[Show abstract][Hide abstract] ABSTRACT: This study evaluated the shear stress presented in glass fiber posts with parallel fiber (0°) and different coronal diameters under fatigue, fracture resistance and FEA. 160 glass-fiber posts (N=160) with eight different coronal diameters were used (DT=double tapered, number of the post=coronal diameter and W=Wider - fiber post with coronal diameter wider than the conventional): DT1.4; DT1.8 W; DT1.6; DT2W; DT1.8; DT2.2 W; DT2; DT2.2. Eighty posts were submitted to mechanical cycling (3×106 cycles; inclination: 45°; load: 50 N; frequency: 4 Hz; temperature: 37 °C) to assess the surviving under intermittent loading and other eighty posts were submitted to fracture resistance testing (resistance [N] and shear-stress [MPa] values were obtained). The eight posts types were 3D modeled (Rhinoceros 4.0) and the shear-stress (MPa) evaluated using FEA (Ansys 13.0). One-way ANOVA showed statistically differences to fracture resistance (DT2.2 W and DT2.2 showed higher values) and shear stress values (DT1.4 showed lower values). Only the DT1.4 fiber posts failed after mechanical cycling. FEA showed similar values of shear stress between the groups and these values were similar to those obtained by shear stress testing. The failure analysis showed that 95% of specimens failed by shear. Posts with parallel fiber (0°) may suffer fractures when an oblique shear load is applied on the structure; except the thinner group, greater coronal diameters promoted the same shear stresses.
Journal of the Mechanical Behavior of Biomedical Materials 03/2015; 43. · 3.05 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Considering that periodontal ligament simulation may influence the stress distribution over teeth restored with intraradicular retainers, this study aimed to assess the combined effect of mechanical cycling and periodontal ligament simulation on both the bond strength between fiber posts and root dentin and the fracture resistance of teeth restored using glass fiber posts.
Ninety roots were randomly distributed into 3 groups (n=10) (C-MC: control; P-MC: polyether; AS-MC: addition silicone) to test bond strength and 6 groups (n=10) (C: control; P: polyether; AS: addition silicone, without mechanical cycling, and C-MC, P-MC and AS-MC with mechanical cycling) to test fracture strength, according to the material used to simulate the periodontal ligament. For the bond strength test, fiber posts were cemented, cores were built, mechanical cycling was applied (2×106 cycles, 88 N, 2.2 Hz, and 45º incline), and the teeth cut into 3 slices (2 mm), which were then subjected to the push-out test at 1 mm/min. For the fracture strength test, fiber posts were cemented, cores were built, and half of the groups received mechanical cycling, followed by the compressive strength (45° to the long axis and 1 mm/min) performed on all groups.
Periodontal ligament simulation did not affect the bond strength (p=0.244) between post and dentin. Simulation of periodontal ligament (p=0.153) and application of mechanical cycling (p=0.97) did not affect fracture resistance.
The materials used to simulate the periodontal ligament did not affect fracture or bond strength, therefore periodontal ligament simulation using the tested materials could be considered optional in the conditions of the study.
Journal of applied oral science: revista FOB 10/2014; 22(5):450-8. · 0.80 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Objective: To evaluate the impact of the type of root canal preparation, intraradicular post and mechanical cycling on the fracture strength of roots. Material and Methods: eighty human single rooted teeth were divided into 8 groups according to the instruments used for root canal preparation (manual or rotary instruments), the type of intraradicular post (fiber posts- FRC and cast post and core- CPC) and the use of mechanical cycling (MC) as follows: Manual and FRC; Manual, FRC and MC; Manual and CPC; Manual, CPC and MC; Rotary and FRC; Rotary, FRC and MC; Rotary and CPC; Rotary, CPC and MC. The filling was performed by lateral compactation. All root canals were prepared for a post with a 10 mm length, using the custom #2 bur of the glass fiber post system. For mechanical cycling, the protocol was applied as follows: an angle of incidence of 45°, 37°C, 88 N, 4 Hz, 2 million pulses. All groups were submitted to fracture strength test in a 45° device with 1 mm/ min cross-head speed until failure occurred. Results: The 3-way ANOVA showed that the root canal preparation strategy (p<0.03) and post type (p<0.0001) affected the fracture strength results, while mechanical cycling (p=0.29) did not. Conclusion: The root canal preparation strategy only influenced the root fracture strength when restoring with a fiber post and mechanical cycling, so it does not seem to be an important factor in this scenario.
