Nanomaterials (NMs) have been used in an increasing number of commercial products, and its rapid expansion could lead to their release into aquatic environments. The accelerated production of the various types of conventional products at nanoscale has been fundamental for the economic progress of several countries. Many types of nanoparticles and nanomaterials are already being used, and other varieties are expected to appear in the future. However, there is little knowledge about the impact of NMs on biota, especially on amphibians. Therefore, there is a need to better classify and understand NMs. The first part of our study has reviewed the historical use of amphibian species as model systems in nanoecotoxicological studies, which summarized data available in the scientific literature on the genotoxic, mutagenic, histopathological, embryotoxic, and reproductive effects of NMs in different groups of amphibians. The interaction, bioaccumulation, mode of action (MoA), and ecotoxicity of NMs in amphibians were also reviewed. The nanoecotoxicological studies were carried out with 12 species of amphibians, eight from the Anura order and three from the Caudata order. Xenopus laevis was the most studied species. Studies were conducted primarily with inorganic NMs (72%) compared to organic ones. Nanoecotoxicity depends on the behavior of the NM, the transformation in the environment, and the developmental stages of the amphibians. The MoA of NMs in amphibians was mainly associated with the production of reactive oxygen species (ROS), oxidative stress, genotoxic and mutagenic effects. The results emphasized the need for more studies that test the ecotoxicity of different NMs, concentrations, and exposure periods in environmentally relevant approaches. In addition, there is a need for standard protocols for nanoecotoxicological testing with amphibians. The reviewed data showed that amphibians are suitable organisms to assess the environmental impact of NMs and indicated essential gaps in research on the ecotoxicity of NMs in freshwater ecosystems, as well as recommendations for future research. In this sense, we observed from the first chapter that the most produced and consumed nanoparticles worldwide are titanium dioxide nanoparticles (TiO2 NPs); whose release into the environment are known to induce toxic effects in aquatic invertebrates and vertebrates. However, knowledge of its impact on neotropical amphibians remains limited. Thus, the second chapter of this thesis aimed to evaluate the toxicity of TiO2 NPs and its dissolved counterpart, titanium dioxide (TiO2), in a species of anuran neotropical amphibian (Dendropsophus minutus). DNA damage, biometric parameters, and behavioral changes were analyzed in tadpoles after exposure to three environmentally relevant concentrations (0.1, 1.0, and 10 mg L-1) of TiO2 and TiO2 NPs for 7 days. As a result, we verified DNA damage in D. minutus tadpoles exposed to both forms of Ti compared to the control group. We also identified a similar reduction in overall size, body length, width, and height of the tail musculature in tadpoles exposed to TiO2 and TiO2 NPs compared to unexposed tadpoles. Regarding the behavioral test, the tadpoles showed less mobility and were more distant from the conspecifics (less aggregated) when exposed to NPs. Therefore, the simultaneous use of multiple biomarkers was essential to assess the adverse effects of the nanomaterial and establish a reliable approach for biomonitoring of aquatic ecosystems. Our study increases the knowledge about the genotoxic, morphological, and behavioral effects of TiO2 and TiO2 NPs in anuran amphibians, contributing to future studies in the environmental risk assessment of nanomaterials.

Flexy-Multi™, a newly introduced finishing wire with the outermost portion of its crosssection composed by nickel-titanium and its core by beta-titanium, was evaluated according to its flexural behavior in bending tests. The aim of this study was to compare the loaddeflection rate of Flexy-Multi™ to stainless-steel, beta titanium and nickel-titanium archwires in three-point bending test. The samples examined included 0.017”x 0.025”-inch stainlesssteel, beta-titanium, nickel-titanium and Flexy-Multi™ wires. Each combination, alloy and manufacturer, was tested 6 times and an average was obtained for comparison. All specimens were tested in a universal testing machine (EMIC DL10.000/700) in a 3-point bending test at a speed of 1mm per minute and deflected for 1.5 mm. Loading and unloading forces were recorded at each 0.5mm of deflection and load-deflection curves were determined. Three self-ligating brackets of lower incisors (In-Ovation – GAC Orthodontics, Roth prescription, slot .022”x.028”) were used as supports to the wires. On loading, there was no difference between Flexy-Multi™ and all nickel-titanium wires tested. On the other hand, Flexy-Multi™ showed lower load-deflection rates than all stainless-steel and betatitanium wires both on loading and unloading (p>0.05). On unloading, Flexy-Multi™ showed lower load-deflection rate than all nickel-titanium wires just to 0.5mm of deflection (p<0.05). Flexy-multi™ presented a lower load-deflection rate than all wires tested, except when compared to nickel-titanium where this difference came up just at the level of 0.5mm of unloading, since this wire lost force by the end of the test.

