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1.
Niger J Clin Pract ; 23(1): 41-45, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31929205

RESUMO

Objective: This in vitro study aimed to compare the cyclic fatigue resistance of HyFlex EDM (HEDM), Vortex Blue (VB), ProTaper Gold (PG), and OneCurve (OC) nickel-titanium (NiTi) instruments. Materials and Methods: About 12 HEDM (25/.~), 12 VB (25/.06), 12 PG (25/.08), and 12°C (25/.06) instruments were included in this study. All the instruments were tested with a 60° angle of curvature and a 3-mm radius of curvature. All the instruments were utilized until fracture occurred, and then the number of cycles to failure (NCF) was calculated. The data were analyzed statistically using Kruskal-Wallis H and Mann-Whitney U-tests. The statistical significance level was set at P < 0.05. Results: HEDM instruments had the highest cyclic fatigue resistance among all the other instruments (P < 0.05). The OC instruments had a significantly higher fatigue resistance than the PG and VB instruments (P < 0.05); however, there was no significant difference between PG and VB instruments in the NCF (P > 0.05). Conclusion: Within the limitations of this in vitro study, it was found that the cyclic fatigue resistance was higher for the HEDM instruments than for the VB, PG, and OC instruments.


Assuntos
Ligas Dentárias/química , Instrumentos Odontológicos , Falha de Equipamento , Teste de Materiais , Preparo de Canal Radicular/instrumentação , Ligas , Desenho de Equipamento , Ouro , Humanos , Níquel/química , Titânio/química
2.
Chemosphere ; 243: 125205, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31726262

RESUMO

To determine whether the potential effects on liver and kidney caused by dental alloys could be reduced or terminated by the removal of nickel-chromium (Ni-Cr) alloy, cobalt-chromium (Co-Cr) alloy, and commercially pure titanium (CP-Ti), they were placed in the cheek pouches of Syrian hamsters according to ISO 10993-10. Then, the peak/plateau and end times of trace metals in the blood were determined with or without the removal of the dental alloys. Based on these time points, the trace metals and their effects on liver and kidney were examined. We found that trace metals released from these dental alloys and titanium were accumulated transiently in the blood, liver, and kidney but had no effect on the histopathology of the liver or kidney. Although the functions of the liver and kidney were compromised, the function of these tissues seemed to be clinically acceptable compared to those in control Syrian hamsters. In addition, the apoptotic effect on renal cells was terminated by removing the Ni-Cr and Co-Cr alloys, and that on hepatocytes was also eliminated by removing the Ni-Cr alloy. In contrast, the effect of the Co-Cr alloy on hepatocytes was temporary and recovered by itself. Taken together, Ni- and Co-based dental alloys and titanium have no effect on the histopathology or function of liver and kidney. Moreover, Ni-Cr and Co-Cr alloys induce transient trace metal accumulation and apoptotic effects in liver and kidney, which can be reduced or terminated by the removal of the alloys, while CP-Ti shows favorable biocompatibility.


Assuntos
Ligas de Cromo/química , Ligas Dentárias/química , Titânio/química , Ligas , Ligas de Cromo/toxicidade , Ligas Dentárias/toxicidade , Rim , Fígado , Teste de Materiais , Titânio/toxicidade
3.
Biomed Res Int ; 2019: 6368958, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31828110

RESUMO

Nickel-titanium (NiTi) rotary files have enabled efficient root canal preparations that maintain the canal center with fewer aberrations compared to hand files. However, NiTi rotary files are susceptible to fracture, which can thereby compromise root canal treatment. Therefore, NiTi files have been developed to enhance fracture resistance by modifying design and thermal treatment. The objective of this study was to compare the torsional fatigue resistance and bending resistance of NiTi files manufactured from different alloys and treatments. ProTaper NEXT X2 (PTN; M-wire), V taper 2H (V2H; controlled memory wire), NRT (heat-treated), and One Shape (OS; conventional alloy) instruments of tip size #25 were compared. Torsional fatigue was evaluated by embedding the 3 mm tip of each instrument (N = 10/brand) in resin and the repetitive application of torsional stress (300 rpm, 1.0 N·cm) by an endodontic motor with autostop when the file fractured. The number of loading cycles to fracture was recorded and analyzed by Kruskal-Wallis and Mann-Whitney U tests with Bonferroni's correction. Bending resistance of the instruments was tested using a cantilever bending test to the 3 mm point from the tip (N = 10/brand). The stress was measured when deflection of 3 mm was subjected and statistically analyzed with a one-way analysis of variance and Tukey's honest significance difference test (α = 0.05). V2H withstood the highest number of load applications during torsional fatigue testing (p < 0.05), followed by NRT, PTN, and OS, where the differences between NRT and PTN (p=0.035) and between PTN and OS (p=0.143) were not statistically significant. V2H showed the lowest bending stiffness, followed by NRT, PTN, and OS (p < 0.001). Thermal treatment of NiTi wire resulted in improved mechanical properties, and controlled memory wire provided improved flexibility and torsional fatigue resistance.


