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Dental implant systems are composed of an implant, prosthetic components, and a crown. Since the implants are made of commercially pure Ti (cp Ti) and prosthetic components are often made of Ti and CoCrMo alloys, a galvanic couple between these two devices may lead to galvanic corrosion, ions release, and even loss of the implant. This study aimed to investigate the corrosion resistance and measure the galvanic potential between cp Ti alloys (annealed microstructured cp Ti G4 and cold-worked nanostructured cp Ti G4) and a CoCrMo alloy. The corrosion resistance has been characterized by measuring the open circuit potential, the potentiodynamic polarization, the potentiostatic polarization, and the zero-resistance current. The cp Ti has been tested before and after a surface acid treatment. The samples’ surfaces have been examined by scanning electron microscopy, and their surface roughness has been measured by a 3D optical profilometer. The polarization results showed that the CoCrMo alloy showed lower corrosion resistance than cp Ti. The surface acid treatment improves dental implant corrosion resistance. The galvanic analysis showed that the cp Ti without surface treatment behaved as an anode and after the acid treatment has a cathodic behavior in relation to the CrCoMo alloy. The highest value of galvanic current was cp TiG4 acid etched in contact with CoCrMo, in pH 2 solution. The galvanic couple with the lowest current has been the nanostructured cp Ti in contact with CoCrMo alloy.

The aim of this work was to study the degradation of yttria-stabilized tetragonal zirconia (Y-TZP) directly exposed to the oral environment. Four groups of Y-TZP were tested G1: TZ-PX-242A, Zpex®; G2: TZ-PX-357, Zpex Yellow®; G3: ProtMat®, and G4: LAVA Frame®. The samples were attached to the base of temporary full dentures of patients and aged for 100 days. In this way, one surface of the samples was exposed to the oral environment. The samples (25 × 2 × 1.5 mm) were cut from noncommercial (G1 and G2) and commercially available (G3 and G4) presintered zirconia blocks. Quantitative and qualitative analyses were performed by X-ray fluorescence (XRF). Microstructural characterization was performed by scanning electron microscopy (SEM), X-ray diffraction (XRD), 3D surface roughness measurements and grain size measurements. The mechanical properties were determined by a four-point bending test. The data were analyzed by one-way ANOVA (p ≤ 0.05), Tukey's test and Weibull analysis. The results showed a tetragonal-monolithic transformation in the zirconia after oral aging. The surface roughness increased in all groups, and groups G3 and G4 showed increases in their flexural strengths.

The aim of this in vitro study was to evaluate the effect of air polishing on the implant abutment surface using different abrasive powders: sodium bicarbonate and amino acid glycine. Fifteen grade III machined surface titanium disks with 8-mm diameter and 2-mm thickness were divided in 3 groups of 5 samples each and subjected to air polishing for 20 seconds with an Ultrajet Flex air-abrasive device and a distinct prophylaxis protocol: air and water (G1); air, water, and sodium bicarbonate (G2); and air, water; and amino acid glycine (G3). After the air polishing, the average roughness (Ra) of the samples was measured using an optical profilometer, and the obtained data were statistically analyzed. We found that G1 and G3 had similar Ra, while Ra values for G2 were significantly higher. This study demonstrated that air-polishing powders containing glycine had less of an effect on the roughness of the surface of titanium disks compared with sodium bicarbonate powders. Future in vivo studies will be conducted to investigate the clinical relevance of the present results.

Made available in DSpace on 2019-10-06T15:35:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-06-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) In this work, the influence of milling strategy and cutter wear on the flexural strength of sintered Y-TZP ceramics machined in a CAD-CAM system, was investigated. Pre-sintered Y-TZP blocks were machined with tungsten carbide (WC) milling cutters and divided into three groups: a) samples machined with New Cutting Tools (NCT); b) samples machined with End-of-life cutting tools (ELCT); and c) samples machined and subsequently polished. The samples were machined parallel and perpendicularly to the diameter of pre-sintered Y-TZP blocks aiming to evaluate the effect of the machining orientation on roughness. After cutting, the specimens were sintered at 1530 °C for 2 h and characterized. After sintering, dense Y-TZP samples presenting grain size average of 0.81 ± 0.23 μm, hardness of 1205 ± 12 HV, K C of 7.7 ± 0.4 MPam 1/2 and flexural strength of 1207 ± 199 MPa were obtained. Furthermore, the control roughness (polished surfaces) presented R a = 0.058 ± 0.011 μm. The surface roughness of the samples was influenced by the machining methodology using NCT mills, with R a = 0.386 ± 0.149 μm and R a = 0.292 ± 0.105 μm for samples machined parallel and perpendicularly to the pre-sintered Y-TZP blocks, respectively. The use of ELCT led to a roughness increasing (R a = 0.582 ± 0.183 μm for samples milled perpendicularly, and R a = 0.919 ± 0.164 μm for samples cut parallel to the pre-sintered blocks. The flexural strength of the sintered Y-TZP decreases with use of ELCT as consequence of surface roughness increasing, resulting from wear of WC mills, which presented chippings with sizes ranging from 30 to 340 μm in the cutting edge. Universidade do Estado do Rio de Janeiro - Faculdade de Tecnologia de Resende UERJ-FAT, Rodovia Presidente Dutra, km 298 Universidade Estadual Paulista - Faculdade de Engenharia de Guaratinguetá UNESP/FEG, Av. Ariberto Pereira da Cunha, 333, Portal das Colinas Centro Universitário de Volta Redonda - UniFOA, Av. Paulo Erlei Alves Abrantes, 1325 - Três Poços Instituto Militar de Engenharia Materials Science Department, Pça Gen. Tibúrcio, 80, Praia Vermelha Universidade Estadual Paulista - Faculdade de Engenharia de Guaratinguetá UNESP/FEG, Av. Ariberto Pereira da Cunha, 333, Portal das Colinas CNPq: n° 311119/2017-4 FAPERJ: n° E26-201.476/2014

The aim of this work was to analyze the properties and shear bond strength (SBS) of lithium disilicate to resin cement before and after etching the glass-ceramic surfaces. Lithium-metasilicate samples were heat treated and characterized by Scanning Electron Microscopy, X-ray diffraction and roughness measurement. For the analysis of the shear bonding strength (SBS) of lithium disilicate to dental resin cement, three groups (n = 12) of Li2Si2O5 were prepared: 1°)without treatment (NT); 2°)surface etching with hydrofluoric acid(HF), followed by silane agent and adhesive treatment; 3°) surface treatment with a self-etching ceramic primer (SECP). After the heat-treatment, the samples had Li2Si2O5 crystalline phase dispersed in a residual amorphous phase. Roughness of the NT and SECP samples was smaller that of the HF samples. Samples without surface treatment (NT) had the lowest SBS (5.5MPa). HF(24.2MPa) and SECP(24.8MPa) samples has similar SBS. Weibull statistics showed that HF-samples are more reliable than NT and SECP. The SBS was significantly increased by either HF etching and SECP surface treatment. While the chemical characteristics of the surface submitted to SECP treatment are considered to be responsible for the SBS increase, the main adhesion mechanism after HF etching is the increase in surface roughness.

