-
Dental Materials Journal Jun 2020Chemical transitions after atmospheric pressure plasma irradiation were investigated by evaluating intermolecular attractions and atomic and molecular reactions. Gold,...
Chemical transitions after atmospheric pressure plasma irradiation were investigated by evaluating intermolecular attractions and atomic and molecular reactions. Gold, titanium and stainless-steel alloy samples were ground with #800 grit SiC waterproof paper and nitrogen gas atmospheric plasma irradiation was conducted. The surface free energies of the treated alloys were calculated and compared statistically. X-ray photoelectron spectroscopy analysis was performed.The surface free energies of all metal surfaces treated by plasma irradiation were 1.5-times higher than those of the untreated metals. The energy of the hydrogen bonding component increased, and all alloy surfaces were coated with metal oxide after only a short period of plasma irradiation. The surfaces oxidized by plasma exhibited a high active energy, mainly due to an increase in the hydrogen bonding component. Reactions with oxygen in the air were promoted on the clean surfaces with exposed reactive elements.
Topics: Alloys; Dental Alloys; Oxides; Surface Properties; Titanium
PubMed: 31852878
DOI: 10.4012/dmj.2019-023 -
Australian Dental Journal Dec 2014The Minamata Convention has agreed to a worldwide reduction and ultimate elimination in the production and use of mercury containing products. This will have... (Review)
Review
The Minamata Convention has agreed to a worldwide reduction and ultimate elimination in the production and use of mercury containing products. This will have implications for the practice of dentistry. Australian organizations' pronouncements on the issue are limited and research examining the Australian context dated. The restoration of teeth with direct materials has changed significantly since the 1980s. Up to this time amalgam was the material of choice for direct posterior restorations. Its properties and guidelines for placement were, and remain, well established. Resin composite has replaced amalgam as the material of choice in many clinical situations. Despite inherent clinical disadvantages compared to amalgam, there continues to be a shift toward greater use of resin composite. There is consensus worldwide that the restoration of posterior teeth using resin composite now exceeds that of amalgam. The reasons for this are reviewed in this article along with current evidence and commentary relating to direct restorative and evidence-based decision-making, minimally invasive approaches, and approaches to education. The implications for these in an 'amalgamless' profession are identified.
Topics: Australia; Composite Resins; Decision Making; Dental Amalgam; Dental Research; Dental Restoration, Permanent; Humans; Practice Patterns, Dentists'
PubMed: 25090909
DOI: 10.1111/adj.12209 -
Dental Materials Journal Jan 2021Binary Ti-Fe alloys of varying concentrations of Fe between 5-25% were made, and their castings evaluated in terms of microstructures formed and mechanical properties....
Binary Ti-Fe alloys of varying concentrations of Fe between 5-25% were made, and their castings evaluated in terms of microstructures formed and mechanical properties. The aim of this study was to explore the composition of Ti-Fe alloys that offers improved wear resistance of titanium. X-ray diffraction and microstructural observation revealed that 5-7% Fe, 8-15% Fe, and 20-25% Fe consisted of α+β, single β, and β+Ti-Fe phases, respectively. The hardness of alloys with 8-13% Fe was almost equal to that of Co-Cr alloys but lower than of the other Ti-Fe alloys. Elongation of the Ti-Fe alloys was negligible. However, dimples were observed in specimen containing 7-11% Fe. Alloys with 9% Fe demonstrated the highest strength of more than 850 MPa. We believe that Ti-Fe alloys with 8-11% Fe may be applicable in development of an alloy with good wear resistance due to the exhibited properties of high hardness and ductility albeit low.
Topics: Alloys; Dental Alloys; Hardness; Materials Testing; Tensile Strength; Titanium; X-Ray Diffraction
PubMed: 32848101
DOI: 10.4012/dmj.2019-254 -
Dental Materials Journal Apr 2022This study assessed the effect of a primer containing 10-methacryloyloxydecyl-(2-thiohydantoin-4-yl)propionate (MDTHP) on the bonding of noble metal alloys to an acrylic...
