Fatigue resistance of the bond of a glass-infiltrated alumina ceramic to human dentin

Purpose: To evaluate the fatigue resistance of the bond between dentin and glass-infiltrated alumina ceramic, using different luting protocols. Materials and Methods: The null hypothesis is that the fatigue resistance varies with the luting strategy. Forty blocks of In-Ceram Alumina were prepared, and one surface of each block was abraded with 110-μm aluminum oxide particles. Then, the blocks were luted to flat dentin surfaces of 40 human third molars, using 4 different luting strategies (luting system [LS]/ceramic surface conditioning [CSC]) (n=10): (G1) [LS] RelyX-Unicem/[CSC] airborne abrasion with 110-μm Al2O3 particles; (G2) [LS] One-Step + Duo-Link (bis-GMA-based resin)/[CSC] etching with 4% hydrofluoric acid + silane agent; (G3) [LS] ED-Primer + Panavia F (MDP-based resin)/[CSC] Al2O 3; (G4) [LS] Scotchbond1+RelyX-ARC (bis-GMA-based resin)/[CSC] chairside tribochemical silica coating (air abrasion with 30-μm SiO x particles + silane). After 24 h of water storage at 37°C, the specimens were subjected to 106 fatigue cycles in shear with a sinusoidal load (0 to 21 N, 8 Hz frequency, 37°C water). A fatigue survivor score was given, considering the number of the fatigue cycles until fracture. The failure modes of failed specimens were observed in a SEM. Results: G3 (score = 5.9, 1 failure) and G4 (score = 6, no failures) were statistically similar (p = 0.33) and had significantly higher fatigue resistance than G1 (score = 3.9, 5 failures) and G2 (score = 3.7, 6 failures) (p < 0.03). SEM analysis of fractured specimens of G1 and G2 showed that almost all the failures were between ceramic and cement. Conclusion: The MDP-based resin cement + sandblasting with Al2O3 particles (G3) and bis-GMA-based resin cement + tribochemical silica coating (G4), both using the respective dentin bonding systems, were the best luting protocols for the alumina ceramic. The null hypothesis was confirmed.

Effect of microwave disinfection procedures on torsional bond strengths of two hard chairside denture reline materials

Purpose: This study evaluated the potential effects of denture base resin water storage time and an effective denture disinfection method (microwave irradiation at 650 W for 6 minutes) on the torsional bond strength between two hard chairside reline resins (GC Reline and New Truliner) and one heat-polymerizing denture base acrylic resin (Lucitone 199). Materials and Methods: Cylindrical (30 x 3.9 mm) denture base specimens (n = 160) were stored in water at 37°C (2 or 30 days) before bonding. A section (3.0 mm) was removed from the center of the specimens, surfaces prepared, and the reline materials packed into the space. After polymerization, specimens were divided into four groups (n = 10): Group 1 (G1) - tests performed after bonding; Group 2 (G2) - specimens immersed in water (200 ml) and irradiated twice (650 W for 6 minutes); Group 3 (G3) - specimens irradiated daily until seven cycles of disinfection; Group 4 (G4) - specimens immersed in water (37°C) for 7 days. Specimens were submitted to a torsional test (0.1 Nm/min), and the torsional strengths (MPa) and the mode of failure were recorded. Data from each reline material were analyzed by a two-way analysis of variance, followed by Neuman-Keuls test (p = 0.05). Results: For both Lucitone 199 water storage periods, before bonding to GC Reline resin, the mean torsional strengths of G2 (2 days - 138 MPa; 30 days - 132 MPa), G3 (2 days - 126 MPa; 30 days - 130 MPa), and G4 (2 days - 130 MPa; 30 days - 137 MPa) were significantly higher (p < 0.05) than G1 (2 days - 108 MPa; 30 days - 115 MPa). Similar results were found for Lucitone 199 specimens bonded to New Truliner resin, with G1 specimens (2 days - 73 MPa; 30 days - 71 MPa) exhibiting significantly lower mean torsional bond strength (p < 0.05) than G2 (2 day - 86 MPa; 30 days - 90 MPa), G3 (2 days - 82 MPa; 30 days - 82 MPa), and G4 specimens (2 days - 78 MPa; 30 days - 79 MPa). The adhesion of both materials was not affected by water storage time of Lucitone 199 (p > 0.05). GC reline showed a mixed mode of failure (adhesive/cohesive) and New Truliner failed adhesively. Conclusions: Up to seven microwave disinfection cycles did not decrease the torsional bond strengths between the hard reline resins, GC Reline and New Truliner to the denture base resin Lucitone 199. The effect of additional disinfection cycles on reline material may be clinically significant and requires further study. Copyright © 2006 by The American College of Prosthodontists.