Journal of applied oral science: revista FOB 06/2014; 22(3):165-173. · 0.80 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study compared the effects of grinding on the surface micromorphology, phase transformation (t→m), biaxial flexural strength and structural reliability (Weibull analysis) of a Y-TZP (Lava) ceramic using diamond-discs and -burs. 170 discs (15×1.2mm) were produced and divided into 5 groups: without treatment (Ctrl, as-sintered), and ground with 4 different systems: extra-fine (25µm, Xfine) and coarse diamond-bur (181µm, Coarse), 600-grit (25µm, D600) and 120-grit diamond-disc (160µm, D120). Grinding with burs was performed using a contra-angle handpiece (T2-Revo R170, Sirona), while for discs (Allied) a Polishing Machine (Ecomet, Buehler) was employed, both under water-cooling. Micromorphological analysis showed distinct patterns generated by grinding with discs and burs, independent of grit size. There was no statistical difference for characteristic strength values (MPa) between smaller grit sizes (D600 - 1050.08 and Xfine - 1171.33), although they presented higher values compared to Ctrl (917.58). For bigger grit sizes, a significant difference was observed (Coarse - 1136.32>D120 - 727.47). Weibull Modules were statistically similar between the tested groups. Within the limits of this study, from a micromorphological point-of-view, the treatments performed did not generate similar effects, so from a methodological point-of-view, diamond-discs should not be employed to simulate clinical abrasion performed with diamond-burs on Y-TZP ceramics.
Journal of the Mechanical Behavior of Biomedical Materials 05/2014; 37C:133-140. · 3.05 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to assess the fracture resistance of extensively damaged teeth after two root canal preparation techniques (hand and rotary files) and after two filling techniques (active and passive compaction). Sixty-eight maxillary canines roots with an apical diameter equal to that of a #25 K-file were embedded in acrylic resin and the periodontal ligament was simulated by using a polyether impression material. The roots were randomly distributed into four groups (n=17): hand preparation and active compaction (HA), hand preparation and passive compaction (HP), rotary preparation and active compaction (RA), and rotary preparation and passive compaction (RP). All roots were restored with glass fiber post and metallic crown. The specimens were mechanically cycled (500,000 cycles, 45°, 37°C, 133 N, 2 Hz) and then subjected to a fracture resistance test. A single blinded examiner analyzed the external root surface and classified the failure pattern as favorable or unfavorable. The fracture resistance values ranged between 621.15 N (HP) and 785.71 N (HA). However, the Kruskal-Wallis test did not reveal differences in the fracture resistance values among the four groups (p =0.247). Under the tested conditions, root canal preparation and filling techniques had no influence on the fracture resistance of extensively damaged teeth restored with fiber post and metallic crown.
[Show abstract][Hide abstract] ABSTRACT: Purpose
To verify the influence of different instruments and operators on the bonding interfacial area and on the push-out bond strength values.
Material and methods
Fifteen anterior human teeth (n=15) were selected, cleaned and standardized to 15 mm length. Root canals were prepared in 12 mm and the fiber posts were cemented using the RelyX U-100 cement. Three slices were obtained per tooth (N=45) and submitted to the push-out bond strength test. The bonding interfacial area (mm2) of each specimen was calculated based on the disc slice dimensions: coronal and apical diameter and height. The bonding area of each specimen was used to calculate the bond strength (Mpa). The dimensions were analyzed by different operators, using two instruments: G1 – Operator A with a digital caliper; G2 – Operator A with a stereomicroscope; G3 – Operator B with a digital caliper; G4 – Operator B with a digital stereomicroscope; G5 – Operator C with a digital caliper; G6 – Operator C with a stereomicroscope. The mean area was submitted to inter-operator and intra-operator analyses, while the mean area and mean of bond strength were submitted to the 2-way ANOVA with repeated measures and the Tukey test (α=0.05).
