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Electrochemical impedance spectroscopy (EIS) has been used to obtain insight into corrosion processes for three Pd-Ag alloys, and compare their behavior with an Au-Pd alloy. Five specimens of each alloy received clinically-appropriate simulated porcelain-firing heat treatment. EIS testing was performed at ambient temperature, using 0.09% NaCl, 0.9% NaCl and Fusayama solutions. EIS data are presented as Bode plots. At the open-circuit potential (OCP), the data fit a modified Randles equivalent electrical circuit with a constant phase element (CPE), and the charge-transfer resistance (R CT ) and the two CPE parameters (CPE-T and CPE-P) were determined. The area-normalized capacitance of the double layer (C dl ) was also calculated. The EIS data at two relevant elevated potentials in the passive range were also found to fit well a modified Randles equivalent circuit with different values for the charge transfer resistance and CPE parameters. At the OCP no significant effect on R CT was found for the alloys and electrolytes, and both alloy and electrolyte significantly affected CPE-P. In vitro corrosion was controlled by charge transfer and charge accumulation processes, and the behavior differed at the elevated potentials compared to the OCP. Significant effects were found for alloy, electrolyte, and alloy/electrolyte interaction on C dl at the OCP. The EIS parameters at elevated potentials indicate that the Pd-Ag alloys should have satisfactory clinical corrosion resistance. The EIS analyses yielded information about in vitro corrosion of these alloys that cannot be obtained from potentiodynamic polarization testing., (© 2021 Wiley Periodicals LLC.)

Statement of Problem: The in vivo release of Pd from palladium alloys into the oral environment and sensitivity reactions by patients has been of concern. However, little information is available about the variation in elemental release from different palladium alloys., Purpose: The purpose of this in vitro study was to compare the elemental release into a corrosion-testing medium from a high-palladium alloy (Freedom Plus, 78Pd-8Cu-5Ga-6In-2Au) and a Pd-Ag alloy (Super Star, 60Pd-28Ag-6In-5Sn) under different conditions., Material and Methods: Alloys were cast into Ø12×1-mm-thick disks, subjected to simulated porcelain-firing heat treatment, polished, and ultrasonically cleaned in ethanol. Three specimens of each alloy were immersed for 700 hours in a solution for in vitro corrosion testing (ISO Standard 10271) that was maintained at 37 °C. Two solution volumes (125 mL and 250 mL) were used, and the solutions were subjected to either no agitation or agitation. Elemental compositions of the solutions were analyzed by using inductively coupled plasma-mass spectroscopy (ICP-MS). Concentrations of released elements from each alloy for the 2 solution volumes and agitation conditions were compared by using the restricted maximum likelihood estimation method with a 4-way repeated-measures ANOVA, the Satterwhite degrees of freedom method, a lognormal response distribution, and the covariance structure of compound symmetry., Results: For the 4 combinations of solution volume and agitation conditions, the mean amount of palladium released was 3 orders of magnitude less for the Pd-Ag alloy (0.009 to 0.017 μg/cm 2 of alloy surface) compared with the Pd-Cu-Ga alloy (17.9 to 28.7 μg/cm 2 ). Larger mean amounts of Sn, Ga, Ag, and In (0.29 to 0.39, 0.57 to 0.83, 0.71 to 1.08, and 0.91 to 1.25 μg/cm 2 , respectively) compared with Pd were released from the Pd-Ag alloy. Smaller amounts of Cu, Ga, and In (4.8 to 9.9, 5.9 to 12.8, and 4.2 to 9.5 μg/cm 2 , respectively) compared with Pd were released from the Pd-Cu-Ga alloy. The Ru released was much lower for the Pd-Ag alloy (0.002 μg/cm 2 ) than the Pd-Cu-Ga alloy (0.032 to 0.053 μg/cm 2 ). Statistically significant differences (P<.001) in elemental release were found for the factors of alloy and element and the alloy×element interaction. Significant differences were found for the solution volume (P=.022), solution volume×element interaction (P=.022), and alloy×solution volume×element interaction (P=.004). No significant effect was found for agitation condition., Conclusions: The relative amounts of released elements from each alloy were not proportional to the relative amounts in the composition. The amounts of Pd and Ga released from the Pd-Cu-Ga alloy were consistent with the breakdown of a Pd 2 Ga microstructural phase and perhaps some dissolution of the palladium solid solution matrix. Precipitates, rather than the palladium solid solution matrix, appeared to undergo greater dissolution in the Pd-Ag alloy. The Pd-Ag alloy should have lower risk of adverse biological reactions than the Pd-Cu-Ga alloy., (Copyright © 2021 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Purpose: To perform a finite element analysis (FEA) and an in vitro experiment to investigate and compare the loading effects (effects on the implant and surrounding bone) of various customized angled abutments to commercial 15-degree angled abutments (control). Materials and Methods: Four customized angled abutment models (21.9, 24.15, 20.22, and 33 degrees) were developed using CBCT images of incisor inclination measurements from patients of various age groups (20 to 23, 24 to 39, and 40 to 65 years). 3D maxillary bone models were created from the CBCT images of four individual patients: One patient from each age group with the respective average incisor inclination measurement and another patient with the overall average were selected. Then, FEA and in vitro strain gauge experiments were conducted by applying 100 N or 50 N of axial or oblique force to each model in order to assess the differences in stress/strain between the customized angled abutments (test) and the control in both the implants and surrounding bone. Results: Under axial loading, the stress values in the implant and surrounding bone were elevated due to the relatively higher angles of the customized angled abutments (21.9, 24.15, 20.22, and 33 degrees) compared to the control angled abutments. Under oblique loading, the control angled abutments exhibited higher stress values in both the implant and surrounding bone. For the in vitro experiment, there was no statistically significant difference in bone strain between the customized (21.9 degree) and the control angled abutments in axial loading. Nevertheless, the control angled abutment with oblique loading induced greater bone strains. Conclusions: Customized angled abutments offer lower stress/strain under oblique loads but higher stress/strain under axial loads compared to the control abutments. Therefore, in the design and application of angled abutments, careful consideration of the occlusal load direction is important for achieving the biomechanical success of an implant. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the tensile strength of five different thicknesses of two resin cements placed between two :tanium surfaces, before and a

This review article presents an evolution of the nickel-titanium wires for orthodontics, following their introduction by the pioneering studies of Andreasen. The original nonsuperelastic wires were followed by the introduction of superelastic Japanese NiTi wire by Miura and colleagues and Chinese NiTi wire by Burstone and colleagues. Subsequently, new nickel-titanium wires with true shape memory in the oral environment were introduced. Manufacturers have marketed special heat-treated wires with variable force delivery at different positions along the archwire. Ion implantation and other surface modification techniques have been used by manufacturers to reduce in vivo nickel release from the nickel-titanium wires, provide a more esthetic appearance, decrease friction, and improve corrosion resistance. The use of several research techniques to provide supporting information about the structures and transformations, mechanical properties, and clinical failure for the different types of the nickel-titanium wires are summarized. The evolution of the ADA/ISO standard for evaluation of these wires is also described. The closing section focuses on the use of surface modification and special coatings for the nickel-titanium wires, a major recent and ongoing area of active research., (Copyright © 2020 World Federation of Orthodontists. Published by Elsevier Inc. All rights reserved.)

Purpose: The aim of this study was to compare the integrity of zirconia, lithium disilicate, and zirconia-reinforced lithium silicate CAD-CAM crowns after being subjected to cyclic loading and then subjected to static loading until fracture., Material and Methods: Zirconia (Zirkonzahn), lithium disilicate (LDS, Ivoclar Vivadent AG), and zirconia-reinforced lithium silicate glass ceramic (ZLS) (Vita Suprinity, Vita Zahnfabrik) monolithic crowns were milled (n = 6). The crowns were bonded using composite resin cements and subjected to cyclic loading under wet conditions. Three specimens from each group were loaded for 10 000 cycles, and the other three specimens were loaded for 50 000 cycles with 250 N. Specimens were subjected to loading until fracture. Load-to-fracture values were analyzed with 2-way (ANOVA) and Tukey-Kramer post hoc test (α = 0.05). Specimens from each group were examined using an SEM., Results: Mean load-to-fracture values among materials were significantly different from each other (P < 0.05). No significant effect of the number of cycles was found on the load-to-fracture values of crowns (P > 0.05)., Conclusion: Load-to-fracture values of zirconia were higher than those of LDS, which were higher than those of ZLS. The number of fatigue loading cycles did not affect the load-to-fracture of the tested crowns for a given material., Clinical Significance: More research needs to be conducted before considering the routine use of ZLS for molars in patients with high risk of parafunctional habits., (© 2019 Wiley Periodicals, Inc.)

