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A biocompatible Ti-12Mo alloy was fabricated by metal injection moulding (MIM) using non-spherical titanium, molybdenum powders and a purposely designed binder. The density, microstructure and tensile properties were characterized. This was followed by a detailed assessment of its in vitro corrosion and biocompatibility performances, compared with that of two commonly used titanium-based materials extra low interstitial (ELI) Ti-6Al-4V and commercially pure (CP) titanium. The MIM-fabricated Ti-12Mo alloy can achieve a wide range of mechanical properties through controlling sintering process. Specimens sintered at 1400 °C are characterized by fairly uniform near-β microstructure and high relative density of 97.6%, leading to the highest tensile strength of 845.3 ± 21 MPa and elongation of 4.15 ± 0.2% while the highest elastic modulus of 73.2 ± 5.1 GPa. Owing to the formation of protective TiO 2 -MoO 3 passive film, the MIM-fabricated Ti-12Mo alloy exhibits the highest corrosion resistance including the noblest corrosion potential, the lowest corrosion current density and the highest pitting potential in four different electrolytes. The in vitro cytotoxicity test suggests that the MIM-fabricated Ti-12Mo alloy displays no adverse effect on MC3T3-E1 cells with cytotoxicity ranking of 0 grade, which is nearly close to ELI Ti-6Al-4V or CP Ti. These properties together with its easy net-shape manufacturability make Ti-12Mo an attractive new dental implant alloy., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The circumferential strains created in the radicular dentin by nickel-titanium (NiTi) and stainless steel (SS) finger spreaders (FSs) during a simulated clinical procedure of lateral compaction were compared after minimal (size 50) and extensive (size 100) canal preparations. Nineteen maxillary central incisors underwent minimal preparation, while 10 underwent an extra phase of extensive preparation. Four miniature strain gauges were bonded circumferentially in the apical third of the root (buccal, lingual, mesial, and distal). Lateral compaction was performed using either NiTi-FSs or SS-FSs. Force and strains were continuously recorded. The maximal strains (with and without normalization according to force) were recorded. The SS-FSs generated higher maximal strains normalized according to force compared with the NiTi-FSs. The maximal normalized strains were higher by 37%-43% for the mesial and distal aspects and by 6%-14% for the buccal and lingual aspects after the minimal preparation and by 24%-28% for the mesial and distal aspects and by 19%-20% for the buccal and lingual aspects after extensive preparation. The maximal normalized strains increased by 30%-70% from minimal to extensive preparations, with two teeth exhibiting vertical root fracture while compaction with SS-FS. The NiTi-FSs induce less strain in root dentin than the SS-FSs and thus may contribute less to the risk of vertical root fracture., (© 2018 Eur J Oral Sci.)

Aim: To evaluate the presence and propagation of defects and their effects on surfaces of nickel-titanium (NiTi) instruments using noncontact, three-dimensional optical profilometry, and to assess the accuracy of this method of investigation., Methodology: The flute surface areas of instruments from two commercial instrumentation systems, namely Reciproc R25 (n = 5) and WaveOne Primary (n = 5), were assessed and compared before and after performing two instrumentation cycles in simulated root canals in clear resin blocks. All the analyses were conducted on areas measuring 211 × 211 μm, located 3 mm from the tips of the instruments. A quantitative analysis was conducted before and after the first and second instrumentation cycles, using the Sa (average roughness over the measurement field), Sq (root mean square roughness) and Sz (average height over the measurement field) amplitude parameters. All the data were submitted to statistical analysis at a 5% level of significance., Results: There was a significant increase (P = 0.007) in wear in both groups, especially between baseline and the second instrumentation cycle, with significantly higher wear values being observed on WaveOne instruments (Sz median values = 33.68 and 2.89 μm, respectively, for WO and RP groups). A significant increase in surface roughness (P = 0.016 and P = 0.008, respectively, for Sa and Sq) was observed in both groups from the first to the second instrumentation cycle, mostly in WaveOne specimens. Qualitative analysis revealed a greater number of defects on the flute topography of all the instruments after use., Conclusions: More defects were identified in WaveOne Primary instruments compared to Reciproc R25, irrespective of the evaluation stage. The investigation method provided an accurate, repeatable and reproducible assessment of NiTi instruments at different time-points., (© 2018 International Endodontic Journal. Published by John Wiley & Sons Ltd.)

Materials and surfaces developed for dental implants need to withstand degradation processes that take place in the oral cavity. Therefore, the aim of the study was to develop and evaluate the topographical, mechanical, chemical, electrochemical and biological properties of Ti-xZr alloys (x = 5, 10, and 15 wt%) with two surface features (machined and double acid etched). Commercially pure titanium (cpTi) and Ti-6Al-4V alloy were used as controls. Surface characterization was performed using dispersive energy spectroscopy, X-ray diffraction, scanning electron microscopy, atomic force microscopy, profilometry and surface energy. The mechanical properties were assessed using Vickers microhardness, elastic modulus and stiffness. The electrochemical behavior analysis was conducted in a body fluid solution (pH 7.4). In addition, MC3T3-E1 cells were used to determine the impact of material and surface treatment on cell morphology by SEM analysis. Data were analyzed by two-way ANOVA and Bonferroni test (α = 0.05). Ti-Zr alloys showed lower surface roughness, elastic modulus and stiffness, as well as higher hardness and surface energy when compared to cpTi. Ti-Zr system increased the polarization resistance values and significantly decreased the capacitance, corrosion current density (i corr ), and passivation current density (i pass ) values. The acid treatment increased the resistance and corrosion potential of the oxide layer. SEM data analysis demonstrated that Ti-Zr alloys displayed normal cell attachment/spreading and slightly changed cell morphology in the double etched surface. In conclusion, Zr addition and surface treatment altered surface, mechanical, biological and electrochemical properties of Ti material., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Objective: To assess the short-term effect of two in vitro erosive challenge protocols on the bond strength of metal orthodontic brackets on bovine enamel., Methods: Sixty bovine incisors were selected and randomly divided into six groups: AS7 (artificial saliva - 7 days, Control Group); CC7 (Coca-Cola™ - 7 days); LJ7 (lime juice - 7 days); AS30 (artificial saliva - 30 days, Control Group); CC30 (Coca-Cola™ - 30 days); LJ30 (lime juice - 30 days). Microhardness testing was performed prior to the erosive challenge to verify the standardization of samples. Immersion was performed 4x/day for five minutes, for either 7 or 30 days. After immersions were concluded, the brackets were bonded and shear bond strength was assessed after 48 hours. The Adhesive Remnant Index (ARI) was also assessed. Data were analyzed by two-way ANOVA, followed by Tukey's post-hoc and Student's t test for paired samples, and the Kruskal-Wallis non-parametric test (α = 5%)., Results: The mean and standard deviation of microhardness testing of total samples were 281.89 ± 44.51 KHN. There was no statistically significant difference in shear bond strength for the time factor (7 or 30 days; F5.54= 0.105; p  = 0.901). However, there was a statistically significant difference for the solution factor (F5.54= 6.671; p  = 0.003). These differences occurred among solutions of Saliva x Coca-Cola™ (p  = 0.003) and Coca-Cola™ x Lime Juice (p = 0.029). The assessment of the Adhesive Remnant Index showed no significant difference between groups., Conclusions: The immersion time used in the erosion protocols did not affect the bond strength of brackets to teeth. Coca-Cola™ induced significantly higher shear bond strength values than lime juice and artificial saliva. However, the short term effects of 7/30 days in this in vitro study may not be extrapolated for in vivo ones. Clinical studies should be conducted, substantiating the laboratory results.

Purpose: To determine whether selective laser melting (SLM) is suitable for the fabrication of dental superstructures., Materials and Methods: Mechanical properties of Ti-6Al-4V, manufactured with SLM or numerically controlled milling, were evaluated and compared., Results and Conclusion: Both groups showed a mechanical strength greater than 500 MPa and an elongation greater than 2%, as required by the International Organization for Standardization 22674 standard. However, a reduced ductility was observed for SLM samples.