The inter-operator kappa was 0.83 to the digital caliper and 0.91 to the stereomicroscope, while the intra-operator kappa was 0.76. The operator and the measurement instrument influenced the interfacial bonding area (p=0.000 and p=0.001) and the push-out bond strength values (p=0.000 and p=0.000, respectively) of the disc slices.
The final push-out bond strength values are influenced by the measuring instrument and by the measurer operator.
International Journal of Adhesion and Adhesives 04/2014; 50:7–10. · 2.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose: To evaluate the microtensile bond strength of indirect resin composite inlays to dentin using two cementation strategies, before and after mechanical aging. Materials and Methods: Standardized inlay cavities (bucco-lingual width: 3 mm; depth: 4 mm) were prepared in 32 human premolars. The teeth were embedded in self-curing acrylic resin up to 3 mm from the cementoenamel junction, impressions were made using a polyvinyl siloxane material, master dies were obtained using type 4 stone, and inlay composite resin restorations were fabricated (Sinfony, 3M ESPE). The teeth were randomly allocated into 4 groups according to the cementation strategy (conventional [C] and simplified [S]) and aging (mechanical cycling [MC] and not aged): C[G1]: Adper SingleBond + RelyX ARC without aging; CMC[G2]: conventional cementation + mechanical cycling (106 cycles, 88 N, 4 Hz, ± 37°C); S[G3]: self-adhesive resin cement (RelyX U-100) without aging; SMC[G4] self-adhesive cementation + mechanical cycling. Intaglio surfaces of composite inlays were treated by tribochemical silica coating in G1 and G2, while G3 and G4 received no surface treatment. Non-aged specimens were stored in a moist environment at ca 37°C for the same period as MC (3 days). Non-trimmed beam specimens (bonding area = 1 mm2) were produced by serial cutting, and microtensile testing was performed (0.5 mm/min). Results: Two-way ANOVA showed that the microtensile bond strength was affected only by cementation strategy (p < 0.0001). Tukey's test showed that groups G1 (35.1 ± 9.1) and G2 (32.7 ± 10.7) presented significantly higher bond strength values than G3 (8.7 ± 6.3) and G4 (5.2 ± 4.6). Conclusion: The use of a conventional adhesive technique and tribochemical silica coating resulted in higher μTBS than the one-step simplified cementation, even after mechanical cycling.
The journal of adhesive dentistry 03/2014; · 1.44 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Objective:
Airborne abrasion using either aluminum oxide (Al2O3) or modified silica-coated (Cojet/3M-ESPE) particles have shown to improve the bonding ability between zirconia/Y-TZP and resin cements. Importantly, it is still controversial whether or not airborne particle abrasion negatively impacts Y-TZP strength due to phase transformation. Therefore, the aims of this study were to evaluate the effect of a chemical surface treatment (i.e., Piranha solution/PS) on the (1) bond strength between Y-TZP and glaze and (2) shear bond strength/SBS between glaze-modified Y-TZP and resin cement. The null hypotheses tested were that chemical treatment would enhance the bond strength glaze/Y-TZP and consequently to the resin cement.
Y-TZP specimens (N=82) were allocated in 5 groups: G1-Y-TZP+glaze; G2-Y-TZP+Al2O3+glaze; G3-Y-TZP+Cojet+glaze; G4-Y-TZP+PS+glaze and G5-Y-TZP+Cojet. Bond strength between Y-TZP and glaze (N=3; except G5) was evaluated using the Scratch Test (ASTM C1624-05) with progressive load (0-30N, 2mm). For SBS test glaze-modified Y-TZP surface was etched (5%HF-60s). Silane coupling agent was applied for 1 min. Resin cement buttons (Multilink Implant–Ivoclar-Vivadent) were bonded using a dedicated jig. Specimens were tested after 24h at 37°C in a Universal Testing Machine (1mm/min). SBS data was analyzed using one-way ANOVA and Tukey’s test (α=0.05).