This study assessed the effect of a primer containing 10-methacryloyloxydecyl-(2-thiohydantoin-4-yl)propionate (MDTHP) on the bonding of noble metal alloys to an acrylic resin. Three noble metal alloys were selected as adherends, and V-Primer containing 6-(4-vinylbenzyl-n-propyl)amino-1,3,5-triazine-2,4-dithione was used as a comparative control. The disk specimens of each noble metal alloy were wet-ground and divided into three conditions: specimens primed with MDTHP primer or V-Primer, and specimens without priming. An acrylic resin was bonded to each specimen, and the specimens were performed the shear bond test. The MDTHP primer showed higher shear bond strength than the V-Primer for all specimens. X-ray photoelectron spectroscopic analysis showed that MDTHP was adsorbed on the Au-Pt-Pd alloy surface even after acetone cleaning. MDTHP binds not only with Cu but also with Au and Ag, promoting the bond strength of noble metal alloys. The effectiveness of MDTHP on dental noble metal alloys was suggested.
Topics: Alloys; Dental Alloys; Dental Bonding; Gold Alloys; Materials Testing; Methacrylates; Resin Cements; Shear Strength; Surface Properties; Thiohydantoins
PubMed: 34980767
DOI: 10.4012/dmj.2021-181 -
PloS One 2021Due to the characteristics of high strength, high chemical activity and low heat conduction, titanium alloy materials are generally difficult to machine. As a typical...
Due to the characteristics of high strength, high chemical activity and low heat conduction, titanium alloy materials are generally difficult to machine. As a typical titanium alloy with higher strength and lower heat conductivity, the machinability of titanium alloy TC21 is very poor and its cutting process is companied with larger cutting force and rapid tool wear. Straight-tooth milling tool is often used to cut the groove and side surface in the titanium alloy parts. And the milling method can be used to investigate the cutting mechanism because the cutting force has only two components and the better chip morphology is obtained. To investigate the straight-tooth milling process of TC21 alloy, a series of milling force experiments have been done. In addition, a 3D finite element model (FEM) for the straight-tooth milling process of TC21 alloy is presented to simulate the milling process. In the model, the constitutive material model, the failure model, the friction model and the heat transfer model were adopted. Through the simulation, chip formation, stress distribution, cutting force and milling temperature were obtained. The cutting force reaches its maximum when the spindle speed reaches about 13000 rpm, and then decreases as the speed continues to increase. The results confirmed that the similar "Salomon" phenomenon existed in the cutting process of TC21 alloy.
Topics: Computer Simulation; Dental Alloys; Dental Soldering; Finite Element Analysis; Titanium
PubMed: 34649269
DOI: 10.1371/journal.pone.0258403 -
Computers in Biology and Medicine Jul 2022To evaluate the effect of guiding structure and 3D-printing material of CAD-CAM guides on the accuracy of guiding planes preparation.
BACKGROUND AND OBJECTIVE
To evaluate the effect of guiding structure and 3D-printing material of CAD-CAM guides on the accuracy of guiding planes preparation.
METHODS
Four types of computer-aided design and computer-aided manufacturing (CAD-CAM) guides for preparing guiding planes of removable partial denture (RPD) were designed in two types of guiding structures (triple-constraint and single-plane constraint) and were 3D printed using resin and cobalt-chromium (Co-Cr) alloy. Guiding plane preparation of identical resin casts was performed using CAD-CAM guides (resin template, metal template, resin guided device, and metal guide device) in four test groups and by freehand in the control group (n = 22 per group). All prepared casts were then scanned (Test) and aligned to the reference cast with designed guiding planes. 3D compare analysis was performed and root-mean-square (RMS) values were calculated for assessing the 3D trueness and 3D precision of guiding plane preparation. The angle between the prepared guiding plane (Test) and the designed path of placement of RPD (Reference) was measured for evaluating the direction trueness.
