Luiz Felipe Valandro

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

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Publications (215)238.62 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 · 3.42 Impact Factor
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    ABSTRACT: This article reviewed the surface treatments used most often to improve adhesion between zirconia and adhesive cements, focusing on their capacity to provide long-term bonding. Traditional and new treatments for zirconia bonding were searched. Some new treatments were discussed along with topographical views of the modified zirconia. New methods, such as selective infiltration etching and the low-fusing glassy porcelain application are promising, but more research is needed.
    Operative Dentistry 07/2015; DOI:10.2341/14-144-L · 1.27 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. The purpose of this study was to evaluate the long-term success rate of teeth restored with quartz fiber posts and fixed dental prostheses (FDPs). Ninety-nine teeth restored with 114 quartz fiber posts and FDPs were evaluated. The evaluation time ranged from 7 months to 9.25 years. The Kaplan-Meier method was used to obtain success curves. The influence of the tooth location, definitive restoration, and failure pattern upon the success function was analyzed with the log-rank test. The Cox regression test was used to evaluate possible predictors among the interactions of the observed parameters. The success rate of the restorations was 85.86% in a mean period of 5.88 ±1.37 years, with an estimated success probability of 85% at 6.17 years. The statistical analysis identified the factors related to the arch (P=.045) and type of definitive restoration (P=.021) as significantly associated with success. Post debonding was the most frequent failure mode, followed by endodontic failure, with the latter not necessarily being related to the post itself. No root fractures were recorded. Twelve teeth out of the 14 that failed were restored again, bringing the overall survival rate of the teeth to 98%. The rehabilitation of abutment teeth with quartz fiber posts can be considered a reliable procedure; however, adhesive techniques and luting materials require improvement. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.
    The Journal of prosthetic dentistry 05/2015; DOI:10.1016/j.prosdent.2015.03.011 · 1.42 Impact Factor
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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; 31(7). DOI:10.1016/ · 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/ · 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 · 3.42 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: Purpose: Following the tendency of all-ceramic crowns, Y-TZP stands out for its biomechanical properties. The literature describes several possibilities of Y-TZP surface treatment aiming to improve the adhesion to substrate, but there is still a controversy about the long-term effects of them. However , clinical studies (which do not analyze those treatments) observe that mostly failures occur cohesively in porcelain and not for lack of adhesion to the substrate. To evaluate the effects of some surface treatments and cementing agents of Y-TZP/porcelain crowns, this study evaluated the fatigue resistance in a simplified model in order to reduce bias and better study the materials themselves. Methods and materials: For this, 90 preparations were machined in epoxy resin that received Y-TZP frameworks made by CAD/CAM system and veneered by feldspathic ceramic. Six groups were tested (n = 15): PN, ZP and GI – cleaning with isopropyl alcohol; OG – overglaze applying; AO – 125 ␮m Al 2 O 3 sandblasting; CJ – 30 ␮m SiO 2 sandblasting. The crowns from the ZP group were cemented with zinc phosphate and the crowns from GI group were cemented with glass ionomer, while the remaining crowns were cemented using Panavia F (Kuraray). The fatigue resistance was evaluated using stepwise stress until failure: 5k cycles at 200 N followed by 10k cycles at 800, 1000, 1200 and 1400 N. The cement thickness and failure modes were analyzed in stereo-microscope and scanning electron microscopy, and the results were statistically analyzed by Kaplan–Meier and Mantel-Cox log rank tests (5%), 1-way ANOVA and Tukey's test and Weibull nonparametric test. Results: The adhesively cemented crowns showed higher fatigue resistance when compared to the non-adhesively crowns, but the treated crowns were also similar to the non-adhesive ones. Weibull's analysis indicated that all specimens had a higher ratio of late to early failures. The predominantly failure mode was the chipping of the veneer. Conclusion: It can be concluded that the surface treatments didn't influenced the fatigue resistance of Y-TZP-porcelain crowns, but the adhesively luting is recommended in this case.
    Academy of Dental Materials; 09/2014
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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 · 3.42 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

Publication Stats

1k Citations
238.62 Total Impact Points


  • 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
  • 2012
    • Mansoura University
      • Department of Dental Bio Materials
      Ṭalkha, Muhafazat ad Daqahliyah, Egypt
  • 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