Different scratch patterns were seen after testing. Scanning electron microscopy revealed circular cracks for G1 and wedging spallation for groups G2, G3 and G4. The SBS showed highest values for G2 (28.75±6.03MPa) and G3 (28.34±10.46MPa) that were significantly higher when compared to G1 (17.83±9.05MPa) and G5 (17.52±6.48MPa). Non-significant differences were seen for G4 (24.57±7.47 MPa) when compared to the other groups.
Our findings suggest that the Y-TZP chemical surface treatment prior to glaze application might be considered an alternative to aluminum oxide or silica-coated traditional conditioning methods, since it led to similar resin bond strength without the need for airborne particle abrasion.
[Show abstract][Hide abstract] ABSTRACT: This study compared the effects of grinding on the surface micromorphology, phase transformation (t→m), biaxial flexural strength and structural reliability (Weibull analysis) of a Y-TZP (Lava) ceramic using diamond-discs and -burs. 170 discs (15×1.2 mm) were produced and divided into 5 groups: without treatment (Ctrl, as-sintered), and ground with 4 different systems: extra-fine (25 µm, Xfine) and coarse diamond-bur (181 µm, Coarse), 600-grit (25 µm, D600) and 120-grit diamond-disc (160 µm, D120). Grinding with burs was performed using a contra-angle handpiece (T2-Revo R170, Sirona), while for discs (Allied) a Polishing Machine (Ecomet, Buehler) was employed, both under water-cooling. Micromorphological analysis showed distinct patterns generated by grinding with discs and burs, independent of grit size. There was no statistical difference for characteristic strength values (MPa) between smaller grit sizes (D600 – 1050.08 and Xfine – 1171.33), although they presented higher values compared to Ctrl (917.58). For bigger grit sizes, a significant difference was observed (Coarse – 1136.32>D120 – 727.47). Weibull Modules were statistically similar between the tested groups. Within the limits of this study, from a micromorphological point-of-view, the treatments performed did not generate similar effects, so from a methodological point-of-view, diamond-discs should not be employed to simulate clinical abrasion performed with diamond-burs on Y-TZP ceramics.
Journal of the Mechanical Behavior of Biomedical Materials 01/2014; 37:133–140. · 3.05 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Aim: This study assessed the effect of fatigue load cycling on human premolars restored with MOD restorations (direct and indirect approaches) on cuspal defection, compared to intact teeth (unprepared) and unrestored teeth with an inlay preparation. Materials and methods: MOD inlay preparations were per- formed on sixty premolars with their roots embedded in acrylic resin. These teeth were divided into six groups (n = 10): (1) intact teeth; (2) unrestored and prepared teeth; (3) teeth restored with direct composite resin; (4) teeth restored with an indirect com- posite resin; (5) teeth restored with injected ceramic inlays (IPS Empress 2 (Ivoclar); (6) teeth restored with CAD/CAM inlays made of feldspathic ceramic (Vita Mark II). All of the indirect restorations were adhesively cemented. Strain-gauges were bonded to the buccal and lingual surfaces of the specimens. Compressive axial loading of 100N was applied on the occlusal face of the specimens to measure the cuspal deflection (microstrain) under compressive loading. These measurements were obtained before and after mechanical cycling (1 Hz, 37°C, 100,000x). Results: Comparing the results obtained before and after fati- guing, the cuspal defection increased only in the CAD/CAM approach. The prepared tooth group had the highest cuspal defection, before and after mechanical cycling. Conclusion: The evaluated restoring approaches decrease the cuspal defection, consequently appear to improve the cuspal reinforcement. Keywords: Inlay restorations, Porcelain, CAD/CAM, Composite resin, Cusp defection, Mechanical loading. How to cite this article: Zamboni SC, Nogueira L, Bottino MA, Sobrinho LC, Valandro LF. Effect of Mechanical Loading on the Cusp Defection of Premolars Restored with Direct and Indirect Techniques. J Contemp Dent Pract 2014;15(1):75-81. Source of support: Nil Confict of interest: None declared.
