Flexible Graphene Platform-based Electrochemical Sensor for Sensitive Determination of Dopamine / 分析化学

The chemical vapor deposition grown graphene was transferred onto flexible polyethylene terephthalate surface to fabricate a graphene platform electrode ( GPE) , and gold nanoparticles ( AuNPs) were electrodeposited on GPE to form an AuNPs modified GPE ( AuNPs/GPE ) . The formation of AuNPs was confirmed by scanning electron microscopy ( SEM) , energy dispersive spectrometer ( EDS) , high-resolution transmission electron microscope ( HR-TEM) , X-ray diffraction ( XRD) and Raman spectra. On AuNPs/GPE, dopamine ( DA ) displayed a pair of well-defined redox peaks with highly enhanced peak currents compared with those on GPE. At detection potential of 0. 20 V, AuNPs/GPE sensor presented a wide linear range of 0. 1 μmol/L to 400. 0 μmol/L of DA with a detection limit of 3. 9 nmol/L (S/N=3). In addition, the proposed sensor allowed highly selective and sensitive, stable and fast amperometric sensing of DA.

Stress distributions on the femur under different gaits before and after hip joint replacement / 医用生物力学

Objective To investigate biomechanical properties of the femur during slow walking and stair climbing before and after total hip replacement (THA), so as to provide theoretical basis for optimal design and manufacturing of the prosthetic hip. Methods The 3D finite element model of hip femur was established and validated first, and the stress distributions and stress shielding rates during slow walking and stair climbing before and after THA were calculated. Results During slow walking, the stress increased gradually from the proximal femur to the distal femur, reaching the maximum 90.6 MPa at the lower part of the femur before THA. A stress shielding phenomenon occurred on the femur after THA, but the stress amplitude decreased, with the maximum stress reaching 82.5 MPa. The maximum shielding rate appeared near the greater trochanter of the proximal femoral prosthesis and the total stress shielding rate reached 14.9%-99.0%. In addition, excessive stress concentration occurred at the prosthetic neck. Meanwhile, the stress distribution during stair climbing had a similar regular pattern as that appeared during slow waling, but with a more obvious stress shielding effect. Conclusions The greater stress shielding of the proximal femur and the excessive stress concentration on the prosthetic hip during stair climbing will both influence the THA surgery quality, so patients should minimize the movement involving large joint angle after THA.

Shaping ability of two nickel-titanium rotary systems in simulated S-shaped canals / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the shaping ability of two nickel-titanium rotary systems (ProTaper and Hero642) in simulated S-shaped canals.</p><p><b>METHODS</b>Thirty simulated S-shaped canals were randomly divided into three groups and prepared by ProTaper, Hero642, ProTaper combined with Hero642 respectively. All the canals were scanned before and after instrumentation, and the amount of material removed in the inner and outer wall and the canal width after instrumentation were measured with a computer image analysis program.</p><p><b>RESULTS</b>There was significant difference in the amount of material removed at the inner side of apical curvature and outer side of apex between ProTaper combined with Hero642 and ProTaper files (P < 0.05) at the same tip size. The inner and outer wall of the canals were evenly prepared by ProTaper combined with Hero642, and the taper of canals were better than those prepared by Hero642.</p><p><b>CONCLUSIONS</b>ProTaper combined with Hero 642 had better shaping ability to maintain the original shape and could create good taper canals in the simulated S-shaped canal model.</p>

Root canal curvature in chinese mandibular permanent incisors / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the root canal curvature in Chinese mandibular permanent incisors.</p><p><b>METHODS</b>Two hundred and ninety nine Chinese mandibular permanent incisors were included in this study. The root canals were inserted with stainless steel 15# K files, and then taken radiography from the facial and proximal view by X-ray paralleling technique. Canal curvatures were evaluated by measuring the angle, the radius of the curvatures, and the length of the curved part of the canal. Based on the curved angle and the shape of curved canals, the root canals were classified.</p><p><b>RESULTS</b>The curved angle, radius, and the curved canal length was 5.28 degrees +/- 5.52 degrees, 16.19 mm +/- 12.38 mm, 4.10 mm+/-2.01 mm, respectively in the facial view; 9.99 degrees +/- 5.84 degrees, 18.86 mm +/- 9.71 mm, 3.27 mm +/- 2.39 mm, respectively in the proximal view. The prevalence of straight, light, moderate, and serve curved root canals in mandibular permanent incisors was 15.7%, 66.9%, 16.7%, and 0.7%, respectively (P<0.05) based on the curved angle. The prevalence of straight, L shape, and S shape curved root canals was 7.7%, 50.5%, and 41.8%, respectively (P < 0.05).</p><p><b>CONCLUSION</b>Most of the root canals in mandibular permanent incisors are curve.</p>

Radiographic anatomy of pulp chamber of Chinese permanent anterior teeth / 华西口腔医学杂志

<p><b>OBJECTIVE</b>The aim of this study was to measure and analyze the anatomic characteristics of the pulp chamber of Chinese permanent anterior teeth radiographically.</p><p><b>METHODS</b>There were 137 human permanent anterior teeth to be used. The crown length, crown width and crown thickness were measured by vernier caliper. Labial-lingual and mesial-distal radiographs were obtained by parallel technique and Photoshop 8.0 was adopted for measuring the largest labial-lingual length, the largest mesial-distal length, the pulp chamber height and the distance between the lingual surface of the crown and the corresponding wall of the pulp chamber; the ratios of the largest labial-lingual length to the crown thickness, the largest mesial-distal length to the crown width and the pulp chamber height to the crown length were calculated. Finally the coefficients of variance were caculated.</p><p><b>RESULTS</b>(1) The ratios of the largest mesial-distal length to the crown width of maxillary and mandibular canines were statistically different from those of the other anterior teeth. There was not statistically significant difference for those ratios either between maxillary and mandibular canines or among incisors. (2) Indexes of the pulp chamber had higher variance than those of the external morphology. (3) The distance between the lingual surface of the crown and the corresponding wall of the pulp chamber had the smallest coefficient of variance. (4) The largest mesial-distal length of the pulp chamber had the largest coefficient of variance, except for the mandibular canines.</p><p><b>CONCLUSION</b>This study provided anatomical basis for clinical work; the distance between the lingual surface of the crown and the corresponding wall of the pulp chamber could be used as a depth reference for the endodontic access, and the access should not be extended excessively in mesial-distal direction.</p>

Shaping ability of multi-taper nickel-titanium files in simulated resin curved root canal / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To compare the shaping ability of ISO standard stainless steel K files and multi-taper ProTaper nickel-titanium files in simulated resin curved root canals. METHODS Thirty simulated resin root canals were randomly divided into three groups and prepared by stainless steel K files, hand ProTaper, rotary ProTaper, respectively. The amount of material removed from inner and outer wall and canal width after canal preparation was measured, while the canal curvature before and after canal preparation and canals aberrations were recorded.</p><p><b>RESULTS</b>The stainless steel K files removed more material than hand ProTaper and rotary ProTaper at the outer side of apex and inner side of curvature (P < 0.05). The mean degree of straightening in stainless steel K files group was significantly bigger than in ProTaper group (P < 0.05). The canals prepared by ProTaper had no evident aberration.</p><p><b>CONCLUSION</b>The shaping ability of ProTaper is better than stainless steel K files.</p>