Finite element study of controlling factors of anterior intrusion and torque during Temporary Skeletal Anchorage Device (TSAD) dependent en masse retraction without posterior appliances: Biocreative hybrid retractor (CH-retractor)

Objectives:To evaluate, using the finite element method (FEM), the factors that allow control of the anterior teeth during en masse retraction with the Biocreative hybrid retractor (CH-retractor) using different sizes of nickel-titanium (NiTi) archwires and various gable bends on the stainless-steel (SS) archwires.Materials and Methods:Using FEM, the anterior archwire section, engaged on the anterior dentition, was modeled in NiTi, and another assembly, the posterior guiding archwire, was modeled in SS. Two dimensions (0.016 × 0.022- and 0.017 × 0.025-inch NiTi) of the anterior archwires and different degrees (0°, 15°, 30°, 45°, and 60°) of the gable bends on the guiding wire were applied to the CH-retractor on the anterior segment to evaluate torque and intrusion with 100-g retraction force to TSADs. Finite element analysis permitted sophisticated analysis of anterior tooth displacement.Results:With a 0° gable bend all anterior teeth experienced extrusion. The canines showed a larger amount of extrusion than did the central and lateral incisors. With a gable bend of >15°, all anterior teeth exhibited intrusion. Bodily movement of the central incisor required a 30°∼45° gable bend when using anterior segments of 0.016 × 0.022-inch NiTi and 15°∼30° gable bend with the 0.017 × 0.025-inch NiTi.Conclusions:With the CH-retractor, varying the size of the NiTi archwire and/or varying the amount of gable bend on the SS archwire affects control of the anterior teeth during en masse retraction without a posterior appliance.     

Embedded NiTi Wires for Improved Dynamic Thermomechanical Performance of Silicone Elastomers

The extraordinary properties of shape memory NiTi alloy are combined with the inherent viscoelastic behavior of a silicon elastomer. NiTi wires are incorporated in a silicon elastomer matrix. Benefits include features as electrical/thermal conductivity, reinforcement along with enhanced damping performance and flexibility. To gain more insight of this composite, a comprehensive dynamic thermomechanical analysis is performed and the temperature- as well as frequency-dependent storage modulus and the mechanical loss factor are obtained. The analyses are realized for the composite and single components. Moreover, the models to express the examined properties and their temperature along with the frequency dependencies are also presented.     

两种根管再治疗镍钛器械去除椭圆形弯曲根管内充填物的效果评价

目的:评价2种根管再治疗镍钛器械去除椭圆形弯曲根管内充填物的效果。方法:离体的80颗根管呈椭圆形且弯曲的下颌前磨牙经Hero642预备、热牙胶垂直加压充填后随机分为4组,分别用ProTaper Universal、R-Endo、Hero642和手用H锉去除根充物,测量各组根充物的残留量百分比和操作时间。结果:4组样本均有根充物残留,ProTaper Universal、R-Endo和Hero642组根充物残留量百分比、操作时间均少于手用H锉组(P<0.01),前3组间的差异无统计学意义(P>0.05)。结论:ProTaper Universal、R-Endo机动镍钛器械对椭圆形弯曲根管内充填物的清除效果优于手用器械,且可减少操作时间,但仍不能彻底清除根充物。     

根管内台阶处理的临床研究

目的：评价根管显微镜以及预弯手用镍钛器械ProTaper去除根管台阶临床效果。方法：将160例根管台阶病例随机分为2组,A组在显微镜下疏通台阶,B组在肉眼下完成,使用用根尖定位仪及x线片评估台阶疏通是否成功;再将疏通成功的118例随机分为2组,C组使用预弯手用不锈钢器械疏通台阶并成形,D组使用手用Pro－Taper消除台阶并成形,记录两组消除台阶并预备到主尖的操作时间。结果：160个阻塞的根管中,成功疏通率为73．75％。根管上中段台阶的疏通率明显高于下段台阶（P〈O．05）;AB两组根管疏通率在根管上段有显著差异性（P〈O．05）;D组的操作时间短于C组（P〈0．05）。结论：使用根管手术显微镜,对根管中下段台阶的疏通结果并无显著影响;预弯手用大锥度镍钛器械能有效的消除台阶,节省预备时间,防止根尖偏移及新的台阶形成。     

Cutting Efficiency of Reciproc and WaveOne Reciprocating Instruments

Introduction

The aim of the present study was to evaluate the cutting efficiency of 2 new reciprocating instruments, Reciproc and WaveOne.

Methods

Twenty-four new Reciproc R25 and 24 new WaveOne Primary files were activated by using a torque-controlled motor (Silver Reciproc) and divided into 4 groups (n = 12): group 1, Reciproc activated by Reciproc ALL program; group 2, Reciproc activated by WaveOne ALL program; group 3, WaveOne activated by Reciproc ALL program; and group 4, WaveOne activated by WaveOne ALL program. The device used for the cutting test consisted of a main frame to which a mobile plastic support for the handpiece is connected and a stainless steel block containing a Plexiglas block (inPlexiglass, Rome, Italy) against which the cutting efficiency of the instruments was tested. The length of the block cut in 1 minute was measured in a computerized program with a precision of 0.1 mm. Means and standard deviations of each group were calculated, and data were statistically analyzed with 1-way analysis of variance and Bonferroni test (P < .05).

Results

Reciproc R25 displayed greater cutting efficiency than WaveOne Primary for both the movements used (P < .05); in particular, Reciproc instruments used with their proper reciprocating motion presented a statistically significant higher cutting efficiency than WaveOne instruments used with their proper reciprocating motion (P < .05). There was no statistically significant difference between the 2 movements for both instruments (P > .05).

Conclusions

Reciproc instruments demonstrated statistically higher cutting efficiency than WaveOne instruments.     

热处理对NiTi自膨式血管支架形状恢复能力的影响

依据NiTi自膨式血管支架的工作机理及临床使用条件,研究不同热处理条件(包括温度和时间)后的NiTi自膨式血管支架在形状恢复能力的变化及耐腐蚀性能.分析不同热处理工艺条件下支架Af温度、弹性变形适应性、径向支撑力、局部抗挤压和耐腐蚀等性能指标的变化.结果表明:在热处理温度为500℃,热处理时间为10 min的试验条件下...