RESULTS
RMS values of the metal template group for 3D trueness (39.7 ± 14.6 μm) and 3D precision (28.6 ± 6.8 μm) were significantly lower than that of other groups (p < .05). For direction trueness, the metal template group showed the least angle deviation (1.09 ± 0.56°), and the freehand group demonstrated the largest angle deviation (7.03 ± 2.83°).
CONCLUSIONS
The Co-Cr alloy guides with triple-constraint guiding structure can assist to prepare accurate guiding planes of RPD.
Topics: Chromium Alloys; Computer-Aided Design; Denture, Partial, Removable; Printing, Three-Dimensional
PubMed: 35569334
DOI: 10.1016/j.compbiomed.2022.105564 -
British Dental Journal Sep 2023Aim This study aimed to explore disparities in experience of UK dental foundation trainees in amalgam use at dental school compared to their first year in dental...
Aim This study aimed to explore disparities in experience of UK dental foundation trainees in amalgam use at dental school compared to their first year in dental practice.Methods A modified version of the 'survey of Yorkshire dentists' targeted the dental foundation trainees. A mixed-method of quantitative and thematic content analysis was undertaken for the close-ended and free-text responses, respectively.Results Only 35% of participants described their confidence level as 'satisfactory' in placing dental amalgam before starting their dental foundation training and 51% scored the level of teaching between 'very poor' and 'satisfactory'. In total, 63% of respondents were in favour of receiving additional support in placing amalgam restorations during their undergraduate training. Participants indicated that the consequences of amalgam phase-out are increased appointment times and decreased quality of care due to patient and health service unaffordability of amalgam alternatives.Conclusion These findings raise concerns regarding newly qualified undergraduates' confidence, experience and skill in placing amalgams. This suggests the need to increase undergraduate education and training to improve undergraduates' skills and confidence in amalgam procedures to reduce the gap between the dental schools and real-world practice.
Topics: Humans; Dental Amalgam; Schools, Dental; Students; Dental Care
PubMed: 37684467
DOI: 10.1038/s41415-023-6228-4 -
The Angle Orthodontist Jul 2021To explore whether the commercial agents recommended for controlling dental biofilm formation had a significant effect in vivo on mechanical and corrosion properties of...
Influence of intraoral application of antiseptics and fluorides during orthodontic treatment on corrosion and mechanical characteristics of nickel-titanium alloy in orthodontic appliances.
OBJECTIVES
To explore whether the commercial agents recommended for controlling dental biofilm formation had a significant effect in vivo on mechanical and corrosion properties of nickel-titanium (NiTi) alloy.
MATERIALS AND METHODS
NiTi archwires (dimensions 0.508 × 0.508 mm) were collected from 36 orthodontic patients aged 13-42 years after a 3-month intraoral exposure. Three experimental groups were formed: (1) subjects conducting regular oral hygiene, (2) subjects who used fluorides for intensive prophylaxis for the first month, and (3) subjects who used chlorhexidine in the same manner. Corrosion behavior, surface characteristics, stiffness, hardness, and friction were analyzed.
RESULTS
Exposure to intraoral conditions significantly reduced the stiffness and hardness of the NiTi alloy (P ≤ .015). Fluoride tended to reduce stiffness and hardness more than did saliva or antiseptic, but not significantly. Roughness and friction were not significantly influenced by oral exposure. Intraoral aging predominantly produced general corrosion independent of the adjuvant prophylactic agent, although localized corrosion may also have occurred.
CONCLUSIONS
Fluorides and the antiseptic chlorhexidine do not increase corrosion more than saliva itself, nor do they further modify the mechanical properties of the NiTi alloy.
Topics: Anti-Infective Agents, Local; Corrosion; Dental Alloys; Fluorides; Humans; Materials Testing; Nickel; Orthodontic Appliances; Orthodontic Wires; Surface Properties; Titanium
PubMed: 33566077
DOI: 10.2319/052620-480.1 -
PloS One 2020Implant-retained custom-milled framework enhances the stability of palatal obturator prostheses. Therefore, to evaluate the mechanical response of implant-retained...