Bond strength of hard chairside reline resins to a rapid polymerizing denture base resin before and after thermal cycling

Purpose: This study assessed the shear bond strength of 4 hard chairside reline resins (Kooliner, Tokuso Rebase Fast, Duraliner II, Ufi Gel Hard) to a rapid polymerizing denture base resin (QC-20) processed using 2 polymerization cycles (A or B), before and after thermal cycling. Materials and Methods: Cylinders (3.5 mm x 5.0 mm) of the reline resins were bonded to cylinders of QC-20 polymerized using cycle A (boiling water-20 minutes) or B (boiling water; remove heat-20 minutes; boiling water-20 minutes). For each reline resin/polymerization cycle combination, 10 specimens (groups CAt e CBt) were thermally cycled (5 and 55°C; dwell time 30 seconds; 2,000 cycles); the other 10 were tested without thermal cycling (groups CAwt ad CBwt). Shear bond tests (0.5 mm/min) were performed on the specimens and the failure mode was assessed. Data were analyzed by 3-way ANOVA and Newman-Keuls post-hoc test (α=.05). Results: QC-20 resin demonstrated the lowest bond strengths among the reline materials (P<.05) and mainly failed cohesively. Overall, the bond strength of the hard chairside reline resins were similar (10.09±1.40 to 15.17±1.73 MPa) and most of the failures were adhesive/cohesive (mixed mode). However, Ufi Gel Hard bonded to QC-20 polymerized using cycle A and not thermally cycled showed the highest bond strength (P<.001). When Tokuso Rebase Fast and Duraliner II were bonded to QC-20 resin polymerized using cycle A, the bond strength was increased (P=.043) after thermal cycling. Conclusions: QC-20 displayed the lowest bond strength values in all groups. In general, the bond strengths of the hard chairside reline resins were comparable and not affected by polymerization cycle of QC-20 resin and thermal cycling.

Bond strength of adhesive systems to human tooth enamel

The purpose of this study was to evaluate in vitro three adhesive systems: a total etching single-component system (G1 Prime & Bond 2.1), a self-etching primer (G2 Clearfil SE Bond), and a self-etching adhesive (G3 One Up Bond F), through shear bond strength to enamel of human teeth, evaluating the type of fracture through stereomicroscopy, following the ISO guidance on adhesive testing. Thirty sound premolars were bisected mesiodistally and the buccal and lingual surfaces were embedded in acrylic resin, polished up to 600-grit sandpapers, and randomly assigned to three experimental groups (n = 20). Composite resin cylinders were added to the tested surfaces. The specimens were kept in distilled water (37°C/24 h), thermocycled for 500 cycles (5°C-55°C) and submitted to shear testing at a crosshead speed of 0.5 mm/min. The type of fracture was analyzed under stereomicroscopy and the data were submitted to Anova, Tukey and Chi-squared (5%) statistical analyses. The mean adhesive strengths were G1: 18.13 ± 6.49 MPa, (55% of resin cohesive fractures); G2: 17.12 ± 5.80 MPa (90% of adhesive fractures); and G3: 10.47 ± 3.14 MPa (85% of adhesive fractures). In terms of bond strength, there were no significant differences between G1 and G2, and G3 was significantly different from the other groups. G1 presented a different type of fracture from that of G2 and G3. In conclusion, although the total etching and self-etching systems presented similar shear bond strength values, the types of fracture presented by them were different, which can have clinical implications.