The addition of carbon and silicon as minor alloying elements was examined as a means to improve the mechanical properties of novel nitrogen-doped Co-Cr-based alloy dental castings. Samples of Co-32Cr-9W-Si-0.25N-C (mass%) alloys were prepared using a dental-casting machine. Microstructural analysis was performed on the alloys using scanning electron microscopy, electron-backscatter diffraction, electron-probe microanalysis, and X-ray diffraction, with a particular focus on the precipitation behavior. The findings were compared with thermodynamic predictions and examined in relation to the tensile properties and Vickers hardness at room temperature. All of the prepared alloys had a face-centered-cubic γ-phase matrix, with grains measuring a few millimeters in diameter and consisting of dendritic substructures. The precipitation of the intermetallic σ-phase, which occurred in the interdendritic regions with solidification segregation of Cr and W, was replaced with M 23 C 6 through the addition of carbon. This significantly increased the ultimate tensile strength of the alloys without severe loss of ductility, although the 0.2% proof stress did not change. The addition of silicon, on the contrary, promoted the formation of the precipitates, which included M 6 C and the σ-phase, making the alloys brittle. The results of this study highlight the role of minor alloying elements, such as carbon and silicon, on the microstructural and mechanical properties; the findings also shed light on the significance of precipitation control in dental castings of Co-Cr alloys, which should aid the design of novel dental alloys., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The introduction of automated instrumentation in endodontics represented a major advance in progress for this specialty, with improvements in the quality and predictability of root canal preparation and a significant reduction in procedural errors. In recent years, endodontic instruments have undergone a series of changes brought about by modifications in design, surface treatments, and thermal treatments. In addition, new movements have also been incorporated to offer greater safety and efficiency, optimizing the properties of the NiTi alloy, especially through eccentric rotary motion. An understanding of the mechanical properties of these new NiTi instruments and their effect on the clinical performance of root canal preparation is essential if dental practitioners are to select the instruments that provide optimal clinical outcomes, especially in curved or flattened canals. The objective of this literature review is to present and discuss the characteristics of the NiTi alloys used in the major instrumentation systems available in the market, as well as the influence of the metallurgical and mechanical properties of NiTi instruments and the movements that drive them, to enable more accurate and predictable planning of root canal preparation.

Objective: Clasps of removable partial dentures (RPDs) often suffer from plastic deformation and failure by fatigue; a common complication of RPDs. A new technology for processing metal frameworks for dental prostheses based on laser-sintering, which allows for precise fabrication of clasp geometry, has been recently developed. This study sought to propose a novel method for designing circumferential clasps for laser-sintered RPDs to avoid plastic deformation or fatigue failure., Methods: An analytical model for designing clasps with semicircular cross-sections was derived based on mechanics. The Euler-Bernoulli elastic curved beam theory and Castigliano's energy method were used to relate the stress and undercut with the clasp length, cross-sectional radius, alloy properties, tooth type, and retention force. Finite element analysis (FEA) was conducted on a case study and the resultant tensile stress and undercut were compared with the analytical model predictions. Pull-out experiments were conducted on laser-sintered cobalt-chromium (Co-Cr) dental prostheses to validate the analytical model results., Results: The proposed circumferential clasp design model yields results in good agreement with FEA and experiments. The results indicate that Co-Cr circumferential clasps in molars that are 13mm long engaging undercuts of 0.25mm should have a cross-section radius of 1.2mm to provide a retention of 10N and to avoid plastic deformation or fatigue failure. However, shorter circumferential clasps such as those in premolars present high stresses and cannot avoid plastic deformation or fatigue failure., Significance: Laser-sintered Co-Cr circumferential clasps in molars are safe, whereas they are susceptible to failure in premolars., (Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.)

Introduction: In this study, we aimed to determine the effect of regular probiotic consumption on microbial colonization in saliva in orthodontic patients and to comparatively evaluate the difference between the systemic consumption of probiotic products and the local application., Methods: This study included 3 groups with 15 orthodontic patients in each. The control group included patients who had no probiotic treatment, the subjects in the kefir group consumed 2 × 100 ml of kefir (Atatürk Orman Ciftligi, Ankara, Turkey) per day, and the subjects in the toothpaste group brushed their teeth with toothpaste with probiotic content (GD toothpaste; Dental Asia Manufacturing, Shah Alam, Selangor, Malaysia) twice a day. Samples were collected at 3 times: beginning of the study, 3 weeks later, and 6 weeks later. The salivary flow rate, buffer capacity, and Streptococcus mutans and Lactobacillus levels in the saliva were evaluated. Chair-side kits were used to determine the S mutans and Lactobacillus levels., Results: A statistically significant decrease was observed in the salivary S mutans and Lactobacillus levels in the kefir and toothpaste groups compared with the control group (P <0.05). A statistically significant increase was observed in the toothpaste group compared with the control and kefir groups in buffer capacity. Changes in the salivary flow rate were not statistically significant., Conclusions: The regular use of probiotics during fixed orthodontic treatment reduces the S mutans and Lactobacillus levels in the saliva., (Copyright © 2018 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

Background: The worldwide dramatic increase in the use of cell phones has generated great concerns about their potential adverse health effects., Objective: The aim of the present study was to evaluate the effects of radiofrequency electromagnetic fields (RF-EMFs) emitted from mobile phones on the level of nickel release from orthodontic brackets., Methods: Twenty stainless steel brackets were divided randomly into experimental and control groups (n=10). Brackets were immersed in artificial saliva at 37°C for 6 months. Experimental group were exposed to GSM 900MHz RF-EMFs emitted from a mobile phone stimulator for 4hours. The specific absorption rate (SAR) was 2.287W/kg. The concentration of nickel in the artificial saliva in both groups was evaluated by using the cold-vapour atomic absorption spectrometry. The Mann-Whitney test was used to assess significant differences in nickel release between the exposed and non-exposed groups., Results: The mean nickel levels in the exposed and non-exposed groups were 11.95 and 2.89μg/l, respectively. This difference between the concentrations of nickel in the artificial saliva of these groups was statistically significant (P=0.001)., Conclusion: Exposure to RF-EMFs emitted from mobile phones can lead to human exposure to higher levels of nickel in saliva in patients with orthodontic appliances. As nickel exposure can lead to allergic reaction in humans and considering this point that about 10-20% of the population can be hypersensitive to nickel, further studies are needed to evaluate the effects of radiofrequency electromagnetic fields (RF-EMFs) emitted from common devices such as mobile phones or Wi-Fi routers on the level of nickel release from orthodontic brackets., (Copyright © 2018. Published by Elsevier Masson SAS.)

Objectives: To investigate the influence of different materials for monolithic full posterior crowns using 3D-Finite Element Analysis (FEA)., Methods: Twelve (12) 3D models of adhesively-restored teeth with different crowns according to the material and its elastic modulus were analysed: Acrylic resin, Polyetheretherketone, Composite resin, Hybrid ceramic, pressable and machinable Zirconia reinforced lithium silicate, Feldspathic, Lithium disilicate, Gold alloy, Cobalt-Chromium alloy (Co-Cr), Zirconia tetragonal partially stabilized with yttria, and Alumina. All materials were assumed to behave elastically throughout the entire deformation. Results in restoration and cementing line were obtained using maximum principal stress. In addition, maximum shear stress criteria was used for the cementing line., Results: Restorative materials with higher elastic modulus present higher stress concentration inside the crown, mainly tensile stress on an intaglio surface. On the other hand, materials with lower elastic modulus allow stress passage for cement, increasing shear stress on this layer. Stiffer materials promote higher stress peak values., Significance: Materials with higher elastic modulus such as Co-Cr, zirconia and alumina enable higher tensile stress concentration on the crown intaglio surface and higher shear stress on the cement layer, facilitating crown debonding., (Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.)

Aim: To evaluate, in vitro, the mini-implant surface changes and the release of ions after immersion in artificial saliva during follow-up of 60 and 120 days., Materials and Methods: As for the surface features, examined in a scanning electron microscope (SEM), before and after immersion in artificial saliva, there was a rough and uneven surface, suggestive of corrosion areas for the two trademarks evaluated after 120 days of immersion. The extracts generated in artificial saliva analysis were submitted to energy dispersive spectroscopy to identify the solid corrosion products produced on the surfaces of miniscrews., Results: Both SIN miniscrews and Neodent brands were observed to release minimal quantities of silver ions, chromium, iron, nickel, titanium, and vanadium. Regarding titanium, this index varied from 88.84% in the control group of Neodent brand, and 91.29% in the control group of SIN brand. For the aluminum content, the quantities ranged from 4.91% in group immersed for 60 days in Neodent brand to 8.71% for the SIN control group. Considering vanadium, the index ranged from 2.65% in the group immersed for 120 days to 4.53% in the control group, both for Neodent brand. Statistically significant differences in iron ion were observed between the control group and the miniscrews brand SIN after 60 and 120 days and for Neodent after 60 days of immersion. The titanium ions suffered statistically significant decrease for both brands after 120 days of storage when compared with the control group., Conclusion: The studied miniscrews showed results consistent with the biosafety of alloys for use, in vivo., Clinical Significance: The knowledge of the physical/chemical state of corrosion products released in the oral cavity is very important for the toxicological assessment of metal alloys used in dental miniscrews.

