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Made available in DSpace on 2022-05-01T06:31:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Objective: Evaluate the effect of four preparation designs, two ceramic materials, and two occlusion contact types on the stress distribution of ceramic veneer in upper central incisor. Material and methods: 3D-models were performed in the modeling software containing enamel, dentin, pulp, periodontal ligament and a base of polyurethane resin. The designs were modeled and exported to the computer aided engineering software to perform the static structural analysis. For the mesh, a total of 155429 tetrahedron elements and 271683 nodes were used, after a 10% convergence test. Two materials, lithium disilicate and feldspathic ceramics, were simulated. A static load of 100 N on 45º was applied on the incisal and middle thirds of the palatal tooth region, guided by the occlusal plane. The base was constrained in all directions. The Maximum Principal Stress was the failure criteria chosen for the analysis. Results: The Finite Element Analysis showed that the most conservative designs presented less stress concentration on the ceramic veneer. However, the highest tensile stress concentrations were observed on lithium disilicate veneer with extend design, on the middle third. The type of occlusal contact presented different stress patterns among the preparation designs; the incisal contact showed higher stress concentration compared to middle third contact regardless the ceramic material. Conclusion: To perform a ceramic veneer in upper central incisor, the feldspathic ceramic presented promising results and should be recommended when the extended design was done. Regarding contact types, the incisal contact is more prone to failure regardless the ceramic and preparation design. São Paulo State University (UNESP) Institute of Science and Technology Department of Restorative Dentistry University of Taubaté (UNITAU) Department Dentistry São Paulo State University (UNESP) Institute of Science and Technology Department of Restorative Dentistry

This short report evaluated the differences in stress concentration and the load to fracture of multilayered and monolayer glass ceramic discs. Using a static structural analysis, the 3D model of the discs received a load of 150N and results in maximum principal stress were obtained. For the in vitro analysis, the samples (ø 12 mm) were submitted to a compressive test (100kgf, 1mm/min). The data was analyzed using one-way analysis of variance and Tukey test (?=5%). The monolayer group showed a lower stress peak (129.24 MPa) and higher load to fracture (118.38N) than the multilayered group with 211.04MPa and 48.34N, respectively. All samples presented catastrophic failure with its origin on the tensile surface. Therefore, the monolayer ceramic group showed superior mechanical behavior than the multilayered group.

This work studied the synthetization and morphological characterization of Polyethylmethacrylate (PEMA) nanofibers (NFs) containing titanium dioxide (TiO 2 ) produced by the electrospinning technique. The solution to produce the nanofibers was prepared by dissolving 2.5g PEMA in 6.75mL of 1.1.2.2- tetrachloroethane and 3.375mL of dimethylformamide (DMF), and 0.405g of TiO 2 was added to the solution. The nanofiber production used different distances between the tip of the needle to the collector (10, 12 and 15 cm) and two flow rates (0.05 mLh -1 and 0.08 mLh -1 ) were employed, while the applied voltage was 17kV. The NF morphology was analyzed by Scanning Electron Microscopy (SEM) and Image J software. We used Fourier Infrared Spectroscopy (FTIR) and Energy Dispersive X-Ray Spectroscopy (EDS) to evaluate the structural properties. All parameters were effective in the NF production, however it was shown that the distance of 12 cm produced the best NFs. The mean diameters showed no statistically significant difference between the samples. The FTIR analysis showed characteristic peaks of PEMA and TiO 2 . It was concluded that the employed method was efficient for NF production containing PEMA and TiO 2 ,and the morphological characteristics of the NFs were influenced by the voltage and distance. Keywords Polymer; Fibers; Electrochemistry.