Implant-retained custom-milled framework enhances the stability of palatal obturator prostheses. Therefore, to evaluate the mechanical response of implant-retained obturator prostheses with bar-clip attachment and milled bars, in three different materials under two load incidences were simulated. A maxilla model which Type IIb maxillary defect received five external hexagon implants (4.1 x 10 mm). An implant-supported palatal obturator prosthesis was simulated in three different materials: polyetheretherketone (PEEK), titanium (Ti:90%, Al:6%, V:4%) and Co-Cr (Co:60.6%, Cr:31.5%, Mo:6%) alloys. The model was imported into the analysis software and divided into a mesh composed of nodes and tetrahedral elements. Each material was assumed isotropic, elastic and homogeneous and all contacts were considered ideal. The bone was fixed and the load was applied in two different regions for each material: at the palatal face (cingulum area) of the central incisors (100 N magnitude at 45°); and at the occlusal surface of the first left molar (150 N magnitude normal to the surface). The microstrain and von-Mises stress were selected as criteria for analysis. The posterior load showed a higher strain concentration in the posterior peri-implant tissue, near the load application side for cortical and cancellous bone, regardless the simulated material. The anterior load showed a lower strain concentration with reduced magnitude and more implants involving in the load dissipation. The stress peak was calculated during posterior loading, which 77.7 MPa in the prosthetic screws and 2,686 με microstrain in the cortical bone. For bone tissue and bar, the material stiffness was inversely proportional to the calculated microstrain and stress. However, for the prosthetic screws and implants the PEEK showed higher stress concentration than the other materials. PEEK showed a promising behavior for the bone tissue and for the integrity of the bar and bar-clip attachments. However, the stress concentration in the prosthetic screws may represent an increase in failure risk. The use of Co-Cr alloy can reduce the stress in the prosthetic screw; however, it increases the bone strain; while the Titanium showed an intermediate behavior.
Topics: Benzophenones; Biomechanical Phenomena; Chromium Alloys; Dental Materials; Humans; Ketones; Materials Testing; Maxilla; Models, Anatomic; Palatal Obturators; Polyethylene Glycols; Polymers; Stress, Mechanical; Titanium
PubMed: 33125441
DOI: 10.1371/journal.pone.0241589 -
Materials (Basel, Switzerland) Dec 2019Higher-noble dental alloys (Au, Ag, and Pd) are the most desirable for dentistry applications, but they are expensive. Low-noble (Ag, Pd, Cu) dental alloys are...
Higher-noble dental alloys (Au, Ag, and Pd) are the most desirable for dentistry applications, but they are expensive. Low-noble (Ag, Pd, Cu) dental alloys are alternatives to higher-noble ones due to their lower price. In this regard, the paper supports the price lowering of dental alloy by increasing the Cu content, i.e., a new 58Ag24Pd11Cu2Au2Zn1.5In1.5Sn dental alloy. The increasing addition of the Cu leads to a complex structure consisting of a solid solution that engulfs compounds of micrometric and nanometric sizes. The 58Ag24Pd11Cu2Au2Zn1.5In1.5Sn has demonstrated a much better electrochemical corrosion behavior in artificial saliva compared to the Paliag and Unique White dental alloys. The improved corrosion behavior of the new alloy is supported by the diminishing of the Cu selective diffusion into the electrolyte due to its retaining into compounds and into Ag-Pd solid solution. Also, the synergic effects of Cu, Zn, In, Sn may improve the corrosion resistance, but they have strengthened the 58Ag24Pd11Cu2Au2Zn1.5In1.5Sn matrix. The main finding addressed in the paper consists in a new 58Ag24Pd11Cu2Au2Zn1.5In1.5Sn dental alloy with improved corrosion resistance in artificial saliva.
PubMed: 31847262
DOI: 10.3390/ma12244199