Luiz Felipe Valandro

Universidade Federal de Santa Maria, Santa Maria da Boca do Monte, Rio Grande do Sul, Brazil

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Publications (206)230.29 Total impact

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    ABSTRACT: Several rotary instruments have been daily employed on clinic to promote cut aiming to adjust the length of fiber posts to the radicular conduct, but there is no information on the literature about the effects of the different rotary instruments and its impact on the micromorphology of surface and mechanical properties of the glass fiber post. This study aimed the impact of rotary instruments upon fiber-matrix integrity, micromorphology and flexural-strength of glass-fiber posts (GFP). GFP (N=110) were divided into 5 groups: Ctrl: as-received posts, DBc: coarse diamond-bur, DBff: extra-fine diamond-bur, CB: carbide-bur, DD: diamond-disc. Cutting procedures were performed under abundant irrigation. Posts exposed to rotary instruments were then subjected to 2-point inclined loading test (compression 45°) (n=10/group) and 3-point flexural-strength test (n=10/group). Fiber-matrix integrity and micromorphology at the cut surface were analyzed using a SEM (n=2/group). Cutting procedures did not significantly affect the 2-point (51.7±4.3-56.7±5.1MPa) (p=0.0233) and 3-point flexural-strength (671.5±35.3-709.1±33.1MPa) (p=0.0968) of the posts (One-way ANOVA and Tukey׳s test). Fiber detachment was observed only at the end point of the cut at the margins of the post. Cut surfaces of the CB group were smoother than those of the other groups. After 3-point flexural strength test, fiber-matrix separation was evident at the tensile side of the post. Rotary instruments tested with simultaneous water-cooling did not affect the resistance of the tested fiber posts but caused disintegration of the fibers from the matrix at the end of the cut, located at the margins. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Journal of the Mechanical Behavior of Biomedical Materials 08/2015; 48. DOI:10.1016/j.jmbbm.2015.04.008 · 3.05 Impact Factor
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    ABSTRACT: Cast metal posts and dowels are inherently dark and, when metal-free restorations are used, could impair the definitive esthetic appearance. Quartz fiber posts could represent a reliable choice for restoring abutment teeth.
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    ABSTRACT: To evaluate the effects of hard machining, glaze firing and hydrofluoric acid etching on the biaxial flexural strength and roughness of a CAD/CAM leucite glass-ceramic; to investigate if ceramic post-machining surface roughness is influenced by the machining order and by the pair of burs used for it. A hundred forty four discs were machined by six nominally identical pairs of burs and divided into groups (n=24): (1) machining-M, (2) machining and glaze firing-MG, (3) machining and hydrofluoric acid etching-MA, (4) machining, glaze firing and hydrofluoric acid etching-MGA, (5) machining followed by polishing, as a control-MP, (6) machining, polishing and hydrofluoric acid etching-MPA. The roughness after each treatment (Ra and Rz) was measured. The discs were submitted to a piston-on-three ball flexure test (ISO 6872/2008) and strength data analyzed through Weibull statistics (95% CI). M resulted in lower characteristic strength (σ0) (128.2MPa) than MP (177.2MPa). The glaze firing reduced σ0 (109MPa), without affecting roughness. Hydrofluoric acid etching increased the roughness without affecting σ0. Spearman's coefficient (rs) indicated strong and significant correlation between machining order and roughness (rsRa=-0.66; rsRz=-0.73). The ceramic post-machining surface roughness differed significantly according to the pair of burs employed (p<0.05). hard machining and glaze firing reduced the leucite ceramic strength, while hydrofluoric acid etching did not affect the strength. Variability in the roughness might be expected after machining, since it was influenced by the machining order and by the bur pairing. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
    Dental materials: official publication of the Academy of Dental Materials 05/2015; DOI:10.1016/j.dental.2015.04.005 · 4.16 Impact Factor
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    ABSTRACT: The purposes of the study were to evaluate the effect of mechanical cycling (MC) on the fracture resistance of endodontically treated weakened roots restored with different intraradicular retainers and to analyze the failure mode. Eighty bovine roots were prepared and restored: 20 roots were reconstructed with cast post-and-cores (CPCs); 20 with fiber posts (FPs); 20 with fiber posts with larger coronal diameter (FPLs); and 20 with anatomic posts (APs). Metal crowns were cemented in all the roots. Half of specimens from each restoration strategy (n = 10) were submitted to MC: CPC-MC, FP-MC, FPL-MC, and AP-MC. The specimens were subjected to a fracture resistance test. The results showed that the type of retainer used was statistically significant (P < 0.0004). The CPC specimens demonstrated a fracture resistance similar to that of the APs, but greater than that of the FPs and FPLs. MC was statistically significant (P < 0.003) and affected AP-MC fracture resistance, which was lower than that of CPC-MC and similar to those of FP-MC and FPL-MC.
    General dentistry 05/2015; 63(3):58-63.