Purpose: The purpose of this in vitro study was to investigate the fracture loads and modes of failure for the full range of natural teeth under simulated occlusal loading., Materials and Methods: One hundred and forty natural teeth were taken from mandibles and maxillas of patients. There were 14 groups of teeth with 10 teeth in each group (5 males and 5 females). Each specimen was embedded in resin and mounted on a positioning jig, with the long axis of the tooth at an inclined angle of 30 degrees. A universal testing machine was used to measure the compression load at which fracture of the tooth specimen occurred; loads were applied on the incisal edge and/or functional cusp., Results: The mean fracture load for the mandibular first premolar was the highest (2002 N) of all the types of teeth, while the mean fracture load for the maxillary first premolar was the lowest (525 N). Mean fracture loads for the mandibular and maxillary incisors, and the first and second maxillary premolars, had significantly lower values compared to the other types of teeth. The mean fracture load for the teeth from males was significantly greater than that for the teeth from females. There was an inverse relationship between age and mean fracture load, in which older teeth had lower fracture loads compared to younger teeth., Conclusion: The mean fracture loads for natural teeth were significantly different, with dependence on tooth position and the sex and age of the individual.

Purpose: The aim of this study was to evaluate the extent of property changes caused by heating the distal portion of heat-activated nickel-titanium (NiTi) wires., Methods: Forty preformed heat-activated NiTi archwires (3M Unitek, Monrovia, CA, USA) with a nominal cross-section of 0.018″ were used in this study. The archwires were divided into a control group, not submitted to heat treatment and, thus, maintaining the as-received properties, and an experimental group, in which the archwires were submitted to heat treatment for distal bending at one end. Wire segments of control and experimental groups were submitted to differential scanning calorimetry (DSC) and Vickers microhardness measurements., Results: The DSC results suggest local recrystallization and precipitate dissolution at the heat-treated tip, which decreases as the distance to the wire's tip increases. Vickers microhardness tests revealed significant changes for distances between 6 and 8 mm from the wire's tip. Heating the distal portion of heat-activated NiTi archwires should be performed with care since this clinical procedure may compromise the performance of these wires to a distance of 8 mm from the archwire end., Conclusion: Heat treatment for distal bending in heat-activated NiTi archwires may be performed, with little impact on the areas adjacent to heat treatment. In cases presenting molars requiring significant orthodontic corrections, it should be preferred to apply other techniques to avoid archwire sliding, such as crimpable stops, or to have flame control to avoid placing a heat-treated section in the tubes of these molars., (© 2024. The Author(s), under exclusive licence to Springer Medizin Verlag GmbH, ein Teil von Springer Nature.)

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.)

Statement of Problem: Computer-aided design and computer-aided manufacturing (CAD-CAM)-fabricated titanium and zirconia implant-supported fixed dental prostheses have become increasingly popular for restoring patients with complete edentulism. However, the distortion level of these frameworks is not well known., Purpose: The purpose of this in vitro study was to compare the 3-dimensional (3D) distortion of CAD-CAM zirconia and titanium implant-fixed screw-retained complete dental prostheses., Material and Methods: A master edentulous model with 4 implants at the positions of the maxillary first molars and canines was used. Multiunit abutments (Nobel Biocare) secured to the model were digitally scanned using scan bodies and a laboratory scanner (S600 ARTI; Zirkonzahn). Titanium (n=5) and zirconia (n=5) frameworks were milled using a CAD-CAM system (Zirkonzahn M1; Zirkonzahn). All frameworks were scanned using an industrial computed tomography (CT) scanner (Nikon/X-Tek XT H 225kV MCT Micro-Focus). The direct CT scans were reconstructed to generate standard tessellation language (STL) files. To calculate the 3D distortion of the frameworks, STL files of the CT scans were aligned to the CAD model using a sum of the least squares best-fit algorithm. Surface comparison points were placed on the CAD model on the midfacial aspect of all teeth. The 3D distortion of each direct scan to the CAD model was calculated. In addition, color maps of the scan-to-CAD comparison were constructed using a ±0.500 mm color scale range., Results: Both materials exhibited distortion; however, no significant difference was found in the amount of distortion from the CAD model between the materials (P=.747). Absolute values of deviations from the CAD model were evident in the x and y plane and less so in the z direction., Conclusions: Zirconia and titanium frameworks showed similar 3D distortion compared with the CAD model for the tested CAD-CAM and implant systems. The distortion was more pronounced in the horizontal and sagittal plane than in the vertical plane., (Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: The dimensions of implant-supported fixed cantilevered prostheses are important to prevent mechanical and biological complications. Information on the optimum thickness and cantilever length for improving the strength of zirconia cantilevered frameworks is limited in the literature., Purpose: The purpose of this in vitro study was to investigate the effect of cantilever length and occlusocervical thickness on the load-to-fracture and strain distribution of zirconia frameworks., Material and Methods: Twenty-seven rectangular prism-shaped specimens (6 mm thick buccolingually) were fabricated using a computer-aided design and computer-aided manufacturing (CAD-CAM) milling technique. The specimens were prepared in 9 groups (n=3) according to their vertical dimensions (6×6 mm, 8×6 mm, and 10×6 mm) and cantilever loading distance (7 mm, 10 mm, and 17 mm). All specimens were heat treated in a porcelain furnace and thermocycled for 20000 cycles before the tests. Each framework was secured using a clamp attached to the first 20 mm of the framework. A 3-dimensional image correlation technique was used for a full-field measurement of strain during testing. A load-to-fracture test was used until the specimens fractured. Maximum force and principal strain data were analyzed by 2-way analysis of variance using the maximum likelihood estimation method (α=.05)., Results: No statistically significant effects (P>.05) were found for occlusocervical thickness and cantilever length or between them on the strain distribution. The results showed that the effect of occlusocervical thickness and cantilever length was significant on the load to fracture (P<.001). No statistically significant interaction was observed between the 2 factors (P>.05)., Conclusions: Increased occlusocervical thickness and decreased cantilever length allowed the cantilever to withstand higher loads. The occlusocervical thicknesses and cantilever lengths of zirconia frameworks tested withstood the maximum reported occlusal force. The properties of components in the implant-abutment framework assembly should be considered in the interpretation of these results., (Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

In this study, wear and inhibition of enamel demineralization by resin-based coating materials were investigated. Seven commercially available coating materials, with and without fillers, were used. A mechanical wear test was performed, and the specimens were then examined with a scanning electron microscope. Hardness and elastic modulus measurements for each material were obtained by nanoindentation testing. Thin layers of each material were applied on human enamel surfaces, which were subjected to alternating immersion in demineralizing and remineralizing solutions. The inhibition ability of enamel demineralization adjacent to the coating was estimated with depth-dependent mechanical properties using the nanoindentation test. The non-filled coating material showed significantly lower hardness, lower elastic modulus, and higher weight loss. There were no significant differences in weight loss among the six filled coating materials. After the alternating immersion protocol, the enamel specimens having application of coating materials with ion-releasing ability were harder than those in the other groups in some locations 1-11 μm from the enamel surface and within 300 μm from the edge of the coating materials. In conclusion, clinical use of the resin-based coating materials with ion-releasing ability may prevent demineralization of exposed enamel adjacent to the coating during treatment., (© 2017 Eur J Oral Sci.)