The reduced marginal bone loss observed when using the platform-switching concept may be the result of reduced amounts of tribocorrosion products released to the peri-implant tissues. Therefore, the purpose of this study was to compare the tribocorrosion product release from various platform-matched and platform-switched implant-abutment couplings under cyclic loading. Forty-eight titanium implants were coupled with pure titanium, gold alloy, cobalt-chrome alloy, and zirconia abutments forming either platform-switched or platform-matched groups ( n = 6). The specimens were subjected to cyclic occlusal forces in a wet acidic environment for 24 h followed by static aqueous immersion for 6 d. The amount of metal ions released was measured using inductively coupled plasma mass spectrometry. Microscopic evaluations were performed pre- and postimmersion under scanning electron microscope (SEM) equipped with energy-dispersive spectroscopy X-ray for corrosion assessment at the interface and wear particle characterization. All platform-switched groups showed less metal ion release compared with their platform-matched counterparts within each abutment material group ( P < 0.001). Implants connected to platform-matched cobalt-chrome abutments demonstrated the highest total mean metal ion release (218 ppb), while the least total mean ion release (11 ppb) was observed in the implants connected to platform-switched titanium abutments ( P ≤ 0.001). Titanium was released from all test groups, with its highest mean release (108 ppb) observed in the implants connected to platform-matched gold abutments ( P < 0.001). SEM images showed surface tribocorrosion features such as pitting and bands of fretting scars. Wear particles were mostly titanium, ranging from submicron to 48 µm in length. The platform-matched groups demonstrated a higher amount of metal ion release and more surface damage. These findings highlight the positive effect of the platform-switching concept in the reduction of tribocorrosion products released from dental implants, which consequently may minimize the adverse tissue reactions that lead to peri-implant bone loss.

Purpose: To evaluate by 3-dimensional (3-D) finite element analysis the stress generated on overdenture-retaining bar system with different cross sections (round, ovoid, or Hader) and misfit levels (50, 100, and 200 μm) manufactured with different metallic alloys (Au type IV, Ag-Pd, Ti cp, and Co-Cr)., Materials and Methods: Three-dimensional finite element models were modeled using specific 3-D software (SolidWorks) and imported into mechanical simulation software (ANSYS). A displacement simulating the settlement of the screw was performed until the infrastructure was settled properly on the prosthetic platform., Results: Higher misfit levels caused higher stress on the overdenture-retaining bar system components, where (1) Hader bar presented the highest values (bar = 730.71; screw = 59.66, and periimplant bone tissue = 42.96, in megapascal) and (2) round bars made with type IV Au alloy presented lower stress values on the bar framework (193.99 MPa) and screw (10.27 MPa)., Conclusions: Higher vertical misfit increased the stress values on the overdenture-retaining bar system; complex cross-sectional designs increased stress values on the bar framework, prosthetic screw, and periimplant bone tissue; stiffer alloys caused higher stress values on all the studied conditions.

The purpose of the study was to evaluate the adaptation and micro-structure of Co-Cr alloy maxillary complete denture base plates fabricated by the selective laser melting (SLM) technique. Twenty pairs of edentulous casts were randomly and evenly divided into two groups, and manufacturing of the Co-Cr alloy maxillary complete denture base was conducted either by the SLM technique or by the conventional method. The base-cast sets were transversally sectioned into three sections at the distal canines, mesial of the first molars and the posterior palatal zone. The gap between the metal base and cast was measured in these three sections with a stereoscopic microscope, and the data were analysed using t tests. A total of five specimens of 5 mm diameter were fabricated with the Co-Cr alloy by SLM and the traditional casting technology. A scanning electron microscope (SEM) was used to evaluate the differences in microstructure between these specimens. There was no statistical difference between the three sections in all four groups (P > 0.05). At the region of the canines, the clearance value for the SLM Co-Cr alloy group was larger than that of the conventional method group (P < 0.05). At the mesial of the first molar region and the posterior palatal zone, there was no statistical difference between the gaps observed in the two groups (P > 0.05). The SLM Co-Cr alloy has a denser microstructure behaviour and less casting defect than the cast Co-Cr alloy. The SLM technique showed initial feasibility for the manufacture of dental bases of complete dentures, but large sample studies are needed to prove its reliability in clinical applications. The mechanical properties and microstructure of the denture frameworks prepared by selective laser melting indicate that these dentures are appropriate for clinical use.

Severe plastic deformation (SPD) has long been known to confer superior mechanical properties for many metals and alloys. In the general field of biomedical devices, and dental implants in particular, the superior strength of SPD-processed commercially pure (CP) titanium, that may surpass that of the stronger Ti6Al4V alloy, has been associated with a superior fatigue resistance. Such a property would make those materials both biocompatible and strong alternatives to the currently used titanium alloy. However, the fatigue characterization reported so far in the literature relies on a very small sample size, thereby precluding any meaningful statistical analysis. This paper reports and compares systematic fatigue testing of various grades as-received and SPD processed Grade 4 CP-Ti using the recently developed random spectrum loading approach, in both air and 0.9% saline solution. The results of this study do not support the claim that the SPD process, albeit causing noticeable strengthening, confers any advantage to Grade 4 CP-Ti in terms of fatigue response., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

We investigated the chemical interaction between zirconia surfaces and functional monomers using X-ray photoelectron spectroscopy (XPS). Two types of zirconia disks cleaned with piranha solution were treated with one of two phosphate primers (Alloy Primer, Clearfil Ceramic Primer) or a carboxylic primer (Super-Bond C&B Monomer), and rinsed 3 times with acetone. XPS analysis revealed that phosphorus was incorporated into zirconia when the surface was treated with a primer containing phosphate monomer (10-methacryloyloxydecyl dihydrogen phosphate; MDP). However, the S 2p peak of a triazine dithiol monomer (6-[N-(4-vinylbenzyl)-n-propylamino]-1,3,5-triazine-2,4-dithione; VTD) and Si 2p peak of silane (3-trimethoxysilylpropyl methacrylate; TMSPMA) were not detected in the spectra of the primed surface. The [C]/[Zr] ratio for the surface treated with a carboxylic anhydride (4-methacryloyloxyethyl trimellitate anhydride; 4-META) primer was smaller than that treated with MDP. These results demonstrated that 4-META and MDP adsorbed to zirconia, whereas the VTD and TMSPMA did not.

Introduction: The effect of any sterilization methods (cold [chemical] or hot) on load-deflection characteristics of aesthetic coated archwires has not yet been investigated. Thus, we assessed it., Methods: In this experimental in vitro study, 90-coated archwires from 3 brands were purchased. Ten wires from each brand (n=30) underwent cold and 10 underwent hot sterilization, while 10 left unsterilized as negative controls. Load-deflection curves were established for each wire (as five 0.2mm intervals between 1.0 and 1.8mm displacements), using a three-bracket test. After determining the plateau phase that was present in all wires, the averages of plateau phase pertaining to loading and unloading curves and their discrepancies (hysteresis) were calculated for each subgroup (n=10). Average plateau values were compared using two-way ANOVA, Tukey, and independent-samples t-test (α=0.05)., Results: Average loading and unloading values were 906.6±129.7 and 295.9±84.5g respectively (t-test P<0.0001). Comparing loading plateaus, ANOVA indicated significant difference among wire brands (P<0.0001) but not among sterilization types (P=0.4793). Comparing unloading plateaus, ANOVA showed significant differences among wire brands (P<0.0001) and sterilization types (P=0.0008). Tukey showed that only cold sterilization and negative control differed significantly (P<0.001); cold and hot sterilization methods, or control and autoclaving were not significantly different (P>0.05). Comparing hysteresis plateaus, ANOVA indicated difference among wire brands (P<0.0053) but not among sterilization types (P=0.9166)., Conclusions: Cold sterilization might reduce unloading plateau of orthodontic wires, but sterilization in general might not affect loading or hysteresis plateaus. Different brands had different plateaus of loading, unloading and hysteresis., (Copyright © 2018. Published by Elsevier Masson SAS.)