The journal of contemporary dental practice 01/2014; 15(1):75-81.
[Show abstract][Hide abstract] ABSTRACT: The aims of this study were to evaluate the effect of root canal filling techniques on root fracture resistance and to analyze, by finite element analysis (FEA), the expansion of the endodontic sealer in two different root canal techniques. Thirty single-rooted human teeth were instrumented with rotary files to a standardized working length of 14 mm. The specimens were embedded in acrylic resin using plastic cylinders as molds, and allocated into 3 groups (n=10): G(lateral) - lateral condensation; G(single-cone) - single cone; G(tagger) - Tagger's hybrid technique. The root canals were prepared to a length of 11 mm with the #3 preparation bur of a tapered glass fiber-reinforced composite post system. All roots received glass fiber posts, which were adhesively cemented and a composite resin core was built. All groups were subjected to a fracture strength test (1 mm/min, 45°). Data were analyzed statistically by one-way ANOVA with a significance level of 5%. FEA was performed using two models: one simulated lateral condensation and Tagger's hybrid technique, and the other one simulated the single-cone technique. The second model was designed with an amount of gutta-percha two times smaller and a sealer layer two times thicker than the first model. The results were analyzed using von Mises stress criteria. One-way ANOVA indicated that the root canal filling technique affected the fracture strength (p=0.004). The G(lateral) and G(tagger) produced similar fracture strength values, while G(single-cone) showed the lowest values. The FEA showed that the single-cone model generated higher stress in the root canal walls. Sealer thickness seems to influence the fracture strength of restored endodontically treated teeth.
[Show abstract][Hide abstract] ABSTRACT: To investigate the adhesive potential of novel zirconia primers and universal adhesives to surface-treated zirconia substrates.
Zirconia bars were manufactured (3.0×3.0×9.0mm) and treated as follows on the surface: no treatment (C); air abrasion with 35μm alumina particles (S); air abrasion with 30μm silica particles using one of two systems (Rocatec or SilJet) and Glazing (G). Groups C and S were subsequentially treated with one of the following primers: ZP (Z-Prime Plus), AZ (AZ Primer); MP (Monobond Plus); SU (ScotchBond Universal); and EA (an Experimental Adhesive). Groups Rocatec and SilJet were silanized prior to cementation. Samples form group G were further etched and silanized. Bars were cemented (Multilink) onto bars of silicate-based ceramic (3.0×3.0×9.0mm), at 90° angle, thermocycled (2.500 cycles, 5-55°C, 30 s dwell time), and tested in tensile strength test. Failure analysis was performed on fractured specimens to measure the bonding area and crack origin.
Specimens from group C did not survive thermocycling, while CMP, CSU and CEA groups survived thermocycling but rendered low values of bond strength. All primers presented a better bond performance after air abrasion with Al2O3 particles. SilJet was similar to Rocatec, both of which presented the best bond strength results, along with SMP, SSU and CEA. G promoted mild values of bond strength. Failure mode was predominately adhesive on zirconia surface combined to cohesive of the cement.
Universal adhesives (MP, SU, EA) may be a considerable option for bonding to zirconia, but air abrasion is still previously required. Air abrasion with silica particles followed by silane application also presented high results of bond strength.