Assuntos
Ligas/química , Ligas Dentárias/química , Teste de Materiais , Níquel/química , Estresse Mecânico , Titânio/química , Preparo de Canal Radicular
4.
Braz Oral Res ; 33: e097, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31664360

RESUMO

To evaluate the torsional properties of engine-driven pathfinding instruments manufactured from different NiTi alloys - R-Pilot (tip size 12.5;.04 taper; M-Wire) and One G (tip size 14;.03 taper; Conventional NiTi). A total of 40 NiTi instruments from engine-driven pathfinding instruments (n = 20) were used. The torsion tests followed ISO 3630-1 (1992). Three millimeters of each instrument tip was fastened to a small load cell by a lever arm linked to the axis of torsion. During the test, the torsion testing machine software measured the maximum torsional strength and angle of rotation (0) before instrument failure. The fractured surface of each instrument was assessed by scanning electron microscopy (SEM). In addition, a supplementary examination was performed to measure the cross-sectional area and the metal mass volume of each instrument 3 mm from the tip. Data were analyzed using a t-test, with significance level set at 5%. R-pilot had significantly higher torsional strength than did One G (p < 0.05). Regarding the angle of rotation to fracture, One G had higher angles than did R-Pilot (p < 0.05). The supplementary examination showed that R-Pilot had the highest cross-sectional area and volume of metal mass at 3 mm from the tip (p < 0.05). R-pilot (M-Wire NiTi alloy) had a significantly higher torsional strength and One-G (superelastic NiTi alloy) had the highest angle of rotation to fracture.


Assuntos
Ligas/química , Ligas Dentárias/química , Instrumentos Odontológicos , Preparo de Canal Radicular/instrumentação , Análise de Variância , Desenho de Equipamento , Análise de Falha de Equipamento , Teste de Materiais , Microscopia Eletrônica de Varredura , Valores de Referência , Reprodutibilidade dos Testes , Estatísticas não Paramétricas , Estresse Mecânico , Propriedades de Superfície , Torque
5.
Colloids Surf B Biointerfaces ; 184: 110492, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31522026

RESUMO

The electrochemical properties of CoCrMo alloy immersed in different artificial saliva with or without Ca2+ and albumin were studied by open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP), and meanwhile the microstructures features, phase identification and chemical composition of the alloy were analyzed by SEM, EDS, XRD and RA-IR to further understand the electrochemical behavior of the alloy. The results indicated that the self-passivation behavior of the alloy occurred universally and was obviously distinct with each other in different acidic artificial saliva. No phase transformation was observed and the oxide layer and corrosion products exhibited amorphous nature. There was an obvious complexation of the adsorbed albumin with the alloy, and the adsorption capacity of albumin increased with the prolongation of immersion time. The adsorbed albumin presenting black stripped spots had a certain inhibition to the formation of passivation film, and Ca2+ in saliva promoted the further adsorption of albumin as an intermediate bridge, going against the improvement of the corrosion resistance of passivation film/alloy system. In addition, the passivation state of the alloy surface was changed by different methods to investigate the adsorption behavior of albumin and its influence on the further passivation behavior in depth. Hitherto, we tried to propose a model to explain the dynamic adsorption process of albumin and its influencing mechanism on the growth behavior of passivation film.


Assuntos
Albuminas/química , Ligas de Cromo/química , Cobalto/química , Ligas Dentárias/química , Molibdênio/química , Saliva Artificial/química , Adsorção , Espectroscopia Dielétrica , Eletroquímica/métodos , Concentração de Íons de Hidrogênio , Teste de Materiais/métodos , Microscopia Eletrônica de Varredura , Propriedades de Superfície , Difração de Raios X
6.
Photobiomodul Photomed Laser Surg ; 37(7): 442-450, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31265379