Introduction: The aim of this study was to identify the fracture resistance of grade 23 Titanium mini-implants recycled for orthodontic purposes and having stayed in the mouth during different periods of time., Materials and Methods: A total of 52 hybrid-designed titanium mini-implants, threaded length L=8mm, self-drilling and self-taping were used in 32 patients presenting orthodontic anomalies which required the use of mini-implants. Two types of tests were performed: polarizing optical imagery to assess the surface characteristics of the mini-implants (polarizing optical microscopy) and (mechanical) torsional strength tests, more quantitative, in order to establish the breaking point of the mini-implants during their re-use., Results: For the mini-implants which had been in the mouth for a short period of time, (immediate removal or after two months of use), it must be noted that their surface characteristics revealed no defect at micron scale, the drilling head did not show any alteration, with a breaking point record of about 53Newton/cm 2 (N/cm 2 ). In contrast, the mini-implants, which had stayed in the mouth for 12 and 14 months, showed surface alterations especially at the "screw-gingiva" interface and the rupture stress ranges from 42 to 39N/cm 2 , respectively., Discussion: Our results show that the resistance to fracture of the re-used mini-implants is inversely proportional to the duration of stay in the mouth., (Copyright © 2018. Published by Elsevier Masson SAS.)

Aim: To evaluate apical transportation and centring ability during root canal preparation in mesial root canals of mandibular molars associated with ProTaper Gold (PTG), ProDesign S (PDS), Hyflex CM (HCM), Hyflex EDM and ProDesign Logic (PDL)., Methodology: Sixty mandibular first molars with two separate canals in the mesial root were selected after root anatomy pairing by microcomputed tomography (microCT). The teeth were randomly divided into five groups (n = 24); the root canal volume was calculated to ensure sample homogeneity. All the root canals were prepared up to size 25 in accordance with the instructions of each rotary system manufacturer. After root canal preparation, the teeth were scanned by microCT to analyse apical transportation, root canal centralization and the pre- and post-preparation root canal volume at the apical and cervical levels. Kruskal-Wallis and Dunn tests were used for comparisons amongst groups for transportation values. For volume changes, the parametric ANOVA and Tukey's tests were used RESULTS: There were no significant differences in apical transportation amongst the rotary systems (P > 0.05). All the systems created apical transportation; values ranging from 0.031 mm (PDL) to 0.072 mm (PTG), and enlargements between 39% (HCM) and 91.1% (PDS) were observed. In relative to cervical transportation, significant differences were observed amongst the systems (P < 0.05). Mean transportation values between 0.07 mm (HCM) and 0.172 mm (PTG) were found, with enlargements between 35.4% (HCM) and 51.5% (PDS)., Conclusion: All the thermally treated systems resulted in similar apical transportation. In the cervical region, the Hyflex CM and Prodesign Logic systems were associated with more centred preparations., (© 2017 International Endodontic Journal. Published by John Wiley & Sons Ltd.)

Aim: To evaluate the torsional properties of pathfinding nickel-titanium (NiTi) rotary instruments manufactured from several NiTi alloys, ProGlider (M-wire), Hyflex GPF (conventional NiTi Wire and controlled memory wire), Logic (conventional NiTi wire and controlled memory wire) and Mtwo (conventional NiTi wire)., Methodology: A total of 56 NiTi instruments from Glidepath rotary systems (n = 8) were used: Logic (size 25, .01 taper), Logic CM (size 25, .01 taper), ProGlider (size 16, .02 taper), Hyflex GPF (size 15, .01 taper), Hyflex GPF CM (size 15, .02 taper; size 20, .02 taper) and Mtwo (size 10, .04 taper). The torsion tests were performed based on ISO 3630-1 (1992). Three millimetres of each instrument tip was clamped to a small load cell by a lever arm linked to the torsion axis. Data were analysed using a one-way analysis of variance (anova) and Tukey test with a significance level at a = 5%., Results: The Logic size 25, .01 taper had significantly higher torsional strength values (P < 0.05). The ProGlider was significantly different when compared with Hyflex GPF size 15, .01 taper and size 15, .02 taper (P < 0.05). The Logic CM size 25, .01 taper had significantly higher torsional strength than Hyflex GPF size 15, .01 taper and size 15, .02 taper (P < 0.05). No difference was found amongst Mtwo size 10, .04 taper and Hyflex GPF groups (size 15, .01 taper; size 15, .02 taper; size 20, .02 taper). In relation to the angle of rotation, Logic CM size 25, .01 taper and Hyflex GPF size 15, .01 taper had the highest angle values (P < 0.05). The ProGlider had the lowest angle values in comparison with all the groups (P < 0.05) followed by Mtwo size 10, .04 taper. The Logic size 25, .01 taper had significantly higher angle of rotation values than ProGlider and Mtwo size 10, .04 taper (P < 0.05)., Conclusion: The Logic size 25, .01 taper instrument made of conventional NiTi alloy had the highest torsional strength of all instruments tested. In addition, the ProGlider instrument manufactured from M-Wire alloy had the lowest angle of rotation to fracture in comparison with the other instruments., (© 2017 International Endodontic Journal. Published by John Wiley & Sons Ltd.)

Objectives: The aim of this study was to evaluate the cyclic and torsional fatigue resistance of the reciprocating single-file systems Reciproc Blue 25.08 (VDW GmbH, Munich, Germany), Prodesign R 25.06 (Easy Dental Equipment, Belo Horizonte, Brazil), and WaveOne Gold 25.07 (Dentsply/Tulsa Dental Specialties, Tulsa, OK, USA)., Materials and Methods: Sixty reciprocating instruments of the systems Reciproc Blue R25 (RB #25 .08 taper), Prodesign R (PDR #25 .06 taper), and WaveOne Gold (WOG #25 .07 taper) (n = 20) were used. Cyclic fatigue resistance testing was performed by measuring the time to failure in an artificial stainless steel canal with a 60° angle of curvature and a 5-mm radius located 5 mm from the tip (n = 10). The torsional test (ISO 3630-1) evaluated the torque and angle of rotation at failure of new instruments (n = 10) in the portion 3 mm from the tip. The fractured surface of each fragment was also observed using scanning electron microscopy (SEM). In addition, a supplementary examination was performed to measure the cross-sectional area of each instrument 3 and 5 mm from the tip. The data were analyzed using one-way ANOVA and Tukey's test, and the level of significance was set at 5%., Results: The cyclic fatigue resistance values of PDR 25.06 were significantly higher (P < 0.05). RB 25.08 showed higher fatigue resistance than WOG 25.07 (P < 0.05). The torsional test showed that PDR 25.06 had lower torsional strength (P < 0.05). No differences were observed between RB 25.08 and WOG 25.07 (P > 0.05). PDR 25.06 showed higher angular rotation values than RB 25.08 and WOG 25.07 (P < 0.05). RB 25.08 presented higher angular rotation than WOG 25.07 (P < 0.05). The cross-sectional area analysis showed that PDR 25.06 presented the smallest cross-sectional areas at 3 and 5 mm from the tip (P < 0.05)., Conclusion: PDR 25.06 presented the highest cyclic fatigue resistance and angular rotation until fracture compared to RB 25.08 and WOG 25.07. In addition, RB 25.08 and WOG 25.07 had higher torsional strength than PDR 25.06., Clinical Relevance: In endodontic practice, thermally treated reciprocating instruments have been used for the root canal preparation of curved and constricted canals; therefore, these instruments should present high flexibility and suitable torsional strength to minimize the risk of instrument fracture.

Statement of Problem: Spark erosion is a fit corrective technology that can be used even after the veneering material has been applied. The framework does not require sectioning, thus preserving its mechanical resistance. However, the spark erosion effect on veneered Co-Cr fixed complete denture (FCD) frameworks has not been investigated., Purpose: The purpose of this in vitro study was to evaluate whether spark erosion is effective in improving marginal fit on screw-retained Co-Cr FCD frameworks veneered with different materials. A comparison between ceramic applications and simulated ceramic firing cycles was also investigated., Material and Methods: Forty FCD frameworks were fabricated with a Co-Cr alloy. Four groups (n=10) were obtained according to the veneer material used on frameworks: HR (heat-polymerized resin); LR (light-polymerized resin); C (ceramic); and SC (simulated ceramic firing cycle). The spark erosion process was conducted for all groups. The marginal fit was analyzed according to the single-screw test protocol, and the measurements were performed at 3 evaluation times: initial, after veneer material application, and after spark erosion process. The results were submitted to a 2-way repeated measures ANOVA and the Tukey honest significant differences test (α=.05)., Results: Poorer marginal fit (in micrometers) was noted after veneer material application, where the HR and C groups presented the worst values (HR: 170; LR: 72; C: 165; SC: 86; P<.05). The spark erosion process was effective in improving the fit for all groups (HR: 109; LR: 52; C: 110; SC: 60; P<.05)., Conclusions: Spark erosion improved the fit of Co-Cr FCD frameworks veneered with different materials. An actual ceramic application should be used to assess distortions generated by veneer material application instead of using only simulated ceramic firing cycles., (Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Objectives: Aim of the present study was twofold. First, to evaluate in vitro, the performance of two different NiTi rotary instruments in one molar case; then, to evaluate their resistance to cyclic fatigue, compared to new ones., Material and Methods: 25 ProTaper Next (PTN) nickel-titanium (NiTi) instruments (Maillefer-Dentsply, Baillagues, CH) for each of the following two sizes: X1 (17.04 ) and X2 (25.06) were randomly divided into two groups. The first group (n = 10) immediately under- went to a cyclic fatigue test. The second group (n = 15) was initially used to prepare 15 extracted molar teeth and then subjected to a cyclic fatigue test. Same was done for 25 Horizen (HZ) instruments (Kerr Endodontics, Orange, Ca) for each of the following two sizes: 20.04 and 25.06. Instruments were rotated in curved artificial canal until fracture occurred and times to fracture were recorded. All data were collected and statistically analyzed using a variance test (confidence interval CI = 95%)., Results: HZ reached working length more rapidly than PTN, and with less deformations. For the fatigue tests, all the new instruments were significantly more resistant than the used ones. The HZ instru- ments were significantly more resistant in all sizes than PTN, both when new and used instruments were tested., Conclusions: Since in previous studies ProTaper Next demonstra- ted a better resistance to cyclic fatigue than most of nickel-titanium instruments, Horizen's performance put them in a high rank amongst the most resistant nickel-titanium rotary instruments.