Os fatores de risco associados à peri-implantite estão relacionados à composição do biofilme ao redor do implante e a habilidade da bactéria aderir na superfície. O objetivo desse estudo foi avaliar a formação do biofilme sobre as diferentes superfícies de Ti cp grau 4, nos tempos de 12, 24, 48 e 168 horas pela técnica do microcosmo e microscopia eletrônica de varredura (MEV). Foram formados biofilmes em placas de micropoços sobre discos de Ti cp (N=160), tendo como inóculo a saliva (microcosmos) de um doador sobre 10 discos para cada inóculo (n=10). Foram 40 espécimes para cada tipo de superfície, sendo elas: lisa (controle - L), jateadas com óxido de alumínio (Al2O3 - J), subtração por ataque com ácido nítrico (A) e por último jateadas com Al2O3 acrescidas de ataque com ácido nítrico (JA). Um disco de cada condição (4) foi avaliado previamente à inoculação quanto a sua topografia pela MEV e rugosidade média (Ra) e dezesseis foram avaliados pela MEV após a técnica do microcosmo totalizando 20 espécimes. Os dados obtidos foram analisados pelo teste análise de variância (ANOVA) de dois fatores e Tukey para comparação das médias (p<0,05). Houve diferença estatística entre a superfície controle (25,34) e A (19,15) em relação às J e JA (43,83 e 32,06) na contagem de UFC/mg nas primeiras 12 horas, onde a formação de biofilme foi maior em J (Ra= 0,62 ?m) e JA (Ra=0,51 ?m). Observou-se que todas as superfícies possibilitaram crescimento microbiano, independentemente do tratamento recebido

Nanocrystalline metals and alloys show promising properties for technological applications. However, their unusual mechanical behavior proved to be a real challenge to be understood. Experimental studies of these materials are affected by complexity and cost in creating a bulk sample free of defects. Thus, molecular dynamics simulations have emerged as an important tool to assess, at atomic level, the phenomena responsible for their behavior. In this thesis, three different nanocrystalline systems (Al80Ti15Ni5 alloy, pure nickel, and pure aluminum) were studied using molecular dynamics. The focus was to analyze the systems´ mechanical behavior with special attention to the inverse Hall-Petch relationship and the related deformation mechanisms. Atomic arrangement analysis of the ternary alloy demonstrated the grain boundary sliding and diffusion as the dominant deformation mechanisms. In addition, deformation mechanisms present in amorphous materials seems to be capable of work in nanocrystalline systems. The results related to nanocrystalline nickel demonstrated that partials dislocation remain active regardless of grain size. However, other deformation mechanisms, such as grain rotation and grain boundary sliding, takes place below a critical grain size of circa 20 nm, leading to the inverse Hall-Petch relationship. Moreover, a distinct strain rate sensitivity behavior was found, in which it decreases with the grain size reduction. Regarding the nanocrystalline aluminum, Coble creep phenomenon was observed and no clearly indication of dislocation pile-up was evidenced.