RESUMO

Objective: This study compared the effects of different surface treatments on the surface roughness (Ra), and shear bond strength (SBS) of resin cement to yttria-stabilized tetragonal zirconia (Y-TZP) ceramic and nickel-chromium (Ni-Cr) base metal alloy, respectively. Materials and methods: Thirty disk-shaped specimens (3 mm height and 10 mm diameter) of each material (Y-TZP and Ni-Cr) were prepared. Both zirconia and metal specimens were randomly assigned to three equal groups, according to the surface treatments (n = 10): sandblasting, sandblasting + Er:YAG laser, and sandblasting + Nd:YAG laser. Resin cement cylinders (4 mm diameter and 3 mm thickness) were placed on each specimen. The SBS tests were performed at a 1 mm per minute crosshead speed through a knife-edge rod after 5000 thermal cycles. The Ra (µm) of the specimens was measured using a profilometer and evaluated topographically by atomic force microscopy and scanning electron microscopy. Analysis of variance, followed by Tukey's honestly significant difference, in addition to the Kruskal-Wallis test, followed by the Mann-Whitney U test, were used for statistical analysis (α = 0.05). Results: Combined sandblasting and laser treatment of the metal groups led to statistically higher Ra values than sandblasting alone (p < 0.05). For Y-TZP, there were no significant differences between the Ra values of the subgroups (p > 0.05). The SBS of the sandblasted metal group was significantly higher than the other two laser-irradiated groups, whereas the SBS of sandblasted zirconia was only significantly higher than the Nd:YAG laser-irradiated group (p < 0.05). Conclusions: Combined laser and sandblasting surface treatments resulted in rougher surfaces than sandblasting alone, especially for the metal specimens. Sandblasting, alone, improved the SBS of resin cement in both metal and zirconia, compared with the laser and sandblasting treatments, combined.


Assuntos
Ligas de Cromo/química , Ligas Dentárias/química , Colagem Dentária/métodos , Corrosão Dentária/métodos , Porcelana Dentária/química , Lasers de Estado Sólido , Cimentos de Resina/química , Ítrio/química , Zircônio/química , Teste de Materiais , Microscopia de Força Atômica , Microscopia Eletrônica de Varredura , Resistência ao Cisalhamento/efeitos da radiação , Propriedades de Superfície
7.
Niger J Clin Pract ; 22(7): 926-931, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31293256

RESUMO

Background: This study was performed to evaluate the amount of apically extruded debris removed from a root canal filled with cold lateral condensation (CLC), and warm vertical compaction (WVC) techniques, using b or a phase gutta-percha with AH-Plus (Dentsply DeTrey, Konstanz, Germany) or Resilon (Resilon Research LLC, Madison, WI) with RealSeal SE (SybronEndo, Amersfoort, The Netherlands). Materials and Methods: About 100 human incisor teeth were prepared with a #25.06 NiTi rotary system and divided into five groups according to the filling material used: Group 1: CLC (gutta-percha, AH-Plus); Group 2: WVC (b phase gutta-percha, AH-Plus); Group 3: WVC (a phase gutta-percha, AH-Plus); Group 4: CLC (Resilon, RealSeal SE); and Group 5: WVC (Resilon, RealSeal SE). Extruded debris during the retreatment procedure was collected in preweighed Eppendorf tubes. The times required for retreatment were recorded. Results: The amount of debris extrusion was significantly greater with WVC than CLC in the gutta-percha and Resilon groups (P < 0.001). Using a phase gutta-percha resulted in significantly more debris extrusion than b phase gutta-percha (P < 0.001). In the WVC groups, Resilon caused significantly more debris extrusion than gutta-percha (P < 0.05). Retreatment was faster for CLC than WVC (P < 0.05). Conclusions: In the retreatment procedure, the amount of apically extruded debris and retreatment duration were dependent on the type of obturation material and technique used.


Assuntos
Cavidade Pulpar/cirurgia , Guta-Percha/química , Materiais Restauradores do Canal Radicular/química , Preparo de Canal Radicular/instrumentação , Preparo de Canal Radicular/métodos , Tratamento do Canal Radicular/instrumentação , Ligas Dentárias/química , Humanos , Níquel , Retratamento , Materiais Restauradores do Canal Radicular/efeitos adversos , Obturação do Canal Radicular/métodos , Titânio/química , Ápice Dentário/patologia
8.
Dentomaxillofac Radiol ; 48(7): 20190036, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31188678