Statement of Problem: Studies have demonstrated the effectiveness of a single-implant-retained mandibular overdenture for elderly patients with edentulism. However, due to the high concentration of stress around the housing portion of the single implant, this prosthesis tends to fracture at the anterior region more than the 2-implant-retained mandibular overdenture., Purpose: The purpose of this finite-element analysis study was to evaluate the stress distribution in a single-implant-retained mandibular overdenture reinforced with a cobalt-chromium framework, to minimize the incidence of denture base fracture., Material and Methods: Two 3-dimensional finite element models of mandibular overdentures supported by a single implant with a stud attachment were designed in SolidWorks 2013 software. The only difference between the models was the presence or absence of a cobalt-chromium framework at the denture base between canines. Subsequently, the models were imported into the mathematical analysis software ANSYS Workbench v15.0. A mesh was generated with an element size of 0.7 mm and submitted to convergence analysis before mechanical simulation. All materials were considered to be homogeneous, isotropic, and linearly elastic. A 100-N load was applied to the incisal edge of the central mandibular incisors at a 30-degree angle. Maximum principal stress was calculated for the overdenture, von Mises stress was calculated for the attachment and implant, and minimum principal stress was calculated for cortical and cancellous bone., Results: In both models, peak stress on the overdenture was localized at the anterior intaglio surface region around the implant. However, the presence of the framework reduced the stress by almost 62% compared with the overdenture without a framework (8.7 MPa and 22.8 MPa, respectively). Both models exhibited similar stress values in the attachment, implant, and bone., Conclusions: A metal framework reinforcement for a single-implant-retained mandibular overdenture concentrates less stress through the anterior area of the prosthesis and could minimize the incidence of fracture., (Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to evaluate the fit of additively manufactured cobalt-chromium and titanium and CNC-milled titanium frameworks before and after ceramic veneering., Materials and Methods: Ten stone casts simulating an edentulous maxilla provided with six abutment analogs were produced. For each stone cast, one additively manufactured cobalt-chromium framework (AM CoCr) and one titanium framework (AM Ti) were fabricated. The fit was analyzed with a coordinate measuring machine in three dimensions (x, y, and z axes) using best-fit virtual matching of center point coordinates, before and after ceramic veneering. CNC-milled titanium frameworks (CNC Ti) and earlier results from CNC-milled cobalt-chromium frameworks (CNC CoCr) were used for comparison., Results: All frameworks presented minor misfit before and after veneering in the horizontal plane (x- and y-axes) between 2.9 and 13.5 μm and in the vertical plane (z-axis) between 1.6 and 5.4 μm. Ceramic veneering affected the fit of all groups of frameworks. Both AM Ti and AM CoCr presented significantly smaller distortion in the vertical plane compared with the CNC-milled frameworks., Conclusion: Implant-supported frameworks can be produced in either Ti or CoCr using either CNC milling or additive manufacturing with a fit well within the range of 20 μm in the horizontal plane and 10 μm in the vertical plane. The fit of frameworks of both materials and production techniques are affected by the ceramic veneering procedure to a small extent.

Purpose: The aim of this study was to evaluate the elemental and mechanical alterations of stainless steel (SS) multistranded orthodontic wires used in fixed retention after intraoral ageing., Materials and Methods: Two types of 0.022-inch, seven-stranded wires, Lingual Retainer Wire (LRW) and Tru-Chrome (TCH), from the same manufacturer (Rocky Mountain Orthodontics, Denver, Colo, USA) were tested. Thirty-three samples from LRW group and thirty-seven from TCH were collected, whereas three unused wires from each package were used as controls. The median ageing time for LRW was 7.4 years and 8.4 for TCH. All samples were subjected to scanning electron microscope/X-ray energy dispersive spectroscopy analysis. Three spectra were taken from the surface of each wire and then all samples were used for the assessment of Martens hardness, indentation modulus (EIT), and elastic index (ηIT) with the instrumented indentation testing method (IIT). The intraoral ageing time was statistically compared between the two groups by Mann-Whitney rank sum test and the compositional and mechanical properties were compared by unpaired t-test. The Spearman correlation between elemental content and ageing time was carried out for all elements (a = 0.05)., Results: No significant differences were found for both the elemental content and for the mechanical properties between the wires tested. Spearman analysis revealed no correlation between elemental content and intraoral time while two groups share statistically equal intraoral ageing times (P > 0.05)., Conclusions: Both wires seemed to maintain their mechanical and elemental integrity within a period of 14-year intraoral exposure, whereas no measurable ionic release could be identified.

The current study aimed at examining surface and chemical composition changes of retrieved mini-implants after different periods of service as aids of anchorage for orthodontic patients. This study examined 72 retrieved orthodontic self-tapping and self-drilling mini-implants, 1.7 mm in diameter and 8 mm in length (OrthoEasy system, Forestadent, Pforzheim, Germany) from 36 adult orthodontic patients (18 men and 18 women, mean age = 23 years). The retrieved mini-implants were divided into 3 groups according to service period: 3-6 months (3M-6M) group, 6-12 months (6M-12M) group, and 12-24 months (12M-24M) group, with 24 mini-implants in each group. The control group (As Received) comprised of 24 unused mini-implants of the same type (AR group). All mini-implant heads and threaded bodies were examined for chemical characterization and topographical features by SEM-EDS. The average weight percentages for the following elements Ti, Al, and O 2 were obtained and compared among the 4 groups. There was significant decrease in titanium content and deterioration for the surface properties for all parts of the mini-implants after being used inside patients' oral cavities for more than 6 months p < 0.05. The period of mini-implant service inside patients' oral cavities should not exceed 6 months.

