Healing of normal and osteopenic bone with titanium implant and low-level laser therapy (GaAlAs): a histomorphometric study in rats

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

In Vivo Osteogenesis and In Vitro Streptococcus mutans Adherence: Porous-Surfaced Cylindrical Implants vs Rough-Surfaced Threaded Implants

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Mechanical and chemical analyses across dental porcelain fused to CP titanium or Ti6Al4V

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A MICROSTRAIN COMPARISON OF PASSIVELY FITTING SCREW-RETAINED AND CEMENTED TITANIUM FRAMEWORKS

Statement of problem. An imprecise fit between frameworks and supporting dental implants in loaded protocols increases the strain transferred to the periimplant bone, which may impair healing or generate microgaps.Purpose. The purpose of this study was to investigate the microstrain between premachined 1-piece screw-retained frameworks (group STF) and screw-retained frameworks fabricated by cementing titanium cylinders to the prefabricated framework (group CTF). This procedure was developed to correct the misfit between frameworks and loaded implants.Material and methods. Four internal hexagon cylindrical implants were placed 10 mm apart in a polyurethane block by using the surgical guides of the corresponding implant system. Previously fabricated titanium frameworks (n=10) were divided into 2 groups. In group STF, prefabricated machined frameworks were used (n=5), and, in group CTF, the frameworks were fabricated by using a passive fit procedure, which was developed to correct the misfit between the cast titanium frameworks and supporting dental implants (n=5). Both groups were screw-retained under torque control (10 Ncm). Six strain gauges were placed on the upper surface of the polyurethane block, and 3 strain measurements were recorded for each framework. Data were analyzed with the Student t test (alpha=.05).Results. The mean microstrain values between the framework and the implants were significantly higher for group STF (2517 me) than for group CTF (844 me) (P<.05).Conclusions. Complete-arch implant frameworks designed for load application and fabricated by using the passive fit procedure decreased the strain between the frameworks and implants more than 1 piece prefabricated machined frameworks.

Corrosion-fatigue life of commercially pure titanium and Ti-6Al-4V alloys in different storage environments

Statement of problem. Removable partial dentures are affected by fatigue because of the cyclic mechanism of the masticatory system ansi frequent insertion and removal. Titanium and its alloys have been used in the manufacture of denture frameworks; however, preventive agents with fluorides are thought to attack titanium alloy surfaces.Purpose. This study evaluated, compared, analyzed the corrosion-fatigue life of commercially pure titanium and Ti-6Al-4V alloy in different storage environments.Material and methods. For each metal, 33 dumbbell rods, 2.3 mm in diameter at the central segment, were cast in the Rematitan system. Corrosion-fatigue strength test was carried out through a universal testing machine with a load 30% lon er than the 0.2% offset yield strength and a combined influence of different: environments: in air at room temperature, with synthetic saliva, and with fluoride synthetic saliva. After failure, the number of cycles were recorded, and fracture surfaces were examined with on SEM.Results. ANOVA and Tukey's multiple comparison rest indicated that Ti-6Al-4V alloy achieved 21,269 cycles (SD = 8,355) against 19,157 cycles (SD = 3,624) for the commercially purr Ti. There were no significant differences between either metal in the corrosion-fatigue life for dry specimens, but when the solutions were present, the fatigue life was significantly reduced, probably because of the product-ion of corrosion pits caused by superficial reactions.

Estudo de tempos e temperaturas de sinterização na obtenção da liga NiTi por metalurgia do pó

The nickel-titanium alloys are very attractive and so it is widely used in industry, engineering applications in general and also in biomedical and dental applications. Besides showing the shape of memory effect, biocompatibility and superelastic, the alloy commercially known as Nitinol, has excellent mechanical properties. Most devices used in Brazil have been produced nationally, but using imported material is also necessary, which shows the need of produce the alloy nationally. In this study we have investigated the influence of sintering temperatures and times to obtain nickel-titanium alloys by powder metallurgy alloys and the characterization of the precipitated intermetallic phases by using the post-mix of elemental nickel and titanium in proportion of 49.5% Ti - 50.5% Ni. The samples were sintered at 930ºC for periods of 30, 40 and 50 hours and were characterized by optical microscopy using metallography and x-ray diffraction. The results of the study show that the 50 hours sintering time was the most suitable time for obtaining the alloy, observing a low volume of precipitated intermetallic phases and absence of Ni and Ti residuals

