3M Single Bond Universal粘接系统对前牙E-max铸瓷贴面修复的远期疗效观察

目的:探究观察3M Single Bond Universal粘接系统对前牙E-max铸瓷贴面修复的远期疗效。方法:选择2017年5月-2019年5月笔者医院收治的需前牙E-max铸瓷贴面修复患者63例(患牙113颗)为研究对象,均行经典贴面修复,根据粘接系统的不同将患者分为观察组(患者21例,患牙40颗,采用3M Single Bond Universal粘接系统)、对照1组(患者21例,患牙36颗,采用VariolinkⅡ粘接系统)、对照2组(患者21例,患牙37颗,采用BISCO CHOICE 2粘接系统)。治疗后三组均于1周、3个月、12个月时进行随访,观察三组治疗后1周、3个月、12个月内贴面修复效果、贴面修复失败率及不良反应发生率。结果:术后1周,三组患者均无失败案例;对照1组存在2颗修复体保存完整度为Ⅰ级的患牙,对照2组存在3颗修复体保存完整度为I级的患牙,观察组未存在该类患者;术后12个月,观察组存在1颗修复体保存完整度Ⅱ级患牙,对照1组存在1颗保存完整度I级患牙,3颗修复体保存完整度Ⅱ级患牙,对照2组存在2颗保存完整度I级患牙,3颗修复体保存完整度Ⅱ级患牙。三组患者治疗效果比较,差异无统计学意义(P>0.05);术后1周、3个月、12个月三组贴面修复失败率比较,差异无统计学意义(P>0.05);随访期间内,三组患者不良反应情况比较差异均无统计学意义(P>0.05)。结论:对于前牙E-max铸瓷贴面修复患者,选取合适的适应证,并做好备牙步骤,3M Single Bond Universal与经典VariolinkⅡ粘接系统及BISCO CHOICE 2粘接系统治疗效果并无显著差异,值得在临床推广使用。

Designer Mg-Mg and Zn-Zn Single Bonds Facilitated by Double Aromaticity in the M2B7^-(M=Mg,Zn)Clusters

The simple homodinuclear M-M single bonds for group II and XII elements are difficult to obtain as a result of the fulfilled s2electronic configurations,consequently,a dicationic prototype is often utilized to design the M^+-M^+single bond.Existing studies generally use sterically bulky organic ligands L^-to synthesize the compounds in the L^--M^+-M^+-L-manner.However,here we report the design of Mg-Mg and Zn-Zn single bonds in two ligandless clusters,Mg2B7-and Zn2B7-,using density functional theory methods.The global minima of both of the clusters are in the form of M2^2+(B7^3-),where the M-M single bonds are positioned above a quasi-planar hexagonal B7 moiety.Chemical bonding analyses further confirm the existence of Mg-Mg and Zn-Zn single bonds in these clusters,which are driven by the unusually stable B7^3-moiety that is bothσandπaromatic.Vertical detachment energies of Mg2B7-and Zn2B7-are calculated to be 2.79 e V and 2.94 e V,respectively,for the future comparisons with experimental data.

The Even-Odd and the Isoelectronicity Rules Applied to Single Covalent Bonds in Ionic, Double-Face-Centered Cubic and Diamond-Like Crystals

Although atom configuration in crystals is precisely known thanks to imaging techniques, there is no experimental way to know the exact location of bonds or charges. Many different representations have been proposed, yet no theory to unify conceptions. The present paper describes methods to derive bonds and charge location in double-face-centered cubic crystals with 4 and 6 atoms per unit cell using two novel rules introduced in earlier works: the even-odd and the isoelectronicity rules. Both of these rules were previously applied to ions, molecules and some solids, and the even-odd rule was also tested on two covalent crystal structures: centered-cubic and single-face-centered cubic crystals. In the present study, the diamond-like structure was subjected to the isoelectronicity rule in order to derive Zinc-blende structures. Rock-salt-like crystals were derived from each other using both rules. These structures represent together more than 230 different crystals. Findings for these structures are threefold: both rules describe a very sure method to obtain valid single covalent-bonded structures;single covalent structures can be used in every case instead of the classical ionic model;covalent bonds and charges positions do not have any relation with the valence number given in the periodic table.

B-C Bond in Diamond Single Crystal Synthesized with h-BN Additive at High Pressure and High Temperature

The synthesis of diamond single crystal in the Fe64Ni36-C system with h-BN additive is investigated at pressure 6.5 GPa and temperature range of 1300-1400℃. The color of the obtained diamond crystals translates from yellow to dark green with increasing the h-BN addition. Fourier-transform infrared （FTIR） results indicate that sp2 hybridization B-N-B and B-N structures generate when the additive content reaches a certain value in the system. The two peaks are located at 745 and 1425cm-1, respectively. Fhrthermore, the FTIR characteristic peak resulting from nitrogen pairs is noticed and it tends to vanish when the h-BN addition reaches 1.1 wt%. Furthermore, Raman peak of the synthesized diamond shifts down to a lower wavenumber with increasing the h-BN ~ddition content in the synthesis system.