Introduction: Excess of adhesive around brackets negatively impact oral health of orthodontic patients. Objective: Evaluate the influence of orthodontic bonding system in removal of adhesive flash around orthodontic brackets. Methods: Based on their characteristics, four orthodontic bonding systems were selected: lightcuring adhesive (G1 - TransbondTM XT); pink pigmented light-curing adhesive (G2- TransbondTM Plus Color Change); resin-modified glass ionomer cement (G3 - FujiOrthoTM LC); and auto-curing adhesive (G4 - ConciseTM). For each group (n=10), a single operator placed metal brackets on bovine teeth (n=40) and used an explorer tip to visually remove flash excess. After curing / setting, the sampleswere taken to a stereomicroscope and the Axio Vision 4.4 software was used to measure the area of remnant adhesive flash around each bracket. The quantitative data obtained was analyzed by the Kruskal-Wallis and Dunn’s post hoc test at = 0.05. Results: The results show that the resin-modified glass ionomer cement (G3) had a larger area of remnant material than the other groups. There was no statistical difference between the other groups (G1, G2, and G4), independently of pigmentation or curing technique. Conclusion: It was concluded that the use of a resin-modified glass ionomer cement results in a larger area of remnant flash excess, which can negatively impact oral health. Pigmentation and curing technique did not influence on remnant flash excess. Introdução: O excesso de material de colagem que permanece ao redor dos bráquetes impacta negativamente a saúde bucal dos pacientes ortodônticos. Objetivo: Avaliar a influência dos sistemas de colagem ortodônticos na remoção de excesso de adesivo ao redor de bráquetes. Métodos: Baseado em suas características, quatro sistemas de colagem ortodônticos foram selecionados: adesivo fotopolimerizável (G1 – TransbondTM XT); adesivo fotopolimerizável com pigmentação rosa (G2 - TransbondTM Plus Color Change); cimento de ionômero de vidro reforçado com resina (G3 - FujiOrthoTM LC); e adesivo autopolimerizável (G4 - ConciseTM). Para cada grupo (n=10), um único operador posicionou os bráquetes em dentes bovinos (n=40) e utilizou uma sonda exploradora para remoção visual do excesso de material de colagem. Após a polimerização / tempo de cura, as amostras foram levadas ao estereomicroscópio e o software Axio Vision 4,4 foi utilizado para mensurar a área de excesso de adesivo remanescente ao redor de cada bráquete. Os dados quantitativos obtidos foram analisados pelos testes de Kruskal-Wallis e post-hoc de Dunn em significância de = 0,05. Resultados: O cimento de ionômero de vidro reforçado por resina (G3) apresentou a maior área de remanescente de excesso. Não houve diferença estatisticamente significativa entre os demais grupos (G1, G2 e G4), independente da pigmentação ou do método de polimerização. Conclusão: O uso de cimento de ionômero de vidro reforçado por resina resulta em maior área de excesso remanescente, o que pode impactar negativamente a saúde bucal. A pigmentação e o método de polimerização não influenciaram no excesso de material remanescente.

Summary Objectives To analyse, in vitro, surface properties and the shear bond strength after debonding and polishing procedures of ceramic brackets directly bonded to 0.3-0.5-mm thick feldspathic veneers. Materials and methods Fifty six feldspathic ceramic veneers samples (0.3 to 0.5-mm thick) were allocated into groups according to veneers surface treatment procedures: (S) glaze layer was retained; (SHF) hydrofluoric (HF) acid etch; (SOXA) Al2O3 sandblasting; and (SB) diamond burs roughening. Specimens were treated with silane Monobond N® and ceramic brackets bonded with Transbond XT®. Shear bonding strength (SBS) was assessed with a universal testing machine and ARI evaluated under a stereomicroscopic coupled to a digital camera. Remaining bonding composite was removed using a porcelain polishing kit and surface roughness assessed with a stylus profilometer. Results No statistically significant differences were identified for SBS among the study groups (S, SHF, SOXA and SB) (P > 0.05). The majority of the specimens presented ARI scores 3 and 2 (P > 0.05). All of the study groups presented increased surface roughness after debonding and polishing procedures (P Conclusions Surface treatment with hydrofluoric acid etch, Al2O3 sandblasting and diamond bur did not enhance SBS of orthodontic brackets bonded to ceramic veneers. Ceramic surfaces treated with diamond burs presented significantly increased roughness after adhesive removal.

Commercially pure titanium (Ti G2 and Ti G4) and the Ti–6Al–4V (Ti G5) alloy have limitations for biomedical applications, due to either low mechanical strength (Ti G2, Ti G4) or the possible release of toxic ions (Ti G5). Since Ti alloys have a low hardening coefficient, it is very difficult to improve their mechanical properties by work hardening. The purpose of this work was to compare the mechanical and clinical properties of Ti G4 nanostructured after severe plastic deformation by ECAP (Ti G4 Hard) with those of Ti G2, Ti G4 and Ti G5. Bars, disks and dental implants made with Ti G2, Ti G4, Ti G5 and Ti G4 Hard were tested. Mechanical tests (tension, compression, hardness, elastic modulus, fatigue and torque) and roughness measurements were performed. The results of the mechanical tests showed that Ti G4 Hard has a higher mechanical strength and a lower elastic modulus than Ti G2, Ti G4 and Ti G5. Scanning electron microscopy and roughness measurements results showed that acid etched Ti G4 Hard nanostructured has better surface morphological features than Ti G2, Ti G4 and Ti G5. The clinical performances of Ti G4 and Ti G4 Hard were similar. The high mechanical strength of Ti G4 Hard means that it can be used to replace Ti G5 in several clinical applications, with the advantage of not releasing toxic ions. The Ti G4 Hard dental implants have adequate mechanical properties and can be inserted in areas with low bone volume. Keywords: Titanium, High strength cp Ti, Strain hardening, Ti nanostructured, Dental implant, ECAP

Objective: This study compared the fatigue behavior of endodontic instruments manufactured with conventional NiTi alloy electropolishing, RaCe (FKG Dentaire, LaChauxdeFonds, Switzerland), with instruments manufactured with NiTi CM Wire subjected to thermomechanical treatment, in the manufacturing process, HyFlex CM (Coltène Whaledent, Cuyahoga Falls, Ohio, USA), both with similar geometry and dimensions in order to determine the influence of the manufacturing process in the fatigue resistance. Methods: The methodoly consisted of twenty HyFlex CM and RaCe instruments with D0 0.25 mm, taper 0.06 mm / mm, 25 mm length, both with triangular cross section. The fracture resistance was evaluated by static fatigue test, using a stainless artificial canal with 5mm of radius (86°), recording the time and calculating the number of cycles until fracture occurs (NCF). For statistical analysis the Student t test was used The fractured instruments surface was analyzed by SEM. Results: The NCF was significantly higher for HyFlex CM instruments in comparison with RaCe files (P˂0.05) being 1336% more resistant to fatigue. The analysis of the fractured surface by SEM showed ductile-kind morphological characteristics for both instruments and the absence of plastic deformation. Conclusion: HyFlex CM instruments present higher values of NCF. Thus, it can be concluded that the thermal treatment to which these instruments with CM Wire alloy are submitted makes them more resistant to fracture than Race instruments manufactured with conventional NiTi alloy electropolishing. RESUMO Objetivo: Este estudo comparou a vida em fadiga de instrumentos endodônticos fabricados com a liga de NiTi convencional com eletropolimento de superfície, RaCe (FKG Dentaire, LaChauxdeFonds, Suiça), com instrumentos fabricados com a liga de NiTi CM Wire, submetidos a tratamento termomecânico, no processo de fabricação, HyFlex CM (Coltene Whaledent, Cuyahoga Falls, Ohio, EUA), ambos com geometria e dimensões semelhantes, visando determinar a influência do processo de fabricação das ligas e do acabamento superficial na resistência à fadiga. Métodos: Foram utilizados vinte instrumentos HyFlex CM e RaCe com D0 0,25mm, conicidade 0,06mm/mm, 25mm de comprimento, ambos com seção transversal triangular. A resistência à fratura foi avaliada através de teste estático de fadiga ciclica, utilizando um canal artificial em aço-inoxidável com 5mm de raio (86°), sendo registrado o tempo e calculado o número de ciclos para ocorrer a fratura (NCF). Para análise estatística empregou-se o teste t de Student. As superfícies de fratura dos instrumentos foram analisadas em MEV. Resultados: O NCF foi significativamente maior para os instrumentos HyFlex CM em comparação com as limas RaCe (p˂0,05), sendo 1336% mais resistentes à fadiga. A análise das superfícies fraturadas em MEV revelou características morfológicas do tipo dúctil para ambos os instrumentos e ausência de deformação plástica. Conclusão: Os instrumentos HyFlex CM apresentaram valores mais elevados de NCF. Deste modo, pode-se concluir que o tratamento térmico a qual estes instrumentos com a liga CM Wire foram submetidos os torna mais resistentes à fratura do que os instrumentos Race, fabricados com a liga de NiTi convencional com eletropolimento.

The aim of this study was to evaluate, in vitro, the microbiological sealing at the implant and different angles frictional prosthetic abutment interface, submitted or not to mechanical cycling, as well as the deactivation force and evaluation of the implant-abutment interface by scanning electron microscopy. For this study, the sealing capacity of eighty sets of abutments/implants of each angle, with and without mechanical cycling, with internal conical connection (locking tapper) (4.3 mm × 9.0 mm) constituted in Titanium alloy (Ti6Al4V), and stainless steel angled prosthetic abutment was evaluated (18Cr14Ni2.5Mo) according to ASTM F138-13a (Arcsys, FGM, Joinville, Brazil), 6 mm high and 4.2 mm in diameter at the coronary portion, and 3.5 mm high transmucosal, in 4 different angles (0, 5, 10 and 20°). After in vitro tests, 100% biological sealing was observed at the implant / prosthetic abutment interface within cycled and non-cycled conditions, for the straight, 5, 10 and 20° inclination groups. There was no statistically significant difference in the removal force of the prosthetic abutments at different angles, under non-cycled conditions; however, under mechanical loading, the deactivation force was significantly higher for straight prosthetic abutments than with 10 and 20° of angulation. Surface analysis revealed good adaptation between implants and abutments, and the presence of wear areas, independently of mechanical loading. It is concluded that the analysis of implant and prosthetic abutment interface revealed good adaptation between the parts, for all analyzed samples.

