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International Endodontic Journal Oct 2019The endodontic literature contains a plethora of studies on static and dynamic cyclic fatigue resistance tests performed on a large array of rotary or reciprocating... (Review)
Review
The endodontic literature contains a plethora of studies on static and dynamic cyclic fatigue resistance tests performed on a large array of rotary or reciprocating nickel-titanium endodontic instruments. It was the aim of this review to summarize the currently available evidence to point out the different outcomes from static versus dynamic tests and to assess whether cyclic fatigue tests provide useful data and information for clinical practice. An electronic literature research in the database PubMed was performed using appropriate search terms, and the titles and abstract were screened for relevance. Language was restricted to English. The review reveals marked differences between the results obtained in static and dynamic tests, and also, the results for the same instruments assessed either under static or dynamic experimental conditions are widely inconsistent. Between the lowest and the highest value for one and the same pathfinding instrument was a factor of about 123 when cyclic fatigue was assessed either under static or dynamic experimental conditions. Moreover, standard deviations of up to 30% have been reported. Environmental temperature has a 500% impact on the lifetime of instruments. In conclusion, fatigue resistance tests conducted under room temperature should be regarded as having little meaning and the scientific and clinical benefits of fatigue resistance tests are very limited. These data should be provided by the manufacturer of the instruments.
Topics: Dental Alloys; Equipment Design; Equipment Failure; Materials Testing; Root Canal Preparation; Stress, Mechanical; Titanium
PubMed: 31267579
DOI: 10.1111/iej.13182 -
International Endodontic Journal Dec 2020To evaluate the bending, buckling and torsional resistance of ProGlider (PG) (Dentsply Sirona, Ballaigues, Switzerland), R-Pilot (RP) (VDW, Munich, Germany) and WaveOne...
AIM
To evaluate the bending, buckling and torsional resistance of ProGlider (PG) (Dentsply Sirona, Ballaigues, Switzerland), R-Pilot (RP) (VDW, Munich, Germany) and WaveOne Gold Glider (WOGG) (Dentsply Sirona).
METHODOLOGY
Ninety instruments were used: 30 PG (size 0.16, .02v taper), 30 RP (size 0.125, .04 taper) and 30 WOGG (size 0.15, .02v taper). The bending resistance test was performed on 10 randomly selected instruments of each system according to ISO 3630-1 specifications. For the buckling resistance test, a loading was applied in the axial direction of each instrument using a universal test machine, with a 20 N cell and 15 mm min speed, in the axial direction. When a lateral elastic displacement of 1 mm occurred, the force was registered. The torsional resistance test was performed according to ISO 3630-1 specifications. Statistical analysis was performed using one-way anova and post hoc Student-Newman-Keuls test (P < 0.05).
RESULTS
WOGG had the lowest bending resistance, whilst RP had the highest bending resistance (P < 0.05). RP also had the highest buckling resistance, and WOGG had the lowest (P < 0.05). PG had intermediate results regarding bending and buckling resistance, with significant differences to RP and WOGG (P < 0.05). RP had the highest torsional strength and the lowest angular deflection when compared to PG and WOGG (P < 0.05). No differences in the torsional strength and angular deflection were observed between WOGG and PG (P> 0.05).
CONCLUSION
The glide path instruments had different behaviours in term of bending, buckling and torsional resistance.
Topics: Dental Alloys; Dental Instruments; Equipment Design; Germany; Gold; Humans; Materials Testing; Mechanical Phenomena; Root Canal Preparation; Titanium; Torsion, Mechanical
PubMed: 32767775
DOI: 10.1111/iej.13385 -
American Journal of Orthodontics and... Nov 2023The objective of this study was to determine and compare the moment-to-force (Mc/F) ratio and the type of tooth movement generated in the anterior and posterior segments...
INTRODUCTION
The objective of this study was to determine and compare the moment-to-force (Mc/F) ratio and the type of tooth movement generated in the anterior and posterior segments in orthodontic space closure with stainless steel and titanium-molybdenum alloy loop archwires.
METHODS
Three-dimensional model of the maxilla from which the first premolar was extracted, 18 × 25-mil slot stainless steel brackets, and 16 × 22-mil stainless steel and β titanium-molybdenum alloy (TMA) closing loop archwires with anterior gable bend of 15° and posterior gable bend of 25° were constructed. The archwires were engaged in the brackets, and 1-mm activations were carried out, which were repeated 5 times. The anterior and posterior segment Mc/F ratio and the type of tooth movement generated by the 2 wires were compared.
RESULTS
It was found that the Mc/F ratio for the anterior segment was approximately 5 mm, and for posterior teeth was approximately 10 mm for both stainless steel and TMA closing loop archwire. The anterior teeth exhibited controlled tipping, whereas the posterior teeth showed bodily tooth movement, which was in accordance with the Mc/F ratio that was obtained.