Journal of dentistry 11/2013; · 3.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The effect of surface-conditioning of fiber-posts on the flexural strength of the post and on the adhesion between the root dentin and cement and between the fiber-post and the composite core were assessed. The fiber-posts were subjected to cleaning with alcohol (AL), treatment with AL + silane (SIL), sandblasting with Al2O3 particles + SIL, H2O2 etching + SIL, hydrofluoric acid etching + SIL, and H3PO4 etching + SIL. For comparison, another group of specimens was left unconditioned (control group). The conditioned fiber-posts were cemented to bovine roots, and standardized cylindrical resin cores were fabricated. The specimens were subjected to 106 mechanical pulses and then sectioned perpendicular to the long axis of the root. Push-out tests were conducted on the sliced root sections, and microtensile testing was applied to the trimmed sliced core sections. The posts were also subjected to three-point bending tests. The surface-conditioning did not have any significant effect on the push-out strength. However, silanization increased the microtensile strength at the resin core. Sandblasting significantly decreased the flexural strength as compared to other surface treatments. Our study indicates that post surface-conditioning did not improve the post retention in the root canal, although silanization enhanced the adhesion to the core resin. Sandblasting with 125-µm alumina particles should be avoided.
The Journal of Adhesion 10/2013; 89(10). · 0.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose: To evaluate the effect of the cementation strategy and mechanical cycling (MC) on the microtensile bond strength (MTBS) of feldspathic inlays cemented to premolars. Materials and Methods: Forty-eight human premolars were prepared and porcelain inlays were produced. Specimens were allocated into 3 groups, based on the cementation strategy: 1) conventional adhesive cementation (RelyX ARC, 3M ESPE): application of etch-and-rinse single bottle adhesive to dentin / ceramic surface treated with hydrofluoric acid (HF) and silane (S) / cementation with resin cement; 2) simplified cementation using a self-adhesive resin cement (RelyX U100, 3M ESPE); 3) modified simplified cementation using a self-adhesive resin cement (RelyX U100, 3M ESPE) with HF+S treatment. Half of the specimens from each group were submitted to MC (2x106 pulses, frequency = 4 Hz, load = 100 N). Each specimen was serially sliced for MTBS and the failures were classified. The stress distribution analysis using FEA was verified. Results: All of the bar-samples from G2 were lost during cutting of the specimens. Mechanical-cycling had no significant effect on bond strength, whereas cementation strategy significant affected MTBS results. The most common type of failure was cohesive of cement. FEA showed that stresses were concentrated mainly at the loading region going up to the root fixation Conclusion: Porcelain inlays cemented with conventional resin cement or self-adhesive resin cement should be associated with ceramic surface treatment. FEA showed the most critical zone for failure is located in the cement region close to the marginal crest.
The journal of adhesive dentistry 09/2013; · 1.44 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Objective: to compare three different designs for measurement of bond strength between Y-TZP ceramic and composite material, before and after ceramic surface treatment, evaluating the influence of the size of adhesive interface in each design.
Method: Tensile, microtensile, shear, microshear, push-out, and micropush-out tests were evaluated, considering 2 YTZP surface treatments: silanization and tribochemical silica coating (30 µm silica-modified Al2O3 particles) of Y-TZP surface. After the tests, failure mode of the samples was evaluated.
Result: Independent of the type of surface treatment, microtensile test and microshear had higher values than their equivalent “macro” test. On contrary, push-out presented the highest values in the “macro” test. Tensile tests presented the greatest variability in results. Silica coating + silanization significantly increased bond strength, detectable by all the tests.
Conclusion: different test designs can change the outcome for Y-TZP / cement interfaces, in terms of mean values and reliability (variability); the ‘micro’ tests expressed higher bond strengths than its correspond ‘macro’ tests, exception for push-out test (macro > micro); the shear tests appear have been ‘more sensitive’ to detect the differences between the silanization and silica-coating groups, since these differences were higher, which could be detected using lower sample size; ‘micro’ tensile test is inapplicable for silanized Y-TZP, due to the impossibility of obtaining bar shaped specimens during cutting; when the Y-TZP surface is conditioned by tribochemical silica coating method, high percentage of mixed failures occur for all the test, which can represent that the nominal value of bond strength can be in part influenced by cohesive resistance of cement.