Exploration and preliminary clinical investigation of an adhesive approach for primary tooth restoration

The current study aims to investigate a suitable adhesive for primary tooth enamel. Shear bond strength(SBS)of primary teeth and the length of resin protrusion were analyzed using one-way ANOVA with Bonferroni multiple comparison tests after etching with 35% H_(3)PO_(4). SBS and marginal microleakage tests were conducted with Single Bond Universal(SBU)/Single Bond 2(SB2) adhesives with or without pre-etching using a nonparametric Kruskal-Wallis test. Clinical investigations were performed to validate the adhesive for primary teeth restoration using Chi-square tests. Results showed that the SBS and length of resin protrusion increased significantly with the etching time. Teeth in the SBU with 35% H_(3)PO_(4)pre-etching groups had higher bond strength and lower marginal microleakage than those in the SB2 groups. Mixed fractures were more common in the 35% H_(3)PO_(4)etched 30 s + SB2/SBU groups. Clinical investigations showed significant differences between the two groups in cumulative retention rates at the 6-, 12-and 18-month follow-up evaluations, as well as in marginal adaptation, discoloration, and secondary caries at the 12-and 18-month follow-up assessments.Together, pre-etching primary teeth enamel for 30 s before SBU treatment improved clinical composite resin restoration, which can provide a suitable approach for restoration of primary teeth.

Single crystal-single crystal bonding of langasite exhibited high strength of 23.28 MPa

Langasite(LGS,La_(3)Ga_(5)SiO_(14))is a promising material in high-temperature piezoelectric devices due to its excellent thermal stability,piezoelectricity,and electrical property.A major challenge in the development of LGS-based devices is to form high-strength bonding of the brittle LGS.Here,we report that the single crystal-single crystal(dual-SC)bonding of LGS is realized through thermal activation under a low com-pression of 50 kPa for the first time.A record bonding strength of 23.28 MPa is achieved within the dual-SC bonded LGS/LGS structure(with a high bonding ratio exceeding 93%),which is 5 times higher than that of the recent reported LGS/LGS bonding structure(in which a relatively fragile amorphous interface layer is formed between the two LGS samples).The smooth and void-free dual-SC bonding interface of LGS is verified via the cross-sectional transmission electron microscopy(TEM)observations.

Pulling growth technique towards rare earth single crystals

Pulling growth technique serves as a popular method to grow congruent melting single crystals with multiscale sizes ranging from micrometers to centimeters.In order to obtain high quality single crystals,the crystal constituents would be arranged at the lattice sites by precisely controlling the crystal growth process.Growing interface is the position where the phase transition of crystal constituents occurs during pulling growth process.The precise control of energy at the growing interface becomes a key technique in pulling growth.In this work,we review some recent advances of pulling technique towards rare earth single crystal growth.In Czochralski pulling growth,the optimized growth parameters were designed for rare earth ions doped Y_3Al_5O_(12)and Ce:(Lu_(1-x)Y_x)_2Si O_5on the basis of anisotropic chemical bonding and isotropic mass transfer calculations at the growing interface.The fast growth of high quality rare earth single crystals is realized by controlling crystallization thermodynamics and kinetics in different size zones.On the other hand,the micro pulling down technique can be used for high throughput screening novel rare earth optical crystals.The growth interface control is realized by improving the crucible bottom and temperature field,which favors the growth of rare earth crystal fibers.The rare earth laser crystal fiber can serve as another kind of laser gain medium between conventional bulk single crystal and glass fiber.The future work on pulling technique might focus on the mass production of rare earth single crystals with extreme size and with the size near that of devices.

不同浓度单宁酸在不同酸蚀模式下对通用型粘接剂粘接强度的影响

目的研究不同浓度单宁酸在全酸蚀与自酸蚀条件对通用型粘接剂在牙本质表面粘接强度的影响。方法将60颗无龋离体人磨牙置于存储盒中随机盲取分成2组(全酸蚀A组与自酸蚀B组,n=30),再将每组随机分为5个亚组(n=6)。在使用通用型粘接剂Single Bond Universal(SBU)前,在牙本质面分别涂抹浓度为0%(对照组)、25%、50%、75%和100%的单宁酸3 min并冲洗吹干。实验试件在37℃水中保存24 h后进行微拉伸强度测试(μTBSt)。使用Two-Way ANOVA与Games-Howell对数据进行统计学分析。用体式显微镜观察断裂面模式并在扫描电镜(SEM)下观察微拉伸试件的牙本质断端。结果在全酸蚀模式下,75%单宁酸组粘接强度[(34.51±8.43)MPa]与100%单宁酸组粘接强度[(36.16±5.20)MPa]显著高于其他各组(F=32.301,P<0.001);在自酸蚀模式下,25%单宁酸[(31.06±3.41)MPa]可显著提升SBU与牙本质粘接强度(F=23.570,P<0.001)。双因素分析结果证实,单宁酸浓度(F=23.134,P<0.001)与酸蚀模式(F=4.465,P=0.036)对粘接强度具有显著影响且两要素间显著相关(F=28.231,P<0.001)。断裂模式分析与电镜观察结果表明,在牙本质表面不同酸蚀模式与不同浓度单宁酸所形成的界面形态差异显著。结论在不同酸蚀模式下,不同浓度的单宁酸均可显著改善SBU与牙本质的粘接强度。