Statement of Problem: Although palladium-silver alloys have been marketed for over 3 decades for metal-ceramic restorations, understanding of the corrosion behavior of current alloys is incomplete; this understanding is critical for evaluating biocompatibility and clinical performance., Purpose: The purpose of this in vitro study was to characterize the corrosion behavior of 3 representative Pd-Ag alloys in simulated body fluid and oral environments and to compare them with a high-noble Au-Pd alloy. The study obtained values of important electrochemical corrosion parameters, with clinical relevance, for the rational selection of casting alloys., Material and Methods: The room temperature in vitro corrosion characteristics of the 3 Pd-Ag alloys and the high-noble Au-Pd alloy were evaluated in 0.9% NaCl, 0.09% NaCl, and Fusayama solutions. After simulated porcelain firing heat treatment, 5 specimens of each alloy were immersed in the electrolytes for 24 hours. For each specimen, the open-circuit potential (OCP) was first recorded, and linear polarization was then performed from -20 mV to +20 mV (versus OCP) at a rate of 0.125 mV/s. Cyclic polarization was subsequently performed on 3 specimens of each alloy from -300 mV to +1000 mV and back to -300 mV (versus OCP) at a scanning rate of 1 mV/s. The differences in OCP and corrosion resistance parameters (zero-current potential and polarization resistance) among alloys and electrolyte combinations were compared with the 2-factor ANOVA (maximum-likelihood method) with post hoc Tukey adjustments (α=.05)., Results: The 24-hour OCPs and polarization resistance values of the 3 Pd-Ag alloys and the Au-Pd alloy were not significantly different (P=.233 and P=.211, respectively) for the same electrolyte, but significant differences were found for corrosion test results in different electrolytes (P<.001 and P=.032, respectively). No significant interaction was found between the factors of alloy and electrolyte (P=.249 and P=.713, respectively). The 3 Pd-Ag silver alloys appeared to be resistant to chloride ion corrosion, and passivation and de-alloying were identified for these alloys., Conclusions: The Pd-Ag alloys test results showed excellent in vitro corrosion resistance and were equivalent to those of the high-noble Au-Pd alloy in simulated body fluid and oral environments. Passivation, de-alloying, and formation of a AgCl layer were identified as possible corrosion mechanisms for Pd-Ag alloys., (Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Objective: The aims of this study were to assess and compare the resistance to cyclic fatigue of XP-endo Shaper (XPS; FKG Dentaire, La Chaux-de-Fonds, Switzerland) instruments with TRUShape (TRS; Dentsply Tulsa Dental Specialties, Tulsa, OK, USA), HyFlex CM (HCM; Coltene, Cuyahoga Falls, OH, USA), Vortex Blue (VB; Dentsply Tulsa Dental Specialties), and iRace (iR; FKG Dentaire) nickel-titanium rotary instruments at body temperature., Materials and Methods: Size 30, 0.01 taper of XPS, size 30, 0.04 taper of HCM, VB, iR, and size 30, 0.06 taper of TRS instruments were immersed in saline at 37 ± 1 °C during cyclic fatigue testing. The instruments were tested with 60° angle of curvature and a 3-mm radius of curvature. The number of cycles to failure (NCF) was calculated and the length of the fractured segment was measured. Fractographic examination of the fractured surface was performed using a scanning electron microscope. The data were analyzed statistically using Kruskal-Wallis H test and Mann-Whitney U tests. Statistical significance was set at P < 0.05., Results: XPS had a significantly greater NCF compared with the other instruments (P < 0.001). The topographic appearance of the fracture surfaces of tested instruments revealed ductile fracture of cyclic fatigue failure., Conclusion: XPS instruments exhibited greater cyclic fatigue resistance compared with the other tested instruments., Clinical Relevance: XP-endo Shaper instruments could be used more safely in curved canals due to their higher fatigue resistance.

The aim of this study was to investigate the effect of three metal priming agents on the bond strength of adhesive resin cement to Silver-Zinc-Tin-Indium (Ag-Zn-Sn-In) alloy and pure Ag, Zn, Sn, and In. The specimens were air-abraded with alumina and then primed with one of three metal priming agents: V-Primer, Estenia Opaque Primer, or Alloy Primer. The metal disks were bonded with adhesive resin cement (Super-Bond Bulk-mix technique). Shear bond strengths (n=10/group) were determined before and after 50,000 thermocycles for Ag-Zn-Sn-In alloy as well as after 5,000 thermocycles for pure Ag, Zn, Sn and In. For Ag-Zn-Sn-In alloy, the post-thermocycling bond strength of the Alloy Primer group was significantly higher than that of the other primers. It can be concluded that Alloy Primer containing both the vinyl-thione monomer (VBATDT) and hydrophobic phosphate monomer (MDP) is effective for bonding Ag-Zn-Sn-In alloy and pure Ag, Zn and Sn.

Titanium nitride (TiN) coating by ion plating has properties such as high hardness, wear resistance, corrosion resistance, and surface lubricity, therefore TiN coating is often used in various dental appliances and materials. In this study, we evaluated the corrosion behaviors and mechanical properties of TiN coated stainless steel (SS) and nickel titanium (Ni-Ti) orthodontic wires prepared by ion plating. TiN coating by ion plating improves the corrosion resistance of orthodontic wires. The corrosion pitting of the TiN coated wire surface become small. The tensile strength and stiffness of SS wire were increased after TiN coating. In contrast, its elastic force, which is a property for Ni-Ti wire, was decreased. In addition, TiN coating provided small friction forces. The low level of friction may increase tooth movement efficiently. Therefore, TiN coated SS wire could be useful for orthodontics treatment.

Ti-Ta thin films exhibit properties that are of interest for applications as microactuators and as biomedical implants. A Ti-Ta thin film materials library was deposited at T = 25 °C by magnetron sputtering employing the combinatorial approach, which led to a compositional range of Ti 87 Ta 13 to Ti 14 Ta 86 . Subsequent high-throughput characterization methods permitted a quick and comprehensive study of the crystallographic, microstructural, and morphological properties, which strongly depend on the chemical composition. SEM investigation revealed a columnar morphology having pyramidal, sharp tips with coarser columns in the Ti-rich and finer columns in the Ta-rich region. By grazing incidence X-ray diffraction four phases were identified, from Ta-lean to Ta-rich: ω phase, α″ martensite, β phase, and a tetragonal Ta-rich phase (Ta (tetr) ). The crystal structure and microstructure were analyzed by Rietveld refinement and clear trends could be determined as a function of Ta-content. The lattice correspondences between β as the parent phase and α″ and ω as derivative phases were expressed in matrix form. The β ⇌ α″ phase transition shows a discontinuity at the composition where the martensitic transformation temperatures fall below room temperature (between 34 and 38 at. % Ta) rendering it first order and confirming its martensitic nature. A short study of the α″ martensite employing the Landau theory is included for a mathematical quantification of the spontaneous lattice strain at room temperature (ϵ̂ max = 22.4(6) % for pure Ti). Martensitic properties of Ti-Ta are beneficial for the development of high-temperature actuators with actuation response at transformation temperatures higher than 100 °C.

Objectives: To characterize the microstructure, mechanical properties, ionic release and tarnish resistance of conventional and experimental Ag-based soldering alloys for orthodontic applications., Methods: Disk shaped specimens were prepared from four commercial Ag based soldering alloys [Dentaurum Universal Silver Solder (DEN), Orthodontic Solders (LEO), Ortho Dental Universal Solder (NOB), and Silver Solder (ORT)] and four experimental alloys Ag12Ga, Ag10Ga5Sn, Ag20In and Ag7Sn. The elemental composition and microstructure was determined by SEM/EDX and XRD analysis, while the mechanical properties were determined by Instrumented Indentation Testing. Ionic release of Ag, Cu, Zn, Ga, In and Sn was determined by ICP-EAS in 0.9% NaCl and Ringer's solutions after 28, 49 and 70 days. Tarnish resistance was also tested and colorimetry was applied to quantify the differences in color (DE) before and after immersion in testing media. DSC was used to determine the melting range of the experimental alloys. Mechanical properties, ionic release and DE were statistically compared by ANOVA and Holm-Sidak multiple comparison test (a=0.05)., Results: All commercially alloys belong to the Ag-Zn-Cu ternary system and consist a Ag rich face centered cubic (FCC) and Cu (FCC) phase. The former is the predominant phase also in experimental alloys. Conventional alloys demonstrated higherhardness, less ductility and lower melting rangers compared to experimental alloys. Immersion testing revealed the release of Cu and Zn ions from the commercially alloys and Ga ions from AgGa and AgGaSn while no ionic release was identified for AgIn and AgSn. All alloys failed tarnish testing according to ISO 10271 showing DE values much higher than the clinical acceptable limit (3.7)., Significance: The conventional Ag based soldering alloys showed substantial differences in their microstructure, mechanical properties and ionic release, and thus different clinical performance is anticipated. Ga, Sn and In might be employed as alloying addition to modify the properties of Ag brazing alloys., (Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)

The metal-resin hybrid full-arch prosthesis has been a traditionally used type of restoration for full-arch implant fixed dentures. A newer development has centered around the use of monolithic zirconia or zirconia veneered with porcelain. Being a ceramic, zirconia has the potential for fracture. This article describes a technique that utilizes a metal substructure to support a chemically and mechanically resinbonded shell of zirconia. The workflow is discussed, ranging from in-office master cast fabrication to the CAD/ CAM production of the provisional and the definitive metal-zirconia prosthesis. The article also highlights the advantages and disadvantages of various materials used for hybrid prostheses.