The objective of the current study was to examine whether peri-implant bone tissue properties are different between the buccal and lingual regions treated by growth factors. Four dental implant groups were used: titanium (Ti) implants, alumina-blasted zirconia implants (ATZ-N), alumina-blasted zirconia implants with demineralized bone matrix (DBM) (ATZ-D), and alumina-blasted zirconia implants with rhBMP-2 (ATZ-B). These implants were placed in mandibles of six male dogs. Nanoindentation elastic modulus (E) and plastic hardness (H) were measured for the buccal and lingual bone tissues adjacent and away from the implants at 3 and 6 weeks post-implantation. A total of 2281 indentations were conducted for 48 placed implants. The peri-implant buccal region had less bone quantity resulting from lower height and narrower width of bone tissue than the lingual region. Buccal bone tissues had significant greater mean values of E and H than lingual bone tissues at each distance and healing period (p<0.007). Nearly all implant treatment groups displayed lower mean values of the E at the lingual bone tissues than at the buccal bone tissues (p<0.046) although the difference was not significant for the Ti implant group (p=0.758). The DBM and rhBMP-2 treatments stimulated more peri-implant bone remodeling at the lingual region, producing more immature new bone tissues with lower E than at the buccal region. This finding suggests that the growth factor treatments to the zirconia implant system may help balance the quantity and quality differences between the peri-implant bone tissues., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Objective: Measure and compare the mechanical properties, translucency, and fluoride-releasing capabilities of EQUIA Forte HT against Fuji IX GP and ChemFil Rock., Materials and Methods: Ten specimens of each material were fabricated for compressive strength (CS), flexural strength (FS), and surface hardness analysis at 24 h and 7 days. The L*a*b* values were measured against a black-and-white background using a spectrophotometer to analyze the translucency parameter (TP). Fluoride release was recorded after 2 months of immersion in distilled water. The mean data was analyzed by 1- and 2-way ANOVA (α = 0.5)., Results: EQUIA Forte HT showed higher CS, surface hardness, and FS values (p < 0.05) compared with Fuji IX GIC, while no significant difference was found in FS values between EQUIA Forte HT and Chemfil Rock (p > 0.05). The EQUIA Forte HT exhibited significantly higher translucency in comparison to both ChemFil Rock (p < 0.001) and Fuji IX GICs (p < 0.05). An increase (p > 0.05) of fluoride release was observed for EQUIA Forte HT., Conclusion: The EQUIA Forte HT Glass-ionomer cements (GIC) offers enhanced translucency, improved strength, and enhanced fluoride-releasing properties compared to the traditionally used Fuji IX GIC and ChemFil Rock GICs. This material might have a wide range of clinical applications due to its improved strength and optical properties., Clinical Significance: Glass-ionomer dental restorative materials possess unique advantageous characteristics. However, its poor mechanical and optical properties have typically limited its clinical applications. Efforts to improve these properties have resulted in enhanced GICs. EQUIA Forte HT GIC offers enhanced mechanical and optical properties with potential applications in posterior and anterior restorative procedures., (© 2023 Wiley Periodicals LLC.)

STATEMENT OF PROBLEM: Production of precisely fitting fixed partial denture implant superstructures with titanium alloys is limited by casting techniques that introduce distortion. After alignment of the framework with existing implants, the remaining misfit may generate stresses that cause screw loosening and adversely affect the implant/bone interface. PURPOSE: The purpose of this study was to prepare diffusion-bonded joints between superplastic (SP) Ti-6Al-4V plates and indenters (representing analogs to implant-supported fixed frameworks and abutments) and determine if this process has potential for producing strong, dimensionally precise prostheses. MATERIAL AND METHODS: Seven sets of trial indenter and plate specimens with dimensions of 6.4 mm x 6.4 mm x 5 cm and 8.5 mm x 1.5 cm, respectively, were prepared. Several indenter designs were used (35- or 45-degree half-angle, presence or absence of a notch, and SP versus no SP condition for Ti-6Al-4V); all plates were prepared from SP Ti-6Al-4V. For the results-guided experimental design, there was 1 trial indenter/plate combination for each design/processing condition. Diffusion bonding was performed at 10(-6) Torr, while the temperature was increased 10 degrees C/min to 900 degrees or 920 degrees C. Following 10 minutes of equilibration, the indenter was pressed 2.5 mm into the plate at 0.13 mm/min. Joint strength was evaluated in tension, and the ductile or brittle character of fracture surfaces was assessed by the presence or absence of a dimpled rupture surface from secondary electron SEM observations. Fractured specimens were cross-sectioned and examined with an optical microscope to evaluate overall joint integrity and quality, and used for Vickers hardness measurements to gain insight into the variation in mechanical properties of the indenter and plate with distance from the joint. One-way ANOVA (alpha=.05) was used to compare hardness at the joint for the trial specimen with highest joint strength with hardness values for adjacent regions at 125-mum intervals in the indenter and plate. The Ryan-Einot-Gabriel-Welsch (REGW) multiple range test was used to identify any specific location having significantly (alpha=.05) different hardness. Backscattered electron SEM observations were also performed on the cross-sectioned specimens to investigate whether a layer of alpha-stabilized titanium, which would decrease joint strength, was present. Fits of Ti-6Al-4V implant analogs prepared by this diffusion-bonding process were assessed qualitatively from visual observation. RESULTS: The maximum joint strength of 820 MPa was achieved for a diffusion bonding temperature of 900 degrees C for an SP Ti-6Al-4V indenter with a 35-degree half-angle and no notch. This joint strength is nearly 90% of the maximum tensile strength of the parent Ti-6Al-4V, which can range from approximately 930 to 1015 MPa. The hardness at the joint was significantly higher (P<.05) than the hardness of the indenter and plate at 125-mum distances from the joint. The mean hardness of the indenter at 125 mum from the joint was significantly greater (P<.05) than the mean hardness of the plate at a distance of 500 mum from the joint. All other mean hardness values at the different measurement distances from the joint were not significantly different. Ductile fracture occurred for all superplastic processing conditions, and no alpha-titanium layer was present. Minimal asperities were observed with the optical microscope, and fits of implant prosthesis analogs were considered acceptable. CONCLUSIONS: A 900 degrees C processing condition for diffusion-bonding an SP Ti-6Al-4V indenter with a 35-degree half-angle and no notch to a Ti-6Al-4V SP plate yielded a joint with nearly the same strength as the parent alloy. Use of this processing temperature with a 0.13 mm/min rate of pressing the indenter into the plate yielded minimal distortions for implant prosthesis analogs when observed visually. [ABSTRACT FROM AUTHOR]

The purpose of this article is to examine the soundness of conventional orthodontic bonding assessment methods. A classification of bond strength studies is proposed with the testing environment (in vivo, in vitro, and ex vivo), loading mode (shear, tensile, and torsion), and bonding substrate (enamel, restorative, and prosthetic materials) serving as discriminating variables. Inconsistencies, throughout the various stages of research protocols are analysed. These include the following: tooth selection, storage, and preparation; bonding; testing; and data analysis with regard to the clinical applicability of the reported information, as well as the scientific integrity of the testing procedure. Contradictory models may partially account for the considerable variability noted for reported bond strength values of different orthodontic bonding systems. Such discrepancies may also explain the conflicting evidence reported on the failure characteristics of the components of the bonding system in different trials examining the efficacy of nominally identical materials. A novel approach to study the fatigue life of materials is proposed to understand the processes occurring prior to bond failure. Mock research data manipulation is also utilized to illustrate the correct statistical treatment of findings, and recommendations for future research are made to ensure scientific soundness and clinical applicability of data. [ABSTRACT FROM AUTHOR]

Purpose: This study investigated and compared the bond strengths, microleakage, microgaps, and marginal adaptation of self-adhesive resin composites (SAC) to dentin with or without universal adhesives. Materials and Methods: Dentin surfaces of 75 molars were prepared for shear and microtensile bond strength testing (SBS and μTBS). Silicon molds were used to build up direct restorations using the following materials to form 5 groups: 1. Surefil One; 2. Prime&Bond active Universal Adhesive + Surefil One; 3. Vertise Flow; 4. OptiBond Universal + Vertise Flow; 5. Scotchbond Universal + Filtek Z500 (control group). Bonded specimens were thermocycled 10,000x before being tested either for SBS or μTBS using a universal testing machine at a crosshead speed of 0.5mm/min. Direct mesial and distal class-II cavities were created on 100 sound premolars, with the gingival margin of distal cavities placed below CEJ and restored according to the five groups. After thermocycling, microleakage scores were assessed following immersion of restored premolars in 2% methylene blue dye for 24h, while marginal gaps and adaptation percentages were investigated on epoxy resin replicas under SEM at magnifications of 2000X and 200X, respectively. Results were statistically analyzed with parametric and non-parametric tests as applicable, with a level of significance set at a = 0.05. Results: Bond strengths, microleakage scores, microgaps, and percent marginal adaptation of Surefil One and Vertise Flow were significantly (p<0.001) inferior to the control group. Dentin preconditioning with universal adhesives significantly increased the study parameter outcomes of Surefil One and Vertise Flow, yet they were still significantly below the performance of the control group. Conclusion: Conventional resin composite outperformed the SAC whether applied solely or in conjunction with their corresponding universal adhesives. [ABSTRACT FROM AUTHOR]