Bond strength of acrylic teeth to denture base resin after various surface conditioning methods before and after thermocycling

This study aimed to evaluate the durability of adhesion between acrylic teeth and denture base acrylic resin. The base surfaces of 24 acrylic teeth were flatted and submitted to 4 surface treatment methods: SM1 (control): No SM; SM2: application of a methyl methacrylate-based bonding agent (Vitacol); SM3: air abrasion with 30-μm silicone oxide plus silane; SM4: SM3 plus SM2. A heat-polymerized acrylic resin was applied to the teeth. Thereafter, bar specimens were produced for the microtensile test at dry and thermocyled conditions (60 days water storage followed by 12,000 cycles). The results showed that bond strength was significantly affected by the SM (P < .0001) (SM4 = SM2 > SM3 > SM1) and storage regimens (P < .0001) (dry > thermocycled). The methyl methacrylate-based adhesive showed the highest bond strength.

Shear bond strength fatigue limit of rest seats made with dental restoratives

Purpose: This study compared the shear bond strength (SBS) to enamel of rest seats made with a glass-ionomer cement (Fuji IX GP Fast), a resin-modified glass-ionomer cement (Fuji II LC), and a composite resin (Z100 MP) under monotonic and cyclic loading. Materials and Methods: Rest seats were built up onto the lingual surfaces of 80 intact human mandibular incisors. Specimens (n=10) were stored in distilled water at 37°C for 30 days and subjected to shear forces in a universal testing machine (0.5 mm/min) until fracture. The SBS values were calculated (MPa) using the bonding area (9.62 mm2) delimited by adhesive tags. A staircase approach was used to determine the SBS fatigue limit of each material. Specimens were submitted to either 10,000 cycles (5 Hz) or until specimen fracture. A minimum of 15 specimens was tested for each material. Scanning electron microscopy was used to examine the mode of failure. Data were statistically analyzed with one-way ANOVA and Tukey HSD tests (α = 0.05). Results: Z100 MP yielded higher (p < 0.05) SBS (12.25 MPa) than Fuji IX GP Fast (7.21 MPa). No differences were found between Fuji II LC (10.29 MPa) and the other two materials (p > 0.05). Fuji II LC (6.54 MPa) and Z100 MP (6.26 MPa) had a similar SBS limit. Fuji IX GP Fast promoted the lowest (p < 0.05) SBS fatigue limit (2.33 MPa). All samples showed cohesive failure patterns. Conclusion: Fatigue testing can provide a better means of estimating the performance of rest seats made with dental restoratives.

Bond strength durability of direct and indirect composite systems following surface conditioning for repair

Purpose: This study evaluated the effect of surface conditioning methods and thermocycling on the bond strength between a resin composite and an indirect composite system in order to test the repair bond strength. Materials and Methods: Eighteen blocks (5 x 5 x 4 mm) of indirect resin composite (Sinfony) were fabricated according to the manufacturer's instructions. The specimens were randomly assigned to one of the following two treatment conditions (9 blocks per treatment): (1) 10% hydrofluoric acid (HF) for 90 s (Dentsply) + silanization, (2) silica coating with 30-Ìm SiOx particles (CoJet) + silanization. After surface conditioning, the bonding agent was applied (Adper Single Bond) and light polymerized. The composite resin (W3D Master) was condensed and polymerized incrementally to form a block. Following storage in distilled water at 37°C for 24 h, the indirect composite/resin blocks were sectioned in two axes (x and y) with a diamond disk under coolant irrigation to obtain nontrimmed specimens (sticks) with approximately 0.6 mm2 of bonding area. Twelve specimens were obtained per block (N = 216, n = 108 sticks). The specimens from each repaired block were again randomly divided into 2 groups and tested either after storage in water for 24 h or thermocycling (6000 cycles, 5°C to 55°C). The microtensile bond strength test was performed in a universal testing machine (crosshead speed: 1 mm/min). The mean bond strengths of the specimens of each block were statistically analyzed using two-way ANOVA (α = 0.05). Results: Both surface conditioning (p = 0.0001) and storage conditions (p = 0.0001) had a significant effect on the results. After 24 h water storage, silica coating and silanization (method 2) showed significantly higher bond strength results (46.4 ± 13.8 MPa) than that of hydrofluoric acid etching and silanization (method 1) (35.8 ± 9.7 MPa) (p < 0.001). After thermocycling, no significant difference was found between the mean bond strengths obtained with method 1 (34.1 ± 8.9 MPa) and method 2 (31.9 ± 7.9 MPa) (p > 0.05). Conclusion: Although after 24 h of testing, silica coating and silanization performed significantly better in resin-resin repair bond strength, both HF acid gel and silica coating followed by silanization revealed comparable bond strength results after thermocycling for 6000 times.