AIM To report the main differences seen by direct visual inspection between original and counterfeit Reciproc instruments, together with an evaluation of instrument bending resistance, cyclic fatigue, surface finish, Vickers microhardness and chemical composition. METHODOLOGY The visual aspects of original Reciproc R25 (VDW, Munich, Germany) and counterfeit Reciproc R25 instruments (claimed to be original, supposedly with dimensions similar to those of Reciproc R25 files, bought at www.mercadolivre.com.br) were evaluated under direct observation, stereomicroscopy and scanning electron microscope. The flexibility of original and counterfeit Reciproc R25 was determined via 45° bending tests according to the ISO 3630-1 specification. Instruments were also subjected to cyclic fatigue resistance, measuring the time to fracture in an artificial stainless steel canal with a 60° angle and 5-mm radius of curvature. The fracture surfaces of all fragments were examined under a scanning electron microscope. Roughness of the instruments was quantified using a profilometer, and the microhardness test was carried out using a Vickers hardness tester. Energy-dispersive X-ray microanalysis (EDX) was also carried out. Results were analysed statistically using the Student's t-test at a significance level of P

The aim of the present study was to evaluate the influence of Blue thermal treatment on the bending resistance and cyclic fatigue of conventional M-Wire Reciproc files (VDW, Munich, Germany). The roughness pattern and the microhardness of the files were also assessed.Flexibility of standard Reciproc R25 files and the corresponding Blue prototypes was determined by 45° bending tests according to the ISO 3630-1 specification. Instruments were also subjected to cyclic fatigue resistance, measuring the time to fracture in an artificial stainless steel canal with a 60° angle and a 5-mm radius of curvature. The fracture surface of all fragments was examined with a scanning electron microscope. The roughness of the working parts was quantified by using a profilometer, and the microhardness test was performed using the Vickers hardness tester. Results were statistically analyzed using the Student t test with a level of significance set at P .05.Reciproc Blue instruments presented a significantly longer cyclic fatigue life and significantly lower bending resistance than the original Reciproc instrument (P .05). Regarding the roughness pattern, there was no significant difference between Reciproc Blue and the original Reciproc instruments (P .05), whereas Reciproc Blue revealed significantly lower microhardness than the original Reciproc instrument (P .05).Reciproc Blue nickel-titanium showed improved all-around performance when compared with conventional M-Wire superelastic nickel-titanium, demonstrating improved flexibility and fatigue resistance, and reduced microhardness while maintaining similar characteristics of the surface.

Statement of problem Modifications have been made in the microstructure and sintering parameters of monolithic zirconia to improve esthetics qualities and avoid chipping of 2-layer restorations. However, how these modifications affect the physical and mechanical properties of zirconia is unclear. Purpose The purpose of this in vitro study was to compare the influence of different sintering parameters on the microstructure, 4-point flexural strength, density, and grain size of 2 commercially available zirconia advocated for the fabrication of monolithic dental prostheses and 1 commercially available zirconia for use as a core material. Material and methods Three presintered blocks (Ceramill Zolid, Prettau, and IPS e.max ZirCAD) were used. Specimens were cut and sintered as per the manufacturer's recommendation or as per a modified heating protocol. Ceramill Zolid (Z1450) was sintered at 1450 °C, Prettau (P1600) was sintered at 1600 °C, and IPS e.max ZirCAD (I1530) was sintered at 1530 °C by following the manufacturer's heating protocol. Groups Ceramill Zolid Z1530 and Z1600 were sintered at temperatures higher than the manufacturer's recommendation. Specimens from each group (n=13) were analyzed with X-ray diffraction (XRD), density calculus, average grain size measurement, and 4-point flexural tests. Data were compared by using ANOVA (α=.05). Results XRD analysis showed the presence of a tetragonal metastable phase in all groups before and after sintering. No significant differences were found in relative density values for the 3 Ceramill groups (5.98 g/cm3). Groups I1530 (6.03 g/cm3) and P1600 (6.03 g/cm3) had similar density results greater than 6.00 g/cm3. The average grain size of all groups remained lower than 1 μm. P1600 had the highest grain size (0.817 μm), and Z1450 presented the lowest grain size (0.465 μm). P1600 showed the most homogeneous flexural strength and the highest Weibull modulus (m=8.22). Z1530 presented the lowest Weibull modulus (m=4.58). IPS e.max ZirCAD (I1530) had the highest flexural strength (1057.41 ±150.54 MPa), and Ceramill Zolid Z1450 had the lowest (621.01 ±138.08 MPa). Conclusions The flexural strength, microstructure, crystal phase, and grain size of the analyzed zirconia varied as per the sintering processing. The IPS e.max ZirCAD had the highest flexural strength (1057.41 ±150.54 MPa), followed by Prettau zirconia (864.18 ±118.21), with a statistically significant difference (P

This work evaluated the mechanical strength and surface roughness of MgZn30Ca5ribbon manufactured via a melt spinning technique for applications in the biomedical field. Annealing was performed at 280°C. The inner side (in contact with the wheel) and the outer side (not in contact with the wheel) of the ribbons were mechanically evaluated using nanoindentation, and its surfaces were analyzed by an optical profilometer. Differential scanning calorimeter (DSC) and X-ray diffraction (XRD) analyses were also performed to identify the structure and devitrification of the magnesium metallic glass (MgMG). The nanohardness and elastic modulus increased after annealing (p 0.05). Although both sides of the ribbons showed different surface profiles (p

The present work presents an experimental study on the behavior of ceramic tile rendering build on concrete block masonry walls loaded to compression failure. The walls were tested considering two different coating systems: a) direct application of adhesive mortar and lastly the ceramic tile; b) with cement plaster followed by the adhesive mortar and finally the ceramic tile. Four events were recorded: noise emission, plaster detachment, ceramic tile detachment and wall rupture. For both coating systems, the fracture loads were similar and ceramic tile detachment occurring at loads above expected service for residential buildings.

Aim To evaluate the influence of controlled memory (CM) thermal treatment on the torsional resistance and surface roughness of nickel-titanium instruments with identical geometric and dimensional characteristics. The influence of environmental temperature on torsional resistance was also evaluated. Methodology A sample of 25 conventional NiTi alloy and 25 CM thermal-treated NiTi instruments, with an identical geometric design and a nominal size of 0.25 mm at D0 and a nominal taper of .06 mm mm-1 were selected. The torsional strength and the angle of rotation of the instruments were tested following ISO 3630-1 at two temperatures: 21 and 35 °C. The fracture surfaces of all tested instruments were verified with a scanning electron microscope. The surface roughness of the blades of conventional NiTi alloy and CM wire files was evaluated by using a New View 7100 Profilometer. Statistical analysis was performed using Student's t-test and paired t-test to analyse the torsional resistance and surface roughness at a significance level of P Results The torsional strength of thermally-treated instruments was significantly lower than nontreated instruments (P 0.05) and the angular rotation (P > 0.05) of the instruments. Regarding the roughness measurements, groove depth was lower at the surface of thermally-treated instruments when compared to nontreated instruments (P Conclusion Thermal treatment influenced the torsional resistance and surface roughness of NiTi instruments with identical geometric and dimensional characteristics. Temperature did not affect torsional behaviour.

The performance of a novel multilayered armor in which the commonly used plies of aramid fabric layer were replaced by an equal thickness layer of distinct curaua fiber-reinforced composites with epoxy or polyester matrices was assessed. The investigated armor, in addition to its polymeric layer (aramid fabric or curaua composite), was also composed of a front Al2O3 ceramic tile and backed by an aluminum alloy sheet. Ballistic impact tests were performed with actual 7.62 caliber ammunitions. Indentation in a clay witness, simulating human body behind the back layer, attested the efficacy of the curaua-reinforced composite as an armor component. The conventional aramid fabric display a similar indentation as the curaua/polyester composite but was less efficient (deeper indentation) than the curaua/epoxy composite. This advantage is shown to be significant, especially in favor of the lighter and cheaper epoxy composite reinforced with 30 vol pct of curaua fiber, as possible substitute for aramid fabric in multilayered ballistic armor for individual protection. Scanning electron microscopy revealed the mechanism associated with the curaua composite ballistic performance.