Background: This study aims to compare design, phase transformation behavior, and torsional resistance of the ProGlider (PG) and ProTaper ultimate slider (PUS) and to compare the performance of two files in the glide-path preparation of a double-curved artificial canal. Methods: Scanning electron microscopy, micro-computed tomography, and differential scanning calorimetry were used to characterize the samples. A torsional resistance test was performed to obtain ultimate strength and distortion angle. Simulated glide-path preparation was conducted with a double-curved resin canal, and both PG and PUS were operated on by 300 and 400 rpms. Maximum screw-in force, torque generated during canal shaping, number of pecking strokes to reach the apex were compared between groups. After canal shaping centering ratio and alteration of files were assessed. Statistical analyses were performed using the Mann-Whitney U test, and the Kruskal-Wallis test with Bonferroni correction. A p value less than 0.05 was considered significant. Results: While the PG had a square cross-section, the PUS had variable square and rhomboid cross-sections and alternating cutting-edge. PG and PUS have austenitic transformation starting and finishing temperatures of 24–25℃, and 57–59℃, respectively. Ultimate strength of PUS are superior to that of PG, whereas the distortion angle of PG is greater than that of PUS (p < 0.05). The maximum screw-in force and clockwise torque generated during glide-path preparation were highest in the PUS group rotated at 300 rpm (p < 0.05). Shaping with the PG at 300 rpm and shaping with the PUS at 400 rpm exhibited comparable maximum screw-in forces. There were no significant differences in the number of pecking strokes to reach the apex and centering ability among groups shaped with PG and PUS at both rotation speeds. PG shaped at 400 rpm demonstrated severe alteration on its surface, while PUS shaped at 300 and 400 rpms exhibited comparable surface alterations. Conclusions: PG has a constant square cross-section, while PUS has a variable cross-section and alternating cutting-edge. Using PUS at recommended speed of 400 rpm ensures safe use with minimal screw-in force and surface alteration. At recommended speeds, both PG and PUS perform comparably and are safe for double-curved canals. [ABSTRACT FROM AUTHOR]

Background: Increasing demand for durable and aesthetically pleasing dental restorations, including laminates, inlays, onlays, and crowns, has led to advancements in all-ceramic systems, particularly with the development of advanced lithium disilicate materials. However, limited data on the fit accuracy and fracture resistance of these materials restricts their wider application in clinical restorative practices. Aim of the study: This in vitro study aims to compare the marginal and internal fit, assess the fracture resistance, and evaluate the failure modes of crowns fabricated from advanced and conventional lithium disilicate materials. Materials and methods: Thirty two (n = 32) crowns were fabricated and categorized into two groups based on the material used: Group (CT), where crowns were milled from CEREC Tessera (n = 16), and Group (EM), where crowns were milled from IPS e.max CAD (n = 16) using a CAD/CAM system. The marginal and internal fit were assessed digitally via a triple scan protocol. All samples were subjected to a fracture resistance test with a universal testing machine, followed by an analysis of failure modes under a stereomicroscope. Results: In the evaluation of marginal, internal and total gaps, CEREC Tessera (CT) showed slightly better fit with lower gap values compared to e.max CAD (EM). However, an independent samples t-test indicated no statistically significant differences between the two groups (p = 0.141, p = 0.471). For fracture resistance (N), the CT group demonstrated higher values than the EM group; however, the independent samples t-test indicated no statistically significant difference (p = 0.053). Additionally, the Chi-squared test with Monte Carlo correction revealed no statistically significant differences in the modes of fracture between the two groups (p = 0.484). Conclusion: Considering the limitations of this study, advanced lithium disilicate crowns demonstrated better results in terms of marginal fit, internal adaptation, and fracture resistance compared to traditional lithium disilicate crowns; however, the differences were not statistically significant. Both materials exhibited comparable fracture patterns. [ABSTRACT FROM AUTHOR]

Background: Mini-screws are valuable devices in orthodontic treatment as they allow effective anchorage. Relocation of a mini-screw may be required due to anatomical limitations. Objectives: To compare the morphology and surface characteristics of three brands of mini-screws before and after use and to check their viability for reinsertion. Methodology: Mini-screws of three commercially available brands, Group I: Orlus, Ortholution, Korea, Group II: Absoanchor, Dentos, Korea, and Group III: S.K. surgical, India, were evaluated for the sharpness of their threads and active tip, surface roughness, and surface chemical composition using scanning electron microscope (SEM)–energy dispersive spectroscope (EDS) before and after clinical use. Results: The sharpness of threads did not differ before and after use in any of the groups. The mean tip deformation values in Groups II and III post-insertion were significantly higher than pre-insertion. The SEM images obtained post-insertion revealed loss of gloss and surface finish with a dull appearance in all groups, but most evident in Group I. EDS analysis post-retrieval shows an increase in the amount of carbon and oxygen in Groups II and III. Conclusion: Mini-screw reuse within the same patient is possible if proper recycling is done, and pilot drilling is done to overcome the decreased cutting ability of the tip due to deformation. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HA) is an engineered biomaterial that closely resembles the hard tissue composition of humans. Biological HA is commonly non-stoichiometric and features lower crystallinity and higher solubility than stoichiometric HA. The chemical compositions of these biomaterials include calcium (Ca), phosphorus (P), and trace amounts of various ions such as magnesium (Mg2+), zinc (Zn2+), and strontium (Sr2+). Significantly, these ions are essential for the metabolic processes of hard tissues. This study involved the application of Co2+-doped HA coatings at different concentrations (5%, 10%, and 20% by weight) onto Ti-6Al-4V, utilizing the spin-coating method. The FTIR, XRD, FESEM, EDS, and AFM techniques were utilized to analyze the coated substrates. Tetraethyl orthosilicate (TEOS (T)) was employed as a binding agent to enhance adhesion and reduce surface cracks in the coating. The adhesion strength of coatings applied to Ti-6Al-4V was assessed for use in biomedical applications. Polarization and electrochemical impedance spectroscopy (EIS) studies in a simulated body fluid (SBF) solution were conducted to evaluate the corrosion behavior of the coatings. The corrosion behavior of the coated samples increased significantly compared to the substrate. The 10Co/HA/T coating demonstrated the highest charge transfer resistance (Rct) value of 13.40 MΩ × cm2, whereas the uncoated substrate exhibited the lowest Rct of 0.14 MΩ × cm2. A cell viability assay was conducted utilizing MG-63 cells for the Ti-6Al-4V and coatings, which prepared coatings demonstrated outstanding biocompatibility. Based on this study, the 10Co/HA/T coating was identified as the most promising sample. These findings suggest that surface modification of Ti-6Al-4V through Co2+-doped HA coatings offers a viable strategy for enhancing its performance in biomedical applications. [ABSTRACT FROM AUTHOR]

Background: Clear aligner treatment (CAT) has emerged as an effective alternative to conventional multibracket systems in orthodontics. The trimline design and extension of aligners may significantly influence their biomechanical performance and tooth movement efficacy. Aim: To systematically review the biomechanical effects of different aligner trimline designs and extensions on orthodontic tooth movement. Methods: A systematic search was conducted across PubMed, Scopus, Embase, ProQuest Dissertations & Theses Global, and Google Scholar for studies published between January 2000 and August 2024. The review included any types of empirical research focusing on the influence of trimline of orthodontic aligners on tooth movement efficacy conducted between January 2000 and August 2024. The Risk of Bias In Non-randomized Studies of Interventions (ROBINS-I) tool was used for quality assessment. Results: Twelve studies met the inclusion criteria, all assessed as having low to moderate risk of bias. Aligner trimline design significantly influenced orthodontic tooth movement efficacy through two primary mechanisms: enhanced force delivery and increased aligner retention. Aligners with straight and extended margins generally exerted higher forces and moments compared to scalloped or shorter designs. This resulted in greater tooth displacement for certain movements, particularly intrusion, translation, tipping, and root torquing. Extended trimlines also demonstrated superior retention. However, the effects varied depending on the type of tooth movement. Conclusion: Aligner trimline designs and extensions can significantly influence biomechanical performance and tooth movement efficacy in CAT. Straight extended trimlines generally demonstrate superior force delivery and retention, leading to more predictable clinical outcomes. This could reduce the need for revisions, thereby decreasing overall treatment time and increasing patient satisfaction. However, further research is needed to investigate the interactions between aligner trimline designs and other factors to develop evidence-based guidelines for their optimal combination in various clinical scenarios. [ABSTRACT FROM AUTHOR]