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    ABSTRACT: To compare three different designs for measuring the bond strength between Y-TZP ceramic and a composite material, before and after ceramic surface treatment, evaluating the influence of the size of the adhesive interface for each design. 'Macro' tensile, microtensile, 'macro' shear, microshear, 'macro' push-out, and micropush-out tests were carried out. Two Y-TZP surface treatments were evaluated: silanization (sil) and tribochemical silica coating (30μm silica-modified Al2O3 particles+silanization) (TBS). Failure mode analysis of tested samples was also performed. Both the surface treatment and the size of the bonded interface significantly affected the results (p=0.00). Regardless of the type of surface treatment, the microtensile and microshear tests had higher values than their equivalent "macro" tests. However, the push-out test showed the highest values for the "macro" test. The tensile tests showed the greatest variability in results. The tribochemical silica coating method significantly increased bond strength for all tests. 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 their equivalent 'macro' tests, with the exception of the push-out test (macro>micro). Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
    Dental materials: official publication of the Academy of Dental Materials 04/2015; 31(6). DOI:10.1016/j.dental.2015.03.002 · 4.16 Impact Factor
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    ABSTRACT: This study evaluated the effects of etching with increasing hydrofluoric (HF) acid concentrations on the roughness and flexural strength of a feldspathic ceramic. One hundred and fifty ceramic specimens (14×4×1.2mm(2)) were produced from ceramic blocks (VitaBlocks Mark II). All specimens were polished, chamfered and sonically cleaned in isopropyl alcohol. Specimens were randomly divided into 5 groups (n=30): SC (control) no ceramic surface etching; HF1, HF3, HF5 and HF10 ceramic surface etching for 60s with 1%, 3%, 5% and 10% HF acid concentrations, respectively. Profilometry was performed in all specimens to evaluate roughness prior to flexural strength testing. Data were analyzed using one-way ANOVA and Tukey׳s test (α=0.05). Weibull module (m) and characteristic stress (σc) were also determined. HF acid etching, regardless of the concentration used, led to significantly rougher surfaces than the control (p<0.05). However, the mean flexural strength values were not statistically different among the etched groups (106.47 to 102.02MPa). Acid etching significantly reduced the mean flexural strength when compared with the control (143.3MPa). Weibull modulus of the groups was similar, except for the HF5 group that was higher compared to HF3. Flexural strength was similarly affected by the different HF acid concentrations tested, but roughness increased higher the acid concentration. Ceramic etching led to a significant reduction in strength when compared to the untreated ceramic, regardless of its concentration. Copyright © 2015 Elsevier Ltd. All rights reserved.
    04/2015; 48:241-248. DOI:10.1016/j.jmbbm.2015.03.025
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    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. DOI:10.1016/j.jmbbm.2014.11.016 · 3.05 Impact Factor
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    ABSTRACT: Objective The purpose of this study was to assess the influence of conditioning methods and thermocycling on the bond strength between composite core and resin cement. Material and Methods Eighty blocks (8×8×4 mm) were prepared with core build-up composite. The cementation surface was roughened with 120-grit carbide paper and the blocks were thermocycled (5,000 cycles, between 5°C and 55°C, with a 30 s dwell time in each bath). A layer of temporary luting agent was applied. After 24 h, the layer was removed, and the blocks were divided into five groups, according to surface treatment: (NT) No treatment (control); (SP) Grinding with 120-grit carbide paper; (AC) Etching with 37% phosphoric acid; (SC) Sandblasting with 30 mm SiO2 particles, silane application; (AO) Sandblasting with 50 mm Al2O3 particles, silane application. Two composite blocks were cemented to each other (n=8) and sectioned into sticks. Half of the specimens from each block were immediately tested for microtensile bond strength (µTBS), while the other half was subjected to storage for 6 months, thermocycling (12,000 cycles, between 5°C and 55°C, with a dwell time of 30 s in each bath) and µTBS test in a mechanical testing machine. Bond strength data were analyzed by repeated measures two-way ANOVA and Tukey test (α=0.05). Results The µTBS was significantly affected by surface treatment (p=0.007) and thermocycling (p=0.000). Before aging, the SP group presented higher bond strength when compared to NT and AC groups, whereas all the other groups were statistically similar. After aging, all the groups were statistically similar. SP submitted to thermocycling showed lower bond strength than SP without thermocycling. Conclusion Core composites should be roughened with a diamond bur before the luting process. Thermocycling tends to reduce the bond strength between composite and resin cement.
    Journal of applied oral science: revista FOB 01/2015; 23(1):71-8. DOI:10.1590/1678-775720140113 · 0.80 Impact Factor
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    ABSTRACT: To evaluate the effect of fiber post surface treatments on push-out bond strength between fiber post and root dentin. Sixty bovine mandibular teeth (N = 60) were sectioned (16 mm), prepared (12 mm), embedded with acrylic resin and then allocated into six groups (n = 10): Gr1- Silane coupling agent (Sil) + Conventional resin cement AllC em (Al C); Gr2- Sil + Conventional resin cement RelyX ARC (ARC); Gr3- tribochemical silica coating (TBS) + AlC; Gr4- TBS + ARC; Gr5- No treatment (NT) + AlC; Gr6- NT+ ARC. Specimens were sectioned in four slices (2 mm) and submitted to push-out test. Fracture analyses were executed at x200. The values of the push-out bond strength were submitted to two-way ANOVA and Tukey test (α = 0.05). Resincement did not affect the bond strength values (p = 0.9674), fiber post surface treatment affected the push-out bond strength (p = 0.0353), interaction between factors did not affected the values (p = 0.338). Tukey test did not show differences between the groups. Adhesive failure between cement and dentin was predominantly. The fiber post surface treatment appears have no Influence on bond strength between fiber post and root dentin. The tested fiber posts surface treatment appears do not Influence the fiber post bond behavior.
