一次性根管治疗中Protaper与K-file根管预备根尖周急性炎症反应的临床对照实验

目的:研究一次性根管治疗中根管预备方法与根尖周急性炎症反应(EIAE)的关系。方法:将符合标准的临床病例配对分配,分别以Protaper和K-file进行根管预备,评价两组间根充质量及EIAE发生率的关系。结果:Protaper组与K-file组根充质量及EIAE发生率差异有统计学意义(P<0.05)。结论:通过使用Protaper进行根管预备,提高根管充填质量,有助于降低EIAE发生率。

Effect of heat-activated nickel-titanium arch wire for orthodontic treatment on local tissue inflammation and bone destruction

Objective:To study the effect of heat-activated nickel-titanium arch wire for orthodontic treatment on local tissue inflammation and bone destruction.Methods:Patients who received orthodontic treatment with nickel-titanium arch wire in Hancheng People's Hospital between March 2012 and October 2017 were retrospectively studied, and according to the nickel-titanium arch wire materials in history data, the patients were divided into the experimental group who used heat-activated nickel-titanium arch wire and the control group who used common nickel-titanium arch wire. 1 week after treatment, the gingival crevicular fluid was collected to determine the contents of inflammatory cytokines as well as the mRNA expression of osteoblast markers and osteoclast markers.Results: 1 week after treatment, IL-1α, IL-1β, sTREM1 and HMGB1 contents as well as RANKL, 5-LOX, LTB4, TRACP5b and ODF mRNA expression in gingival crevicular fluid of experimental group were significantly lower than those of control group whereas OPG, Wnt3a, Runx2, OC, ALP and OCIF mRNA expression were significantly higher than those of control group.Conclusion: Heat-activated nickel-titanium arch wire for orthodontic treatment can be more effective than common nickel-titanium arch wire to reduce the local tissue inflammation and inhibit the bone destruction.

机用镍钛器械Mtwo及K3预备磨牙弯曲根管成形能力的比较

背景:重度弯曲根管的预备是临床根管预备的难点,如预备不当容易出现台阶、根管偏移、根尖孔敞开等并发症,影响根充质量和根尖封闭性,因此选择切削能力和成形能力俱佳的根管预备器械对与弯曲根管预备效果的保证有着重要意义。目的:比较Mtwo、K3机用镍钛器械与不锈钢手动K-file预备磨牙重度弯曲根管的成形效果。方法:将30颗新鲜拔除的人离体上颌第一磨牙重度弯曲近颊根管随机均分为3组,分别采用Mtwo机用镍钛器械、K3机用镍钛器械与不锈钢手动K-file进行根管预备。记录3组根管预备前后根管影像中器械尖端所在位置,测量并比较3组间根管弯曲度的变化、工作长度变化和操作时间。结果与结论:根管预备前,3组根管弯曲度比较差异无显著性意义(P>0.05);根管预备后,Mtwo机用镍钛器械组、K3机用镍钛器械组根管弯曲度变化小于不锈钢手动K-file组(P<0.01),Mtwo机用镍钛器械组、K3机用镍钛器械组根管弯曲度变化比较差异无显著性意义(P>0.05)。3组根管预备时间比较差异有显著性意义(P<0.01),Mtwo机用镍钛器械组最短,不锈钢手动K-file组最长。3组根管预备后根管工作长度改变比较差异无显著性意义(P>0.05)。表明Mtwo与K3机用镍钛器械预备后牙弯曲根管时效率高、成形能力强。

Microstructures and mechanical properties of nanocrystalline NiTi intermetallics formed by mechanosynthesis

The formulation of nanocrystallinc NiTi shape memory alloys has potential effects in mechanical stimulation and medical im- plantology. The present work elucidates the effect of milling time on the product＇s structural characteristics, chemical composition, and mi- crohardness for NiTi synthesized by mechanical alloying for different milling durations. Increasing the milling duration led to the formation of a nanocrystalline NiTi intermetallic at a higher level. The formation of nanocrystalline materials was directed through cold fusion, fractur- ing, and the development of a steady state, which were influenced by the accumulation of strain energy. In the morphological study, uninter- rupted cold diffusion and fracturing were visualized using transmission electron microscopy. Particle size analysis revealed that the mean particle size was reduced to -93 μm after 20 h of milling. The mechanical strength was enhanced by the formation of a nanocrystalline in- termetallic phase at longer milling time, which was confirmed by the results of Vickers hardness analyses.

