195 research outputs found
Surface and cross-sectional characterization of titanium-nitride coated nickelâtitanium endodontic files
Background/purpose Although the effect of experimental surface modifications on various properties (e.g., fatigue, wear) on coated files have been tested in the past, there is no report for the coating quality of commercially available TiN coated files. The aim of this study was to characterize the surface and cross section of TiN coated endodontic files. Materials and methods TiN coated nickelâtitanium endodontic files (EasyShape) were surface and cross-sectionally analyzed via scanning electron microscopy backscattered electron imaging and energy-dispersive X-ray spectroscopy analysis in spot, area, and line scan modes. Results Surface imaging revealed parallel oblong regions with higher mean atomic contrast, a finding attributed to increased Ni content. Cross-sectional analysis showed that the coatingâs average total thickness was 0.31 ÎŒm and consisted of a thin layered film. Energy-dispersive X-ray spectroscopy analysis revealed the presence of Ti, Ni, N, and O in the coating, whereas only Ni and Ti were identified in the bulk of the file. Ti and O showed their peak compositions at the bulk/coating and coating/surface interfaces, respectively, whereas N displayed a rather constant content within the coated region. The N and O contents started increasing inner to the coating/bulk interface, denoting possible diffusion of both elements to the subcoating region. Conclusion Surface and bulk characterization showed no uncoated areas of the files tested. Apart from Ti, Ni, and N, oxygen was also identified within the coating region
Titanium Nitride and Nitrogen Ion Implanted Coated Dental Materials
Titanium nitride and/or nitrogen ion implanted coated dental materials have been investigated since the mid-1980s and considered in various applications in dentistry such as implants, abutments, orthodontic wires, endodontic files, periodontal/oral hygiene instruments, and casting alloys for fixed restorations. Multiple methodologies have been employed to create the coatings, but detailed structural analysis of the coatings is generally lacking in the dental literature. Depending on application, the purpose of the coating is to provide increased surface hardness, abrasion/wear resistance, esthetics, and corrosion resistance, lower friction, as well as greater beneficial interaction with adjacent biological and material substrates. While many studies have reported on the achievement of these properties, a consensus is not always clear. Additionally, few studies have been conducted to assess the efficacy of the coatings in a clinical setting. Overall, titanium nitride and/or nitrogen ion implanted coated dental materials potentially offer advantages over uncoated counterparts, but more investigation is needed to document the structure of the coatings and their clinical effectiveness
Fracture toughness and hardness of in-office, 3D-printed ceramic brackets
Objectives: Threeâdimensional (3D) printing technology is a promising manufacturing technique for fabricating ceramic brackets. The aim of this research was to assess fundamental mechanical properties of inâoffice, 3D printed ceramic brackets.
Materials and Methods: 3Dâprinted zirconia brackets, commercially available polycrystalline alumina ceramic brackets (Clarity, 3âMâSt. Paul, MN) and 3Dâprinted customized polycrystalline alumina ceramic ones (LightForceâą, Burlington, Massachusetts) were included in this study. Seven 3D printed zirconia brackets and equal number of ceramic ones from each manufacturer underwent metallographic grinding and polishing followed by Vickers indentation testing. Hardness (HV) and fracture toughness (K1c) were estimated by measuring impression average diagonal length and crack length, respectively. After descriptive statistics calculation, group differences were analysed with 1 Way ANOVA and Holm Sidak post hoc multiple comparison test at significance level α =â.05.
Results: Statistically significant differences were found among the materials tested with respect to hardness and fracture toughness. The 3Dâprinted zirconia proved to be less hard (1261â±â39 vs 2000â±â49 vs 1840â±â38) but more resistant to crack propagation (K1c = 6.62â±â0.61 vs 5.30â±â0.48 vs 4.44â±â0.30âMPaâm) than the alumina brackets (Clarity and Light Force respectivelty). Significant differences were observed between the 3D printed and the commercially available polycrystalline alumina ceramic brackets but to a lesser extent.ConclusionsUnder the limitations of this study, the 3D printed zirconia bracket tested is characterized by mechanical properties associated with advantageous orthodontic fixed appliances traits regarding clinically relevant parameters
Assessment of geometrical characteristics of dental endodontic micro-instruments utilizing X-ray micro computed tomography
OBJECTIVE: The aim of this study was to quantify the surface area, volume and specific surface area of endodontic files employing quantitative X-ray micro computed tomography (mXCT). MATERIAL AND METHODS: Three sets (six files each) of the Flex-Master Ni-Ti system (NÂș 20, 25 and 30, taper .04) were utilized in this study. The files were scanned by mXCT. The surface area and volume of all files were determined from the cutting tip up to 16 mm. The data from the surface area, volume and specific area were statistically evaluated using the one-way ANOVA and SNK multiple comparison tests at α=0.05, employing the file size as a discriminating variable. The correlation between the surface area and volume with nominal ISO sizes were tested employing linear regression analysis. RESULTS: The surface area and volume of NÂș 30 files showed the highest value followed by NÂș 25 and NÂș 20 and the differences were statistically significant. The NÂș 20 files showed a significantly higher specific surface area compared to NÂș 25 and NÂș 30. The increase in surface and volume towards higher file sizes follows a linear relationship with the nominal ISO sizes (rÂČ=0.930 for surface area and rÂČ=0.974 for volume respectively). Results indicated that the surface area and volume demonstrated an almost linear increase while the specific surface area exhibited an abrupt decrease towards higher sizes. CONCLUSIONS: This study demonstrates that mXCT can be effectively applied to discriminate very small differences in the geometrical features of endodontic micro-instruments, while providing quantitative information for their geometrical properties