Background: Nickel titanium (NiTi) rotary files have drastically altered the treatment protocol in endodontics, allowing for faster and easier preparation and more thorough irrigation of the root canal system. Despite the advantages of the NiTi files, instrument separation still remains a major concern. The aim of this study was to compare the cyclic fatigue resistance of three different single-file NiTi systems after clinical use: WaveOne Gold (WOG, Dentsply Maillefer, Ballaigues, Switzerland), One Curve (OC, Micro Mega, Besancon, France), and Reciproc Blue (RPC Blue, VDW, Munich, Germany). Methods: A total of 120 patients requiring endodontic treatment to first or second mandibular molars, were randomly divided into three groups (patient n = 40) and root canals were prepared with WOG, OC or RPC Blue. Each group consists of 2 subgroups: first use (file n = 10, patient n = 10) and third use of file (file n = 10, patient n = 30). In control group, files were subjected to cyclic fatigue test without use (file n = 10). Cyclic fatigue resistance of files was assessed by groove method. The data was evaluated by two-way ANOVA, Games & Howell post hoc and Weibull reliability analyses (p <.05). Results: RPC Blue files showed the highest failure time value in all groups. In third use group, OC and RPC Blue files showed significantly higher failure time values compared to WOG files (p <.05). In general, RPC Blue files show the highest values in terms of number of cycles to fracture (NCF) in all groups, while OC and WOG files follow RPC Blue files respectively. There was statistically significant difference among groups considering the fragment length (p <.05). Conclusions: Within the limitations of this study, RPC Blue files exhibited highest cyclic fatigue resistance after clinical use. [ABSTRACT FROM AUTHOR]

OBJECTIVE: This study aimed at determining the effect of pH changes on nickel titanium wire seen based on the corrosion rate and surface roughness of the wire after immersion in pandan leaves extract. MATERIAL AND METHODS: The sample used nickel titanium wire of 0.016 inches diameter and 5 cm length and consists of five treatment groups: control group, 0.2% chlorhexidine, and 1000 ppm, 2000 ppm, and 4000 ppm pandan leaves extract. The solutions were put into an incubator for 7, 14, and 21 days at 37 °C and removed according to the sample immersion time. The corrosion rate was determined using the weight-loss method, and microstructure roughness was analyzed using a scanning electron microscope. RESULTS: Kruskal–Wallis test showed that there was a significant difference in corrosion rate of orthodontic wires of nickel titanium after control submersion, 0.2% chlorhexidine, and pandan leaves extract on 7, 14, and 21 days (P ≤ 0.05), and pandan leaves extract submersion shows that the surface structure is not as bad as artificial saliva and 0.2% chlorhexidine. CONCLUSIONS: Pandan leaves extract could inhibit the corrosion rate of nickel titanium orthodontic wire, which might be due to tannin content as an active antioxidant. [ABSTRACT FROM AUTHOR]

Objective: The present study aimed to evaluate the phase transformation behavior and elemental analysis of thermomechanical-treated nickel–titanium (NiTi) rotary instruments, TruNatomy (Dentsply Sirona), HyFlex CM (coltene, Whaledent), and Neoendo Flex (Orikam healthcare India), using differential scanning calorimetry (DSC), X-ray diffraction (XRD), and energy dispersive X-ray spectrometry. Materials and Methods: A total of 18 NiTi rotary instruments, TruNatomy, Hyflex CM, Neoendo Flex, taper. 04, size 25 (except TruNatomy, size 26) were selected and were divided into three groups (n = 6). Three NiTi files from each group were investigated for the DSC test (n = 3). The two segments of each sample were cut carefully by slow-speed water-cooling carborundum disc at 3 mm from the tip and then 4 mm from the previous section. The mass of the samples was measured on the electronic balance and samples that weighed 10–15 mg were loaded into a 40 µL aluminum crucible. The samples are then subjected first to a heating cycle from 0°C to 100°C and subsequently a cooling cycle from 100°C to 0°C in the differential scanning calorimeter (Mettler-Toledo, NIT Srinagar) at a rate of 10°C min−1. XRD (Make. Rigaku Japan, smart lab 3kW, NIT Srinagar.) was performed to verify the DSC results. The remaining two samples from each group (n = 2) were subjected to XRD analysis. The sample preparation for XRD analyses was done precisely with slow speed water cooled carborundum disc and samples were sectioned into three segments. Each segment was 5 mm long and grounded to obtain a uniform smooth plane. The data obtained from DSC and XRD were subjected to origin 8.5 software and graphs were obtained that depict the transformation temperature and phase composition, respectively. Alloy distribution and trace elements of the NiTi rotary instruments were done using energy dispersive spectrometry microanalysis. Results: The DSC results showed that the TruNatomy, Hyflex CM, and Neo Endo instruments had an Austenite finish (Af) temperature exceeding 37°C. The XRD graphs show the different intensity peaks that correspond to the various phases of NiTi rotary instruments. The TruNatomy is predominantly Austenite, Hyflex CM exists mainly in R-phase with a variable amount of austenite and martensite, while Neoendo flex endo mostly contains austenite phase. The elemental analysis revealed that all three file systems show Nickel and Titanium within their bulk structure in an equiatomic ratio. Conclusion: This study concluded that TruNatomy is predominantly martensite with a variable amount of austenite phase. There are differences in thermal transition temperature between the files. [ABSTRACT FROM AUTHOR]

Objective: To investigate the effects of third-order torque on frictional properties of self-ligating brackets (SLBs)., Materials and Methods: Three SLBs (two passive and one active) and three archwires (0.016 × 0.022-inch nickel-titanium, and 0.017 × 0.025-inch and 0.019 × 0.025-inch stainless steel) were used. Static friction was measured by drawing archwires though bracket slots with four torque levels (0°, 10°, 20°, 30°), using a mechanical testing machine (n  =  10). A conventional stainless-steel bracket was used for comparison. RESULTS were subjected to Kruskal-Wallis and Mann-Whitney U-tests. Contact between the bracket and wire was studied using a scanning electron microscope., Results: In most bracket-wire combinations, increasing the torque produced a significant increase in static friction. Most SLB-wire combinations at all torques produced less friction than that from the conventional bracket. Active-type SLB-wire combinations showed higher friction than that from passive-type SLB-wire combinations in most conditions. When increasing the torque, more contact between the wall of a bracket slot and the edge of a wire was observed for all bracket types., Conclusions: Increasing torque when using SLBs causes an increase in friction, since contact between the bracket slot wall and the wire edge becomes greater; the design of brackets influences static friction.