Mechanical properties of nickel-titanium archwire used in the final treatment phase of Tip-Edge Plus technique： an in vitro study

Background As the only active component in final treatment phase of Tip-Edge Plus technique, the activation of nickel-titanium orthodontic archwires is one of the factors that affect the torque expression. It is necessary to evaluate the mechanical properties of the nickel-titanium wire used in the final treatment phase in simulated oral environments to forecast the treatment outcomes. Methods The mechanical properties of 171 thermal nickel-titanium wires of 0.35 mm （0.014-in） in diameters with different deflection of 40 mm in length were investigated with three-point bending test. The samples were divided into 2 groups： as-received and bended groups. In the bended group, samples were divided into 7 subgroups according to the amounts of deflection and named by the canine angulations （-25~, -19~, -13~, -7~, -1~, ＋5~, ＋11~）. The deflection of wires was made by inserting the wires into the deep tunnel of Tip-Edge Plus brackets positioned in plaster casts with different canine angulations to mimic the use of nickel-titanium wires in the final treatment phase. Immersed the bended group in artificial saliva （pH 6.8） and preserved at 37.0~C. Eight durations of incubation were tested： 1 to 8 weeks. Three analogous samples of each group and subgroups were tested per week. Stiffness （YS：E） and the load-deflection characteristics of unloading plateau section were obtained. Results Significant changes in specific mechanical properties were observed in long-term immersed and large deflected wires compared with as-received groups. Both immersion time and deflection affected the mechanical properties of wires in the simulated oral environment, and the two factors had synergistic effect. In groups -25~, -19~ and -13~, stiffness （YS：E） increased then decreased and average plateau force and ratio of variance decreased then increased correspondingly at specific time. Conclusions In the final treatment phase of Tip-Edge Plus technique, the mechanical properties of nickel-titanium wire are associated with the using time and amounts of deflection and it may affect treatment outcomes. As the main reason for wire deflection, canine crown angulation plays an important role in the wire performance. It may be wise to focus on the canine crown angulations and using time in clinic with Tip-Edge Plus technique and make proper adjustment to help to make sure the treatment outcomes.

Phase transformation analysis of varied nickel-titanium orthodontic wires

Background The shape memory effect of nickel-titanium （NiTi） archwires is largely determined by the phase transition temperature. It is associated with a reversible transformation from martensite to austenite. The aim of this study was to characterize austenite, martensite and R phase temperatures as well as transition temperature ranges of the commonly used clinical NiTi orthodontic arch wires selected from several manufacturers. Methods Differential scanning calorimetry （DSC） method was used to study the phase transformation temperatures and the phase transition processes of 9 commonly used clinical NiTi alloys （types： 0.40 mm （0.016 inch）, 0.40 mm × 0.56 mm （0.016 inch × 0.022 inch））.Results The austenite finish temperatures （Af） of 0.40 mm Smart, Ormco and 3M NiTi wires were lower than the room temperature, and no phase transformation was detected during oral temperature. Therefore, we predicted that these types of NiTi did not possess shape memory property. For 0.40 mm and 0.40 mm × 0.56 mm Youyan I NiTi wires, no phase transformation was detected during the scanning temperature range, suggesting that these two types of wires did not possess shape memory either. The Af of 0.40 mm × 0.56 mm Smart, L＆H, Youyan II Ni-Ti wires were close to the oral temperature and presented as martensitic-austenitic structures at room temperature, suggesting the NiTi wires listed above have good shape memory effect. Although the 0.40 mm × 0.56 mm Damon CuNiTi wire showed martensitic- austenitic structures at oral temperature, its Af was much higher than the oral temperature. It means that transformation from martensite to austenite for this type of NiTi only finishes when oral temperature is above normal. Conclusion The phase transformation temperatures and transformation behavior varied among different commonly used NiTi orthodontic arch wires, leading to variability in shape memory effect.