Effect of Nd:YAG Laser Parameters on the Penetration Depth of a Representative NiâCr Dental Casting Alloy
The effects of voltage and laser beam (spot) diameter on the penetration depth during laser beam welding in a representative nickelâchromium (NiâCr) dental alloy were the subject of this study. The cast alloy specimens were butted against each other and laser welded at their interface using various voltages (160â390 V) and spot diameters (0.2â1.8 mm) and a constant pulse duration of 10 ms. After welding, the laser beam penetration depths in the alloy were measured. The results were plotted and were statistically analyzed with a two-way ANOVA, employing voltage and spot diameter as the discriminating variables and using HolmâSidak post hoc method (aâ=â0.05). The maximum penetration depth was 4.7 mm. The penetration depth increased as the spot diameter decreased at a fixed voltage and increased as the voltage increased at a fixed spot diameter. Varying the parameters of voltage and laser spot diameter significantly affected the depth of penetration of the dental cast NiâCr alloy. The penetration depth of laser-welded NiâCr dental alloys can be accurately adjusted based on the aforementioned results, leading to successfully joined/repaired dental restorations, saving manufacturing time, reducing final cost, and enhancing the longevity of dental prostheses
Elemental, Morphological, and Corrosion Characterization of Different Surface States of Co-Cr Alloy for Prosthodontic Applications
In this study, four different groups were prepared in a cast model of an arch
that received four implants made with a Co-Cr dental alloy. The surface of
each group was prepared by four different surface treatments, including
sandblasting with Al2O3 grains (SB), conventional finishing with dental burs
(CF), milling with a CAD/CAM device (MIL), and electrodischarge machining
(EDM). The characterization of the roughness parameters, morphology, elemental
composition, and electrochemical properties of a dental Co-Cr alloy in
different surface states exposed to an oral environment were reported. The
electrochemical properties were tested with open-circuit potential (OCP) and
anodic scan in Ringerâs solutions. The results of roughness parameters,
elemental composition, OCP, corrosion potential and pitting potential were
statistically analyzed by one-way ANOVA and the Tukey-Kramer multiple-
comparison test at 95% confidence level. The roughness parameters classified
the surfaces from smoothest to roughest according to the following order; CF,
MIL, EDM, and SB. The CF group has the best corrosion resistance followed by
the EDM, MIL, and SB groups
Galvanic coupling of steel and gold alloy lingual brackets with orthodontic wires: Is corrosion a concern?
OBJECTIVES The aim of this research was to assess galvanic behavior of lingual orthodontic brackets coupled with representative types of orthodontic wires.
MATERIALS AND METHODS Three types of lingual brackets: Incognito (INC), In-Ovation L (IOV), and STb (STB) were combined with a stainless steel (SS) and a nickel-titanium (NiTi) orthodontic archwire. All materials were initially investigated by scanning electron microscopy / x-ray energy dispersive spectroscopy (SEM/EDX) while wires were also tested by x-ray diffraction spectroscopy (XRD). All bracket-wire combinations were immersed in acidic 0.1M NaCl 0.1M lactic acid and neutral NaF 0.3% (wt) electrolyte, and the potential differences were continuously recorded for 48 hours.
RESULTS The SEM/EDX analysis revealed that INC is a single-unit bracket made of a high gold (Au) alloy while IOV and STB are two-piece appliances in which the base and wing are made of SS alloys. The SS wire demonstrated austenite and martensite iron phase, while NiTi wire illustrated an intense austenite crystallographic structure with limited martensite. All bracket wire combinations showed potential differences below the threshold of galvanic corrosion (200 mV) except for INC and STB coupled with NiTi wire in NaF media.
CONCLUSIONS The electrochemical results indicate that all brackets tested demonstrated galvanic compatibility with SS wire, but fluoride treatment should be used cautiously with NiTi wires coupled with Au and SS brackets
Mechanical properties of orthodontic wires derived by instrumented indentation testing (IIT) according to ISO 14577
BACKGROUND: The aim of this study was the characterization of mechanical properties of representative types of orthodontic wires employing instrumented indentation testing (IIT) according to ISO 14577.
METHODS: Segments were cut from ten wires. The first six are made of stainless steel (SS), two are made of Ni-Ti, and the last two are made of titanium molybdenum alloys (TMA). Then, the Martens hardness (HM), the Vickers hardness (HVIT) based on indentation hardness (H IT), the indentation modulus (E IT), the ratio of elastic to total work (η IT), and the traditional Vickers hardness (HV1) were measured by IIT. The results were statistically analyzed by one-way ANOVA followed by Student-Newman-Keuls (SNK) test at aâ=â0.05. The HVIT and HV1 data were analyzed by paired t test (aâ=â0.05).
RESULTS: SS wires showed the highest hardness followed by TMA and Ni-Ti alloys. However, all wires showed significantly lower HVIT compared to corresponding HV1, a finding probably appended to elastic recovery around the indentation. E IT for all wires tested was determined much lower than the nominal values of the corresponding alloys due to the implication of residual stress field at the slope of unloading curve. Elastic to total work ratio was ranged from 45.8 to 64.4Â % which is higher than that expected for ductile alloys (<30Â %).
CONCLUSIONS: The products tested illustrated significant differences in their mechanical properties. Although IIT provides reliable data for hardness and elastic index of materials tested, the intense residual stress field developed during the manufacturing process significantly affects the determination of modulus of elasticity
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