-
International Orthodontics Dec 2022The aim of this in vitro study was to compare friction forces generated by the following archwires: rhodium-plated aesthetic Gummetal® (E-GM), Gummetal® (GM),...
OBJECTIVE
The aim of this in vitro study was to compare friction forces generated by the following archwires: rhodium-plated aesthetic Gummetal® (E-GM), Gummetal® (GM), stainless steel (SS) and titanium-molybdenum alloy (TMA), according to bracket-wire angulation and archwire cleanliness.
METHODS
One hundred and ninety-two samples of four orthodontic alloys (E-GM, GM, SS, and TMA) were prepared. The samples were divided into two groups: uncleaned and cleaned using 99% isopropanol in an ultrasonic bath, then subdivided into three subgroups according to bracket-wire angulation: 0°, 5° and 10°. Using a universal testing machine, the wires were pulled through SS maxillary right canine brackets to test static friction forces according to bracket-wire angulation and wire cleanliness. Representative specimens were evaluated to assess surface morphology and roughness.
RESULTS
There were significant differences in static friction forces between archwires when analysed by bracket-wire angulation and cleanliness (P<0.001) except for the 0° uncleaned group. Overall, TMA archwires produced the highest friction while SS wires showed the lowest friction at 0° and 5°. E-GM wires showed comparable friction to SS at 0 (cleaned and uncleaned), but significantly higher friction than SS at 5 (uncleaned) and 10° (cleaned). GM wires had comparable friction to SS at 0° (cleaned and uncleaned), but significantly less friction at the 5° (cleaned) and 10° (cleaned and uncleaned). Compared to GM, E-GM had significantly higher friction at 5 and 10° (cleaned and uncleaned). Cleaning wires reduced surface roughness but increased overall friction.
CONCLUSION
E-GM wires generate higher frictional resistance forces compared to GM and SS, especially at higher bracket-wire angulations and when cleaned. GM friction forces are comparable to SS and thus could be used for space closure with sliding mechanics. However, E-GM wires are not ideal for the same purpose.
Topics: Orthodontic Wires; Friction; Dental Alloys; Orthodontic Brackets; Titanium; Dental Stress Analysis; Materials Testing; Esthetics, Dental; Niobium; Stainless Steel; Orthodontic Appliance Design
PubMed: 35995715
DOI: 10.1016/j.ortho.2022.100683 -
The Journal of Prosthetic Dentistry Mar 2022How axial displacement may be affected by the mechanical properties and internal discrepancy of a cement-retained implant-supported prosthesis is unclear.
STATEMENT OF PROBLEM
How axial displacement may be affected by the mechanical properties and internal discrepancy of a cement-retained implant-supported prosthesis is unclear.
PURPOSE
The purpose of this in vitro study was to assess the difference in internal discrepancy and axial displacement according to the prosthesis material in cement-retained prostheses splinting nonparallel implants.
MATERIAL AND METHODS
Computer-aided design and computer-aided manufacture (CAD-CAM) titanium abutments were fabricated for a vertically placed implant and a 15-degree tilted implant. Three types of prostheses, in zirconia, cobalt-chromium (Co-Cr) alloy, and polymethylmethacrylate resin (PMMA), were fabricated (n=10). The internal discrepancy between the CAD-CAM titanium abutment and the prosthesis was measured by using the replica technique. After luting with an interim cement, they were mounted in Type IV gypsum. The specimens were cyclic loaded, and axial displacement of the prosthesis was measured after 3, 10, 100, and 10 cycles. The internal discrepancy and cumulative axial displacement were assessed by using a 3-way analysis of variance and repeated measures analysis of variance (α=.05).
RESULTS
The internal discrepancy of the prosthesis did not differ based on the prosthesis material (P=.869); however, it was significantly different based on the measurement location, with the occlusal discrepancy (224 ±29 μm) being greater than the axial discrepancy (21 ±10 μm) (P<.05). Implants with an angled placement exhibited less axial displacement than implants with vertical placement (P<.05). The PMMA prosthesis demonstrated significantly greater axial displacement than the zirconia or Co-Cr prostheses (P<.05), which were similar (P=.623).
CONCLUSIONS
Prostheses made with high-elastic moduli materials exhibited less axial displacement than PMMA prostheses, even though the internal discrepancy was not different. Moreover, vertically placed implants presented a greater axial displacement of the prosthesis than implants with angled placement.