Annual Meeting of the IADR Continental European Division 2013; 09/2013
[Show abstract][Hide abstract] ABSTRACT: Purpose: To evaluate the influence of the number of porcelain layers on its cohesive strength and on bonding to zirconia. Materials and Methods: Y-TZP blocks were cut into 1 cm3 specimens (n = 30). The feldspathic porcelain (V9) was applied to the zirconia in different numbers of layers up to 1 cm total thickness (n = 10): ZP1 - one layer; ZP2 - two layers; ZP3 - three layers. Ten specimens with V9 were prepared following the same protocols of groups 1 (P1) and 3 (P3). All study specimens were sintered three times. The specimens were cut into 1 mm2 microbars and tested under tension in a universal testing machine (0.5 mm/min). We calculated strength (σ, in MPa) by dividing the fracture load (N) by the fractured area (mm2). The failure mode was classified as cohesive (used to calculate the cohesive strength, σc) or adhesive (bond strength, σa). The data were analyzed by Kruskal-Wallis and Dunn's tests (α = 0.05) or ANOVA and Tukey's test (α = 0.05), according to their distribution parameters. Results: The ZP1 group presented the highest values for σa data, compared with other groups, which were statistically similar. The predominant failure mode for the bonded specimens was cohesive. With regard to the cohesive strength (σc), ZP1 presented the highest values. Conclusion: It can be concluded that the presence of more than one porcelain layer decreases its cohesive strength and its bonding strength to zirconia.
The journal of adhesive dentistry 08/2013; · 1.44 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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-µm Al2O3) + core + veneer: silane (ESPE-Sil); group 2: core: Al2O3 (50 µm) + veneer: HF + core + veneer: silane; group 3: veneer: HF + core: 30 µm aluminum trioxide particles coated with silica (30 µm SiO2) + core + veneer: silane; group 4: core: 30 µm 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°C-55°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 (α = 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.
The journal of adhesive dentistry 05/2013; · 1.44 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study evaluated the effect of different air-particle abrasion protocols on the biaxial flexural strength and structural stability of zirconia ceramics. Zirconia ceramic specimens (ISO 6872) (Lava, 3M ESPE) were obtained (N=336). The specimens (N=118, n=20 per group) were randomly assigned to one of the air-abrasion protocols: Gr1: Control (as-sintered); Gr2: 50 µm Al2O3 (2.5 bar); Gr3: 50 µm Al2O3 (3.5 bar); Gr4: 110 µm Al2O3(2.5 bar); Gr5: 110 µm Al2O3 (3.5 bar); Gr6: 30 µm SiO2 (2.5 bar) (CoJet); Gr7: 30 µm SiO2(3.5 bar); Gr8: 110 µm SiO2 (2.5 bar) (Rocatec Plus); and Gr9: 110 µm SiO2 (3.5 bar) (duration: 20 s, distance: 10 mm). While half of the specimens were tested immediately, the other half was subjected to cyclic loading in water (100,000 cycles; 50 N, 4 Hz, 37 °°C) prior to biaxial flexural strength test (ISO 6872). Phase transformation (t→m), relative amount of transformed monoclinic zirconia (FM), transformed zone depth (TZD) and surface roughness were measured. Particle type (p=0.2746), pressure (p=0.5084) and cyclic loading (p=0.1610) did not influence the flexural strength. Except for the air-abraded group with 110 µm Al2O3 at 3.5 bar, all air-abrasion protocols increased the biaxial flexural strength (MPa) (Controlnon-aged: 1030±153, Controlaged: 1138±138; Experimentalnon-aged: 1307±184-1554±124; Experimentalaged: 1308±118-1451±135) in both non-aged and aged conditions, respectively. Surface roughness (Ra) was the highest with 110 µm Al2O3(0.84 µm. FM values ranged from 0% to 27.21%, higher value for the Rocatec Plus (110 µm SiO2) and 110 µm Al2O3 groups at 3.5 bar pressure. TZD ranged between 0 and 1.43 µm, with the highest values for Rocatec Plus and 110 µm Al2O3 groups at 3.5 bar pressure.
Journal of the mechanical behavior of biomedical materials. 05/2013;