The aim of the present study was to evaluate the cyclic fatigue of two anatomic finishing files: XP-Endo Finisher and XP-Clean. Roughness pattern and the micro-hardness of the files were also assessed. Instruments were subjected to cyclic fatigue resistance measuring the time to fracture in an artificial stainless-steel canal with a 60° angle and a 5-mm radius of curvature. The fracture surface of all fragments was examined with a scanning electron microscope. The roughness of the working parts was quantified by using a profilometer and the micro-hardness test was carried out using a Vickers hardness tester. Results were statistically analyzed using a student´s t-test at a significance level of P < 0.05. Weibull analysis was also performed. XP-Endo Finisher presented significantly longer cyclic fatigue life than XP-Clean instruments (P0.05). It can be concluded that XP-Endo Finisher instruments showed improved performance when compared with XP-Clean instruments, demonstrating higher cyclic fatigue resistance and lower roughness. Resumo O objetivo do presente estudo foi avaliar a fadiga cíclica de dois instrumentos finalizadores anatômicos: XP-Endo Finisher e XP-Clean. O padrão de rugosidade e a micro dureza dos instrumentos também foram avaliados. Os instrumentos foram submetidos à resistência à fadiga cíclica, medindo o tempo de fratura em um canal artificial de aço inoxidável com um ângulo de 60 ° e um raio de curvatura de 5 mm. A superfície de fratura de todos os fragmentos foi examinada com um microscópio eletrônico de varredura. A rugosidade dos instrumentos foi quantificada usando um perfilômetro e o teste de micro dureza foi realizado usando um testador de dureza Vickers. Os resultados foram analisados estatisticamente usando o teste t de student em um nível de significância de p0,05). Pode-se concluir que os instrumentos XP-Endo Finisher apresentaram desempenho melhorado em comparação com os instrumentos XP-Clean, demonstrando maior resistência à fadiga cíclica e menor rugosidade.

INTRODUCTION: The finishing and polishing phases are essential to improve smoothness and shining on the surface of acrylic resins used to make removable orthodontic appliances. A good surface finishing reduces roughness, which facilitates hygiene, prevents staining and provides greater comfort to the patients. OBJECTIVE: The aim of this paper was to analyze the changes on surface morphology of acrylic resins during finishing and polishing phases. METHODS: Thirty discs (10 mm in diameter and 5 mm in length) were made with acrylic resin and randomly divided into ten groups. The control group did not receive any treatment while the other groups received gradual finishing and polishing. The last group received the entire finishing and polishing procedures. Surface morphology was qualitatively analyzed through scanning electron microscopy and quantitatively analyzed through a laser profilometer test. RESULTS: The acrylic resin surfaces without treatment showed bubbles which were not observed in the subsequent phases. Wearing out with multilaminated burs, finishing with wood sandpaper and finishing with water sandpaper resulted in surfaces with decreasing irregularities. The surfaces that were polished with pumice and with low abrasive liquids showed high superficial smoothness. CONCLUSION: Highly smooth acrylic resin surfaces can be obtained after mechanical finishing and polishing performed with multilaminated burs, wood sandpaper, water sandpaper, pumice and low abrasive liquids. INTRODUÇÃO: as etapas de acabamento e polimento são essenciais para a obtenção de lisura e brilho da superfície de resinas acrílicas utilizadas na confecção de aparelhos ortodônticos. O bom acabamento da resina facilita a higiene, previne o manchamento e propicia maior conforto ao paciente. OBJETIVO: o objetivo desse trabalho foi analisar as alterações na morfologia superficial de resinas acrílicas (Clássico, São Paulo) durante as etapas do acabamento e polimento mecânico. MÉTODOS: foram confeccionados 30 discos (10mm de diâmetro e 5mm de altura) de resina acrílica autopolimerizável, que foram divididos aleatoriamente em dez grupos. O grupo controle não recebeu nenhum tratamento. Os demais grupos receberam acabamento e polimento graduais. O último grupo recebeu todo o tratamento de acabamento e polimento. A morfologia superficial foi avaliada qualitativamente por microscopia eletrônica de varredura e quantitativamente pela análise da rugosidade superficial. RESULTADOS: as superfícies de resina acrílica sem tratamento apresentaram bolhas, as quais não foram observadas nas fases subsequentes. O desgaste com fresa multilaminada seguido de acabamento com lixa de madeira e lixa d'água produziram superfícies com irregularidades decrescentes. As superfícies polidas com branco de Espanha e líquido de baixa abrasividade (Kaol) apresentaram bom acabamento superficial. CONCLUSÃO: é possível obter resina acrílica com alta lisura superficial após acabamento e polimento mecânico com fresas, lixas de madeira, lixas d'água, branco de Espanha e líquidos de baixa abrasividade (Kaol).

The objective of this article is to investigate the mechanical properties and surface morphology of fiber-reinforced composite (FRC) wires. FRC (Optis) wire and a NiTi 0.016 in diameter were evaluated with a 3-point bending test on a universal testing machine at temperatures of 23±1oC and 37±1oC. The sample was cut to a size of 30mm and divided into 5 groups, each consisting of 6 specimens. Group 1, 2 and 5 were tested at 3.1-mm deflection, groups 3 and 4 at 1.5mm deflection. The hysteresis curves were compared and the surface morphology of the FRC wires was observed by SEM. Clear breakages occurred between fibers and Polymethylmethacrylate (PMMA) matrix union between 1.5-mm and 2.0-mm deflection. Before 1.5-mm, the wires showed no significant changes in their surface structure. The flexural load required to produce a deflection of 1.5 mm on NiTi was near double that for the FRC wires. ANOVA indicated differences (P .05). FRC wires displayed comparable load-deflection curves to NiTi until deflection of 2.0mm, whereas it could be considered a viable alternative to metallic wires during mild irregular alignment situations. Failure occurs due to fibers pullout and breakage at the fiber/composite matrix interface.

The manufacturing of ceramics fixed dental prostheses (FDPs) is not the same as that of standardized samples and, therefore, the surface finishing are not necessarily the same in both cases. Standardized samples and FDPs were sintered, polished, hydrothermally aged in saliva, and submitted to mechanical tests. The results showed a difference in bending strength between machined (911.19 MPa) and polished FDPs (573.84 MPa). ANOVA statistical analysis did not show a difference in flexural strength between nondegraded (911.19 MPa) and degraded (871.94 MPa) FDPs. No differences were found in the bending strength and toughness of standardized samples and FDPs.

Introduction This study evaluated the influence of flexibility and reciprocating movement on the fatigue life of endodontic instruments subjected to static and dynamic tests. Methods The rotary nickel-titanium instruments used in this study were Reciproc and Mtwo. The instruments were initially subjected to a cantilever-bending test and then to static and dynamic fatigue tests. Reciproc instruments were operated in reciprocating movement, whereas Mtwo instruments were worked in continuous rotation. Results The means of bending resistance (maximum load in grams) of the instruments were 274.9 for Reciproc and 429 for Mtwo. The mean times (in seconds) to fracture of the instruments subjected to static and dynamic tests were 214.5 (static) and 286.3 (dynamic) for Reciproc and 38.9 (static) and 99 (dynamic) for Mtwo. The Student's t test revealed significant differences in all tests (P Conclusions The results of the present study showed longer fatigue life for instruments with higher flexibility, driven by reciprocating movement, and in the dynamic testing model. These findings reinforce the assumption that use of reciprocating movement is a means to prolong the fatigue life of rotary nickel-titanium endodontic instruments during instrumentation of curved canals.

Introduction There has been continuing interest in the development and use of esthetic and effective orthodontic archwires. The aims of this study were to evaluate the inner alloy core dimensions of 4 brands of as-received esthetic coated wires and their mechanical properties before and after 21 days of oral exposure, compared with conventional stainless steel and nickel titanium wires. Methods Four groups (Ortho Organizers, Carlsbad, Calif; TP Orthodontics, LaPorte, Ind; Orthometric, Beijing, China; and Trianeiro, Rio Claro, Sao Paulo, Brazil) of orthodontic archwires were tested. Five properties were evaluated: inner wire dimensions, modulus of elasticity, modulus of resilience, maximum deflection force, and load deflection curve characteristics. Images of the transverse sections from the specimens were made with a stereoscope. The inner alloy core dimensions of each wire were measured by using Image Pro Plus software (version 4.5; Media Cybernetics, Silver Spring, Md). All specimens were tested in a universal testing machine in a 3-point bending test. Results Coated wires of the Ortho Organizers and Trianeiro groups showed greater reductions in their inner alloy core dimensions and produced lower loading and unloading forces and lower modulus of elasticity, modulus of resilience, and maximum deflection force values than did their control wires. Inner alloy core dimensions and the mechanical behavior of coated wires practically did not differ from the control wires in the TP Orthodontics and Orthometric groups. Conclusions The reduction on the inner alloy core dimensions to compensate for the coating thickness seems to be the variable responsible for greater changes in the mechanical properties of esthetic coated wires.