Effect of ultrasonic instrumentation on the bond strength of crowns cemented with zinc phosphate cement to natural teeth. An in vitro study

Several studies have reported the benefits of sonic and/or ultrasonic instrumentation for root debridement, with most of them focusing on changes in periodontal clinical parameters. The present study investigated possible alterations in the tensile bond strength of crowns cemented with zinc phosphate cement to natural teeth after ultrasonic instrumentation. Forty recently extracted intact human third molars were selected, cleaned and stored in physiologic serum at 4°C. They received standard preparations, at a 16° convergence angle, and AgPd alloy crowns. The crowns were cemented with zinc phosphate cement and then divided into four groups of 10 teeth each. Each group was then subdivided into two subgroups, with one of the subgroups being submitted to 5,000 thermal cycles ranging from 55 ± 2 to 5 ± 2°C, while the other was not. Each group was submitted to ultrasonic instrumentation for different periods of time: group 1 - 0 min (control), group 2 - 5 min, group 3 - 10 min, and group 4 - 15 min. Tensile bond strength tests were performed with an Instron testing machine (model 4310). Statistical analysis was performed using ANOVA and Tukey's test at the 5% level of significance. A significant reduction in the tensile bond strength of crowns cemented with zinc phosphate and submitted to thermal cycles was observed at 15 min (196.75 N versus 0 min = 452.01 N, 5 min = 444.23 N and 10 min = 470.85 N). Thermal cycling and ultrasonic instrumentation for 15 min caused a significant reduction in tensile bond strength (p < .05).

Effect of ridge lap surface treatment and thermocycling on microtensile bond strength of acrylic teeth to denture base resins

This study evaluated the effect of denture base polymer type (heat- and microwave-polymerized), ridge lap surface treatment (with and without methyl methacrylate-MMA etching) and thermocycling on the microtensile bond strength (mTBS) of Biotone acrylic teeth. Flat-ground, ridge-lap surface of posterior artifcial teeth were bonded to cylinders of each denture base resin, resulting in the following groups (n=6): G1a - Clássico/with MMA etching; G1b - Clássico/without MMA etching; G2a - OndaCryl/with MMA etching; G2b - OndaCryl/without MMA etching. Rectangular bar specimens with a cross-sectional area of 1 mm 2 were prepared. Half of the bars in each group were thermocycled (5,000 cycles between 4°C and 60°C). mTBS testing was performed in an universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed statistically by three-way ANOVA (a=0.05). There was no statisti-caly signifcant difference (p>0.05) for the factors (resin, surface treatment,and thermocycling) or their interactions. The mean mTBS values (MPa) and standard deviations were as follows: Thermocycling - G1a: 41.00 (14.00); G1b: 31.00 (17.00); G2a: 50.00 (27.00); G2b: 40.00 (18.00); No thermocycling - G1a: 37.00 (14.00); G1b: 43.00 (25.00); G2a: 43.00 (14.00); G2b: 40.00 (27.00). The mTBS of Biotone artifcial teeth to the denture base acrylic resins was not infuenced by the polymer type, surface treatment or thermocycling.