RESUMO

OBJECTIVES: To evaluate the effects of syngo WARP on reducing metal artefacts from dental materials. METHODS: Short tau inversion recovery (STIR) with syngo WARP [a dedicated metal artefact reduction sequence in combination with view-angle-tilting (VAT)] was performed using phantoms of three dental alloys: cobalt-chromium (Co-Cr), nickel-chromium (Ni-Cr), and titanium (Ti). Artefact volumes and reduction ratios of black, white and overall artefacts in the standard STIR and syngo WARP images with several different parameter settings were quantified according to standards of the American Society for Testing and Materials F2119-07. In all sequences, the artefact volumes and reduction ratios were compared. The modulation transfer function (MTF) and contrast-to-noise ratio (CNR) were also measured for evaluation of image quality. RESULTS: In standard STIR, the overall artefact volume of Co-Cr was markedly larger than those of Ni-Cr and Ti. All types of artefacts tended to be reduced with increasing receiver bandwidth (rBW) and VAT. The effect of artefact reduction tended to be more obvious in the axial plane than in the sagittal plane. Compared with standard STIR, syngo WARP with a matrix of 384 × 384, receiver bandwidth of 620 Hz/pixel, and VAT of 100 % in the axial plane obtained reduction effects of 30 % (white artefacts), 45 % (black artefacts), and 38 % (overall artefacts) although MTF and CNR decreased by 30 and 22 % compared with those of standard STIR, respectively. CONCLUSIONS: syngo WARP for STIR can effectively reduce metal artefacts from dental materials.


Assuntos
Artefatos , Ligas Dentárias , Radiografia Dentária , Ligas Dentárias/química , Aumento da Imagem , Imagem por Ressonância Magnética , Imagens de Fantasmas , Radiografia Dentária/métodos
9.
Microsc Res Tech ; 82(9): 1384-1391, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31111992

RESUMO

The aims of this study were: (a) to determine if the presence of probiotic bacteria in an aging medium, that is, artificial saliva in this study, has relevant effects on the surface roughness and the chemical composition of two main alloys used in dentistry (NiTi and stainless steel [SS]) and (b) in the case of NiTi, if these effects are influenced by the coating of the alloy (rhodium and titanium nitride). Atomic force microscopy and Raman spectroscopy were used to study the surface morphology and identify metal oxides formed on the surface of the alloys. Experiments demonstrated that the probiotic bacteria Lactobacillus reuteri can induce processes that alter some features of the surface such as roughness and chemical composition. The effect is dependent on the type of alloy and coating. The bacteria increased roughness in the case of uncoated NiTi more than saliva alone (pH = 4.8). Probiotic bacteria tend to decrease the corrosive influence of saliva on NiTi when the alloy is coated with rhodium or titanium nitride and this effect was also evidenced on SS. Raman spectroscopy confirmed that only SS samples are prone to oxidation processes, predominantly associated with exposure to saliva rather than probiotic bacteria.


Assuntos
Ligas Dentárias/química , Lactobacillus reuteri/crescimento & desenvolvimento , Lactobacillus reuteri/metabolismo , Probióticos/metabolismo , Saliva/microbiologia , Propriedades de Superfície , Corrosão , Microscopia de Força Atômica , Óxidos/análise , Análise Espectral Raman
10.
Niger J Clin Pract ; 22(4): 496-502, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30975953

RESUMO

Aim: The aim of this research was to investigate the effect of microwave glazing, conventional oven glazing, and polishing on surface roughness and wettability of porcelains. Materials and Methods: The initial surface roughness values (Ra0) of the prepared specimens for four different porcelains (Vita VM 9, VitaVM 13, Vita VMK 95, IPS e.maxCeram) were determined by profilometry. Then, the specimens were divided randomly into three groups as polishing, conventional oven glazing, and microwave glazing. Final surface roughness values were evaluated by profilometry (Ra1) and scanning electron microscopy. Wettability of glazed specimens were evaluated by contact angle goniometer. Results: Although microwave-glazed specimens had lower Ra1 values compared with the conventional oven-glazed ones for IPS e.maxCeram (P < 0.05), there were not any statistically significant differences between these two procedures in terms of Ra1 values for the other porcelains (P > 0.05). Microwave-glazed specimens had lower wettability values than conventional oven-glazed ones for Vita VM 9. Conclusions: Microwave glazing procedure may be considered as an alternative method because of the advantages of providing volumetric heating, time, and energy saving.


Assuntos
Ligas Dentárias/química , Polimento Dentário/métodos , Porcelana Dentária/química , Teste de Materiais/métodos , Microscopia Eletrônica de Varredura , Micro-Ondas , Molhabilidade , Cerâmica , Temperatura Alta , Humanos , Propriedades de Superfície
11.
PLoS One ; 14(1): e0210530, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30703125