Effect of the iron doping on the thermal decomposition of the polymeric precursor for the titanium dioxide powder synthesis

The Polymeric Precursor Method has proved suitable for synthesizing reactive powders using low temperatures of calcination, especially when compared with conventional methods. However, during the thermal decomposition of the polymeric precursor the combustion event can be releases an additional heat that raises the temperature of the sample in several tens of degrees Celsius above the set temperature of the oven. This event may be detrimental to some material types, such as the titanium dioxide semiconductor. This ceramic material has a phase transition at around 600 ° C, which involves the irreversible structural rearrangement, characterized by the phase transition from anatase to rutile TiO2 phase. The control of the calcination step then becomes very important because the efficiency of the photocatalyst is dependent on the amount of anatase phase in the material. Furthermore, use of dopant in the material aims to improve various properties, such as increasing the absorption of radiation and in the time of the excited state, shifting of the absorption edge to the visible region, and increasing of the thermal stability of anatase. In this work, samples of titanium dioxide were synthesized by the Polymeric Precursor Method in order to investigate the effect of Fe (III) doping on the calcination stages. Thermal analysis has demonstrated that the Fe (III) insertion at 1 mol% anticipates the organic decomposition, reducing the combustion event in the final calcination. Furthermore, FTIR-PAS, XRD and SEM results showed that organic matter amount was reduced in the Fe (III)-doped TiO2 sample, which reduced the rutile phase amount and increased the reactivity and crystallinity of the powder samples.

Cutting Ability of Nickel-titanium rotary systems protaper, mtwo and k3

Nickel-titanium rotatory systems should remove dentin during the root canal preparation to promote the enlargement and tapered shape with continuously narrowing towards the apex. Objective: The aim of this study was to analyze the cutting ability of three NiTi rotatory systems (n = 12): ProTaper (group 1), Mtwo (group 2), and K3 (group 3). Material and methods: Thirty six maxillary molar teeth were weighted on an analytical balance before and after the rotatory preparation of the mesio-buccal root canal. Data was statistically analyzed by ANOVA and Tukey s test with a significance level of 5%. Results: The results revealed the following mass differences (g) before and after the root canal preparation: ProTaper (group 1 – 0.0159 ± 0.004), Mtwo (group 2 – 0.0125 ± 0.002), and K3 (group 3 – 0.007 ± 0.003). Conclusion: ProTaper showed the highest cutting ability among the three tested nickel-titanium rotatory systems followed by Mtwo and K3.

Orbital wall reconstruction with titanium mesh:Retrospective study of 24 patients

The aim of this study was to evaluate the efficacy and safety of traumatic orbital defect reconstruction with titanium mesh. A retrospective study was made. Evaluations were made after a minimum postoperative follow-up of 12 months, looking for the main complications. Twenty-four patients were included in this evaluation; 19 were male (79.1%) and 5 (20.8%) were female. The main injury etiology was vehicle accidents (50%) followed by other causes. Fourteen patients (58.3%) presented orbital floor fractures, and 10 had more than one wall fractured (41.6%). Permanent infraorbital nerve hypoesthesia was observed in two patients (8.3%), enophthalmos occurred in five patients (20.8%), and exophthalmos was found in two patients (8.3%). Four patients (16.6%) still presented evidence of residual prolapsed intraorbital content, and one of those needed further surgical correction; sinusitis occurred in one patient (4.1%). Titanium mesh is a reliable option for orbital reconstruction, despite some complications found in this sample.

Effect of two formulations of 10% sodium ascorbate on fracture resistance of endodontically treated tooth submitted to dental bleaching with hydrogen peroxide associated titanium dioxide nanoparticles