Made available in DSpace on 2021-06-25T11:15:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-04-01 Objective: The purpose of the present study was to synthesize and characterize lithium disilicate glass-ceramics through the Li2O-SiO2 system for determining the most satisfactory sintering parameter by evaluating the crystalline composition, microstructure and mechanical properties. Material and methods: The glass-ceramics were prepared from a glass precursor by means of the melting/cooling technique with a composition of 33.33 Li2O and 66.67 SiO2 (mol.%). The specimens were compressed by the uniaxial pressing technique and three different thermal treatments were used for sintering: 850 °C (Group 1), 900 °C (Group 2), and 950 °C (Group 3), which were determined based on the differential scanning calorimetry (DSC) result. The glass-ceramics were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Archimedes method, microhardness and biaxial flexural strength analyses. Results: The results regarding XRD predominantly showed lithium disilicate phase for all the heat treatments performed. Moreover, grains with a needle form were more predominantly observed in the SEM images for Group 3, as well as a higher densification and consequently higher mechanical properties. In contrast, Group 1 presented the lowest mechanical properties and densification, as well as the highest porosity. Conclusion: The present study demonstrated how extremely important it is to follow the heat treatment recommended by the manufacturers of ceramics, including time and temperature, which possess direct effects in the crystalline phase formation, as well as in the material’s microstructure and mechanical properties. São Paulo State University (Unesp) Institute of Science and Technology Department of Dental Materials and Prosthodontics Department of Bioceramics Federal University of São Paulo (Unifesp) Aeronautics Technological Institute (ITA) São Paulo State University (Unesp) Institute of Science and Technology Department of Dental Materials and Prosthodontics

The aim of this study was to evaluate the influence of mixing method and the empiric water/powder ratio on the dimensional change of two types of dental stones (type III and type IV) at different setting times: baseline, loss of brightness, initial and final setting (1/4 and 1pound Gilmore´s needle, respectively) and, after 48 hours at 37°C. Five mixing methods were used: Gc – manufacturer´s recommendation, G1 – weighed powder/ empiric water volume and powder on water, G2 - weighed powder/ empiric water volume and water on powder, G3 – empiric powder volume, graduated water and powder on water, G4 - empiric powder volume, graduated water and water on powder. The linear expansion was measured according to ISO 6873. The expansion values (x10-2mm) were analyzed by Two-way ANOVA and Tukey HSD test (?=0.05). For type III, the results showed significance for both factors and for interaction; for type IV, only the time were significant (p

Objective: This study evaluated the effects of the incorporation of silver nanoparticles (AgNPs) obtained from Fusarium oxysporum on heat-activated acrylic resin (HAAR) and their influence on resin’s surface roughness, hardness, color alteration and antimicrobial capacity against Candida albicans . Material and Methods: For this, 50 discs of HAAR (2x5 mm) were produced and divided into three groups, Control: HAAR; Ag1: HAAR plus 0.539 mg of AgNPs; and Ag2: HAAR plus 1.1 mg of AgNPs. Knopp hardness (HK), surface roughness (Ra and Rz) and color alteration according to the CIE Lab were measured. Specimens were then evaluated in vitro with regard to C. albicans biofilm formation through formed colony count (CFU/mL). Scanning Electron Microscopy (SEM) and Atomic force microscopy (AFM) analyses were performed. Results: The addition of AgNPs of both concentrations changed Ra, Rz and HK significantly. There was statistically significant difference for L (p=0.00); a*(p=0.00) and b*(p=0.00) parameters. There were no differences between Ag1 and Ag2 biofilm formation, but the comparison of both with the control group presented a significant reduction (p=0.0091) on biofilm formation. SEM and AFM images showed no signs of NPs clustering. Conclusion: It can be concluded tha AgNPs incorporation in HAAR was effective in reducing C. albicans activity, with a slight change in color and hardness of the material, being effective therefore, in regions such as the dental prostheses palate, which have lesser aesthetic appeal. Keywords Acrylic resins; Silver; Antimicrobial agents.

Objective: The aim of this study was to evaluate the effect of different surface clinical treatments on the roughness (Ra) of a lithium disilicate ceramic veneer. Material and Methods: Forty-eight lithium disilicate discs with ceramic veneer and glaze layer were manufactured and distributed into six groups (n=8) according to the surface treatment performed: G1, glaze layer (control group); G2, diamond bur 4138F; G3, diamond bur 4138F + 4138FF; G4, diamond bur 4138F + new glaze layer; G5, diamond bur 4138F + ceramic polishing kit; G6, diamond bur 4138F + rubber cup with diamond paste + felt with diamond paste. Surface Ra measurement (µm) was performed using a profilometer before and after surface treatments, and one specimen from each group was subjected to Scanning Electron Microscopy (SEM) after treatment. Two-way ANOVA and Tukey's test (5%) were used for data analysis. Results: Group 2 (3,00 ± 0,61) b showed higher values of Ra, followed by Group 3 (1,93 ± 0,45) c , Group 6 (1,56 ± 0,22) ac , Group 5 (1,14 ± 0,68) a and Group 4 (0,90 ± 0,26) a . G4, G5 and G6 were not different between each other and control group (1,11 ± 0,21) a . SEM imaging revealed surface smoothness in G1, G4 and G5, and presence of irregularities in G2, G3 and G6. Conclusion: it is possible to conclude that different surface clinical treatments influences the roughness of a lithium disilicate ceramic veneer. Keywords : Ceramics; Dental porcelain; Dental polishing.