RESUMO

BACKGROUND: Titanium (Ti) and its alloys possess high biocompatibility and corrosion resistance due to Ti ability to form a passive oxide film, i.e. TiO2, immediately after contact with oxygen. This passive layer is considered stable during function in the oral cavity, however, emerging information associate inflammatory peri-implantitis to vast increases in Ti corrosion products around diseased implants as compared to healthy ones. Thus, it is imperative to identify which factors in the peri-implant micro-environment may reduce Ti corrosion resistance. METHODS: The aim of this work is to simulate peri-implant inflammatory conditions in vitro to determine which factors affect corrosion susceptibility of Ti-6Al-4V dental implants. The effects of hydrogen peroxide (surrogate for reactive oxygen species, ROS, found during inflammation), albumin (a protein typical of physiological fluids), deaeration (to simulate reduced pO2 conditions during inflammation), in an acidic environment (pH 3), which is typical of inflammation condition, were investigated. Corrosion resistance of Ti-6Al-4V clinically-relevant acid etched surfaces was investigated by electrochemical techniques: Open Circuit Potential; Electrochemical Impedance Spectroscopy; and Anodic Polarization. RESULTS: Electrochemical tests confirmed that most aggressive conditions to the Ti-6Al-4V alloy were those typical of occluded cells, i.e. oxidizing conditions (H2O2), in the presence of protein and deaeration of the physiological medium. CONCLUSIONS: Our results provide evidence that titanium's corrosion resistance can be reduced by intense inflammatory conditions. This observation indicates that the micro-environment to which the implant is exposed during peri-implant inflammation is highly aggressive and may lead to TiO2 passive layer attack. Further investigation of the effect of these aggressive conditions on titanium dissolution is warranted.


Assuntos
Ligas Dentárias/química , Implantes Dentários/normas , Teste de Materiais/métodos , Titânio/química , Ácidos/química , Corrosão , Técnicas Eletroquímicas/métodos , Humanos , Peróxido de Hidrogênio/química , Concentração de Íons de Hidrogênio , Inflamação/induzido quimicamente , Inflamação/complicações , Microscopia Eletrônica de Varredura , Modelos Químicos , Propriedades de Superfície
12.
J Int Med Res ; 47(2): 803-814, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30616411

RESUMO

OBJECTIVE: To examine the effect of clinical use on both force retention and the deactivation of closed-coil nickel-titanium (NiTi) springs in a 16-week trial. METHODS: The force-activation curves for NiTi springs were determined before and after clinical use. The rate of tooth movement and maximum force (MF), hysteresis between activation and deactivation, and mean force of the deactivation plateau (MDF) were examined and correlated as a function of 4, 8, 12 and 16 weeks of clinical use. To recover the force properties, the springs were heat treated at 100°C and the results were compared with the preceding data. RESULTS: A total of 36 springs were analysed. The MF loss after use was 60, 74, 55, and 48 g for the 4-, 8-, 12- and 16-week springs, respectively. Heat treating had little effect on the MF. Clinical use lowered hysteresis by a mean of 180 g*mm compared with the pre-clinical use data, and heat treating increased the hysteresis by a mean of 59 g*mm above the post clinic testing data. The MDF was nominally 100 g less than the MF. Teeth moved approximately 1 mm/month, independent of the force loss. CONCLUSIONS: The loss of MF and the lowering of the MDF was not time dependent. Heat treating can partially recover the mechanical properties of the used springs.


Assuntos
Ligas Dentárias/química , Níquel/química , Fechamento de Espaço Ortodôntico/instrumentação , Fios Ortodônticos , Titânio/química , Adolescente , Criança , Feminino , Seguimentos , Humanos , Masculino , Teste de Materiais , Fenômenos Mecânicos , Prognóstico , Estudos Prospectivos
13.
J Mech Behav Biomed Mater ; 90: 523-529, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30458336

RESUMO

In this study, we examined the effect of pre-existing dislocation structures in a face-centered cubic γ-phase on strain-induced martensitic transformation (SIMT) to produce a hexagonal close-packed ε-phase in a hot-rolled biomedical Co-Cr-Mo alloy. The as-rolled microstructure was characterized by numerous dislocations as well as stacking faults and deformation twins. SIMT occurred just after macroscopic yielding in tensile deformation. Using synchrotron X-ray diffraction line-profile analysis, we successfully captured the nucleation of ε-martensite during tensile deformation in terms of structural evolution in the surrounding γ-matrix: many dislocations that were introduced into the γ-matrix during the hot-rolling process were consumed to produce ε-martensite, together with strong interactions between dislocations in the γ-matrix. As a result, the SIMT behavior during tensile deformation was accelerated through the consumption of these lattice defects, and the nucleation sites for the SIMT ε-phase transformed into intergranular regions upon hot rolling. Consequently, the hot-rolled Co-Cr-Mo alloy simultaneously exhibited an enhanced strain hardening and a high yield strength. The results of this study suggest the possibility of a novel approach for controlling the γ → ε SIMT behavior, and ultimately, the performance of the alloy in service by manipulating the initial dislocation structures.