Topics: Chromium Alloys; Computer-Aided Design; Dental Abutments; Dental Cements; Dental Implants; Dental Materials; Dental Prosthesis Design; Dental Prosthesis, Implant-Supported; Zirconium
PubMed: 33309295
DOI: 10.1016/j.prosdent.2020.08.044 -
Dental and Medical Problems 2021Orthodontic mini-implants can undergo corrosion and the release of metal ions can affect cellular behavior. Osteoclasts are involved in orthodontic tooth movement and...
BACKGROUND
Orthodontic mini-implants can undergo corrosion and the release of metal ions can affect cellular behavior. Osteoclasts are involved in orthodontic tooth movement and implant stability. Osteoclasts and their precursors can be exposed to metal ions released from orthodontic mini-implants.
OBJECTIVES
This study aimed to investigate the effect of metal ions released from orthodontic miniimplants on human osteoclastogenesis.
MATERIAL AND METHODS
Stainless steel and titanium alloy mini-implants were separately immersed in culture media for 14 days (days 1-14), and then moved to new media for a further 14 days (days 15-28). The concentration of the released metal ions was measured. Osteoclast precursors derived from human CD14+ monocytes were cultured in these media and in a control medium without mini-implant immersion. Cell viability, the number of osteoclasts and the area of resorption were investigated.
RESULTS
A higher concentration of metal ions was detected during the first 14 days as compared to the control. The concentration of these metal ions then declined after this period. The viability of osteoclast precursors was not affected by the released metal ions. There was a significant reduction in the number of osteoclasts when cultured in the medium with the titanium alloy mini-implants immersed for days 1-14. The area of resorption was also significantly reduced in this group. The media with the titanium alloy mini-implants immersed for days 15-28 and with the stainless steel mini-implants immersed for both study periods did not show statistically significant changes in the number of osteoclasts.
CONCLUSIONS
Metal ions were released from orthodontic mini-implants in the early period and declined thereafter. Metal ions released from titanium mini-implants in the early period inhibited osteoclastogenesis, while metal ions from stainless steel mini-implants had no effect on osteoclast differentiation.
Topics: Dental Alloys; Dental Implants; Humans; Ions; Orthodontic Anchorage Procedures; Osteogenesis
PubMed: 34449135
DOI: 10.17219/dmp/133891 -
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 -
Colloids and Surfaces. B, Biointerfaces Dec 2019The electrochemical properties of CoCrMo alloy immersed in different artificial saliva with or without Ca and albumin were studied by open circuit potential (OCP),...
The electrochemical properties of CoCrMo alloy immersed in different artificial saliva with or without Ca 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 Ca 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.
Topics: Adsorption; Albumins; Chromium Alloys; Cobalt; Dental Alloys; Dielectric Spectroscopy; Electrochemistry; Hydrogen-Ion Concentration; Materials Testing; Microscopy, Electron, Scanning; Molybdenum; Saliva, Artificial; Surface Properties; X-Ray Diffraction
PubMed: 31522026
DOI: 10.1016/j.colsurfb.2019.110492 -
BioMed Research International 2023Despite of having improved endodontic file designs as well as the reinforced metal alloy file structure, intracanal endodontic file separation (EFS) is still a very...
BACKGROUND
Despite of having improved endodontic file designs as well as the reinforced metal alloy file structure, intracanal endodontic file separation (EFS) is still a very problematic and worrisome dental incident, which usually occurs without any visible signs of permanent deformation. Further, there have been conflicting reports regarding the clinical significance of leaving separated files within root canals.
AIMS
The aim of this study was to look into the current perceptions and awareness about file separation during endodontic treatment among the dental house officers (DHOs).
MATERIALS AND METHODS
A novel validated questionnaire comprising of 15 close-ended questions was distributed anonymously via Google Forms through email to 1100 DHOs across Pakistan. The questionnaire consisted of two parts: the first component (Section I) collected demographic data and the second component (Section II) investigated the causes of EFS during root canal treatment. Following the completion of socioeconomic information, including age and gender, the DHOs were asked to answer a few questions about the various reasons for endodontic instrument fracture.
RESULTS
A total of 800 responses were recorded, with an effective rate of 72.8%. The majority of the DHOs ( value < 0.001) perceived that endodontic instrument fracture occurred in the posterior (61.5%) and apical third of the canal (50.5%) and in older permanent dentition (67.3%), possibly due to patient anxiety (62%). Better choice of instrument (61.15%), operators' experience (95.3%), knowledge (87.5%), and proper root canal cleaning (91.1%) are believed to be the vital steps in reducing endodontic file separation/fracture. Furthermore, majority of them ( value < 0.001) perceived that stainless steel was a superior alloy for filing instruments. Manual files tend to be more prone to fractures due to repeated use than rotary files.