The mechanical, chemical, roughness and wettability properties of 70/30 poly (L,DL-lactide acid) three-dimensional (3D)-printed surgical plates made with extruded polymer filaments developed in the first part of this work were investigated. The plates were printed with horizontal (HRZ) and vertical (VRT) running layer orientations and evaluated by tensile, Fourier transform infrared (FTIR), optical perfilometry and wettability tests before and after degradation in simulated body fluid (SBF) for 21 days. The results show that the ultimate tensile strength (UTS) of HRZ plates before immersion in SBF was higher (34.1 MPa) than that of VRT plates (31.8 MPa). The Young’s modulus (E) of HRZ plates and VRT plates are similar (4 GPa). After immersion in SBF, the UTS of HRZ plates dropped to 20.5 MPa and E decreased to 3.3 GPa. VRT were not tested after SBF immersion due to the large degradation. FTIR analysis showed no evidence of chemical change in the plates after immersion in SBF. The roughness parameter R3z of VRT surfaces (19.54 µm) was higher than that of the HRZ surfaces (12.80 µm). The roughness parameters increased after degradation in SBF (p = 0.7048). The contact angles of HRZ surfaces before immersion in SBF (66.28°) were higher than after immersion in SBF (18.12°); the same behavior was also observed in VRT plates. Refereed/Peer-reviewed

The aim of this work was to manufacture 70/30 poly-l-dl-lactic acid (PLDLLA) filaments for three-dimensional (3D) printers by using the extrusion technique and to study the properties of filaments and printed plates for surgical fracture stabilization. Different extrusion methodologies were tested and filaments were analyzed in terms of homogeneity, accuracy diameter, finishing surface morphology, and chemical degradation. X-ray diffraction and differential scanning calorimetry showed that the filaments have less crystallinity than does the raw material. Infrared and thermogravimetric analysis showed no evidence of chemical degradation. Surgical plates made with the filaments revealed small changes in the material properties after the printing process. PLDLLA filament extrusion and 3D printing are a promising way to satisfy the demand of implantable bioabsorbable products. Refereed/Peer-reviewed

OBJECTIVE: To evaluate and compare "in vitro" the maximum friction force generated by three types of esthetic brackets, two types of polycrystalline conventional ceramic brackets (20/40 and InVu) and one type of sapphire monocrystalline bracket (Radiance) in dry and artificial saliva wet settings. Also, to evaluate the influence exerted by artificial saliva on the friction forces of those brackets. METHODS: Tests were performed in dry and artificial saliva wet setting (Oral Balance) by using an EMIC DL 10000 testing machine, simulating a 2 mm slide of 0.019 x 0.025-in rectangular stainless steel wires over the pre-angulated and pre-torqued (right superior canine, Roth prescription, slot 0.022 x 0.030-in) brackets (n = 18 for each bracket). In order to compare groups in dry and wet settings, the ANOVA was used. For comparisons related to the dry versus wet setting, the student t test was used for each group. RESULTS: The results showed that in the absence of saliva the Radiance monocrystalline brackets showed the highest friction coefficients, followed by the 20/40 and the InVu polycrystalline brackets. In tests with artificial saliva, the Radiance and the 20/40 brackets had statistically similar friction coefficients and both were greater than that presented by the InVu brackets. The artificial saliva did not change the maximum friction force of the Radiance brackets, but, for the others (20/40 and InVu), an increase of friction was observed in its presence. CONCLUSION: The InVu brackets showed, in the absence and in the presence of saliva, the lowest friction coefficient.OBJETIVO: avaliar e comparar in vitro as cargas máximas de atrito geradas por três tipos de braquetes estéticos, sendo dois deles cerâmicos policristalinos convencionais (20/40 e InVu) e um monocristalino de safira (Radiance), em ambientes seco e umedecido por saliva artificial. Também avaliar a influência exercida pela saliva artificial sobre as cargas de atrito dos referidos braquetes. MÉTODOS: os ensaios foram realizados em ambiente seco e em ambiente umedecido com saliva artificial em gel (Oral Balance), utilizando uma máquina de ensaios mecânicos (EMIC, modelo DL10000), simulando um deslizamento de 2mm de fios retangulares 0,019" x 0,025" de aço sobre os braquetes (n = 18, para cada braquete), pré-angulados e pré-torqueados (canino superior direito prescrição Roth, slot 0,022" x 0,030"). Para comparação entre os braquetes, em ambiente seco ou umedecido, utilizou-se a análise de variância; e para a comparação dos braquetes em ambiente seco e umedecido, utilizou-se o teste t para amostras independentes. RESULTADOS: os resultados obtidos indicaram que, na ausência de saliva, os braquetes monocristalinos Radiance demonstraram o maior coeficiente de atrito, seguidos pelos braquetes policristalinos 20/40 e InVu. Nos ensaios realizados em ambiente umedecido, os braquetes Radiance e 20/40 apresentaram coeficientes de atrito estatisticamente semelhantes, e superiores ao apresentado pelos braquetes InVu. A saliva artificial não promoveu alterações na força máxima de atrito para os braquetes Radiance; todavia, para os demais (20/40 e InVu), promoveu aumento significativo nos coeficientes de atrito. CONCLUSÃO: os braquetes InVu apresentaram, tanto nos ensaios realizados na ausência, quanto na presença de saliva, os menores coeficientes de atrito, entre os braquetes ensaiados.

Objectives: To compare the sliding resistance forces produced by polycarbonate self-ligating brackets with esthetic archwires. Materials and methods: Samples of Opal, Oyster and conventional Blonde brackets were tested each one with 30 segments of .018x.025-in wires. The archwires were slipped at 8. mm/min for 40. seconds with an universal testing machine. Two way ANOVA with Bonferroni correction were used. Results: Blonde brackets presented the highest sliding resistance, followed in decreasing order by Oyster and Opal. The TP Shiny Bright Wire produced the highest surface friction, while the lowest was observed for Imagination archwires (except for Opal brackets where the TP Pearltone Wire achieved the best performance). Conclusions: Self-ligating system is more effective to reduce the sliding force resistance than conventional brackets. Esthetic stainless steel archwires produce less friction resistance than those without surface treatment. Polycarbonate self-ligating brackets are more effective to reduce the frictional forces than esthetic archwires with surface treatment. Refereed/Peer-reviewed

The brittle behavior of ceramics limits the use of these materials under conditions of cyclic loading, as is the case of fixed partial dentures. To improve toughness and biocompatibility of ceramics is necessary to employ powders with better purities, adjust the conditions of compaction and sintering, microstructure control and explore mechanisms for increasing the toughness. Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) is generally used for dental ceramic restorations. The zirconia framework is fabricated using the CAD/CAM system. The ceramic mechanical properties are determined by testing polished sample. Previous work did not analyze the influence of surface defects induced during dentures grinding. Ceramic restorations manufacturing are made with coarse grinding high-speed diamond rotatory cutting instruments. This process induces residual stresses and the high temperature induces surface cracks. Consequently, a lower strength and reliability of the material is observed. In this work the mechanical properties of yttria stabilized zirconia were determined with the use of samples of dental prostheses molded in patients and machined with the use of a dental laboratory CAD/CAM system. The results showed that the mechanical properties of pre-sintered blocks are different from prosthetics machined by CAD/CAM and sintered under the same conditions used in the laboratories of the prosthesis. The defects created during machining reduce the mechanical properties of zirconia.