Assuntos
Ligas/química , Materiais Biocompatíveis/química , Cromo/química , Cobalto/química , Ligas Dentárias/química , Molibdênio/química , Estresse Mecânico , Teste de Materiais , Resistência à Tração
14.
Dent Mater J ; 38(1): 150-156, 2019 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-30449828

RESUMO

The purpose of this study was to investigate how differences in dental implant and screw materials affected screw loosening. Screws (pure titanium; Ti4S, titanium alloy; TiAS), blocks (Y-TZP; ZrB, pure titanium; Ti4B) and plates (Y-TZP; ZrP), representing abutment screws, implant bodies and superstructures, respectably, were used. Plates were fastened to blocks by screws using a torque of 20 N•cm, and the loosening torque was measured after cyclic loading. Tests was performed on 13 specimens per group, with four groups for loading at the eccentric point (9 mm from screw center) and one group at the centric point (3 mm from screw center). In eccentric point tests, Ti4S screws led to significantly more loosening than TiAS screws (p<0.01). The block material had no effect. For ZrBTi4S, there was no difference in loosening before and after the centric point tests. More loosening occurred for eccentric point than for centric point tests (p<0.05).


Assuntos
Parafusos Ósseos , Dente Suporte , Implantes Dentários , Materiais Dentários/química , Falha de Restauração Dentária , Ligas Dentárias/química , Planejamento de Prótese Dentária , Análise do Estresse Dentário , Teste de Materiais , Titânio/química , Torque , Zircônio/química
15.
Int Endod J ; 52(1): 94-104, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29969837

RESUMO

AIM: To assess the real-time dynamic torque values and axial forces during preparation of straight root canals using three different endodontic motors and hand preparation. METHODOLOGY: Sixty maxillary incisors were divided into four homogeneous groups (n = 15). After glide path establishment (size 20) the root canals were prepared to an apical size 40 using the rotary NiTi system F6 SkyTaper. Motors (DentaPort ZX OTR, EndoPilot and VDW.silver) were set to 'auto-torque-reverse' mode and DentaPort ZX was set to its specific OTR mode (optimum torque reverse). One group served as a control using manual balanced-force canal preparation with K-Flexofiles. Teeth were embedded in resin and fixed in a multi-component sensor measuring axial and torsional load during active instrumentation with 50 Hz. Preparation time was also recorded. Data were statistically analysed using the Kruskal-Wallis test. RESULTS: The maximum axial forces (peak) and both peaks of dynamic clockwise and counter-clockwise torque did not differ significantly when using the three different motors despite different gear ratios and pre-settings. Only the VDW.silver motor exceeded the torque values during the use of 30 instruments (3.3%). The Morita OTR motor exceeded the maximum intrinsic torque set at 1.0 Ncm in approximately 53% of cases. The larger tapered F6 SkyTaper instruments (size 20, .06 taper and size 30, .06 taper) created significantly higher torque values (P < 0.0001). Manual instrumentation created significantly lower torque levels and higher axial values compared to rotary instrumentation (P < 0.0001) and was significantly more time consuming (P < 0.0001). CONCLUSIONS: Manual preparation was associated with significantly lower torque peaks compared to rotary instrumentation. The three motors remained well within the safety torque values of the instruments.


Assuntos
Instrumentos Odontológicos , Equipamentos e Provisões Elétricas , Preparo de Canal Radicular/instrumentação , Estresse Mecânico , Torque , Ligas Dentárias/química , Análise do Estresse Dentário , Desenho de Equipamento , Humanos , Incisivo/anatomia & histologia , Níquel/química , Rotação , Titânio/química
16.
Int Endod J ; 52(2): 244-249, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30040121

RESUMO

AIM: To determine the distortional angle and torsional load at the pseudoelastic limit of Reciproc Blue instruments and to verify the safety of using pre-set dedicated motors designed for use with the original Reciproc instruments. METHODOLOGY: Two torsional conditions of Reciproc R25 and Reciproc Blue R25 were tested using a custom device. The first condition fixed the file tips at 3 mm and repetitively rotated them, with gradually increasing angles, from 10° to 270°, and the resulting torque was recorded (n = 15). The second test involved a single continuous rotation until fracture (n = 15). The pseudoelastic limits of the instruments were determined from their torque-rotation curves. For statistical analysis, two-way analysis of variance and t-tests were used, at a 95% significance level. Tested specimens were examined using field-emission scanning electron microscopy (FE-SEM). RESULTS: The angle at the pseudoelastic limit was significantly greater for Reciproc Blue than Reciproc, regardless of test mode (P < 0.05). When torsional loading was repeated, using gradually increasing rotational angles, the torsional resistance was significantly lower than for a single rotation (P < 0.05). However, under all test conditions, the pseudoelastic limit was below the pre-set 170° of the dedicated reciprocating motor. FE-SEM evaluation of the lateral aspects of the instruments revealed numerous longitudinal microcracks running along their long axis. For Reciproc Blue groups, the file shaft machining grooves were distorted after repetitive and continuous torsional tests. CONCLUSIONS: The 170° pre-set angle of the dedicated endodontic motors for the Reciproc system was safe for Reciproc Blue in single or time-restricted use.