CONCLUSIONS
The Mc/F ratio and the type of tooth movement exhibited by stainless steel and TMA closing loop archwires were similar in both anterior and posterior segments.
Topics: Humans; Stainless Steel; Molybdenum; Titanium; Finite Element Analysis; Friction; Orthodontic Brackets; Orthodontic Wires; Dental Stress Analysis; Alloys; Dental Alloys; Materials Testing; Orthodontic Appliance Design
PubMed: 37656072
DOI: 10.1016/j.ajodo.2023.06.010 -
Folia Medica Aug 2023CAD/CAM technologies are becoming widely used for the production of metal ceramic dental restorations. Powder Co-based alloys are developed for selective laser melting....
CAD/CAM technologies are becoming widely used for the production of metal ceramic dental restorations. Powder Co-based alloys are developed for selective laser melting. The corrosion resistance of the dental alloy affects the biocompatibility, functional suitability, and longevity of the prosthetic restoration.
PubMed: 37655388
DOI: 10.3897/folmed.65.e73531 -
The Journal of Prosthetic Dentistry Jun 2020Materials used for dental restorations should cause wear similar to that of natural teeth. Studies on the wear of dental alloys against monolithic zirconia are lacking.
STATEMENT OF PROBLEM
Materials used for dental restorations should cause wear similar to that of natural teeth. Studies on the wear of dental alloys against monolithic zirconia are lacking.
PURPOSE
The purpose of this in vitro study was to compare the wear of Co-Cr, gold, and Ni-Cr alloys against monolithic zirconia of different surface roughness.
MATERIAL AND METHODS
Cylindrical monolithic zirconia specimens were prepared by a sintering process. Sintered zirconia was then polished to prepare 30 zirconia substrate specimens with a smooth surface (Ra<0.1 μm) and 30 with a rough surface (3.5 μm
alloys (Co-Cr, gold, and Ni-Cr alloys) were used. Twenty cast crowns were prepared from each metal alloy in the shape of a maxillary premolar. For each alloy, 10 cast crowns were randomly selected to oppose the smooth-surface zirconia specimens and 10 to oppose the rough-surface zirconia specimens. A total of 6 wear test groups were formed. Wear tests were performed by using a mastication simulator at 240 000 mastication cycles. Wear on the antagonist specimens was measured by using a laser 3D scanner. After wear testing, antagonist and substrate specimens were inspected by using a scanning electron microscope (SEM). For statistical analysis of the data, the 2-way ANOVA and the Scheffé multiple comparison tests were used (α=.05). RESULTS
Of the 6 test groups, the gold alloy specimens opposed to rough-surface zirconia exhibited the most wear, while the Co-Cr alloy specimens opposed to smooth-surface zirconia exhibited the least wear (P<.05). Rough-surface monolithic zirconia caused significantly more wear of the metal alloy specimens than did smooth-surface monolithic zirconia (P<.01).
CONCLUSIONS
Increased surface roughness of monolithic zirconia was associated with increased wear of the opposing dental alloy. When monolithic zirconia surface roughness was increased, wear of dental alloys increased most for gold alloys, followed by Ni-Cr, and then Co-Cr alloys.
Topics: Dental Alloys; Dental Enamel; Dental Porcelain; Materials Testing; Surface Properties; Zirconium
PubMed: 31653400
DOI: 10.1016/j.prosdent.2019.06.002 -
Journal of Functional Biomaterials Dec 2023The interaction of different dental alloys with the oral environment may cause severe side effects (e.g., burning sensation, inflammatory reactions, carcinogenesis) as a...
The interaction of different dental alloys with the oral environment may cause severe side effects (e.g., burning sensation, inflammatory reactions, carcinogenesis) as a result of oral galvanism. However, the pathogenesis of side effects associated with oral galvanism is still unclear, and the effects of direct current and alloy corrosion ions are considered potentially contributing factors. Therefore, the aim of this study was to systemically compare the damaging effects of (1) galvanism as a synergistic process (direct current + corrosion ions), (2) direct current separately, and (3) corrosion ions separately on an in vitro mucosa-like model based on a cell line of immortalized human keratinocytes (HaCaTs) to reveal the factors playing a pivotal role in dental alloys side effects. For this, we chose and compared the dental alloys with the highest risk of oral galvanism: Ti64-AgPd and NiCr-AgPd. We showed that galvanic current may be the leading damaging factor in the cytotoxic processes associated with galvanic coupling of metallic intraoral appliances in the oral cavity, especially in the short-term period (28 days). However, the contribution of corrosion ions (Ni) to the synergistic toxicity was also shown, and quite possibly, in the long term, it could be no less dangerous.