This study examined the effect of ice-quenching after oxidation treatment on hardness change of a Pd-Cu-Ga-Zn metal-ceramic alloy during porcelain firing simulation. Although not statistically significant, the alloy was softened slightly during porcelain firing simulation with conventional slow cooling rate. On the other hand, the hardness increased significantly by ice-quenching instead of the slow cooling after oxidation (p<0.001). The gap in the final hardness depending on ice-quenching occurred in the matrix and plate-like precipitates but not in the particle-like structure without plate-like precipitates (p<0.05). The mechanism of ice-quenching after oxidation to prevent softening and induce hardening during porcelain firing simulation involved the more active precipitation and retardation of microstructural coarsening. In conclusion, for practical work on Pd-Cu-Ga-Zn alloys, the oxidation treatment followed by ice-quenching instead of slow cooling is recommended for the simultaneous oxidation and hardening effects on the alloy., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Objective: To give a current review of silane adhesion chemistry, applications of silane coupling agents and related surface pretreatment methods in contemporary dentistry., Methods: Silane coupling agents are adhesion promoters to chemically unify dissimilar materials used in dentistry. Silanes are very effective in adhesion promotion between resin composites and silica-based or silica-coated indirect restorative materials. It is generally accepted that for non-silica-based restorations, surface pretreatment is a mandatory preliminary step to increase the silica content and then, with help of silane, improve resin bonding. This review discusses the silane-based adhesion chemistry, silane applications in dentistry, surface pretreatment methods, and presents the recent development of silane coupling agents., Results: A silane coupling agent is considered a reliable, good adhesion promoter to silica-based (or silica-coated) indirect restorations. Surface pre-treatment steps, e.g., acid etching for porcelain and tribo-chemical silica-coating for metal alloys, is used before silanization to attain strong, durable bonding of the substrate to resin composite. In clinical practice, however, the main problem of resin bonding using silanes and other coupling agents is the weakening of the bond (degradation) in the wet oral environment over time., Significance: A silane coupling agent is a justified and popular adhesion promoter (adhesive primer) used in dentistry. The commercial available silane coupling agents can fulfil the requirements in clinical practice for durable bonding. Development of new silane coupling agents, their optimization, and surface treatment methods are in progress to address the long term resin bond durability and are highly important., (Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)

Background and Objectives: The release of metal ions from orthodontic appliances is part of the dissolution and biomechanical processes of alloys. Nickel (Ni) and chromium (Cr) are the elements commonly used in the manufacture of various components of fixed orthodontic appliances, including bands, brackets and wires. This study was aimed to measure the Ni and Cr ions levels in the scalp hair of patients treated with fixed orthodontic appliances in comparison of the control group., Materials and Methods: The patient group consisted of 24 patients treated with fixed orthodontic appliances for one year, while the control group included 28 healthy individuals without orthodontic appliances. Analysis of the Cr and Ni was performed using atomic absorption spectrophotometer by graphite furnace method. The data were analyzed via student and paired samples t-test and ANOVA repeated measurement test., Results: After one year, the levels of Ni and Cr in two groups showed significant differences (0.086 ± 0.007 and 0.258 ± 0.009 µg/g for control group and 0.149 ± 0.010 and 0.339 ± 0.013 µg/g for patient group, respectively for Ni and Cr, p < .001). ANCOVA test by removing the effects of age, gender and the baseline levels of Ni and Cr showed that changes in these ions in the scalp hair of both groups after one year were statistically significant., Conclusion: Due to the slightly elevated levels of Ni and Cr ions in the scalp hair of patients treated with fixed orthodontic appliances and considering the cytotoxic and allergic effects of these ions, changing the ingredients in fixed orthodontic appliances is suggested for the future.

NiTi arch wires are used widely in orthodontic treatment due to its superelastic and biocompatibility properties. In brackets configuration, the force released from the arch wire is influenced by the sliding resistances developed on the arch wire-bracket contact. This study investigated the evolution of the forces released by a rectangular NiTi arch wire towards possible intraoral temperature and deflection changes. A three dimensional finite element model was developed to measure the force-deflection behavior of superelastic arch wire. Finite element analysis was used to distinguish the martensite fraction and phase state of arch wire microstructure in relation to the magnitude of wire deflection. The predicted tensile and bending results from the numerical model showed a good agreement with the experimental results. As contact developed between the wire and bracket, binding influenced the force-deflection curve by changing the martensitic transformation plateau into a slope. The arch wire recovered from greater magnitude of deflection released lower force than one recovered from smaller deflection. In contrast, it was observed that the plateau slope increased from 0.66N/mm to 1.1N/mm when the temperature was increased from 26°C to 46°C., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Background: The aim of this study was to compare the degradation resistance of nickel-chromium (Ni-Cr) and cobalt-chromium (Co-Cr) alloys used as a base material for partial dentures in contact with saliva., Methods: Wiron® 99 and Wironit Extra-Hard® were selected as representative casting alloys for Ni-Cr and Co-Cr alloys, respectively. The alloys were tested in contact with deionized water, artificial saliva and acidified artificial saliva. Material characterization was performed by X-ray diffractometry (XRD) and microhardness and nanohardness testing. The corrosion properties of the materials were then analyzed using open circuit potential analysis and potentiodynamic analysis. Alloy leaching in solution was assessed by inductively coupled plasma mass spectrometry techniques., Results: Co-Cr alloy was more stable than the Ni-Cr alloy in all solutions tested. Leaching of nickel and corrosion attack was higher in Ni-Cr alloy in artificial saliva compared with the acidified saliva. The corrosion resistance of the Co-Cr alloy was seen to be superior to that of the Ni-Cr alloy, with the former exhibiting a lower corrosion current in all test solutions. Microstructural topographical changes were observed for Ni-Cr alloy in contact with artificial saliva. The Ni-Cr alloy exhibited microstructural changes and lower corrosion resistance in artificial saliva. The acidic changes did not enhance the alloy degradation., Conclusions: Ni-Cr alloys are unstable in solution and leach nickel. Co-Cr alloys should be preferred for clinical use.

Background: Patients susceptible to periodontal disease and dental caries, including those who undergo fixed prosthodontic treatments use chemical plaque control agents. However, these mouthrinses may result in adverse effects such as discoloration of the restorative materials. The aim of this study was to compare the color stability of monolithic zirconia and feldspathic porcelain after immersion in two different mouthrinses: 0.2% Chlorhexidine digluconate (CHX), or Listerine®. Color change was evaluated by color spectrophotometer and according to the Commission Internationale de l'Eclairage (CIELab) system., Methods: We prepared 72 disc-shaped porcelains (n = 36) as follows: Group A consisted of dental direkt cube X2 discs (49% translucency) as the monolithic zirconia and group B consisted of VITA VMK 95 as a feldspathic porcelain. Groups A and B were divided into three subgroups (n = 12 per group). Each subgroup was immersed in one of the following three solutions: distilled water (control), CHX, or Listerine® for 2 min, once per day. We recorded the samples' baseline color values according to the CIELab system by using a color spectrophotometer operated by an experienced operator. Color measurements were subsequently obtained following 7 days of immersion, and after the samples were rinsed with distilled water and allowed to dry. We measured CIE L*, a*, and b*and calculated the color difference (ΔE*ab). All data were analyzed by the Mann-Whitney and Kruskal-Wallis tests., Results: Color changes occurred in the experimental groups. The ΔE*ab values were significantly greater in VMK 95 porcelain compared to cube X2 (both p < 0.001) following immersion in CHX and Listerine® mouthrinses. However no significant difference was founded when distilled water was used (p = 0.630). For the two materials, the ΔE values were highest in CHX, followed by the Listerine® and distilled water., Conclusion: Both monolithic zirconia and feldspathic porcelain were susceptible to color changes following immersion in CHX and Listerine® mouthrinses.

Objective: Composite resins do not adhere well to dental alloys. This weak bond can result in failure at the composite-metal interface in fixed dental prostheses and orthodontic brackets. The aim of this study was to develop a new adhesive, based on diazonium chemistry, to facilitate chemical bonding between dental alloys and composite resin., Methods: Samples of two types of dental alloys, stainless steel and cobalt chromium were primed with a diazonium layer in order to create a surface coating favorable for composite adhesion. Untreated metal samples served as controls. The surface chemical composition of the treated and untreated samples was analyzed by X-ray photoelectron spectroscopy (XPS) and the tensile strength of the bond with composite resin was measured. The diazonium adhesive was also tested for shear bond strength between stainless steel orthodontic brackets and teeth., Results: XPS confirmed the presence of a diazonium coating on the treated metals. The coating significantly increased the tensile and shear bond strengths by three and four folds respectively between the treated alloys and composite resin., Conclusion: diazonium chemistry can be used to develop composite adhesives for dental alloys., Significance: Diazonium adhesion can effectively achieve a strong chemical bond between dental alloys and composite resin. This technology can be used for composite repair of fractured crowns, for crown cementation with resin based cements, and for bracket bonding., (Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)

Objective: Evaluate changes in the force system of T-Loop Springs (TLS) preactivated by curvature, due to stress relaxation., Methods: Ninety TLSs measuring 6 x 10 mm, produced out with 0.017 x 0.025-in TMA® wire and preactived by gradual curvature, were randomly distributed into nine groups according to time point of evaluation. Group 1 was tested immediately after spring preactivation and stress relief, by trial activation. The other eight groups were tested after 24, 48 and 72 hours, 1, 2, 4, 8 and 12 weeks, respectively. Using a moment transducer coupled to a digital extensometer indicator adapted to a universal testing machine, the amount of horizontal force, moment and moment-to-force ratios were recorded at every 0.5 mm of deactivation from 5 mm of the initial activation, in an interbracket distance of 23 mm., Results: The horizontal forces decreased gradually among the groups (p< 0.001) and the moments showed a significant and slow decrease over time among the groups (p< 0.001). All groups produced similar M/F ratios (p= 0.532), with no influence of time., Conclusions: The TLSs preactivated by curvature suffered a gradual deformation over time, which affected the force system, specifically the moments, which affected the horizontal forces produced.