    The journal of contemporary dental practice 01/2015; 16(1):7-12. DOI:10.5005/jp-journals-10024-1627
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    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. DOI:10.1590/1678-775720140067 · 0.80 Impact Factor
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    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. DOI:10.1590/1678-775720130051 · 0.80 Impact Factor
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    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. DOI:10.1016/j.jmbbm.2014.05.010 · 3.05 Impact Factor
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    ABSTRACT: This study evaluated the influence of silica-based film coatings on the surface of yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP), in particular on the durability of the bond strength between the ceramic and resin cement. Eighty Y-TZP (In-Ceram YZ, Vita) blocks (4 × 4 × 3 mm) were obtained and divided into four groups according to the surface treatments (n = 20): tribochemical silica coating (TBS; Cojet, 3M/ESPE), 5 nm SiO2 nanofilm and silanization (F-5), 500 nm SiO2 nanofilm and silanization (F-500), and 500 nm SiO2 nanofilm + hydrofluoric-acid-etching + silanization (F-500HF). Specimens of composite resin (3.25 mm in diameter and 3 mm in height) were cemented to Y-TZP blocks using resin cement (Relyx ARC). Half of the specimens from each group were tested 24 h after adhesion (B: baseline condition), and the other half were subjected to aging (A: storage for 90 days and 10,000 thermal cycles). The specimens were subjected to shear testing (SBS) (1 mm/min). After testing, the surfaces were analyzed with a stereomicroscope and scanning electron microscope. Micromorphologic and elemental chemical analyses of the treated Y-TZP surface were made by X-ray energy dispersive spectroscopy. Bond strength data were statistically analyzed by Kruskal–Wallis/Mann–Whitney tests (α = 0.05). The surface treatment showed significant differences for B (p = 0.0001) and A (p = 0.0000) conditions. In both storage conditions, TBS and F-5 groups promoted the significantly highest bond strength. Most of the specimens presented adhesive failure. The X-ray energy dispersive spectroscopy analysis depicted the highest peak of silica in the TBS, F-5, and F-500 groups. The adhesion to zirconia can be improved if the surface receives a 5 nm layer of SiO2 nanofilm or is subjected to sandblasting with silica particles, followed by silanization. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 143–150, 2015.
    Journal of Biomedical Materials Research Part B Applied Biomaterials 05/2014; 103(1):143. DOI:10.1002/jbm.b.33184 · 2.33 Impact Factor
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    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). Results 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. Conclusion 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. DOI:10.1016/j.ijadhadh.2013.12.024 · 2.22 Impact Factor
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    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.
    Brazilian Dental Journal 04/2014; 25(2):129-135. DOI:10.1590/0103-6440201302392
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    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; 16(4). DOI:10.3290/j.jad.a31801 · 1.44 Impact Factor
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    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. Method: 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). Result: 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. Conclusion: 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.
    AADR Annual Meeting & Exhibition 2014; 03/2014
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    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
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    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. DOI:10.5005/jp-journals-10024-1191
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    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.
    Brazilian dental journal 12/2013; 24(6):619-25. DOI:10.1590/0103-6440201301996

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1k Citations
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Institutions

  • 2003–2015
    • Universidade Federal de Santa Maria
      • Department of Restorative Dentistry
      Santa Maria da Boca do Monte, Rio Grande do Sul, Brazil
    • Universidad Católica de Santa María
      SMG, Lima Region, Peru
  • 2007–2013
    • University of Bologna
      • Department of Biomedical Science and Neuromotor Sciences DIBINEM
      Bolonia, Emilia-Romagna, Italy
  • 2011–2012
    • University of Zurich
      Zürich, Zurich, Switzerland
  • 2006–2011
    • São Paulo State University
      • Departamento de Materiais Odontológicos e Prótese (Araçatuba)
      São Paulo, Estado de Sao Paulo, Brazil
    • University of Granada
      • Department of Stomatology
      Granata, Andalusia, Spain
  • 2009
    • Fatec Sao Jose dos Campos
      São José dos Campos, São Paulo, Brazil