Statement of Problem: New noble alloys for metal ceramic restorations introduced by manufacturers are generally lower-cost alternatives to traditional higher-gold alloys. Information about the metal-to-ceramic bond strength for these alloys, which is needed for rational clinical selection, is often lacking., Purpose: The purpose of this study was to evaluate the bond strength of 4 recently introduced noble alloys by using 2 techniques for porcelain application., Material and Methods: Aquarius Hard (high-gold: 86.1 gold, 8.5 platinum, 2.6 palladium, 1.4 indium; values in wt. %), Evolution Lite (reduced-gold: 40.3 gold, 39.3 palladium, 9.3 indium, 9.2 silver, 1.8 gallium), Callisto 75 Pd (palladium-silver containing gold: 75.2 palladium, 7.1 silver, 2.5 gold, 9.3 tin, 1.0 indium), and Aries, (conventional palladium-silver: 63.7 palladium, 26.0 silver, 7.0 tin, 1.8 gallium, 1.5 indium) were selected for bonding to leucite-containing veneering porcelains. Ten metal ceramic specimens that met dimensional requirements for International Organization for Standardization (ISO) Standard 9693 were prepared for each alloy by using conventional porcelain layering and press-on-metal methods. The 3-point bending test in ISO Standard 9693 was used to determine bond strength. Values were compared with 2-way ANOVA (maximum likelihood analysis, SAS Mixed Procedure) and the Tukey test (α=.05)., Results: Means (standard deviations) for bond strength with conventional porcelain layering were as follows: Aquarius Hard (50.7 ±5.5 MPa), Evolution Lite (40.2 ±3.3 MPa), Callisto 75 Pd (37.2 ±3.9 MPa), and Aries (34.0 ±4.9 MPa). For the press-on-metal technique, bond strength results were as follows: Aquarius Hard (33.7 ±11.5 MPa), Evolution Lite (34.9 ±4.5 MPa), Callisto 75 Pd (37.2 ±11.9 MPa), and Aries (30.7 ±10.8 MPa). From statistical analyses, the following 3 significant differences were found for metal-to-ceramic bond strength: the bond strength for Aquarius Hard was significantly higher for conventional porcelain layers compared with the press-on-metal technique; the bond strength for Aquarius Hard with conventional porcelain layers was significantly higher than the bond strengths for the other 3 alloys with conventional porcelain layers; and the bond strength for Aquarius Hard with conventional porcelain layers was significantly higher than the bond strength for Callisto 75 Pd with conventional porcelain layers and the other 3 alloys with the press-on-metal technique., Conclusions: For both conventional layering and press-on-metal techniques, all 4 noble alloys had a mean metal-to-ceramic bond strength that substantially exceeded the 25 MPa minimum in the ISO Standard 9693. The results for Aries support the manufacturer's recommendation not to use the press-on-metal technique for alloys that contain more than 10% silver., (Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Hydroxyapatite precipitation on nanotube surfaces of Ti-35Ta-xNb alloys was investigated using electrochemical methods. The alloys were prepared by arc-melting, heat treated at 1050 degrees C for 12 h in an Ar atmosphere, and quenched in 0 degrees C water. Nanotubes were created on the Ti-35Ta-xNb alloys in a 1 M H3PO4 + 1.2 wt.% NaF electrolyte at room temperature. Hydroxyapatite precipitation was carried out in a 0.03 M Ca(NO3)2 x 4H2O + 0.018 M NH4H2PO4 solution at 80 ± 1 degrees C, using 10 deposition cycles. Information about morphology and composition was obtained by FE-SEM and EDS. The microstructure of the Ti-35Ta-xNb alloys was transformed from α phase to βphase as the Nb content increased. The HA precipitates had a plate-like morphology on bulk Ti-35Ta-xNb alloys and a flower-like morphology on nanotubular Ti-35Ta-xNb alloys.

The purpose of this study was to investigate nanotube nucleation phenomena on the Ti-25Ta-xZr alloys for implant materials, using an anodic titanium oxide (ATO) technique. Ti-25Ta-(0 wt.%-15 wt.%) Zr alloys were prepared using a vacuum arc-melting furnace. The Ti-25Ta-xZr alloys were then homogenized for 12 hr at 1000 degrees C, followed by water quenching. Formation of the nanotubular oxide surface structure was achieved initially on the Ti-25Ta-xZr alloys by anodization in a 1 M H3PO4 electrolyte containing 0.8 wt.% NaF at room temperature, using a potentiostat. After the first formation of the nanotubes was achieved, this initial nanotube layer was eliminated, and further anodization was carried out repeatedly. The microstructure, phase transformation, and morphology of nanotubular Ti-25Ta-xZr alloys and the process of nanotube growth using this ATO method were analyzed by X-ray diffraction, field-emission scanning electron microscopy, and energy dispersive X-ray spectroscopy. Microstructures of the Ti-25Ta-xZr alloys changed from α" phase to β phase. Nanotubes formed with the ATO technique had pit-like top holes, with thinner walls and lower contact angle, compared to the initially formed nanotubes.

Purpose: To assess if the implant-retained prostheses produced with laser-sintering technique present an accuracy and passive fit comparable to their milled counterpart. Materials and Methods: Two regular neck Straumann analogs were placed in a block of PMMA 15 mm apart and parallel to each other. The PMMA block was then scanned and two groups of cobalt-chromium, screw-retained, three-unit implant prostheses were fabricated using milling (control) and laser-sintering (test) techniques. The prostheses were then screwed on the PMMA block and the verFcal marginal gap between the prostheses and the analogs at the implant-abutment juncFon was measured twice, (1) when only one screw was Fghtened, and (2) when both screws were fully Fghtened. The average of each marginal gap measurement was compared to assess the difference in term of passive fit between the laser-sintered and the milled prostheses. Results: The mean marginal gap of the milled and the laser-sintered groups were 23.18 µm (SD = 6.2) and 23.71 µm (SD = 19.5) respecFvely. Conclusions: Laser-sintered prostheses presented a marginal fit comparable to their milled counterpart and represent a clinically valid alternaFve to their milled counterpart. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the fracture-behavior of monolithic crowns made of lithium disilicate (IPS e.max CAD, Ivoclar Vivadent; IniBal LiSi Block, GC Dental) and zirconia-reinforced lithium silicate (Celtra Duo, DeguDent; VITA Zahnfabrik) materials before and aKer cyclic faBgue aging. Materials and Methods: Four groups (n = 22/group) of CAD/CAM fabricated upper incisor crowns were produced. All crowns were luted on metal dies with an adhesive dualcure resin cement (G-CEM LinkForce, GC Dental). Half of the crowns in each group (n = 11) were staBcally loaded unBl fracture, without aging. The remaining crowns were subjected to cyclic faBgue aging for 120,000 cycles (Fmax = 220 N) and then loaded staBcally unBl fracture. The fractured models were then visually examined. Scanning electron microsopy (SEM) and energy-dispersive spectroscopy (EDS) were used to evaluate the microstructure of CAD/CAM ceramic materials. The data were staBsBcally analyzed with two-way ANOVA followed by the Tukey HSD test (a = .05). Results: Before cyclic aging, there was no staBsBcally significant difference in load-bearing capacity among the four groups (P = .371). AKer cyclic aging, load-bearing capacity significantly decreased for all groups (P = .000). While the e.max CAD blocks had significantly higher load-bearing capacity (1061 ± 94 N) than both monolithic ceramic crowns (load-bearing capaciBes of the groups) (P < .05), no significant difference was obtained with the IniBal LiSi Block group (920 ± 140 N) (P = .061). Conclusions: The mechanical performance of monolithic ceramic crowns fabricated from lithium disilicate was befer than zirconia-reinforced lithium silicate aKer cyclic faBgue aging. [ABSTRACT FROM AUTHOR]

Objectives: Optical and physical properties of dental restorative composite materials are affected by composition. Basic optical absorption and scattering properties have been derived through the use of a corrected reflectance model, but practical and important optical properties are not easily derived from these basic spectral characteristics. The purposes of this study are to derive and compare colour and translucency characteristics of two cured contemporary nanohybrid composites being marketed as universal composites, and to evaluate colour difference between each composite material and published shade guide data., Methods: Previously derived optical scattering and absorption coefficients for five diverse shades of these composite materials were used to calculate the CIE colour parameters of L*, a* and b* at infinite thickness under various illuminants and to derive ideal translucency parameters at various thicknesses using two colour difference formulae., Results: Differences were found in the inherent colour parameters and in the translucency parameters between the brands for some of the shades studied. The colour differences of the inherent colours from published shade guide data were always higher than the perceptibility limit, and often higher than the acceptability limit., Conclusions: Inherent colours and ideal translucency parameters may be calculated from optical coefficients for a variety of illuminants. Different inherent colour parameters of composite materials marked for the same shade indicate the influence of compositional differences between these materials., Clinical Significance: Since patients are seen under various illuminations, the ability to assess appearance matching characteristics under diverse illuminants will help assure an optimum match for the patient., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Objective: To measure the forces delivered by thermoplastic appliances made from three materials and investigate effects of mechanical properties, material thickness, and amount of activation on orthodontic forces., Materials and Methods: Three thermoplastic materials, Duran (Scheu Dental), Erkodur (Erkodent Erich Kopp GmbH), and Hardcast (Scheu Dental), with two different thicknesses were selected. Values of elastic modulus and hardness were obtained from nanoindentation measurements at 28°C. A custom-fabricated system with a force sensor was employed to obtain measurements of in vitro force delivered by the thermoplastic appliances for 0.5-mm and 1.0-mm activation for bodily tooth movement. Experimental results were subjected to several statistical analyses., Results: Hardcast had significantly lower elastic modulus and hardness than Duran and Erkodur, whose properties were not significantly different. Appliances fabricated from thicker material (0.75 mm or 0.8 mm) always produced significantly greater force than those fabricated from thinner material (0.4 mm or 0.5 mm). Appliances with 1.0-mm activation produced significantly lower force than those with 0.5-mm activation, except for 0.4-mm thick Hardcast appliances. A strong correlation was found between mechanical properties of the thermoplastic materials and force produced by the appliances., Conclusions: Orthodontic forces delivered by thermoplastic appliances depend on the material, thickness, and amount of activation. Mechanical properties of the polymers obtained by nanoindentation testing are predictive of force delivery by these appliances.

