with Clearfil Photo Bond and Estenia Opaque Primer, respectively. All restorations were cemented on the abutments with glass-ionomer cement and then subjected to thermal cycling and cyclic loading. All specimens survived thermal cycling and cyclic loading. The fracture load of the ZIC-P group (2.72 kN) was not significantly different from that of the ZAC group (3.05 kN). The fracture load of the zirconia-based composite-layered restoration primed with Clearfil Photo Bond (ZIC-P) was comparable to that of the zirconia-based all-ceramic restoration (ZAC) after artificial aging.

Shear bond strengths of an indirect composite layering material to a tribochemically silica-coated zirconia framework material

This study evaluated shear bond strengths of a layering indirect composite material to a zirconia framework material treated with tribochemical silica coating. Zirconia disks were divided into two groups: ZR-PRE (airborne-particle abrasion) and ZR-PLU (tribochemical silica coating). Indirect composite was bonded to zirconia treated with one of the following primers: Clearfil Ceramic Primer (CCP), Clearfil Mega Bond Primer with Clearfil Porcelain Bond Activator (MGP+Act), ESPE-Sil (SIL), Estenia Opaque Primer, MR. Bond, Super-Bond PZ Primer Liquid A with Liquid B (PZA+PZB), and Super-Bond PZ Primer Liquid B (PZB), or no treatment. Shear bond testing was performed at 0 and 20,000 thermocycles. Post-thermocycling shear bond strengths of ZR-PLU were higher than those of ZR-PRE in CCP, MGP+Act, SIL, PZA+PZB, and PZB groups. Application of silane yielded better durable bond strengths of a layering indirect composite material to a tribochemically silica-coated zirconia framework material.

Surface Treatments of Zirconia to Enhance Bonding Durability

This article reviewed the surface treatments used most often to improve adhesion between zirconia and adhesive cements, focusing on their capacity to provide long-term bonding. Traditional and new treatments for zirconia bonding were searched. Some new treatments were discussed along with topographical views of the modified zirconia. New methods, such as selective infiltration etching and the low-fusing glassy porcelain application are promising, but more research is needed.

Evaluation of the bond strength between aged composite cores and luting agent

PURPOSE

The aim of this study was to evaluate effect of different surface treatment methods on the bond strength between aged composite-resin core and luting agent.

MATERIALS AND METHODS

Seventy-five resin composites and also seventy-five zirconia ceramic discs were prepared. 60 composite samples were exposed to thermal aging (10,000 cycles, 5 to 55℃) and different surface treatment. All specimens were separated into 5 groups (n=15): 1) Intact specimens 2) Thermal aging-air polishing 3) Thermal aging- Er:YAG laser irradiation 4) Thermal aging- acid etching 5) Thermal-aging. All specimens were bonded to the zirconia discs with resin cement and fixed to universal testing machine and bond strength testing loaded to failure with a crosshead speed of 0.5 mm/min. The fractured surface was classified as adhesive failure, cohesive failure and adhesive-cohesive failure. The bond strength data was statistically compared by the Kruskal-Wallis method complemented by the Bonferroni correction Mann-Whitney U test. The probability level for statistical significance was set at α=.05.

RESULTS

Thermal aging and different surface treatment methods have significant effect on the bond strength between composite-resin cores and luting-agent (P<.05). The mean baseline bond strength values ranged between 7.07 ± 2.11 and 26.05 ± 6.53 N. The highest bond strength of 26.05 ± 6.53 N was obtained with Group 3. Group 5 showed the lowest value of bond strength.

CONCLUSION

Appropriate surface treatment method should be applied to aged composite resin cores or aged-composites restorations should be replaced for the optimal bond strength and the clinical success.

Resin bond to indirect composite and new ceramic/polymer materials: a review of the literature

STATEMENT OF THE PROBLEM

Resin bonding is essential for clinical longevity of indirect restorations. Especially in light of the increasing popularity of computer-aided design/computer-aided manufacturing-fabricated indirect restorations, there is a need to assess optimal bonding protocols for new ceramic/polymer materials and indirect composites.

PURPOSE OF THE STUDY

The aim of this article was to review and assess the current scientific evidence on the resin bond to indirect composite and new ceramic/polymer materials.

MATERIALS AND METHODS

An electronic PubMed database search was conducted from 1966 to September 2013 for in vitro studies pertaining the resin bond to indirect composite and new ceramic/polymer materials.

RESULTS

The search revealed 198 titles. Full-text screening was carried out for 43 studies, yielding 18 relevant articles that complied with inclusion criteria. No relevant studies could be identified regarding new ceramic/polymer materials. Most common surface treatments are aluminum-oxide air-abrasion, silane treatment, and hydrofluoric acid-etching for indirect composite restoration. Self-adhesive cements achieve lower bond strengths in comparison with etch-and-rinse systems. Thermocycling has a greater impact on bonding behavior than water storage.

CONCLUSIONS

Air-particle abrasion and additional silane treatment should be applied to enhance the resin bond to laboratory-processed composites. However, there is an urgent need for in vitro studies that evaluate the bond strength to new ceramic/polymer materials.

CLINICAL SIGNIFICANCE

This article reviews the available dental literature on resin bond of laboratory composites and gives scientifically based guidance for their successful placement. Furthermore, this review demonstrated that future research for new ceramic/polymer materials is required.