O objetivo deste estudo in vitro foi analisar o comportamento superficial do titânio comercialmente puro (grau 2 ASTM) usinado e obtido pelo processamento de metalurgia do pó sob a ação de diferentes soluções fluoretadas, através da análise do grau de corrosão em microscopia óptica (MO) e da rugosidade superficial. Além disso, o estudo se propôs a comparar essas análises com os resultados obtidos com o titânio fundido da dissertação de mestrado de Barros (2004). Todas as amostras receberam procedimento metalográfico padrão e foram divididas em grupos: Gr.1- saliva artificial com pH 7.0 (controle), Gr.2- gel de flúor fosfato acidulado a 1,23% com pH 3.5, Gr.3- gel de NaF a 2% com pH 6.5, Gr.4- solução de NaF a 0,05% com pH 4.0 e Gr.5- solução de NaF a 0,05% com pH 7.5. As amostras foram expostas a estas soluções por 1, 4, 8 e 16 min, intercaladas com imersão em saliva artificial por 24 h, e depois foram observadas em MO e MEV, a cada intervalo de tempo. As imagens em MO, 100x, foram classificadas através de escores de 0 a 4, conforme o grau de corrosão. A rugosidade foi analisada utilizando o parâmetro Ra. Os resultados da análise de MO foram tratados estatisticamente pelo teste qui-quadrado e da rugosidade pelo teste F de Snedecor e de Bonferroni (p<0,05). Nos três tipos de amostras, o Gr2 apresentou a corrosão mais severa, e os Gr.4 e 5 apresentaram os menores graus de corrosão. Entretanto, nas amostras usinadas o Gr5 apresentou uma corrosão menos acentuada em relação ao Gr4. No Gr3 houve um aumento da corrosão em função do tempo, sendo que as amostras fundidas mostraram este aumento mais rapidamente. Houve um aumento significativo na rugosidade superficial no Gr.2 nos três tipos de amostras. Nos diversos grupos, os valores de rugosidade superficial das amostras fundidas foram significantemente maiores que os das usinadas e as de metalurgia do pó. Os autores concluíram que as soluções fluoretadas de uso odontológico são danosas às superfícies do titânio fundido, usinado e metalurgia do pó, principalmente as soluções com alta concentração de fluoreto.

There is little information regarding bond strengths of polyglass to metal alloys. This study evaluated the influence of bonding system on shear bond strength of a composite resin (Artglass/Heraeus Kulzer) to cast titanium (Ti). Twenty metallic structures (4mm in diameter, 5mm thick) of titanium grade I were cast shaped and abraded with 250mm aluminum oxide and separated into two groups. For each group was applied one bonding system (Siloc or Retention Flow) before opaque and dentin polymer superposition. This procedure was managed using teflon matrices. They were manipulated and polymerized according to the manufacturer's recommendations. The samples were stored in distilled water for 24 hours at 37º and thermocycled (5º and 55ºC/500 cycles). Shear bond strength tests were performed by using an Instron Universal testing machine at a crosshead speed of 5mm/min. Results were analyzed statistically with one-way ANOVA (a=0,5) and they indicated that the Retention Flow system was statistically better than Siloc (20.74 MPa and 11.65 MPa , respectively). It was possible to conclude that the bonding agent influenced the adhesion between polymer and cast titanium.

The bond strength by three point bending strength of two metal substrates (commercially pure titanium or grade II, and Ti-6Al-4V alloy or grade V) combined to three distinct low-fusing ceramic systems (LFC) and the nature of porcelain-metal fracture by scanning electron microscopy (SEM) were evaluated. The results were compared to a combination of palladium-silver (Pd-Ag) alloy and conventional porcelain (Duceram VMK68). Sixty metal strips measuring 25x3x0.5mm were made - 30 of titanium grade II and 30 of titanium grade V, with application of the following types of porcelain: Vita Titankeramik, Triceram or Duceratin (10 specimens for each porcelain). The porcelains were bonded to the strips with dimensions limited to 8x3x1mm. The control group consisted of ten specimens Pd-Ag alloy/Duceram VMK68 porcelain. Statistical analyses were made by one-way analysis of variance (ANOVA) and Tukey test at 5% significance level. Results showed that the bond strength in control group (48.0MPa ± 4.0) was significantly higher than the Ti grade II (26.7MPa ± 4.1) and Ti grade V (25.2MPa ± 2.2) combinations. When Duceratin porcelain was applied in both substrates, Ti grade II and Ti grade V, the results were significantly lower than in Ti grade II/Vitatitankeramik. SEM analysis indicated a predominance of adhesive fractures for the groups Ti grade II and Ti grade V, and cohesive fracture for control group Pd-Ag/Duceram. Control group showed the best bond strength compared to the groups that employed LFC. Among LFC, the worst results were obtained when Duceratin porcelain was used in both substrates. SEM confirmed the results of three point bending strength.