This study investigated the effects of a diamond-like carbon (DLC) coating on frictional and mechanical properties of orthodontic brackets. DLC films were deposited on stainless steel brackets using the plasma-based ion implantation/deposition (PBIID) method under two different atmospheric conditions. As-received metal brackets served as the control. Two sizes of stainless steel archwires, 0.018 inch diameter and 0.017 × 0.025 inch cross-section dimensions, were used for measuring static and kinetic friction by drawing the archwires through the bracket slots, using a mechanical testing machine (n = 10). The DLC-coated brackets were observed with a scanning electron microscope (SEM). Values of hardness and elastic modulus were obtained by nanoindentation testing (n = 10). Friction forces were compared by one-way analysis of variance and the Scheffé test. The hardness and elastic modulus of the brackets were compared using Kruskal-Wallis and Mann-Whitney U-tests. SEM photomicrographs showed DLC layers on the bracket surfaces with thickness of approximately 5-7 μm. DLC-coated brackets deposited under condition 2 showed significantly less static frictional force for the stainless steel wire with 0.017 × 0.025 inch cross-section dimensions than as-received brackets and DLC-coated brackets deposited under condition 1, although both DLC-coated brackets showed significantly less kinetic frictional force than as-received brackets. The hardness of the DLC layers was much higher than that of the as-received bracket surfaces. In conclusion, the surfaces of metal brackets can be successfully modified by the PBIID method to create a DLC layer, and the DLC-coating process significantly reduces frictional forces.

Introduction: Orthodontic elastomeric chains are commercially available in various colors from many manufacturers. In this study, we investigated the viscoelastic properties of elastomeric chains using dynamic mechanical analysis to perform color and brand comparisons., Methods: Ten colors of Sunburst chains (GAC International, Bohemia, NY) were selected for the color study. Three colors of Sunburst, Bobbin Alastik (3M Unitek, Monrovia, Calif), and Energy (Rocky Mountain Orthodontics, Denver, Colo) chains were selected for the brand study. Nine specimens of each type were measured and tested. Dynamic mechanical analysis was performed at room temperature at 8 frequencies ranging from 0.125 to 16.0 Hz. Three variables (storage stiffness, loss stiffness, and tan δ) were analyzed by using repeated-measures analysis of variance (ANOVA) and pairwise t tests, comparing all frequencies for each specimen type and all specimen types for each frequency (with Bonferroni corrections). Significance was set at α = 0.05., Results: Significant differences were found among all specimen dimensions, all frequencies, and all 3 dynamic mechanical analysis variables in both the color and brand studies. Comparisons focused on tan δ, which does not depend on specimen dimensions as do storage stiffness and loss stiffness., Conclusions: Statistically significant differences in tan δ values among colors were relatively small, so the clinical significance is questionable and requires further investigation. Differences in tan δ values among brands were greater and more likely to be clinically significant. Further studies are needed to relate viscoelastic properties to force decay., (Copyright © 2012 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

Statement of Problem: Casting a high-gold alloy to a wrought prefabricated noble implant-component increases the cost of an implant. Selecting a less expensive noble alloy would decrease implant treatment costs., Purpose: The purpose of this study was to investigate the interfacial regions of a representative noble implant component and cast noble dental alloys and to evaluate the effects of porcelain firing cycles on the interface., Material and Methods: Six representative alloys (n=3) were cast to gold implant abutments (ComOcta). Scanning electron microscopy (SEM) was used to characterize microstructures. Compositions of interfacial regions and bulk alloys were obtained by energy-dispersive spectroscopy. Vickers hardness was also measured across the interface. By using Micro-X-ray diffraction, the phases were evaluated at 7 points perpendicular to the interface. The effects of porcelain firing cycles on microstructures, diffusion, hardness, and phases were also evaluated. For statistical evaluation of diffusion length and hardness, a 3-way repeated measures ANOVA was used. Pairwise comparisons of interest were conducted with Tukey pairwise comparisons or, when a significant interaction was found, Bonferroni-adjusted t-tests (overall α=.05)., Results: Microstructures of bulk alloys were predominantly maintained to a well-defined boundary for both as-cast and heat-treated conditions. An interaction band, 5-6 μm wide, was observed. The alloy grain size at the interface and the interaction band width increased after simulated porcelain firing. The extent of elemental diffusion from the interface was about 30 μm and not affected by simulated porcelain firing. Differences in Vickers hardness for the alloys were consistent with their compositions. Micro-XRD patterns indicated that substantial amounts of new phases had not formed at the interfacial regions., Conclusions: Less expensive noble alternatives to high-gold alloys provided comparable metallurgical compatibility with the noble implant component., (Copyright © 2011 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.)

The aims of this study were to investigate the torsional properties of three experimental titanium miniscrew implants for orthodontic anchorage and to determine the relationship between the torsional properties and metallurgical structures. Experimental miniscrew implants with a diameter of 1.4 mm were fabricated from commercially pure (CP) titanium (alpha-titanium), Ti-4Al-4V (duplex alpha-beta-titanium), and Ti-33Nb-15Ta-6Zr (beta-titanium). Micro-X-ray diffraction (XRD) was performed to identify phases, and microstructures of etched cross-sections were obtained with scanning electron microscopy (SEM). Implants were loaded in torsion (n = 5), and mean moments and twist angles at fracture were statistically compared using the Kruskal-Wallis and Mann-Whitney U-tests. Cyclic torsional moment for fracture of starting square wires (2 × 2 × 30 mm) was measured (n = 3). At fracture, the Ti-4Al-4V and Ti-33Nb-15Ta-6Zr implants demonstrated significantly higher mean torque than the CP titanium implant, while the Ti-33Nb-15Ta-6Zr implant had a significantly higher mean twist angle than the other two implants. The CP titanium and Ti-33Nb-15Ta-6Zr implants displayed good fatigue performance and excellent ductility. Ti-33Nb-15Ta-6Zr beta-titanium alloy is suitable for manufacturing miniscrew implants since it has excellent torsional properties.

Statement of Problem: Because noble dental casting alloys for metal ceramic restorations have a wide range of mechanical properties, knowledge of these properties is needed for rational alloy selection in different clinical situations where cast metal restorations are indicated., Purpose: The purpose of this study was to compare the mechanical properties and examine both the fracture and polished surfaces of 6 noble casting alloys that span many currently marketed systems. Five alloys were designed for metal ceramic restorations, and a sixth Type GPT has Type IV alloy for fixed prosthodontics (Maxigold KF) was included for comparison., Material and Methods: Specimens (n=6) meeting dimensional requirements for ISO Standards 9693 and 8891 were loaded to failure in tension using a universal testing machine at a crosshead speed of 2 mm/min. Values of 0.1% and 0.2% yield strength, ultimate tensile strength, elastic modulus, and percentage elongation were obtained. Statistical comparisons of the alloy mechanical properties were made using 1-way ANOVA and the REGW multiple-range test (α=.05). Following fracture surface characterization using scanning electron microscopy (SEM), specimens were embedded in epoxy resin, polished, and again, examined with the SEM., Results: When the multiple comparisons were considered, there were generally no significant differences in the elastic modulus, 0.1% and 0.2% offset yield strength, and ultimate tensile strength for the d.SIGN 91 (Au-Pd), d.SIGN 59 (Pd-Ag), Capricorn 15 (Pd-Ag-Au) and Maxigold KF (Au-Ag-Pd) alloys, except that the ultimate tensile strength was significantly lower (P<.05) for Maxigold KF than these other 3 alloys. These 4 mechanical properties were generally significantly lower (P<.05) for Aquarius XH (Au-Pt-Pd) and Brite Gold XH (Au-Pt). The d.SIGN 59 (14.6%) and Capricorn 15 (13.8%) alloys had the highest values of mean percentage elongation, which were not significantly different. Aquarius XH (6.0%) and Maxigold KF (4.2%) had the lower mean values of percentage elongation, which were also not significantly different. The polished and etched surfaces for all alloys revealed equiaxed, fine-grain microstructures, and all fracture surfaces contained casting porosity. Incomplete solidification suggestive of dendritic structures was observed for some alloys. Fracture surfaces were complex, with characteristic features of both brittle and ductile fracture. Precipitate particles on the fracture surfaces indicated the multi-phase character of the alloys., Conclusions: For the important mechanical property of yield strength, there were generally no significant differences among the Au-Pd, Pd-Ag, Pd-Ag-Au and Au-Ag-Pd alloys. Wide variation was found in percentage elongation, with the Pd-Ag and Pd-Ag-Au alloys having the highest values and the Au-Pd-Pt and Au-Ag-Pd alloys having the lowest values., (Copyright © 2011 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.)