Objective: The aim of this study was to observe the influence of different occlusal contacts in a superior pre-molar structure using Finite Element Analysis. Material and Methods: A three-dimensional model of a superior pre-molar was designed to simulate three occlusion situations, namely central occlusion and two types of lateral occlusion contacts. The model presents enamel, dentin, a periodontal ligament and a fixation cylinder separately. All materials were considered isotropic, linear and homogeneous, and the contacts of each structure were perfectly bonded. On analysis software, a load was applied to an occlusal surface at 40° to the long axis on lateral contacts, and directed to the long axis on central occlusion contact. Results: The results were obtained in stress maps and the maximum values were then plotted in table for quantitative comparison, with the enamel concentrating more stress than dentin and the occlusal contact presenting the worst biomechanical behavior. Conclusion: Within the limitations of this study, it is possible conclude that: eccentric contacts have higher potential to develop abfraction lesions on the cervical region of teeth, thus increasing the magnitude of tensile and shear stresses.KeywordsFinite Elements Analysis, Abfraction; Stress distribution; Occlusion, Premolar.

Objective: The electrospinning is a widely adopted technique used to produce the polymeric fibers. The process depends on process parameters (voltage, flow rate and distance from capillary to the collector). The present study aimed to evaluate the influence of these parameters on chitosan fibers, a biopolymer used as scaffolds in dental and oral tissue engineering. Material and Methods: A solution of 7%(m/w) was prepared dissolving 0.7g of chitosan in 7 mL of trifluoroacetic acid (TFA) and 0.3mL of dichloromethane (DCM) (TFA/DCM - 70:30). After 12 hours, polymer solution (5 mL) was drawn into the syringe and pumped through needles of 0.4 mm internal diameter, at a rate of 0.8 mLh-1, different needle-tip-to-collector distances and voltages, for 10 min. Electrospun fibers micrographies were obtained using the Scanning Electron Microscope for morphological analysis. Results: All voltages showed significant difference (p < 0.0001) between them. At 15kV fibers showed higher concentration of beads. At 10 and 12 cm of distance there was no statistical significance (p > 0.0001) but at 15 cm beads formation increased significantly (p < 0.0001). At 12 cm fibers showed lowest fibers diameter in comparison to 10 and 15 cm (p < 0.0001). There was no difference between 10 and 12 cm (p > 0.0001) but in comparison to 15 cm both distances presented significantly difference (p < 0.0001). Conclusion: Thus, it can be concluded that morphology, in chitosan electrospun fibers, is influenced by the voltage and distance and this could describe the mohphological control of these structures. KeywordsChitosan; Fibers; Electrochemical.

Objective: An ideal biomechanics minimizes the stress between implant and bone that can provide success for osseointegrated implants. This study evaluated the strain concentration in surrounding tissue and stress in the components of two implants with different prosthetic connections through an in vitro and in silico methods. Methods: Twenty polyurethane blocks were divided into two groups (n=10) followed by the installation of internal hexagon (IH) (AS Technology – Titanium Fix, Sao Jose dos Campos, Brazil) or locking taper implants (LT) (Bicon Dental Implants). For strain gauge (SG) method, four sensors were placed around the implants. For finite element analysis (FEA), the same block was modeled and analyzed. An axial load (30 kgf) was applied for both methodologies. The values of stress and strain were analyzed for correlation to SG. Results: For SG, LT presented a mean of strain most aggressive (-932) than IH (-632). For FEA, LT showed less stress (-547) then IH (-1169). Conclusion: For two implant’s system, microstrain values capable to induce unwanted bone remodeling were not measured. However, for IH implant, the presence of a retention screw has the disadvantage to concentrate stress while a solid abutment dissipates the axial load through the implant that suggests a better performance for LT group. Keywords: Finite elements analyses; Dental implant; Strain gauge.