Improving exposure of anodically ordered Ni-Ti-O and corrosion resistance and biological properties of NiTi alloys by substrate electropolishing

Although Ni-Ti-O nanopores(NPs) can be fabricated by anodization of mechanically polished NiTi alloys, the top disordered layer is difficult to remove thus hindering the functionality of the Ni-Ti-O NPs. In this work, an electropolishing(EP) pretreatment was performed on the NiTi substrate prior to anodization to thoroughly expose the NPs. Our results show that the EP pretreatment for 5 min perfectly removes the top disordered layer on the Ni-Ti-O NPs to expose the underlying NPs and consequently, the corrosion resistance and antibacterial ability are enhanced. The exposed NPs can elongate bone marrow mesenchymal stem cells, which may be responsible for the upregulated alkaline phosphatase activity, secretion of Type I collagen, and extracellular matrix mineralization. These results suggest that EP is a desirable pretreatment before anodization of the NiTi alloys because the irregular surface layer on the Ni-Ti-O NPs can be removed to enhance the corrosion resistance and biological functions.

Self-assembled nanosheets on NiTi alloy facilitate endothelial cell function and manipulate macrophage immune response

Stenting has been widely adopted for the treatment of cardiovascular diseases,but the complications such as in-stent restenosis and late stent thrombosis cannot be completely avoided,which are closely related to endothelial dysfunction and inflammatory response.In the present work,oxide nanosheets were grown on the surface of nearly equiatomic Ni Ti alloy by alkaline corrosion(AC),aiming at yielding favorable endothelial functionality and immune microenvironment.The results show nanosheets mainly composed of TiO_(2),Ni(OH)_(2),and K_(2)TiO_(3)can be grown on the alloy in KOH solution of 2.5–15 M at room temperature.The AC-treated samples significantly promote endothelial cell(EC)functionality such as proliferation,migration,NO production,VEGF secretion,and angiogenesis.In addition,the sample grown in KOH of 15 M can switch macrophages to an anti-inflammatory M2 phenotype and up-regulate the gene expression of VEGF to facilitate EC functionality.These results demonstrate that the nanosheets can directly and indirectly up-regulate EC functionality,possibly leading to rapid re-endothelialization of the stents thus addressing the stent-related complications.

Porous nickel–titanium alloy prepared by gel-casting

To explore the preparation of porous nickel- titanium alloy with excellent properties, larger size and complex shape, the premixed powder of Ni and Ti with atomic ratio of 1：1 was shaped by gel-casting. The effects of solids loading and the content of dispersant on flow ability of nickel-titanium slurry and the mechanical properties of nickel-titanium sintered body were studied. The drying models under different solids loading were also discussed. The results show that the viscosity of slurries significantly increases with an increase in solids loading. After a proper process of drying, the green body with complex shape is obtained. The sintered body with porosity rate reaching up to 49.5 % and compression strength reaching to 364.74 MPa could meet the basic demands of implant materials.

Corrosion behavior,antibacterial ability,and osteogenic activity of Zn-incorporated Ni-Ti-O nanopore layers on NiTi alloy

Development of bone fixation devices with excellent corrosion resistance,antibacterial ability,and osteogenic activity is critical for promoting fracture healing.In this study,Zn-incorporated nanopore(NP)layers were prepared on the NiTi alloy through anodization and hydrothermal treatment.Results show that Zn can be evenly incorporated into the NP layers in the form of ZnTiO_(2).The Zn-incorporated samples exhibit good corrosion resistance and significantly reduce Ni^(2+)release.Meanwhile,the samples can continuously release Zn^(2+),which is responsible for excellent long-term antibacterial ability.Furthermore,the synergetic effect of Zn^(2+) release and nanoporous structure of the NP layers endues the NiTi alloy excellent osteogenic activity,as verified by upregulated alkaline phosphatase activity,secretion of type I collagen,and extracellular matrix mineralization.Therefore,Zn-incorporated Ni-Ti-O NP layers have great potential as biomedical coatings of NiTi-based implant materials.