Giant Anisotropic Magnetoresistance due to Purely Orbital Rearrangement in the Quadrupolar Heavy Fermion Superconductor PrV_{2}Al_{20}.

We report the discovery of giant and anisotropic magnetoresistance due to the orbital rearrangement in a non magnetic correlated metal. In particular, we measured the magnetoresistance under fields up to 31.4 T in the cubic Pr-based heavy fermion superconductor PrV_{2}Al_{20} with a non magnetic Γ_{3} doublet ground state, exhibiting antiferroquadrupole ordering below 0.7 K. For the [100] direction, we find that the high-field phase appears between 12 and 25 T, accompanied by a large jump at 12 T in the magnetoresistance (ΔMR∼100%) and in the anisotropic magnetoresistivity ratio by ∼20%. These observations indicate that the strong hybridization between the conduction electrons and anisotropic quadrupole moments leads to the Fermi surface reconstruction upon crossing the field-induced antiferroquadrupole (orbital) rearrangement.

Heavy-fermion superconductivity in the quadrupole ordered state of PrV2Al20.

PrV2Al20 is a rare example of a heavy-fermion system based on strong hybridization between conduction electrons and nonmagnetic quadrupolar moments of the cubic Γ3 ground doublet. Here, we report that a high-quality single crystal of PrV2Al20 exhibits superconductivity at Tc=50 mK in the antiferroquadrupole-ordered state under ambient pressure. The heavy-fermion character of the superconductivity is evident from the specific heat jump of ΔC/T∼0.3 J/mol K(2) and the effective mass m*/m0∼140 estimated from the temperature dependence of the upper critical field. Furthermore, the high-quality single crystals exhibit double transitions at TQ=0.75 K and T*=0.65 K associated with quadrupole and octupole degrees of freedom of the Γ3 doublet. In the ordered state, the specific heat C/T shows a T(3) dependence, indicating the gapless mode associated with the quadrupole order, the octupole order, or both. The strong sensitivity to impurity of the superconductivity suggests unconventional character due to significant quadrupolar fluctuations.

Characterization of a glucose sensor prepared by electropolymerization of pyrroles containing a tris-bipyridine osmium complex.

A glucose sensor was developed by electrocopolymerization using pyrroles containing a tris-bipyridine (bpy) osmium complex (Os-py), pyrrole (py), pyrrole propanoic acid (PPA) and glucose oxidase (GOx) to improve the key performance characteristics, such as the sensitivity, selectivity, and long-term stability. Tris-bipyridine osmium pyrrole complexes with four different methylene moieties were utilized to correlate the methylene length with the glucose sensor performance. The electrocatalytic response of glucose was clearly observed at electrodes modified with Os-py, except for the electrode immobilized with the Os-py complex containing the shortest methylene moiety. The current response to glucose increased up to a concentration of 100 mmol dm(-3). The electrocatalytic response to glucose at the [Os(bpy)(2)(py(6)-bpy)](2+/3+)/py/PPA/GOx electrode was stable for more than 100 days. Dissolved oxygen and potential interference compounds (ascorbic acid, uric acid, and acetaminophen) minimally perturbed the current response to glucose at the [Os(DM-bpy)(2)(py(6)-bpy)](2+/3+)/py/PPA/GOx electrode. Based on these results, a longer methylene moiety appears to improve the performance characteristics of a glucose sensor fabricated via the electropolymerization of tris-bipyridine osmium pyrrole complexes.

The clinical findings and managements in 44 cases of cracked vital molars.

BACKGROUND/PURPOSE: The aim of this study was to evaluate the associations between the clinical findings and managements in cracked vital molars that were caused by various factors including restoration and occlusion. MATERIALS AND METHODS: The subjects' gender, age, chief complaint, type of tooth, percussion test results, pulp vitality, restoration material and cavity classification, clinical depth of the crack, evaluation of occlusion, depth of periodontal probing, and final management were recorded. RESULTS: A total of 44 vital cracked teeth (molars) were diagnosed in 40 patients. Regarding the type of tooth, a greater number of mandibular molars were affected than maxillary molars. Nonworking-side interference (NWI) was recognized in 38 cases (86.4%). Eight teeth (18.2%) had not been restored. Thirty-six teeth (81.8%) had been restored; 26 teeth (72.2%) with a metal inlay, 6 (16.7%) with an amalgam, and 4 (11.1%) with a composite resin. Regarding the final treatment in the endodontically-treated group, all 17 teeth were covered with a metal full crown. Regarding the final treatment in the pulp-reserved group, 19 teeth (70.4%) were covered with a metal full crown, and the other managements were as follows: occlusal adjustment (n = 4, 14.8%), composite resin (n = 2, 7.4%), and only follow-up without treatment (n = 2, 7.4%). All of the cases showed a good clinical prognosis. CONCLUSION: The NWI group restored with 58% of metal inlay accounted for more than 86% of the cracked teeth. Thus, in order to achieve a good outcome, cracked teeth, particularly those originating due to occlusal interference should be protected with coverage-type restorations.

Scanning electron microscopy reveals severe external root resorption in the large periapical lesion.