Objective: This study aimed to evaluate the retention of acetate resin clasp as when compared to metal clasp. Material and methods: For this purpose, we constructed 10 conventional Co-Cr metal clasps (Ackers) and 20 acetate resin clasps. The acetate resin clasps had the opposition, support and retaining arms made of Co-Cr. Of the 20 esthetic clasps, 10 had the thickness of the retention arm decreased to make it more esthetic. The initial retentive force of the specimens was tested in a universal testing machine through tensile test. After that, the specimens were subjected to 7,000 cycles, each one, in an adapted machine, immersed into artificial saliva, for 36 months of simulated clinical use of a removable partial denture. Data were tabulated for statistical analysis of the retention effectiveness. Results: After cycling, 3-mm-thick and 2-mm-thick acetate resin clasps lost more retention than metal clasps. The material type (p=0.0000) and cycling (p=0.0039) showed a significant effect, but the material/cycling interaction (p=0.1436) did not. Conclusions: Therefore, esthetic clasps presented retention force lower than that of metal clasps. Notwithstanding, the esthetic clasps can be used in clinical cases requiring minimum retention. KeywordsRemovable partial denture; Esthetic clasp; Metal clasp.

Objective: The aim of this study was to analyze the reproducibility of the anatomic models of edentulous maxillary and mandibular arches. Material and Methods: Alginate molds of the edentulous arches of standard model were performed and the tray was placed to the special device. These models received three metal spheres on surface with two positioned on the crest of the alveolar ridge (spheres 1 and 2) and other one perpendicular to the intersection of the midpalatal suture (sphere 3) and impression was performed using alginate. The proportion powder/liquid was measured according manufacturer for both arches. To double molding technique with alginate was necessary to uniformly relieve using an acetate film. After that, were performed the first impression and the second layer of alginate with conventional water-powder-proportion and also the second layer of alginate with altered water-powder-proportion. The distances of each spheres were obtained using a three-dimensional measuring-machine, and the data were analyzed by Dunnet, ANOVA and Tukey tests with a significant level of 5%. Results: A comparison of the water-powder-proportion showed significant differences in the maxillary archer with sphere distance between 3-2 (p < 0.0001) and 1-3 (p < 0.0001). The mandibular archer showed significant differences when relief between distance 1-2 (p

Made available in DSpace on 2021-06-25T11:15:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-04-01 Objetives: this study aimed to fabricate electrospun-based polyetherimide (PEI) fibers, under controlled parameters, and to perform a diameter analysis for potential mechanical improvement of dental materials. Material and Methods: PEI pallets (0.75 g) were dissolved in 2 mL of chloroform and then processed by electrospinning, under a flow rate of 1mLh- 1, three different electrical voltages (10kV, 15kV and 20kV) and three distances (10 cm, 15 cm and 18 cm) between the needle tip and collector. These parameter combinations resulted in nine experimental groups that were analyzed using scanning electron microscopy (SEM) and image processing program for diameter measurement. Statistical analysis was performed using two-way ANOVA with post-hoc Tukey (5% significance). Results: from SEM images it was possible to observe formation of solid, misaligned and flawless defect-free fibers. And from the statistical analysis, distance (p = 0,0026) and the electric tension (p = 0,0012) showed a significant difference, but not for interaction between then (p = 0,4486). Conclusion: thus, it can be concluded that there is a possibility of the morphology control of PEI electrospun fibers, such as diameter, that can be used for a variety of applications such as incorporation in dental materials in order to improve its properties. Institute of Science and Technology of Sao Jose dos Campos São Paulo State University (UNESP) Institute of Science and Technology of Sao Jose dos Campos São Paulo State University (UNESP)