Several CAD/CAM systems are available to dental prosthesis laboratories that can be used to make all-ceramic copings and frameworks. In Brazil, the use of these systems presents low demand, due principally the high blocks ceramics cost used for theses systems. The ceramic blocks are imported. To increase the dental ceramic CAD/CAM applications is necessary develop and produce the ceramics blocks in Brazil. The purpose of the present work is to compare the mechanical properties of blocks of zirconium developed in the Brazil (ProtMat® Co) and imported (VITA). It was determined the mechanical and physics properties of the two types of blocks of zirconium stabilized with ytria. The blocks have been sinterized at 1530 °C and their mechanical and physics properties were measured. The x-ray diffraction analysis showed only tetragonal phase, which improve the blocks toughness. The Vickers hardness and fracture toughness were 1300HV and 9 MPam1/2, respectively. High bending fracture resistance was obtained for both materials with average values of 910MPa. The Weibull modulus was m=10 for Brazilian and imported blocks. It was not observed an important difference among the microstructures and mechanical properties of the analyzed zirconium blocks.

Introduction The aim of this study was to evaluate, by static and dynamic cyclic fatigue tests, the number of cycles to fracture (NCF) 2 types of rotary NiTi instruments: Twisted File (SybronEndo, Orange, CA), which is manufactured by a proprietary twisting process, and RaCe files (FKG Dentaire, La Chaux-de-Fonds, Switzerland), which are manufactured by grinding. Methods Twenty Twisted Files (TFs) and 20 RaCe files #25/.006 taper instruments were allowed to rotate freely in an artificial curved canal at 310 rpm in a static or a dynamic model until fracture occurred. Results Measurements of the fractured fragments showed that fracture occurred at the point of maximum flexure in the midpoint of the curved segment. The NCF was significantly lower for RaCe instruments compared with TFs. The NCF was also lower for instruments subjected to the static test compared with the dynamic model in both groups. Scanning electron microscopic analysis revealed ductile morphologic characteristics on the fractured surfaces of all instruments and no plastic deformation in their helical shafts. Conclusions Rotary NiTi endodontic instruments manufactured by twisting present greater resistance to cyclic fatigue compared with instruments manufactured by grinding. The fracture mode observed in all instruments was of the ductile type.

During the preparation of curved canals, rotary nickel-titanium (NiTi) instruments are subjected to cyclic fatigue, which can lead to instrument fracture. Although several factors may influence the cyclic fatigue resistance of instruments, the role of the rotational speed remains uncertain. This study was intended to evaluate the effects of rotational speed on the number of cycles to fracture of rotary NiTi instruments.ProTaper Universal instruments F3 and F4 (Maillefer SA, Ballaigues, Switzerland) were used in an artificial curved canal under rotational speeds of 300 rpm or 600 rpm. The artificial canal was made of stainless steel, with an inner diameter of 1.5 mm, total length of 20 mm, and arc at the end with a curvature radius of 6 mm. The arc length was 9.4 mm and 10.6 mm on the straight part. The number of cycles required to fracture was recorded. Fractured surfaces and the helical shafts of the fractured instruments were analyzed by scanning electron microscopy.The results showed approximately a 30% reduction in the observed number of cycles to fracture as rotational speed was increased from 300 to 600 RPM (p0.05). The morphology of the fractured surface was always of ductile type, and no plastic deformation was observed on the helical shaft of fractured instruments.The present findings for both F3 and F4 ProTaper instruments revealed that the increase in rotational speed significantly reduced the number of cycles to fracture.

The influence of Al 2 O 3 addition and sintering parameters on the mechanical properties and cytotoxicity of tetragonal ZrO 2 –3 mol% Y 2 O 3 ceramics was evaluated. Samples containing 0, 10, 20 and 30 wt.% of Al 2 O 3 particles were prepared by cold uniaxial pressing (80 MPa) and sintered in air at 1500, 1550 and 1600 °C for 120 min. The effects of the sintering conditions on the microstructure were analyzed by X-ray diffraction analysis and scanning electron microscopy. Hardness and fracture toughness were determined by the Vickers indentation method and the mechanical resistance by four-point bending tests. As a preliminary biological evaluation, “in vitro” cytotoxicity tests were realized to determine the cytotoxic level of the ZrO 2 –Al 2 O 3 composites, using the neutral red uptake method with NCTC clones L929 from the American Type Culture Collection (ATCC) bank. Fully dense ceramic materials were obtained with a hardness ranging between 1340 HV and 1585 HV, depending on the amount of Al 2 O 3 in the ZrO 2 matrix. On the other hand, no significant influence of the Al 2 O 3 addition on fracture toughness was observed, exhibiting values near 8 MPa m 1/2 for all compositions and sintering conditions studied. The non-cytotoxic behavior, the elevated fracture toughness, the good bending strength ( σ f = 690 MPa) and the elevated Weibull's modulus ( m = 11) exhibited by the material, show that these ceramic composites are highly suitable biomaterials for dental implant applications.

Several CAD/CAM systems are available to dental prosthesis laboratories which can be used to fabricate all-ceramic copings and frameworks. The use of these systems presents low demand, due principally the high blocks ceramics cost used for theses systems. Usually, these ceramic blocks are sintered at high temperatures, between 1450 and 15500C, resulting in micrometric ZrO2 microstructure. A considerable innovation in these ceramics systems used in CAD/CAM applications was introduced by the use of nanometric-tetragonal ZrO2 blocks, which are sintered at low sintering temperatures resulting in nanometric grains morphology and improved mechanical properties. The purpose of the present work is to characterize the mechanical properties of nanoparticled zirconium oxide blocks comparing with commercial micrometric ceramic parts. XRD patterns showed that the blocks have only the tetragonal-ZrO2 as crystalline phase. The tetragonal-monoclinic transformation phase was responsible for the excellent mechanical properties. Nanometric blocks presented hardness of 13GPa, fracture toughness of 11MPam1/2 , bending strength of 1020MPa and Weibull modulus, m=14, while micrometric ZrO2 blocks similar hardness, fracture toughness 8.5MPam1/2, bending strength of 850MPa and Weibull modulus of 10.

Yttria stabilized tetragonal zirconia (Y-TZP) ceramics were sintered by liquid phase sintering at low temperatures using bioglass as sintering additive. ZrO2–bioglass ceramics were prepared by mixing a ZrO2 stabilized with 3 mol%Y2O3 and different amounts of bioglass based on 3CaO·P2O5–MgO–SiO2 system. Mixtures were compacted by uniaxial cold pressing and sintered in air, at 1200 and 1300 °C for 120 min. The influence of the bioglass content on the densification, tetragonal phase stability, bending strength, hardness and fracture toughness was investigated. The ceramics sintered at 1300 °C and prepared by addition of 3% of bioglass, exhibited the highest strength of 435 MPa, hardness of 1170 HV and fracture toughness of 6.3 MPa m1/2. These results are related to the low monoclinic phase content, high relative density and the presence of the thermal residual stress generated between the ZrO2-matrix and bioglass grain boundary, contributing to the activation of the toughening mechanisms.

In this work, the static mechanical properties and cyclic fatigue life of 3 mol. (%) Y2O3-stabilized tetragonal zirconia polycrystalline (3Y-TZP) ceramics were investigated. Pre-sintered samples were sintered in air at 1600 °C for 120 minutes, and characterized by X ray diffraction and scanning electronic microscopy. Hardness and fracture toughness were determined by Vicker's indentation method, and Modulus of Rupture was determined by four-point bending testing. Fully dense sintered samples, near to 100% of theoretical density, presented hardness, fracture toughness and bending strength of 13.5 GPa, 8.2 MPa.m½ and 880 MPa, respectively. The cyclic fatigue tests were also realized using four-point bending testing, within a frequency of 25 Hz and stress ratio R of 0.1. The increasing of load stress lead to decreasing of the number of cycles and the run-out specimens number. The tetragonal-monoclinic (t-m) ZrO2-transformation observed by X ray diffraction contributes to the increasing of the fatigue life. The 3Y-TZP samples clearly presents a range of loading conditions where cyclic fatigue can be detected.