CONCLUSION
This study demonstrated that young DHOs had adequate knowledge and awareness regarding the potential predisposing factors and handling techniques for EFS. This study thereby provides an evaluating tool to access the insights of the current perceptions and awareness of DHOs concerning EFS.
Topics: Humans; Aged; Root Canal Preparation; Equipment Failure; Equipment Design; Root Canal Therapy; Perception; Dental Pulp Cavity; Dental Alloys; Dental Instruments; Titanium
PubMed: 36845639
DOI: 10.1155/2023/1044541 -
Computers in Biology and Medicine May 2023The retention of selective laser melting (SLM)-built denture clasps is inferior to that of cast cobalt-chromium (Co-Cr) clasps engaging 0.01-in undercuts, which are...
BACKGROUND AND OBJECTIVE
The retention of selective laser melting (SLM)-built denture clasps is inferior to that of cast cobalt-chromium (Co-Cr) clasps engaging 0.01-in undercuts, which are commonly used in clinical practice. Either the clasps engage in excessively deep undercuts or inappropriate printing process parameters are applied. With appropriate undercut engagement and levels of process parameters, the retention of SLM-built clasps (including Co-Cr, commercially pure titanium [CP Ti], and Ti alloy [Ti-6Al-4V] ones) may be comparable to that of cast Co-Cr clasps. Therefore, this feasibility study aimed to evaluate their retention to guide dentists during material selection for the powder-bed fusion process during the printing of denture clasps.
METHODS
We engaged the clasp arm at an appropriate undercut depth (0.01 or 0.02 in), built clasps at the orientation of their longitudinal axes approximately parallel to the build platform, generated square prism support structures at a critical overhang angle of 30°, applied optimized laser parameters (laser power, scan speed, and hatch space), and adopted annealing treatment for Co-Cr, CP Ti, and Ti-6Al-4V clasps. After postprocessing and accuracy measurement, an insertion/removal test of the clasps for 15,000 cycles was performed to simulate 10 years of clinical use, and the retentive force was recorded every 1500 cycles. Permanent deformation of the retentive arms of the clasps was measured. Cast Co-Cr clasps engaging 0.01-in undercuts were designated the control group.
RESULTS
The initial retentive forces of the SLM-built Co-Cr clasps engaging 0.01-in undercuts and CP Ti and Ti-6Al-4V clasps engaging 0.02-in undercuts were comparable to those of the control group. SLM-built Co-Cr clasps engaging 0.01-in undercuts and Ti-6Al-4V clasps engaging 0.02-in undercuts had similar final retentive force and less permanent deformation compared with those of the control group; SLM-built CP Ti clasps engaging 0.02-in undercuts had lower final retentive force and greater permanent deformation.
CONCLUSIONS
Considering the long-term retention and permanent deformation of the retentive arms, Co-Cr and Ti-6Al-4V alloys, except CP Ti, are recommended for printing denture clasps. SLM-built Co-Cr clasps should engage 0.01-in undercuts, and Ti-6Al-4V clasps should engage 0.02-in undercuts.
Topics: Chromium Alloys; Powders; Feasibility Studies; Dental Clasps; Denture Retention; Denture, Partial, Removable; Materials Testing; Surface Properties; Titanium; Printing, Three-Dimensional
PubMed: 36963354
DOI: 10.1016/j.compbiomed.2023.106772 -
BMC Oral Health Sep 2021To investigate the efficacy of a nickel-titanium (NiTi) file with an automated computerized numerical control (CNC) system for root canal shaping.
BACKGROUND
To investigate the efficacy of a nickel-titanium (NiTi) file with an automated computerized numerical control (CNC) system for root canal shaping.
METHODS
The movement of the automated device and the insertion angle were investigated. In Experiment 1, simulated resin root canals were randomly divided into four groups (n = 20): manual downward movement using a handpiece (Group 1), vertical downward movement by CNC (Group 2), reciprocating up and down movement by CNC (Group 3), and spiral up and down movement by CNC (Group 4). In Experiment 2, five different insertion angles of the NiTi file were evaluated (n = 20). Four parameters were used to evaluate the shaping ability: change in the working length, central axis offset, curvature variation, and preparation time. Groups were compared using one-way analysis of variance (ANOVA) with significance was set at P < 0.05.