Objective : This study evaluated the hypothesis that different treatments of surface upon three metal alloys for metal ceramic dental prostheses (Gold; Nickel-Chromium; Titanium) do not Influence the values of bond strength with resin cement. Material and Methods: Twenty blocks, 5x5x5 mm, of each alloy were divided into two subgroups (n = 10) according to surface treatments: 1 (Primer): sandblasting with aluminum oxide particles 110 µm (Al 2 O 3 ) + Alloy Primer (Kuraray); 2 (Cojet): sandblasting with silica oxide particles with Cojet-Sand + Silane ESPE-Sil. The conditioned blocks of each group were cemented, with Panavia F, to resin blocks under constant load of 750 g/10 min. The sets were cut to obtain 4 samples with dimensions of 10x1x1 mm per block (n = 10) and the adhesive surface with approximately 1 mm 2 . The microtensile test was done in the universal testing machine at 1 mm/min crosshead speed. The values of bond strength and standard deviation (MPa) were: Au P: 7.33 ± 1.93 d ; Au C: 13.35 ± 2.18 c ; NiCr P: 23.56 ± 6.5 b ; NiCr C: 42.6 ± 5.84 a ; Ti P: 26.17 ± 1.94 b ; Ti C: 44.30 ± 2.3 a . Data were analyzed by variance test (ANOVA) and Tukey’s test, p < 0.05. Results: The results indicated that the conditioning with treatment 2 increased the bond strength between the resin cement and alloys. The lowest bond strengths values were obtained with gold alloy, regardless the surface treatment. Conclusion: The results denied the hypothesis that the metallic alloys surface treatments do not alter the bond strengths values.

The correct parallelism of guiding planes when constructing a Removable Partial Denture not only defines the axis of insertion and removal of the prosthesis, but also limits the possible axes of movement during functioning. Therefore, the purpose of the study was to compare some techniques and the use of an intra-oral device for those preparations. Dummies were performed in a direct manner, simulating the absence of teeth 15, 45, 12 and 42. The four preparation techniques chosen were: Group 1 – freehand preparation; group 2 - guide pins; Group 3 - crown guides and Group 4 - parallel intraoral device – ParalAB. No statistical difference was shown between the mean values of angles found for the freehand (82.85°) and guide pin (83.60°) groups. Also, no statistical significant difference was observed between the mean values of angles found for the resin cap (of 88.83) and intraoral device (88.58 º) groups; however they were superior to the findings for the freehand and guide pin groups. The studied methods are effective for what they were proposed; however, one should select the method according to the experience and skills, to promote the best results.

Objective: The aim of this study was to evaluatethe surface roughness of indirect composites afterpolishing with aluminum oxide (Al2O3) discs. Materialand Methods: One-hundred and eighty specimenswere confectioned with 6 indirect composites using aprefabricated matrix, resulting in six groups (n-30):Group SO - Solidex, Group SI - Signum, Group SF- Sinfony, Group OP - Opallis; Group RE - Resilab,Group EP - Epricord, Group AD - Adoro. Each groupwas divided into three subgroups according to thepolishing (n-10): Subgroup C (Control) - withoutpolishing (polyester strip); Subgroup S - polishingwith Sof-Lex discs; Subgroup T - polishing with TDVdiscs. The surface roughness was measured with aprofilometer. Results: The results were analyzed byANOVA and Tukey tests (5%), resulting in p = 0.00.The mean values (±standard-deviation) measured inRa (?m) for each Group/Subgroup were: RE/C - 0.14(± 0.14) a; EP/C - 0.18 (± 0.46) ab; SO/C - 0.24 (±0.22) abc; SF/S - 0.24 (± 0.17) abc; SF/C - 0.26 (±2.54)abc; SI/C - 0.30 (± 0.34)abcd; SO/T - 0.33(±0.42) abcd; AD/S - 0.34(± 0.88)abcd; AD/C - 0.37(±0.60)ab; SI/S - 0.37(± 1.39)bcd; SO/S - 0.43(± 0.26)cd; EP/S – 0.44 (± 1.02) cd; RE/S - 0.54(±2.02) de;SI/T - 0.65(± 0.88)ef; RE/T - 0.83 (± 0.54) fg; SF/T- 0.85 (± 0.21) fg; AD/T - 0.88 (± 1.74) fg; EP/T- 0.91(± 0.89) g. Conclusion: It is concluded thatpolyester strip resulted in significantly lowest surfaceroughness; polishing with TDV discs resulted insignificantly higher surface roughness compared toSof-Lex discs and that the surface roughness resultsdepend on the composite tested.KeywordsComposite resins; Dental polishing; Biofilms.