The present study was designed to investigate the relationships between clinicopathological findings and the resorptive conditions of root apices of teeth with periodontitis. The samples included 21 root apices with large periapical radiolucent lesions. The preoperative computed tomography (CT) and intraoperative findings were correlated with the presence, extension, and the progression pattern of periapical resorption using a scanning electron microscope. The subjects' age, gender, chief complaint, type of tooth, percussion test results, size of periapical lesion using CT, and intraoperative findings were recorded. All apicoectomies were performed under an operative microscope for endodontic microsurgery. A significant large size was observed in cystic lesions compared with granulomatous lesions. The cementum surface at the periphery of the lesion was covered with globular structures (2-3 µm in diameter). Cementum resorption started as small defect formations at the surface. As the defect formation progressed, a lamellar structure appeared at the resorption area, and the size of globular structures became smaller than that of globules at the surface. Further resorption produced typical lacuna formation, which was particularly observed in fracture cases. The most morphologically severe destructive pattern of dentin resorption was observed in large cystic lesions. This study is the first report to elucidate the relationships between three clinical types of undesirable periapical lesions: (1) undertreatment, (2) periapical fracture, (3) macro-level resorption, and the microstructure of external root resorption including from small defects at the cementum surface to a significant destructive pattern inside the dentin. Microsc. Res. Tech. 79:495-500, 2016. © 2016 Wiley Periodicals, Inc.

Comparison of conventional and new-generation nickel-titanium files in regard to their physical properties.

INTRODUCTION: This study investigated the surface, fractured structure, and physicochemical properties related to cyclic fatigue in various nickel-titanium (NiTi) files. METHODS: Among a total of 10 groups of NiTi files, conventional NiTi files (ProFile [Dentsply Maillefer, Ballaigues, Switzerland] and K3 [SybronEndo, Orange, CA]) and new-generation NiTi files (ProFile Vortex [PV; Tulsa Dental Specialties, Tulsa, OK], Vortex Blue [VB; Tulsa Dental Specialties], and K3 XF [XF; SybronEndo, Orange, CA]) with the same tip diameter (ISO size 25) and 2 types of taper (0.04 and 0.06) were used in this study. Scanning electron microscopy of the file surface structure, differential scanning calorimetry, and cyclic fatigue resistance tests were conducted. RESULTS: Many mechanical grooves were recognized on the file surface. The surface in the ProFile group was extremely smooth compared with that observed for the other files. Many shallow hollows besides mechanical grooves were noted on the surface in the XF group. A smooth curve was observed in the ProFile, K3, and PV groups. Defined peaks in differential scanning calorimetry were observed in the VB and XF groups. The 0.04 taper files exhibited a statistically higher number of cycles to fracture than the 0.06 taper files in all groups (P < .05). Cracks along the mechanical grooves were observed in the NiTi files, with the exception of the XF group. The start of cracking was detected at U-shape sites in the ProFile group, the cutting edge in the PV and VB groups, and radial islands in the K3 and XF groups. CONCLUSIONS: The present findings suggest that new-generation NiTi files are not necessarily improved compared with conventional files.

Timing for composite resin placement on mineral trioxide aggregate.

INTRODUCTION: The aim of this study was to investigate the proper time to restore composite resin over mineral trioxide aggregate (MTA). METHODS: Thirty-five samples of MTA blocks were divided into 7 groups with 3 different times (10 minutes, 1 day, and 7 days) selected for restoring the composite resin over MTA with and without bonding resin, and a control group was included for comparison. After 21 days, the distances between MTA and the composite resin or between MTA and the bonding agent on sectioned planes along the long axis were measured using a scanning electron microscope (×2,000 magnification). The hardness of the MTA near the composite resin was presented as the Vickers microhardness. RESULTS: There were no gaps at the interface in the 10-minute groups, the 1-day group with a bonding agent, and the 7-day group with a bonding agent. The groups without a bonding agent at 1 and 7 days presented a separation or gap at the interface. The value of the Vickers microhardness in the 1-day groups was significantly decreased compared with those of the other groups regardless of the presence or absence of a bonding agent. CONCLUSIONS: These findings suggest that composite resin with a bonding agent over MTA can be restored almost immediately after MTA mixing during a single visit.

Surface changes of mineral trioxide aggregate after the application of bleaching agents: electron microscopy and an energy-dispersive X-ray microanalysis.

INTRODUCTION: The aim of this study was to investigate the changes in the surface structure and chemical composition after applying bleaching agents to completely hardened mineral trioxide aggregate. METHODS: A total of 12 samples of MTA blocks were divided into three groups, two different bleaching agents, and a control group. The surface structure was observed using a scanning electron microscope. The changes in elemental composition were analyzed by an energy-dispersive x-ray microanalysis (EDX) system. RESULTS: The surface of the MTA covered with each bleaching agent changed in terms of both color and structure compared with the control. EDX showed that both bleaching agents affected the elemental distribution. A decrease in Ca and an increase in Si were shown, and this tendency was especially pronounced in the higher hydrogen peroxide concentration group. CONCLUSIONS: The acidic conditions induced by bleaching agents brought about the deterioration of the MTA surface. These findings suggest that MTA is an insufficient barrier against tooth bleaching.

Analysis of arsenic in gray and white mineral trioxide aggregates by using atomic absorption spectrometry.

INTRODUCTION: The aim of the present study was to investigate whether the concentration of arsenic (As) released from gray or white mineral trioxide aggregates (MTAs) met the requirement of the International Standards Organization (ISO) for dental cements. METHODS: Sample preparations were carried out according to the ISO methods. After centrifugation of dissolved samples, As (III) concentration in the final supernatant was analyzed by a high-performance atomic absorption spectrophotometer. RESULTS: As (III) concentration from both MTAs was much less than the required value (2 ppm) for dental cements regulated by the ISO. An experiment simulating pulp capping by using MTA revealed that As concentration was also below the standard value of the ISO. The As concentration in white MTA was lower than the value (10 ppb) recommended for tap water and environmental standards. CONCLUSIONS: The present in vitro studies demonstrated that there is no threat to patient health in using commercially available brands of MTA for endodontic practices.