Analysis of the effects of thermal cycling on the microtensile shear bond strength of a self-etching and a conventional pit and fissure sealants to dental enamel

Objective: To analyze the effects of thermal cycling on the microtensile shear bond strength of a self-etching and a conventional pit and fissure sealants to dental enamel. Material and Method: Twenty-four healthy human molars extracted for orthodontic reasons, were sectioned in the mesio-distal direction and divided into two groups (n=24) according to the sealant to be applied: GI - conventional sealant Climpro (3M/ESPE) and GII - self-etching sealant Enamel Loc (Premier Dental). The sealants were applied on flattened enamel in matrixes 1 mm in diameter, in accordance with the manufacturers' recommendations. The specimens were stored in distilled water at 37°C for 24 hours. After this, half the samples of both groups were submitted to 500 thermal cycles in 30s baths at temperatures between 5 and 55°C. Forty-eight hours after the samples were made, the microtensile shear test was performed in an Instron 4411 test machine, with a stainless steel wire with a cylindrical cross section of 0.2mm in diameter at a constant speed of 0.5mm/s. The bond strength values were submitted to ANOVA for 2 factors and the fracture patterns were examined under an optical microscope at 65X magnification. Results: Thermal cycling did not influence the bond strength of the two sealants. The conventional sealant Climpro presented a statistically higher microtensile shear bond strength (11.72MPa, 11.34MPa with and without cycling, respectively) than the self-etching sealant Enamel Loc (5.92MPa, 5.02MPa with and without cycling, respectively). Fracture pattern analysis showed the occurrence of 100% of adhesive failures for Enamel Loc, while the conventional sealant Climpro presented 95% of adhesive failures and 5% of mixed failures. Conclusion: The conventional sealant presented higher microtensile shear bond strength to dental enamel in comparison with the self-etching sealant. Thermal cycling did not affect the bond strength of the sealants used in this study. © 2011 Nova Science Publishers, Inc.

Effect of ceramic surface treatment on the shear bond strength of a resin cement to different ceramic systems

This study evaluated three surface treatments and their effects on the shear bond strength between a resin cement and one of three ceramics. The ceramic surfaces were evaluated with scanning electron microscopy (SEM ) as well. Specimens were treated with 50 μm aluminum oxide airborne particles, 10% hydrofluoric acid etching, or a combination of the two. Using a matrix with a center hole (5.0 mm × 3.0 mm), the ceramic bonding areas were filled with resin cement following treatment. The specimens were submitted to thermal cycling (1,000 cycles) and the shear bond strength was tested (0.5 mm/minute). The failure mode and the effect of surface treatment were analyzed under SEM . Data were submitted to ANOVA and a Tukey test (α = 0.05). Duceram Plus and IPS Empress 2 composite specimens produced similar shear bond strength results (p > 0.05), regardless of the treatment method used. Hydrofluoric acid decreased the shear bond strength of In-Ceram Alumina specimens. For all materials, surface treatments changed the morphological surface. All treatments influenced the shear bond strength and failure mode of the ceramic/resin cement composites.

Effects of three restorative techniques in the bond strength and nanoleakage at gingival wall of Class II restorations subjected to simulated aging