Zirconia and alumina based ceramics present interesting properties for their application as implants, such as biocompatibility, good fracture resistance, as well as high fracture toughness and hardness. In this work the influence of sintering time on the properties of a ZrO 2 –Al 2 O 3 composite material, containing 20 wt% of Al 2 O 3 , has been investigated. The ceramic composites were obtained by sintering, in air, at 1600 °C for sintering times between 0 and 1440 min. Sintered samples were characterized by microstructure and crystalline phases, as well as by mechanical properties. The grain growth exponents, n , for the ZrO 2 and Al 2 O 3 were 2.8 and 4.1, respectively, indicating that different mechanisms are responsible for grain growth of each phase. After sintering at 1600 °C, the material exhibited a dependency of hardness as function of sintering time, with hardness values between 1500 HV (120 min) and 1310 HV (1440 min) and a fracture toughness of 8 MPa m 1/2 , which makes it suitable for bioapplications, such as dental implants.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T19:05:37Z No. of bitstreams: 1 S1516-14392007000100011.pdf: 1230549 bytes, checksum: 4852a7a3e94a624d9987724c612c883f (MD5) Made available in DSpace on 2013-08-22T19:05:37Z (GMT). No. of bitstreams: 1 S1516-14392007000100011.pdf: 1230549 bytes, checksum: 4852a7a3e94a624d9987724c612c883f (MD5) Previous issue date: 2007-03-01 Made available in DSpace on 2013-09-30T20:09:31Z (GMT). No. of bitstreams: 2 S1516-14392007000100011.pdf: 1230549 bytes, checksum: 4852a7a3e94a624d9987724c612c883f (MD5) S1516-14392007000100011.pdf.txt: 15810 bytes, checksum: eac5a94e2e92abeed52708937a4b5001 (MD5) Previous issue date: 2007-03-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T15:17:43Z No. of bitstreams: 2 S1516-14392007000100011.pdf: 1230549 bytes, checksum: 4852a7a3e94a624d9987724c612c883f (MD5) S1516-14392007000100011.pdf.txt: 15810 bytes, checksum: eac5a94e2e92abeed52708937a4b5001 (MD5) Made available in DSpace on 2014-05-20T15:17:43Z (GMT). No. of bitstreams: 2 S1516-14392007000100011.pdf: 1230549 bytes, checksum: 4852a7a3e94a624d9987724c612c883f (MD5) S1516-14392007000100011.pdf.txt: 15810 bytes, checksum: eac5a94e2e92abeed52708937a4b5001 (MD5) Previous issue date: 2007-03-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) InCeram (Vita Zahnfabrik- Germany) is known as a high strength ceramic being used for core crowns and for fixed partial denture frameworks. InCeram system consists of slip-casting technique which is used for to build the framework, which is then pre-sintered obtaining an open-pore microstructure. The material gains its strength by infiltration of the lanthanum glass into the porous microstructure. In this work, commercial alumina (Al2O3), alumina-zirconia (Al2O3-ZrO2) and glasses lanthanum oxide-rich powders, used in InCeram system, were characterized, using x ray diffraction, dilatometry and scanning electron microscopy. The characteristics of these powders were related aiming to consider their substitution for new ceramic materials. Universidade de São Paulo Escola de Engenharia de Lorena Departamento de Engenharia de Materiais Universidade Estadual de São Paulo Faculdade de Odontologia de São José dos Campos Instituto Militar de Engenharia

STATEMENT OF PROBLEM: In clinical practice, loss of adhesion between the silicone-based denture liner and the denture base resin is always an undesirable event that might cause loss of material softness, water sorption, bacterial colonization and functional failure of the prosthesis. PURPOSE: This study evaluated the effect of thermocycling on tensile and shear bond strengths of three soft liner materials to a denture base acrylic resin. MATERIAL AND METHODS: Three resilient liners (Mucopren-Soft, Mollosil-Plus and Dentusil) and a heat-polymerized acrylic resin (QC-20) were processed according to manufacturers' directions. Sixty specimens (14 x 14 mm cross-sectional area) per bond strength test (20 for each liner) were fabricated and either stored in water at 37oC for 24 hours (control groups; n=10) or thermocycled 3,000 times in water between 5oC and 55oC (test groups; n=10). The specimens were tested in tensile and shear strength in a universal testing machine until fracture. Bond strength means were compared between water-stored and thermocycled groups for each material, as well as among materials for each treatment (water storage or thermocycling). Failure mode (adhesive, cohesive and mixed) after debonding was assessed. Data were analyzed statistically by paired Student's t-test and ANOVA at 5% significance level. RESULTS: The water-stored groups had statistically significant higher bond strengths than the thermocycled groups (p

In this work, the effects of alumina additions on the properties of the ZrO2-Al2O3 ceramic composites were investigated. Samples of ZrO2 with Al2O3 additions varying between 0 and 30wt-% were prepared. The powder mixtures were milled, compacted by uniaxial cold pressing and sintered at 16000C, in air, for 2 hours. The sintered samples were characterized by their relative density, phase composition and microstructure. As mechanical properties at room temperature, their Vickers hardness and fracture toughness were determined: In all sintering conditions and Al2O3 amounts, the samples presented relative density higher that 99%. The Al2O3 addition produces a linear increase of the hardness, reaching values between 1350 and 1610 HV for the addition of 0 and 30% of alumina, respectively. The fracture toughness was near to 8 MPam1/2 in all conditions. The phase composition, microstructure and relative density were correlated in order to interpret the mechanical properties obtained.

Dental implant abutment screw joints tend to loosen and prosthesis rotation has been observed under clinical conditions. Some dental implant manufacturers suggest coated abutment screw to prevent the displacement of dental prosthesis. In the present work, the opening torque (N cm) was measured as a function of tightening torque (N cm) for dental implant abutment screws coated with four different materials (TiC, TiCN, Teflon and Parylene) to clarify the influence of the coating material on abutment screw stability and to analyze the relationship between preload and opening torque. On a first series of tests, closing and opening torque (N cm) of abutment screws without coating and with coating tightened to 20, 30, 32, 35 and 40 N cm was recorded. In a second series of tests, changes in opening torque values were analyzed after successive closures that were tightened at constant values of 30, 32 and 35 N cm. On a third series of tests, abutment screws without coating and with Teflon coating were tightened to 32 N cm and submitted to cyclic loading. The results showed that for all abutment screws the opening torque was less than the tightening torque. For a given applied tightening torque (35 N cm), the screws without a coating had the highest opening torque (31.6 ± 0.9 N cm [mean ± S.D.]). The screw coated with TiN had the smallest average opening torque (12.2 ± 0.6 N cm) after tightening at 20 N cm. A progressive decrease in opening torque values was measured in all screw groups after repeated closures. After six retightenings (35 N cm) a statistically significant difference (P

The aim of this study was to evaluate the frictional force between orthodontic brackets and archwires. The differences in magnitude of the frictional forces generated by ceramic brackets, ceramic brackets with metal reinforced slot, and stainless steel brackets in combination with stainless steel, nickel-titanium, and beta-titanium orthodontic archwires were investigated. Brackets and wire were tested with tip angulations of 0 degrees and 10 degrees. Friction testing was done with the Emic DL 10000 testing machine (São José do Rio Preto, PR, Brazil), and the wires were pulled from the slot brackets with a speed of 0.5 cm/min for 2 minutes. The ligation force between the bracket and the wire was 200 g. According to the data obtained, the brackets had frictional force values that were statistically significant in this progressive order: stainless steel bracket, ceramic bracket with a metal reinforced slot, and traditional ceramic bracket with a ceramic slot. The beta-titanium wire showed the highest statistically significant frictional force value, followed by the nickel-titanium and the stainless steel archwires, in decreasing order. The frictional force values were directly proportional to the angulation increase between the bracket and the wire.

There are two main mechanisms of bone-dental implant attachment: mechanical attachment and chemical attachment. Roughness mainly improves mechanical attachment and permits bone growth through pores or features on the surface of the implant. The surface ability to adsorb organic molecules like proteins is directly related to biocompatibility. In this context, surface roughness has been found to positively influence the cell response to titanium implants. In the present work, pure titanium dental implants were analysed with four different surface finishes: as machined, acid etched, as Al2O blasted, and as TiO blasted. Samples of the 3 2 dental implants were inserted in rabbit bone. Scanning electron microscopy with energy dispersive X-ray and X-ray photoelectron spectroscopy were used in the implant surface analysis, while laser profilometry was used to characterise the roughness of the surfaces. The implant that was Al2O sandblasted had a roughness 3 value similar to that obtained for TiO shot peen...