Objectives: To investigate the effect of the thermal treatment on the bending strength of ceramic bars (VM7) treated by the cementation protocol. Material and Methods: Forty ceramic bars (20 x 4 x 1.2 mm) were constructed and randomly distributed into 2 groups (n=20): NT - without treatment/control and T – with treatment (50°C above the glass transition temperature, for 15 min). All specimens underwent the cementation process in which one surface of the ceramic bar was etched (20 s) with 10% hydrofluoridric acid, followed by air-water jet washing (60 s), drying (30 s), silane agent application and resin cementation. After storage (distilled water/seven days at 37 oC), the specimens were submitted to 3-point flexure test at 100% humidity/37 oC (v=1 mm/min, load cell of 10 kgf). Results: The bending strength values and standard deviations (MPa) were : NT: 19.98 (3.17) a ; T: 20.45 (4.67) a (one-way ANOVA and Tukey test, σ=0.05). Conclusions: The thermal treatment did not influence on the bending strength mean values of the ceramics studied.

RESUMO: Este estudo teve o proposito de investigar as propriedades microdureza superficial e resistencia a compressao de 5 marcas comerciais de compositos indiretos. Confeccionaram-se 25 especimes de 5 marcas comerciais de compositos (n=5) para cada tipo de ensaio: Signum (Heraeus Kulzer), Solidex (Shofu Inc.), Resilab (Wilcos), Adoro (Ivoclair Vivadent), Sinfony (3M/ESPE). Os especimes foram armazenados em agua destilada a 37oC por 15 dias e submetidos ao ensaio de microdureza superficial com Microdurometro digital Vickers, realizando tres endentacoes com carga de 50g/15s. Para o teste de resistencia a compressao atraves de carga axial foi utilizada com uma ponta de extremidade arredondada de 2 mm diâmetro, adaptada a maquina de Ensaio Universal (DL 2000 – EMIC) a uma velocidade de 0.5mm/min. Os dados foram submetidos aos testes ANOVA e Tukey (5%). Houve diferenca significante entre os compositos (p= 0,00) para a propriedade mecânica de dureza. Os valores medios em microdureza Vickers: Resilab: 56,68a, 4 Signum : 34,60b , Solidex: 31,34c , Adoro: 27,20d , Sinfony: 25,79d . O composito indireto Resilab apresentou valores de dureza significantemente maiores do que todos os compositos testados. O composito indireto Signum apresentou valores de dureza significantemente maiores do que os compositos indiretos Solidex, Adoro e Sinfony. O composito indireto Solidex apresentou valores de dureza significantemente maiores do que Adoro e Sinfony.

Este estudo teve o proposito de investigar a correlacao entre as propriedades microdureza superficial e resistencia a compressao de compositos indiretos. Confeccionaram-se 25 cilindros de 5 marcas comerciais de compositos (n=5) de dimensoes 13 X 4 mm. Signum (Heraeus Kulzer), Solidex (Shofu Inc.), Resilab (Wilcos), Adoro (Ivoclair Vivadent), Sinfony (3M/ESPE). Os especimes foram armazenados em agua destilada a 37oC por 15 dias. Em seguida, foram seccionados, obtendo especimes com dimensoes de 2 X 4 mm, para o ensaio de dureza, e especimes com dimensoes de 8 X 4mm, para o ensaio de resistencia a compressao. Para o ensaio de microdureza superficial com Microdurometro digital Vickers, foi realizada tres endentacoes com carga de 50g/15s. Para o teste de resistencia a compressao atraves de carga axial, foi utilizada com uma ponta de extremidade arredondada de 2 mm diâmetro, adaptada a maquina de Ensaio Universal (DL 2000 – EMIC) a uma velocidade de 0.5mm/min e celula de carga de 50 Kgf. Os dados foram submetidos ao teste de Correlacao de Pearson. A Correlacao de Pearson apresentou um valor de p=0,08, o que significa fraca correlacao entre as duas propriedades mecânicas. A propriedade mecânica dureza nao apresenta relacao com a propriedade mecânica resistencia a compressao. Descritores: Forca compressiva, Dureza, Resina composta