Objective: To evaluate the effects of simulated aging in bond strength and nanoleakage of class II restorations using three different restorative techniques. Materials and methods: Class II preparations (n = 12) were restored using: FS - composite resin Filtek Supreme Plus (3M/ESPE); RMGIC + FS - resin-modified glass ionomer cement Vitrebond Plus (3M/ESPE) + FS; and FFS + FS - flowable composite resin Filtek Supreme Plus Flowable (3M ESPE) + FS. The teeth were assigned into two groups: Control and Simulated Aging - Thermal/Mechanical cycling (3,000 cycles, 20-80 °C/500,000 cycles, 50 N). From each tooth, two slabs were assessed to microtensile bond strength test (μTBS) (MPa), and two slabs were prepared for nanoleakage assessment, calculated as penetration along the restoration margin considering the penetration length (%) and as the area of silver nitrate particle deposition (μm2). Data were analyzed by two-way analysis of variance (ANOVA) followed by Tukey's post hoc test (p < 0. 05). Results: FS presented the highest μTBS to dentin (22. 39 ± 7. 55 MPa) after simulated aging, while the presence of flowable resin significantly decreased μTBS (14. 53 ± 11. 65 MPa) when compared to no aging condition. Both control and aging groups of RMGIC + FS presented the highest values of silver nitrate penetration (89. 90 ± 16. 31 % and 97. 14 ± 5. 76 %) and deposition area (33. 05 ± 12. 49 and 28. 08 ± 9. 76 μm2). Nanoleakage was not affected by simulated aging. Conclusions: FS presented higher bond strength and lower nanoleakage and was not affected by simulated aging. Use of flowable resin compromised the bond strength after simulated aging. Clinical relevance: The use of an intermediate layer did not improve the dentin bond strength neither reduced nanoleakage at the gingival margins of class II restorations under simulated aging conditions. © 2012 Springer-Verlag.

Effects of cement-curing mode and light-curing unit on the bond durability of ceramic cemented to dentin

The aim of this study was to evaluate the effects of different light-curing units and resin cement curing types on the bond durability of a feldspathic ceramic bonded to dentin. The crowns of 40 human molars were sectioned, exposing the dentin. Forty ceramic blocks of VITA VM7 were produced according to the manufacturer's recommendations. The ceramic surface was etched with 10% hydrofluoric acid/60s and silanized. The dentin was treated with37% phosphoric acid/15s, and the adhesive was applied. The ceramic blocks were divided and cemented to dentin according to resin cement/RC curing type(dual-and photocured), light-curing unit (halogen light/QTH and LED), and storage conditions (dry and storage/150 days + 12,000 cycles/thermocycling). All blocks were stored in distilled water (37°C/24h) and sectioned (n = 10): G1-QTH + RC Photo, G2-QTH + RC Dual, G3-LED + RC Photo, G4-LED + RC Dual. Groups G5, G6, G7, and G8 were obtained exactly as G1 through G4, respectively, and then stored and thermocycled. Microtensile bond strength tests were performed (EMIC), and data were statistically analyzed by ANOVA and Tukey's test (5%). The bond strength values (MPa) were: G1-12.95 (6.40)ab; G2-12.02 (4.59)ab; G3-13.09 (5.62)ab; G4-15.96 (6.32)a; G5-6.22 (5.90)c; G6-9.48 (5.99)bc; G7-12.78 (11.30)ab; and G8-8.34 (5.98)bc. The same superscript letters indicate no significant differences. Different light-curing units affected the bond strength betweenceramic cemented to dentin when the photocured cement was used, and only after aging (LED>QTH). There was no difference between the effects of dual-and photo-cured resin-luting agents on the microtensile bond strength of the cement used in this study.

Efficacy of Surface Treatments on the Bond Strength of Resin Cements to Two Brands of Zirconia Ceramic