Objective: Hyflex CM instruments were developed for debridement of the root canal system. The control-memory alloy recovers its shape on sterilization, thereby allowing instrument reuse. This study investigated the effect of shape recovery by sterilization on the fatigue life and crack formation of Hyflex CM NiTi instruments. Material and Methods: the cyclic fatigue test was performed in two groups: In the first, it was continuously performed to establish the fatigue life (group 1, n = 10); in the second, it was performed with outages of 30s to evaluate cracks’ nucleation and propagation (group 2, n = 10). The test was performed using a stainless steel canal that was 1.5mm in diameter and 3.5mm in depth, with an arc of 9.42mm and radius of curvature of 6mm. The instruments were driven at 300 rpm. The fatigue time was recorded using a digital stopwatch (Technos). An electronic microscope (Quanta 250) was used to observe the crack formation and growth during the cyclic fatigue. Results: the autoclaved instruments endured 1196.67+214.63 cycles, and the non-autoclaved endured 1000+199.42 cycles until the occurrence of fracture. The t-student test (?=5%) revealed a significant difference. The cyclic fatigue test with pauses demonstrated a significantly longer cyclic fatigue life than the continuous cyclic fatigue test (p Objetivo: Instrumentos Hyflex CM foram desenvolvidos para desbridamento do sistema de canais radiculares. A liga de memória de controle recupera sua forma na esterilização, permitindo a reutilização do instrumento. Este estudo investigou o efeito da recuperação da forma pela esterilização na vida de fadiga e formação de trinca de instrumentos Hyflex CM NiTi. Material e Métodos: o teste de fadiga cíclica foi realizado em dois grupos: no primeiro, foi realizado continuamente para estabelecer a duração da fadiga (grupo 1, n = 10); no segundo, foi realizada com falhas de 30s para avaliar a nucleação e propagação de fissuras (grupo 2, n = 10). O teste foi realizado utilizando um canal de aço inoxidável com 1,5 mm de diâmetro e 3,5 mm de profundidade, com arco de 9,42 mm e raio de curvatura de 6 mm. Os instrumentos foram acionados a 300 rpm. O tempo de fadiga foi registrado usando um cronômetro digital (Technos). Um microscópio eletrônico (Quanta 250) foi utilizado para observar a formação e crescimento de fissuras durante a fadiga cíclica. Resultados: os instrumentos autoclavados sofreram 1196,67 + 214,63 ciclos e os não autoclavados sofreram 1000 + 199,42 ciclos até a ocorrência de fratura. O teste t-student (? = 5%) revelou uma diferença significativa. O teste de fadiga cíclica com pausas demonstrou uma vida de fadiga cíclica significativamente mais longa que o teste de fadiga cíclica contínua (p

Cylindrical dental implants made of commercially pure titanium were analysed in four different surface finishes: as-machined, Al2O3 blasted with Al2O3 particles, plasma-sprayed with titanium beads and electrolytically coated with hydroxyapatite. Scanning electron microscopy (SEM) with Energy Dispersive X-ray Analysis (EDX) revealed the topography of the surfaces and provided qualitative results of the chemical composition of the different implants. X-ray Photoelectron Spectroscopy (XPS) was used to perform chemical analysis on the surface of the implants while Laser Scanning Confocal Microscopy (LSM) produced topographic maps of the analysed surfaces. Optical Profilometry was used to quantitatively characterise the level of roughness of the surfaces. The implant that was plasma-sprayed and the hydroxyapatite coated implant showed the roughest surface, followed by the implant blasted with alumina and the as-machined implant. Some remnant contamination from the processes of blasting, coating and cleaning was detected by XPS.

The mechanical properties of superelastic (SE) and heat activated (HA) .014 inch NiTi orthodontic wires were evaluated and compared. A total of 132 wires were divided in 22 groups (n=6) according to six commercial brands, two lots from each wire, and SE or HA properties. Three-point bending test were conducted up to 3.1 mm at 36±loC. Stress-deflection diagrams were determined and different mechanical properties were compared by analysis of variance and Tukey test (P=.05).HA wires showed a lower load (LMS) unload (UMS) mean stress, total (TR) and potential (PR) resilience than SE wires. However, HA wires demonstrated a higher hysteresis resilience (HR) and mechanical hysteresis (MH) than SE wires. According to comparisons between different lots from the same manufacturer and wire types, four groups matched in LMS, UMS, TR and PR (P>.05). These conclusions could lead clinicians in choosing archwires which exhibit similar performance, however are commercial offered at different costs.

Introduction This study compared the mechanical properties of endodontic instruments made of conventional nickel-titanium (NiTi) wire (K3 and Revo-S SU), M-Wire (ProFile Vortex), or NiTi alloy in R-phase (K3XF). Methods The test instruments were subjected to mechanical tests to evaluate resistance to bending (flexibility), cyclic fatigue, and torsional load in clockwise rotation. Data were statistically evaluated by the analysis of variance test and the Student-Newman-Keuls test for multiple comparisons. Results In the bending resistance test, flexibility decreased in the following order: K3XF > Revo-S SU > ProFile Vortex > K3. The ranking in the fatigue resistance test was the following: K3XF > K3 > ProFile Vortex > Revo-S SU. In the torsional assay, the angular deflection at failure decreased in the following order: K3XF > Revo-S SU > K3 > ProFile Vortex. For the maximum torque values, the ranking was K3 > K3XF > ProFile Vortex > Revo-S SU. Conclusions The results showed that the K3XF instrument, which is made of NiTi alloy in R-phase, had the overall best performance in terms of flexibility, angular deflection at failure, and cyclic fatigue resistance. In addition to the alloy from which the instrument is manufactured, the design and dimensions are important determinants of the mechanical performance of endodontic instruments.

The purpose of this study was to evaluate the flexibility, shape, and surface finishing of stainless steel (SS) and nickel-titanium (NiTi) finger spreaders as well as to compare the load required to insert these spreaders along a gutta-percha point adapted to the apical segment of curved or straight artificial canals. Instrument flexibility was investigated by using a universal testing machine in the cantilever-flexibility test. Scanning electron microscopy (SEM) was used to examine the shape and surface finishing of different sizes of SS and NiTi finger spreaders. Penetration load was evaluated only for spreaders size C by using the universal testing machine in a compressive test. As for flexibility, the load needed to bend the SS finger spreader sizes A, B, C, and D was approximately 167%, 146%, 102%, and 64% greater than the respective sizes of NiTi finger spreaders. SEM analysis revealed that the instrument tips were always tapered, but with different vertices. NiTi spreaders showed tips with circumferential grooves; whereas, those from SS spreaders exhibited longitudinal grooves. NiTi finger spreaders required a significantly higher penetration load than SS spreaders. This difference was probably related to the different shapes and surface finishing of the instrument tips. Different characteristics of finger spreaders may result in different clinical performance during the lateral compaction technique.

Foi estudado o efeito da adição de Al2O3 nas propriedades de cerâmicas à base de ZrO2 tetragonal estabilizada com ítria (Y-TZP) visando sua aplicação como material dentário. Amostras contendo 0, 10, 20 e 30% em peso de Al2O3 foram compactadas por prensagem uniaxial a frio (80 MPa) e em seguida sinterizadas ao ar a 1500, 1550 e 1600 °C por 120 min. Os efeitos destas condições de sinterização nas propriedades dos materiais foram analisados por difração de raios X e microscopia eletrônica de varredura. As propriedades mecânicas de dureza e tenacidade à fratura foram determinadas, utilizando-se o método de indentação Vickers. Além disso, algumas amostras foram submetidas a ensaio de flexão em 4 pontos. Cerâmicas de elevada densidade relativa foram obtidas, com dureza variando entre 13,4 e 15,8 GPa, dependendo da quantidade de Al2O3 adicionada à matriz de ZrO2. Por outro lado, não foi verificada uma influencia significativa da adição de Al2O3 na tenacidade à fratura, que apresentou valores próximos de 8 MPa.m½, em quase todas as situações. A boa dureza, a elevada tenacidade à fratura, a boa resistência à fratura (sigmaf = 685 MPa) e o módulo de Weibull (m=11) apresentados pelos materiais com adições de 20% de Al2O3, indicam a confiabilidade do compósito como um potencial biomaterial para uso na implantodontia.

The biological properties of titanium depend on its surface oxide film. Several mechanical and chemical treatments have been used to modify the surface morphology and properties of titanium dental implants. One possible method of improving dental implant biocompatibility is to increase surface roughness and decrease the contact angle. In the present work, the biological properties of dental implants were investigated through in vivo and in vitro tests. The effects of surface roughness, contact angle and surface morphology on titanium dental implant removal torque were investigated. Machined dental implants and discs made with commercially pure titanium ASTM grade 4 were submitted to sandblasting treatments, acid etching and anodizing. The sample surface morphologies were characterized by SEM, the surface roughness parameters were quantified using a laser non-contact profilometer, and a contact angle measurement was taken. Dental implants were placed in the tibia of rabbits and removed 12 weeks after the surgery. It was found that: (i) acid etching homogenized the surface roughness parameters; (ii) the anodized surface presented the smallest contact angle; (iii) the in vivo test suggested that, in similar conditions, the surface treatment had a beneficial effect on the implant biocompatibility measured through removal torque; and (iv) the anodized dental implant presented the highest removal torque.