Objective To evaluate the amount of apically extruded debris, percentage of foraminal enlargement and apical foramen (AF) deformation that occurred during root canal preparation with different reciprocation systems: Reciproc, WaveOne (M-Wire), and ProDesign R (Shape Memory Technology Wire) at two different working lengths (WLs): 0.0 and 1.0 mm beyond the AF. Material and methods The AF of 120 root canals in 60 mesial roots of mandibular molars were photographed with stereomicroscope and randomly assigned into four groups: manual, Reciproc (REC), WaveOne (WO), and ProDesign R (PDR); subsequently, they were further subdivided according to the WL (n=15). Teeth were instrumented, coupled to a dual collecting chamber, and then another photograph of each AF was captured. Extrusion was analysed by determining the weight of extruded debris. Each AF diameter was measured in pre- and post-instrumentation images to determine deformation, which was analysed, and afterwards the final format of AFs was classified (circular/oval/deformed). Results We found no significant differences when analysing each system at different WLs. When considering each WL, REC and WO showed highest extrusion values (P

Titanium tetrafluoride (TiF4) is known for interacting with enamel reducing demineralization. However, no information is available about its potential antimicrobial effect. Objectives This study evaluated the antimicrobial and anti-caries potential of TiF4 varnish compared to NaF varnish, chlorhexidine gel (positive control), placebo varnish and untreated (negative controls) using a dental microcosm biofilm model. Material and Methods A microcosm biofilm was produced on bovine enamel previously treated with the varnishes, using inoculum from human saliva mixed with McBain saliva, under 0.2% sucrose exposure, for 14 days. All experiments were performed in biological triplicate (n=4/group in each experiment). Factors evaluated were: bacterial viability (% dead and live bacteria); CFU counting (log10 CFU/mL); and enamel demineralization (transverse microradiography – TMR). Data were analysed using ANOVA/Tukey's test or Kruskal-Wallis/Dunn's test (p

Objective:The present study aimed to investigate the participation of focal adhesion kinases (FAK) in interactions between osteoblastic cells and titanium (Ti) surfaces with three different topographies, namely, untreated (US), microstructured (MS), and nanostructured (NS). Methodology; Osteoblasts harvested from the calvarial bones of 3-day-old rats were cultured on US, MS and NS discs in the presence of PF-573228 (FAK inhibitor) to evaluate osteoblastic differentiation. After 24 h, we evaluated osteoblast morphology and vinculin expression, and on day 10, the following parameters: gene expression of osteoblastic markers and integrin signaling components, FAK protein expression and alkaline phosphatase (ALP) activity. A smooth surface, porosities at the microscale level, and nanocavities were observed in US, MS, and NS, respectively. Results: FAK inhibition decreased the number of filopodia in cells grown on US and MS compared with that in NS. FAK inhibition decreased the gene expression of Alp, bone sialoprotein, osteocalcin, and ALP activity in cells grown on all evaluated surfaces. FAK inhibition did not affect the gene expression of Fak, integrin alpha 1 ( Itga1 ) and integrin beta 1 ( Itgb1 ) in cells grown on MS, increased the gene expression of Fak in cells grown on NS, and increased the gene expression of Itga1 and Itgb1 in cells grown on US and NS. Moreover, FAK protein expression decreased in cells cultured on US but increased in cells cultured on MS and NS after FAK inhibition; no difference in the expression of vinculin was observed among cells grown on all surfaces. Conclusions: Our data demonstrate the relevance of FAK in the interactions between osteoblastic cells and Ti surfaces regardless of surface topography. Nanotopography positively regulated FAK expression and integrin signaling pathway components during osteoblast differentiation. In this context, the development of Ti surfaces with the ability to upregulate FAK activity could positively impact the process of implant osseointegration.