Objectives: The etiology of the reduced marginal bone loss observed around platform-switched implant-abutment connections is not clear but could be related to the release of variable amounts of corrosion products. The present study evaluated the effect of different concentrations of metal ions released from different implant abutment couples on osteoblastic cell viability, apoptosis and expression of genes related to bone resorption., Methods: Osteoblastic cells were exposed to five conditions of culture media prepared containing metal ions (titanium, aluminum, vanadium, cobalt, chromium and molybdenum) in different concentrations representing the amounts released from platform-matched and platform-switched implant-abutment couples as a result of an earlier accelerated corrosion experiment. Cell viability was evaluated over 21days using the Alamar Blue assay. Induction of apoptosis was measured after 24h of exposure using flow cytometry. Expression of interleukin-6, interleukin-8, cyclooxygenase-2, caspase-8, osteoprotegerin and receptor activator of nuclear factor kappa-B ligand (RANKL) by osteoblastic cells were analysed after exposure for 1, 3 and 21days using real-time quantitative polymerase chain reaction assay RESULTS: Metal ions in concentrations representing the platform-matched groups led to a reduction in cell viability (P<0.01) up to 7days of exposure. Stimulated cells showed higher rates of early apoptosis (P<0.01) compared to non-treated cells. Metal ions up-regulated the expression of interleukin-6, interleukin-8, cyclooxygenase-2 and RANKL in a dose dependent manner after 1day of exposure (P<0.05). The up-regulation was more pronounced in the groups containing the corrosion products of platform-matched implant-abutment couples., Conclusion: Osteoblastic cell viability, apoptosis, and regulation of bone resorbing mediators were significantly altered in the presence of metal ions. The change in cytokine levels expressed was directly proportional to the metal ion concentration., Clinical Significance: The observed biological responses to decreased amounts of metal ions released from platform-switched implant-abutment couples compared to platform-matched couples may partly explain the positive radiographic findings in respect to crestal bone level when utilising the "platform-switching" concept, which highlights the possible role of corrosion products in the mediation of crestal bone loss around dental implants., (Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Orthodontic brackets made from stainless steel were introduced in dentistry, though they have less ability in reducing enamel demineralization and are not successful in preventing microbial as well as biofilm growth. In this study, we evaluated the significant role of different brackets in reducing enamel demineralization indirectly. Results from different tests indicate the significant reduction in adhesion, biofilm formation and slow growth of tested bacterial species on brackets coated with Ag + TiO2 and found to be statistically significant lower than control. There was no loss in cell viability in all brackets indicating that the cells are biocompatible with different bracket materials. Scanning electron microscopy showed less bacteria attached with the surface coated with Ag + TiO2 indicated that bacteria were losing adherent nature on coated surface. In conclusion, TiO2+Ag coating on stainless steel brackets possessed anti-adherent properties and also have demonstrable antibacterial properties therefore helps in preventing dental caries and plaque accumulation indirectly. The cell compatibility of TiO2+Ag coated brackets is superior to the uncoated samples therefore can be used in orthodontics as it not only provide suitable antimicrobial activity and resistance to biofilm formation but also sustained the cell viability of human gingival fibroblast (HGF) cell lines., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The scaling behavior of Ti-Ni-Cu shape memory thin-film micro- and nanowires of different geometry is investigated with respect to its influence on the martensitic transformation properties. Two processes for the high-throughput fabrication of Ti-Ni-Cu micro- to nanoscale thin film wire libraries and the subsequent investigation of the transformation properties are reported. The libraries are fabricated with compositional and geometrical (wire width) variations to investigate the influence of these parameters on the transformation properties. Interesting behaviors were observed: Phase transformation temperatures change in the range from 1 to 72 °C (austenite finish, (A f ), 13 to 66 °C (martensite start, M s ) and the thermal hysteresis from -3.5 to 20 K. It is shown that a vanishing hysteresis can be achieved for special combinations of sample geometry and composition.

Objective: To biomechanically test a new elastic slot system and V-wire mechanics., Materials and Methods: Conventional twin and self-ligating brackets and the new elastodynamic bracket were biomechanically tested. The conventional brackets had a rectangular 0.022'' slot and the new elastodynamic bracket had a V-slot, a new slot geometry. Torque measurements were performed with 0.018'' × 0.025'' and 0.019'' × 0.025'' stainless steel (ss) archwires. A nickel-titanium V wire was used for the biomechanical measurements on the elastodynamic bracket. The measurements were done with the aid of a six-component measuring sensor., Results: The results of the biomechanical testing revealed play in the brackets with rectangular slot geometry. The V slot in the elastodynamic bracket assured that the wire fit perfectly in the slot. Dynamic moments of 5 to 10 Nmm were transmitted without any play. No permanent deformation of the slot occurred in the new elastodynamic bracket because of the elastic slot., Conclusion: Control of torque for three-dimensional positioning of the teeth in the dental arch with rectangular slot geometry as used in straight-wire therapy is difficult. If torque is bent into the wire, because of the play there is a high risk that either too much, too little, or no moment is transmitted to the teeth. The V-slot archwire/bracket geometry in conjunction with nickel titanium composition has no play and allows a reduction of forces and moments with direct and continuous transmission of torque in the bracket. Because of the elasticity of the bracket, there is an upper limit to the moment possible.

A technique is described to generate a framework for an implant-supported fixed complete denture. The main advantage of the described technique is the low production cost of a framework that has high strength, passive fit, and distinct retentive structures for each denture tooth., (Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

In order to obtain material with low elastic modulus, good abrasion resistance and high corrosion stability as screw for dental implant, the biomedical Zr-20Nb and Zr-20Nb-3Ti alloy with low elastic modulus were thermal oxidized respectively at 700°C for 1h and 600°C for 1.25h to obtain the compact oxidized layer to improve its wear resistance and corrosion resistance. The results show that smooth compact oxidized layer (composed of monoclinic ZrO 2 , tetragonal ZrO 2 and 6ZrO 2 -Nb 2 O 5 ) with 22.6μm-43.5μm thickness and 1252-1306HV hardness can be in-situ formed on the surface of the Zr-20Nb-xTi (x=0, 3). The adhesion of oxidized layers to the substrates is determined to be 58.35-66.25N. The oxidized Zr-20Nb-xTi alloys reveal great improvement of the pitting corrosion resistance in comparison with the un-oxidized alloys. In addition, the oxidized Zr-20Nb-3Ti exhibits sharply reduction of the corrosion rates and the oxidized Zr-20Nb shows higher corrosion rates than un-oxidized alloys, which is relevant with the content of the t-ZrO 2 . Wear test in artificial saliva demonstrates that the wear losses of the oxidized Zr-20Nb-xTi (x=0, 3) are superior to pure Ti. All of the un-oxidized Zr-20Nb-xTi (x=0, 3) alloys suffer from serious adhesive wear due to its high plasticity. Because of the protection from compact oxide layer with high adhesion and high hardness, the coefficients of friction and wear losses of the oxidized Zr-20Nb-xTi (x=0, 3) alloys decrease 50% and 95%, respectively. The defects on the oxidized Zr-20Nb have a negative effect on the friction and wear properties. In addition, after the thermal oxidation, compression test show that elastic modulus and strength of Zr-20Nb-xTi (x=0, 3) increase slightly with plastic deformation after 40% of transformation. Furthermore, stripping of the oxidized layer from the alloy matrix did not occur during the whole experiments. As the surface oxidized Zr-20Nb-3Ti alloy has a combination of excellent performance such as high chemical stability, good wear resistance performance and low elastic modulus, moderate strength, it is considered an alternative material as dental implant., (Copyright © 2017 Elsevier B.V. All rights reserved.)