Purpose: To compare the shear bond strength (SBS) of two cements to two Y-TZP ceramics subjected to different surface treatments.Materials and Methods: Zirconia specimens were made from Lava (n = 36) and IPS e.max ZirCAD (n = 36), and their surfaces were treated as follows: no treatment (control), silica coating with 30-mu m silica-modified alumina (Al2O3) particles (CoJet Sand), or coating with liners Lava Ceram for Lava and Intensive ZirLiner for IPS e.max ZirCAD. Composite resin cylinders were bonded to zirconia with Panavia F or RelyX Unicem resin cements. All specimens were thermocycled (6000 cycles at 5 degrees C/55 degrees C) and subjected to SBS testing. Data were analyzed by post-hoc test Tamhane T2 and Scheffe tests (alpha = 0.05). Failure mode was analyzed by stereomicroscope and SEM.Results: With both zirconia brands, CoJet Sand showed significantly higher SBS values than control groups only when used with RelyX Unicem (p = 0.0001). Surface treatment with liners gave higher SBS than control groups with both ceramic brands and cements (p < 0.001). With both zirconia brands, the highest SBS values were obtained with the CoJet and RelyX Unicem combination (> 13.47 MPa). Panavia F cement showed significantly better results when coupled with liner surface treatment rather than with CoJet (p = 0.0001, SBS > 12.23 MPa). In untreated controls, Panavia F showed higher bond strength than RelyX Unicem; the difference was significant (p = 0.016) in IPS e.max ZirCAD. The nontreated specimens and those treated with CoJet Sand exhibited a high percentage of adhesive and mixed A (primarily adhesive) failures, while the specimens treated with liners presented an increase in mixed A and mixed C (primarily cohesive) failures as well as some cohesive failure in the bulk of Lava Ceram for both cements.Conclusion: CoJet Sand and liner application effectively improved the SBS between zirconia and luting cements. This study suggests that different interactions between surface treatments and luting cements yield different SBS: in clinical practice, these interactions should be considered when combining luting cements with surface treatments in order to obtain the maximum bond strength to zirconia restorations.

Effect of Surface Conditioning Modalities on the Repair Bond Strength of Resin Composite to the Zirconia Core / Veneering Ceramic Complex

Purpose: This study evaluated the effect of different surface conditioning protocols on the repair strength of resin composite to the zirconia core / veneering ceramic complex, simulating the clinical chipping phenomenon.Materials and Methods: Forty disk-shaped zirconia core (Lava Zirconia, 3M ESPE) (diameter: 3 mm) specimens were veneered circumferentially with a feldspathic veneering ceramic (VM7, Vita Zahnfabrik) (thickness: 2 mm) using a split metal mold. They were then embedded in autopolymerizing acrylic with the bonding surfaces exposed. Specimens were randomly assigned to one of the following surface conditioning protocols (n = 10 per group): group 1, veneer: 4% hydrofluoric acid (HF) (Porcelain Etch) + core: aluminum trioxide (50-mu m Al2O3) + core + veneer: silane (ESPE-Sil); group 2: core: Al2O3 (50 mu m) + veneer: HF + core + veneer: silane; group 3: veneer: HF + core: 30 mu m aluminum trioxide particles coated with silica (30 mu m SiO2) + core + veneer: silane; group 4: core: 30 mu m SiO2 + veneer: HF + core + veneer: silane. Core and veneer ceramic were conditioned individually but no attempt was made to avoid cross contamination of conditioning, simulating the clinical intraoral repair situation. Adhesive resin (VisioBond) was applied to both the core and the veneer ceramic, and resin composite (Quadrant Posterior) was bonded onto both substrates using polyethylene molds and photopolymerized. After thermocycling (6000 cycles, 5 degrees C-55 degrees C), the specimens were subjected to shear bond testing using a universal testing machine (1 mm/min). Failure modes were identified using an optical microscope, and scanning electron microscope images were obtained. Bond strength data (MPa) were analyzed statistically using the non-parametric Kruskal-Wallis test followed by the Wilcoxon rank-sum test and the Bonferroni Holm correction (alpha = 0.05).Results: Group 3 demonstrated significantly higher values (MPa) (8.6 +/- 2.7) than those of the other groups (3.2 +/- 3.1, 3.2 +/- 3, and 3.1 +/- 3.5 for groups 1, 2, and 4, respectively) (p < 0.001). All groups showed exclusively adhesive failure between the repair resin and the core zirconia. The incidence of cohesive failure in the ceramic was highest in group 3 (8 out of 10) compared to the other groups (0/10, 2/10, and 2/10, in groups 1, 2, and 4, respectively). SEM images showed that air abrasion on the zirconia core only also impinged on the veneering ceramic where the etching pattern was affected.Conclusion: Etching the veneer ceramic with HF gel and silica coating of the zirconia core followed by silanization of both substrates could be advised for the repair of the zirconia core / veneering ceramic complex.