Purpose: This study evaluated the effect of 10% sodium ascorbate (10SA), in gel (10SAg) or aqueous solution (10SAs) formulations, on fracture resistance of endodontically treated tooth submitted to dental bleaching procedures with 15% hydrogen peroxide associated with titanium dioxide (15HP-TiO2) nanoparticles and photoactivated by LED-laser. Material and methods: Forty maxillary premolars were endodontically-treated and embedded in acrylic resin up to the cement-enamel junction. The specimens were divided into four groups (n=10): G1 (negative control): no bleaching, coronal access restored with composite resin; G2 (positive control): three dental bleaching sessions using 15HP-TiO2 and LED-laser photoactivation and restored with composite resin (positive control); G3 (10SAg): similar procedures to G2, but applied 10SA, in gel formulation, for 24 hours before restoration; G4 (10SAs): similar procedures to G3, but applied 10SA, in aqueous solution formulation. The 15HP-TiO2 was applied on buccal and lingual surfaces of the crown tooth and inside the pulp chamber and photoactivated by LED-laser. Between each bleaching session, the teeth were maintained in artificial saliva, at 37oC, for 7 days. In sequence, the teeth were submitted to fracture resistance testing using an eletromechanical machine test. The data was analyzed using Kruskal Wallis test (p = 0.05) Results: There are no differences significant among the groups in relation to fracture resistance of endodontically treated teeth (p>0.05). Conclusions: The use of 10% sodium ascorbate, in gel or aqueous solution formulations, did not interfered on the fracture resistance teeth after dental bleaching using 15HP-TiO2 and LED-laser photoactivation.

Fracture resistance of endodontically-treated teeth submitted to bleaching treatment with hydrogen peroxide and titanium dioxide nanoparticles photoactivated by LED-laser

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effect of clinical use of nickel-titanium springs

Introduction: Our objectives were to determine whether there are changes on the load deflection rate (L/DP) and the average force (FP) of the superelastic pseudoplateau, and whether permanent deformation is changed in nickel-titanium closed-coil springs (CCSs) after 6 months of clinical use. Methods: Twenty-two nickel-titanium CCSs (Sentalloy 100 g; Dentsply GAC, York, Pa) were subjected to tensile mechanical testing at 37 degrees C on activations varying from 3.2 to 16.0 mm before and after 6 months of clinical use. A regression line was fitted over the most horizontal area of the unloading part of the stress-strain graph of every CCS, and its slope was used as L/DP. The FP was determined by the midpoint of the longest segment of the curve that could be fit within the regression line with a R-2 of at least 0.999, and permanent deformation was determined graphically by obtaining the strain value when the measured stress reached zero. The data were analyzed by 3 analyses of variance at 2 levels, with 5% of significance. Results: Time and activation significantly influenced the variables tested (P < 0.001). Time increased the L/DP and permanent deformation but decreased the FP. Activation decreased L/DP, FP, and permanent deformation. Significant interactions between time and activation were detected for FP (P = 0.013) and deformation (P < 0.001). Conclusions: After 6 months of active clinical use, the analyzed springs had a significant but small increase in their L/DP; FP dropped up to 88%, and the CCSs deformed up to 1.26 mm.

How do titanium and Ti6A14V corrode in fluoridated medium as found in the oral cavity? an in vitro study

The purpose of this work was to evaluate the corrosion of commercially pure (CP) titanium and Ti6Al4V in vitro at different F- concentrations regularly found in the oral cavity by using different electrochemical tests and surface analysis techniques. electrochemical impedance spectroscopy (EIS), open circuit potential (OCP) and potentio-dynamic polarization tests were associated to advanced characterization techniques such as SEM, EDS, AFM, ICP-MS and XPS. OCP tests revealed a higher reactivity of both CP titanium and Ti6Al4V at 12,300 ppm F- concentration than that recorded at 227 ppm F-. Also, a significant decrease of the corrosion resistance of both materials was noticed by EIS in fluoride solutions. Material loss caused by corrosion was noticed on titanium surfaces by SEM and AFM in the presence of high F- concentration. CP titanium degraded by pitting corrosion while Ti6Al4V suffered from general corrosion showing micro-cracks on surface. Furthermore, a high release of metallic ions from the test samples after immersion at high F concentrations was detected by ICP-MS, that can be potentially toxic to oral tissues. (C) 2014 Elsevier B.V. All rights reserved.

Titanium K-edge XAS study on local structure of Pb1-xCaxTiO3 ferroelectric ceramics

In order to characterize the local structure of Pb1-xCaxTiO3 (PCT) samples, Ti K-edge XANES measurements were performed and showed that Ca incorporation to PbTiO3 structure leads to a decreasing of local distortion of Ti atoms in relation to oxygen atoms at the TiO6 octahedra. Moreover, according to EXAFS measurements, the local structure around Ti atoms exhibits tetragonal symmetry with P4mm space group for samples with x <= 0.475, whereas orthorhombic symmetry with Pbnm space group was observed for x equals to 0.50 and 0.55.