Assuntos
Instrumentos Odontológicos , Desenho de Equipamento , Preparo de Canal Radicular/instrumentação , Torção Mecânica , Análise de Variância , Ligas Dentárias/química , Falha de Equipamento , Análise de Falha de Equipamento , Segurança de Equipamentos , Humanos , Teste de Materiais , Microscopia Eletrônica de Varredura , Níquel/química , Rotação , Estresse Mecânico , Propriedades de Superfície , Titânio/química , Torque
17.
J Prosthodont ; 28(1): e265-e270, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29271021

RESUMO

PURPOSE: To evaluate the effect of the triad finish line design, axial wall convergence angle, and luting cement on the marginal fit of metal copings used in metal-ceramic crowns. MATERIALS AND METHODS: Schematic dies and their respective copings were cast in NiCr alloy. The dies exhibited the following finish line/convergence angle combinations: sloping shoulder/6°, sloping shoulder/20°, shoulder/6°, shoulder/20°. Marginal fit was evaluated under a stereomicroscope, before and after cementation. Copings were air-abraded with 50 µm Al2 O3 particles and cemented with Cimento de Zinco, RelyX U100, or Panavia F cements (n = 10/group). Data were square-root transformed and analyzed by 3-way factorial random effect model and Tukey's post hoc test (α = 0.05). RESULTS: Statistical analysis showed significance for the interactions finish line and convergence angle (p < 0.05), convergence angle and time (p < 0.001), and luting cement and time (p < 0.001). Sloping shoulder/20° provided the highest marginal discrepancy when compared to the other finish line/convergence angle combinations, which were statistically similar among each other. For both convergence angles and for all luting cements, the marginal discrepancy was significantly higher after cementation. Before and after cementation, 6° provided better marginal fit than 20°. After cementation, Panavia F provided higher marginal discrepancy than Cimento de Zinco. CONCLUSION: Lower convergence angle combined with shoulder and a low-consistency luting cement is preferable to cement metal copings.


Assuntos
Cimentação/métodos , Cimentos Dentários/química , Adaptação Marginal Dentária , Teste de Materiais , Ligas Metalo-Cerâmicas/química , Preparo Prostodôntico do Dente/métodos , Ligas Dentárias/química , Porcelana Dentária/química , Planejamento de Prótese Dentária , Falha de Restauração Dentária , Cimentos de Ionômeros de Vidro/química , Humanos , Cimentos de Resina , Estresse Mecânico , Propriedades de Superfície , Preparo do Dente/métodos
18.
Int Endod J ; 52(2): 250-257, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30091141

RESUMO

AIM: To compare the efficiency of M-Wire Reciproc and Reciproc Blue instruments in the removal of root filling material and in their ability to regain apical patency through micro-computed tomographic (micro-CT) analysis. METHODOLOGY: Ten anatomically matched pairs of teeth, with a single oval-shaped straight canal, were selected and scanned in a micro-CT device. The root canals were prepared with M-Wire Reciproc R25 instruments and filled with gutta-percha and AH Plus sealer. The root canals were then randomly allocated into two groups (n = 10), according to the instrument used: M-Wire Reciproc and Reciproc Blue. The canals were retreated up to instrument sizes 25 and then 40 in both groups. The surface area and volume of residual filling material were assessed using micro-CT imaging after the retreatment procedures. The time required to remove the root fillings was recorded. Data were analysed statistically using t-test with a significance level of 5%. RESULTS: No significant difference (P > 0.05) was observed between the instruments in terms of the volume of residual root filling material. Apical enlargement from size 25 to 40 significantly improved the removal of filling materials (P < 0.05). It was possible to regain apical patency in all specimens from both M-Wire Reciproc and Reciproc Blue groups. No difference was observed in the time required to perform the retreatment between the instruments. CONCLUSIONS: Both M-Wire Reciproc and Reciproc Blue instruments were effective in removing filling materials from oval-shaped straight canals. Apical patency was reestablished in all specimens.