PubMed: 38132818
DOI: 10.3390/jfb14120564 -
Dental Materials Journal Mar 2020The artifact volume generated in magnetic resonance (MR) images was quantitatively evaluated to investigate how artifact behavior correlates to the magnetic...
The artifact volume generated in magnetic resonance (MR) images was quantitatively evaluated to investigate how artifact behavior correlates to the magnetic susceptibility and volume of an implanted metal device. For this, a new low-magnetic-susceptibility Zr-14Nb alloy was compared with two conventional dental alloys, Ti-6Al-7Nb alloy and Co-Cr-Mo alloy, using spherical specimens of each alloy prepared with four different diameters. Then, MR images were recorded under fast spin echo and gradient echo conditions, from which the artifact volume was measured. The artifact volume decreased with the magnetic susceptibility, volume, and mass of the specimens, and significant linear correlations were observed. The artifact volume can be estimated by the equations presented here; nevertheless, further studies are necessary to interpret the influence of some important factors (e.g., imaging conditions, shape, and orientation) to predict the artifact volume more precisely.
Topics: Alloys; Artifacts; Dental Alloys; Magnetic Resonance Imaging; Magnetics; Titanium
PubMed: 31723091
DOI: 10.4012/dmj.2018-426 -
Photodiagnosis and Photodynamic Therapy Dec 2021The present study aimed to evaluate the effect of different cleansers and photodynamic therapy (PDT) on disinfection of Co/Cr removable partial denture colonized with C....
AIM
The present study aimed to evaluate the effect of different cleansers and photodynamic therapy (PDT) on disinfection of Co/Cr removable partial denture colonized with C. albicans, S.aureus and S.mutans.
MATERIAL AND METHODS
Twenty-five Co/Cr removable partial dentures were constructed. and inoculated by American Type Culture Collection (ATCC) of Candida albicans, S.aureus, and S.mutans in an in-vitro setup. Co/Cr removable partial dentures were randomly allocated into five groups and framework was immersed in 15 mL of contaminated culture medium broth. Based on the cleansing method, disinfected dentures in group 1 were cleansed with porphyrin derivative; group 2 was exposed to 0.12% chlorhexidine digluconate; samples in group 3 and group 4 were subjected to sodium perborate enzyme and citric acid respectively. Through a surface analyzer, the surface roughness of Co/Cr and methacrylate resin was measured in 3 different zones in micrometers before and after disinfection. Two-way ANOVA and Tukey's test was used to analyze the data. Levene test was used to assess the normal distribution of data. Significance level p< 0.05 RESULTS: The results of metal roughness displayed that Co/Cr used as an alloy did not exhibit significant difference when exposed to different chemical disinfectants and photosensitizer (p > 0.05). Similarly, surface roughness (Ra) of heat polymerized acrylic resin using cleansers and PDT demonstrated no significant difference. Intergroup comparison showed that, hematoporphyrin derivative displayed comparable cleansing property against S. aureus, C.albicans, and S. mutans compared to to 0.12% CHX digluconate (p>0.05). The intragroup comparison showed hematoporphyrin derivative and CHX were equally effective against all bacteria (p>0.05).
CONCLUSION
CHX digluconate and hematoporphyrin derivative demonstrated high antimicrobial activity against S.aureus, S.mutans, and C.albicans with minimum Ra of an acrylic denture and Co/Cr metallic framework.
Topics: Chlorhexidine; Chromium Alloys; Denture, Partial, Removable; Dentures; Disinfection; Materials Testing; Photochemotherapy; Photosensitizing Agents; Porphyrins; Staphylococcus aureus
PubMed: 34469796
DOI: 10.1016/j.pdpdt.2021.102515 -
Australian Endodontic Journal : the... Sep 2023We evaluated in vitro the influence of nickel-titanium instruments kinematics on the accuracy and variation of root canal working length measurements, performed with an...
We evaluated in vitro the influence of nickel-titanium instruments kinematics on the accuracy and variation of root canal working length measurements, performed with an integrated apex locator, at glide path and at the end of shaping. Forty-four mandibular incisors, included in an alginate model, were allocated at random to two groups: reciprocating and rotary. Working length was determined at glide path stage and at the end of shaping. Measurements given by the integrated apex locator were matched with visual measurements. The apex locator accuracy was based on inter-group comparison. The variation in working length was based on intra-group comparison. Kinematics influenced the accuracy of measurements only after shaping (p < 0.05), and not in the glide path (p > 0.05). Rotary had values closer to the visual measurements. Diminishing of measures occurred after shaping for reciprocating (p < 0.05); and at glide-path stage for rotary (p > 0.05). The integrated apex locator was more accurate with rotary kinematics.
Topics: Root Canal Preparation; Dental Pulp Cavity; Tooth Apex; Biomechanical Phenomena; Dental Alloys
PubMed: 36401568
DOI: 10.1111/aej.12717 -
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