Introduction: Effects of sodium fluoride (NaF) mouth rinse solutions on torsional properties of a miniscrew implant were investigated., Methods: As-received Ti-6Al-4V miniscrew implants (AbsoAnchor [Dentos, Inc., Daigu, Korea]) were immersed in 0.1% or 0.2% NaF mouth rinse solution (pH 5.12 and 5.14, respectively) for 1 hour or 24 hours. Miniscrew implants selected as controls were not immersed. Each implant was subjected to increasing torque until fracture (n = 5 in sample groups). Mean moment and twist angle for fracture were compared using 1-way analysis of variance (ANOVA). Surfaces of implants after immersion were observed with a scanning electron microscope (SEM). Electron microprobe and micro-x-ray diffraction analyses were performed to obtain composition information about deposits on implant surfaces., Results: Pits and cracks formed on the implant surfaces after immersion in both NaF mouth rinse solutions. Corrosion products, probably sodium aluminum fluoride (Na(3)AlF(6)), were observed on the implants after immersion in both NaF solutions for both time periods. There were no significant differences for mean torque (P = 0.063) and twist angle (P = 0.696) at fracture compared with control implants., Conclusions: Although titanium alloy miniscrew implants corroded slightly from immersion in 0.1% or 0.2% NaF solutions, mouth rinsing by patients with the same fluoride solution concentrations should not cause deterioration of their torsional performance., (Copyright © 2011 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

Statement of Problem: N-vinylcaprolactam (NVC)-containing glass ionomers are promising dental restorative materials with improved mechanical properties; however, little information is available on other physical characteristics of these types of modified glass ionomers, especially their surface properties. Understanding the surface characteristics and behavior of glass ionomers is important for understanding their clinical behavior and predictability as dental restorative materials., Purpose: The purpose of this study was to investigate the effect of NVC-containing terpolymers on the surface properties and bond strength to dentin of GIC (glass-ionomer cement), and to evaluate the effect of NVC-containing terpolymer as a dentin conditioner., Material and Methods: The terpolymer of acrylic acid (AA)-itaconic acid (IA)-N-vinylcaprolactam (NVC) with a molar ratio of 8:1:1 (AA:IA:NVC) was synthesized by free radical polymerization and characterized using nuclear magnetic resonance ((1)H-NMR) and Fourier transform infrared spectroscopy (FTIR). The synthesized terpolymer was used in glass-ionomer cement formulations (Fuji IX GP). Ten disc-shaped specimens (12 × 1 mm) were mixed and fabricated at room temperature. Surface properties (wettability) of modified cements were studied by contact angle measurements as a function of time. Work of adhesion values of different surfaces were also determined. The effect of NVC-modified polyacid on the bond strength of glass-ionomer cement to dentin was investigated. The mean data obtained from contact angle and bonding strength measurements were subjected to t test and 2-way ANOVA (α=.05)., Results: NVC-modified glass-ionomer cements showed significantly (P<.05) lower contact angles (46 degrees) and higher work of adhesion (W(A)=60.33 erg/cm(2)) in comparison to commercially available Fuji IX GP (57 degrees and W(A)=53.01 erg/cm(2)). The wettability of dentin surfaces conditioned with NVC-containing terpolymer was significantly higher (P<.05) (22 degrees, WA=73.77 erg/cm(2)) than dentin conditioned with GC dentin conditioner (29 degrees, W(A)=70.52 erg/cm(2)). The experimental cement also showed significantly higher values for shear bond strength to dentin (8.7 ±0.15 MPa after 1 month) when compared to the control group (8.4 ±0.13 MPa after 1 month)., Conclusions: NVC-containing terpolymers may enhance the surface properties of GICs and increase their bond strength to the dentin. Furthermore, NVC-containing polyelectrolytes are better dentin conditioners than a commercially available dentin conditioner (GC dentin conditioner)., (Copyright © 2011 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.)

Objective. The purpose of this review paper is to review the literature regarding the toxicology of mercury from dental amalgam and evaluate current statements on dental amalgam. Materials and Methods. Two key-words "dental amalgam" and "toxicity" were used to search publications on dental amalgam biocompatibility published in peer-reviewed journals written in English. Manual search was also conducted. The most recent declarations and statements were evaluated using information available on the internet. Case reports were excluded from the study. Results. The literature show that mercury released from dental amalgam restorations does not contribute to systemic disease or systemic toxicological effects. No significant effects on the immune system have been demonstrated with the amounts of mercury released from dental amalgam restorations. Only very rarely have there been reported allergic reactions to mercury from amalgam restorations. No evidence supports a relationship between mercury released from dental amalgam and neurological diseases. Almost all of the declarations accessed by the internet stated by official organizations concluded that current data are not sufficient to relate various complaints and mercury release from dental amalgam. Conclusions. Available scientific data do not justify the discontinuation of amalgam use from dental practice or replacement with alternative restorative dental materials.

This study investigated transformations of nickel-titanium wires using differential scanning calorimetry (DSC) and thermomechanical analysis (TMA) under tensile load (100 gf or 500 gf). Two nickel-titanium wires, 35°C Copper Ni-Ti and Nitinol SE, were selected. DSC analyses were performed between -90° and 100°C. Specimens prepared for TMA were approximately 150 µm thick and 12 mm long. TMA analyses were performed between -120° and 100°C. With TMA, all transformation temperatures for a tensile load of 500 gf, obtained from both the heating and cooling curves, were higher than those for a tensile load of 100 gf. While mean A(s) and A(f) temperatures for Copper Ni-Ti obtained by TMA were much higher than those obtained by DSC analysis, mean M(s) and M(f) temperatures obtained by TMA were much lower than those obtained by DSC analysis. The transformation behavior of nickel-titanium wires with change in temperature was affected by application of tensile load.

The effect of anodizing on corrosion resistance of Ti-xHf alloys has been investigated. Ti-xHf alloys were prepared and anodized at 120, 170 and 220 V in 1 M H(3)PO(4) solution, and crystallized at 300 and 500°C. Corrosion experiments were carried out using a potentiostat in 0.15 M NaCl solution at 36.5 ± 1°C. The Ti-xHf alloys exhibited the α' and anatase phases. The pore size on the anodized surface increases as the applied voltage is increased, whereas the pore size decreases as the Hf content is increased. The anodized Ti-xHf alloys exhibited better corrosion resistance than non-anodized Ti-xHf alloys.

Objective: To test the hypothesis that a diamond-like carbon coating does not affect the frictional properties of orthodontic wires., Materials and Methods: Two types of wires (nickel-titanium and stainless steel) were used, and diamond-like carbon (DLC) films were deposited on the wires. Three types of brackets, a conventional stainless steel bracket and two self-ligating brackets, were used for measuring static friction. DLC layers were observed by three-dimensional scanning electron microscopy (3D-SEM), and the surface roughness was measured. Hardness and elastic modulus were obtained by nanoindentation testing. Frictional forces and surface roughness were compared by the Kruskal-Wallis and Mann-Whitney U-tests. The hardness and elastic modulus of the wires were compared using Student's t-test., Results: When angulation was increased, the DLC-coated wires showed significantly less frictional force than the as-received wires, except for some wire/bracket combinations. Thin DLC layers were observed on the wire surfaces by SEM. As-received and DLC-coated wires had similar surface morphologies, and the DLC-coating process did not affect the surface roughness. The hardness of the surface layer of the DLC-coated wires was much higher than for the as-received wires. The elastic modulus of the surface layer of the DLC-coated stainless steel wire was less than that of the as-received stainless steel wire, whereas similar values were found for the nickel-titanium wires., Conclusions: The hypothesis is rejected. A DLC-coating process does reduce the frictional force.