Assuntos
Instrumentos Odontológicos , Materiais Restauradores do Canal Radicular/química , Obturação do Canal Radicular/instrumentação , Obturação do Canal Radicular/métodos , Preparo de Canal Radicular/instrumentação , Preparo de Canal Radicular/métodos , Anatomia Transversal , Ligas Dentárias/química , Cavidade Pulpar/diagnóstico por imagem , Desenho de Equipamento , Guta-Percha/química , Humanos , Incisivo/anatomia & histologia , Incisivo/diagnóstico por imagem , Incisivo/cirurgia , Mandíbula , Teste de Materiais , Níquel/química , Retratamento , Irrigantes do Canal Radicular , Hipoclorito de Sódio/química , Propriedades de Superfície , Titânio , Ápice Dentário/anatomia & histologia , Microtomografia por Raio-X/métodos
19.
J Mech Behav Biomed Mater ; 90: 655-664, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30502674

RESUMO

The effects of fretting on Ni-rich ultra-fine grained NiTi superelastic wires have been characterized. Fretting tests have been performed using wire on wire in 90° cross-cylinder configuration until 105 cycles in air at 25 °C. Constant displacement amplitude of 50 µm and normal loads of 10, 20 and 50 N were considered. For a normal load of 10 N, the tribosystem performed in Gross Slip Regime and the predominance of wear damage was observed. Mixed Fretting Regime was instead observed for normal loads of 20 N and 50 N. In these cases, the predominant damage mechanism was crack formation with the cracks oriented normal to the displacement direction. Occurrence of martensitic transformation in the contact region was inferred from the particular shape of the fretting loops. Due to their possible impact on biocompatibility, the debris detached from the tribosystem during the different experiments were collected and characterized by TEM. They consisted in agglomerations of nano-crystalline TiO2 (rutile) and NiO oxide particles sized between 10 and 20 nm.


Assuntos
Elasticidade , Teste de Materiais , Níquel/química , Titânio/química , Ligas Dentárias/química , Pressão , Temperatura , Suporte de Carga
20.
J Prosthet Dent ; 121(1): 156-165, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30093130

RESUMO

STATEMENT OF PROBLEM: The grayish appearance of titanium abutments adversely affects peri-implant esthetics in patients with thin mucosa, impacting patient satisfaction with implant-supported restorations in esthetic regions. PURPOSE: The purpose of this in vitro study was to change the color of titanium alloys with anodic oxidation and to evaluate alterations in the esthetic, physical, and biological properties of the anodized titanium alloys. MATERIAL AND METHODS: Pink and yellow titanium alloys produced by anodization were the experimental groups, and the untreated titanium alloy and zirconia were used as the control groups. Pig gingiva was placed on the tested specimens to evaluate the esthetic effect by recording the color change in the gingiva. Physical properties including morphology, chemical composition, roughness, and contact angle were evaluated by scanning electron microscopy, atomic force microscopy, and a contact angle analysis system. Biological properties were evaluated by observing the cell behaviors of human gingival fibroblasts, using scanning electron microscopy, fluorescence microscopy, a live/dead viability assay, and a cell counting assay. RESULTS: A variety of colors can be produced on the surfaces of titanium alloys by anodization at different voltages. Titanium alloys anodized at 60 and 65 V exhibited yellow and pink appearances, respectively. Color differences of gingiva caused by anodized titanium alloys were lower than those of the untreated titanium alloy, but they were higher than those of zirconia. Compared with the untreated titanium alloy, the anodized titanium alloys exhibited grain formation, a lower contact angle, and higher roughness. Cell morphology, proliferation, and viability on surfaces of anodized titanium alloys were similar to those of the untreated titanium alloy but lower than those of zirconia. CONCLUSIONS: Anodization could change the color of titanium alloys to pink or yellow at different voltages. Grain formation, roughness, and hydrophilicity were increased after treatment. The esthetics and biocompatibility of anodized titanium alloys were not as good as that of zirconia, but the pink and yellow titanium alloys treated by anodization achieved better gingival esthetics than the untreated titanium alloy.


Assuntos
Materiais Biocompatíveis/química , Ligas Dentárias/química , Implantes Dentários , Estética Dentária , Titânio/química , Animais , Sobrevivência Celular , Cor , Dente Suporte , Implantes Dentários para Um Único Dente , Eletrodos , Fibroblastos/fisiologia , Gengiva/citologia , Humanos , Teste de Materiais , Maxila , Propriedades de Superfície , Suínos , Zircônio/química
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