RESULTS
The change in central axis position in the curved part of the root canal was found to be smaller in Group 4 than in other groups (P < 0.05). The curvature changes and preparation time of Groups 1 and 4 were significantly reduced compared with Groups 2 and 3 (P < 0.05). The variation in working length and curvature in the 5° insertion angle group was significantly smaller than in the other groups (P < 0.05).
CONCLUSIONS
A spiral up and down movement, controlled by the CNC machine, and 5° insertion angle, maintained original root canal shape more precisely than other methods.
Topics: Dental Alloys; Dental Pulp Cavity; Equipment Design; Humans; Nickel; Root Canal Preparation; Titanium
PubMed: 34583658
DOI: 10.1186/s12903-021-01841-4 -
Shanghai Kou Qiang Yi Xue = Shanghai... Apr 2022To detect and analyze dental dust pollution in the department of prosthodontics and propose reasonable protective measures.
PURPOSE
To detect and analyze dental dust pollution in the department of prosthodontics and propose reasonable protective measures.
METHODS
Individual dust sampling pumps were used to detect the concentration of respirable dust produced by five common dental materials (hard resin base, advanced artificial teeth, photosensitive plastic, cobalt-chromium alloy, veneering ceramics) in the department of prosthodontics. X-ray diffraction (XRD) was used to detect the concentration of free silica respirable dust in veneer porcelain dust. Inductively coupled atomic emission spectrometry (ICP-AES) was used to detect the thoracic dust of cobalt element and the inhalable dust concentration of chromium element in cobalt-chromium alloy dust. The results were compared with the occupational exposure limits set by China and the United States.
RESULTS
The respiratory dust concentration of the five common dusts in the department of prosthodontics was far lower than occupational exposure limits set by China and the United States. The concentration of free silica in veneer porcelain, cobalt and its compounds in cobalt-chromium alloys were below the lower detection limit. Chromium and its compounds can be detected, and its concentration was also far below the occupational exposure limit.
CONCLUSIONS
Problem of dust pollution in the department of prosthodontics exists, which is mainly caused by heavy metal pollution (such as chromium). Protective measures such as ventilation and wearing professional mask should be taken to protect the health of dental practitioners.
Topics: Chromium; Chromium Alloys; Cobalt; Dental Porcelain; Dentists; Dust; Humans; Plastics; Professional Role; Prosthodontics; Silicon Dioxide
PubMed: 36110069
DOI: No ID Found -
Journal of Prosthodontic Research Jul 2022Evaluating the fitness accuracy and retentive force of cobalt-chrome (Co-Cr) alloy clasps fabricated using the selective laser melting (SLM) technique.
PURPOSE
Evaluating the fitness accuracy and retentive force of cobalt-chrome (Co-Cr) alloy clasps fabricated using the selective laser melting (SLM) technique.
METHODS
Premolar and molar abutment models with a 0.5-mm undercut depth, 1.5-mm-thick occlusal rest seats, and guiding planes were designed and fabricated using a milling machine. On these models, Akers clasps with 0.25- and 0.5-mm undercut depths were designed and fabricated with SLM and a traditional lost wax casting method. Based on the manufacturing methods, abutment types, and undercut depths, the clasps were divided into eight groups (10 per group). The fitness accuracy of the clasps was evaluated by measuring the gap distance between the clasps and abutments using a silicone film method. The initial retentive force and changes in retention up to 7,200 insertion/removal cycles of the clasps were also measured. The data were analyzed using multiple linear regression, paired t-tests, and one-way ANOVA (α=0.05).
RESULTS
For both the SLM and cast clasps, the fitness accuracy of the rest was greater than that of the clasp tip and shoulder. No significant difference was found in the fitness accuracy between the SLM and cast clasps, regardless of the abutment type and undercut depth before or after insertion/removal cycles (p>0.05). There was also no significant difference in the initial retentive force between the SLM and cast clasps (p>0.05). After 7,200 insertion/removal cycles, the SLM clasp exhibited a greater residual retentive force (p<0.05).
CONCLUSION
The SLM technique for manufacturing the clasps of removable partial dentures has promising clinical applications.
Topics: Chromium Alloys; Cobalt; Dental Clasps; Denture Retention; Denture, Partial, Removable
PubMed: 34615841
DOI: 10.2186/jpr.JPR_D_21_00017