下颌骨骨折动力加压固定断面应力分析

实验采用反射光弹模拟应力分析法,通过受力模型等差线条纹图观测、分析、量化换算,对下颌骨骨折轴向和偏心动力加压固定作断面压应力比较研究.结果显示两种固定状态下骨折断面均表现为挤压应力,沿骨折线应力分布不均匀,板周区和牙槽区呈压应力高峰带,最大应力分量在轴向和偏心加压分别为1.8MPa和2.3MPa(板周区),以及0.5MPa和1.0MPa(牙槽区),中间区受力较弱.轴向动力加压总压力为100N,偏心动力加压总压力为140N,后者比前者断面应力分布稍趋合理.     

应用牵张成骨技术行牙槽嵴增高术的研究进展

牵张成骨 (distractionosteogenesis,DO)指在骨缝处或在截开的骨段用牵张装置按一定的速度和频率牵开 ,因此产生的骨间隙中形成新骨 ,从而达到使骨延长或增宽的目的。该技术用于四肢长骨已有近百年历史 ,在颅面部治疗颌骨缺损、畸形及阻塞性睡眠呼吸暂停综合征等领域也获得了成功。近年来 ,用牵张成骨技术增高牙槽嵴逐渐成为研究热点 ,现综述如下。一、牵张成骨技术与传统牙槽嵴增高术的比较牙槽嵴增高术分相对增高及绝对增高两种 ,前者指唇颊沟加深或牙槽嵴延伸术 ,后者指牙槽嵴增高术。唇颊沟加深术通过改变黏膜及肌附着的位置 ,使牙槽嵴…     

MAB225对人唾液腺腺样囊性癌细胞放射敏感性的影响

目的:研究表皮生长因子受体单克隆抗体(MAB225)对人唾液腺腺样囊性癌(ACC)细胞放射敏感性的影响。方法:通过双荧光染色法、四氮唑还原法(MTT)、流式细胞仪观察经MAB225处理后的ACC-2细胞放射后凋亡的变化,以评价MAB225对ACC-2细胞放射敏感性的影响。采用SPSS11.0软件包的单因素方差分析对数据进行统计学处理。结果:经MTT检测、双荧光染色和流式细胞仪检测,经MAB225和放射联合处理后的ACC-2细胞,其细胞凋亡比例较未处理组上升3倍;而单纯放射处理的ACC-2细胞,其细胞凋亡比例只增加1倍。结论:MAB225可以提高放射线对ACC-2细胞的杀伤作用,降低ACC-2细胞的放射后生存率。     

Shear bond strengths of plastic brackets with a mechanical base

This study compares the shear bond strengths of plastic brackets with a mechanical base and metal brackets using two different adhesives, and examines the modes of failure using a scanning electron microscope (SEM). Forty extracted human premolars were selected for bonding. Two types of brackets: metal and plastic-Spirit MB, and two orthodontic adhesives: System 1 + and Enlight, were used. After bonding, all samples were put into a 37 degrees C distilled water bath for 24 hours before shear bond strengths were tested. The bond strengths of the plastic brackets were significantly lower than those of the metal brackets (P < .0001). There was a statistically significant difference in bond strengths between System 1 + and Enlight for plastic brackets (P < .05), but not for metal brackets. The modes of failure predominantly occurred at the enamel/adhesive interface in the metal bracket-System 1 + group, within the adhesive in the metal bracket-Enlight and plastic bracket-System 1 + groups, and at the bracket/adhesive interface in the plastic bracket-Enlight group.     

差速传代纯化大鼠牙囊细胞

目的:建立一种简捷的分离培养和纯化大鼠牙囊细胞的方法。方法:分离出生后6dSD大鼠上下颌第一和第二磨牙完整牙胚,剥离牙囊和成釉器,剪碎后酶消化并混合培养,再利用多次差速传代纯化牙囊细胞。结果:原代细胞为牙囊细胞和成釉器细胞混合生长,差速传代培养到第4代可获得纯化的牙囊细胞。倒置显微镜下观察牙囊细胞呈长梭形或三角形,免疫组化染色抗波形丝蛋白阳性,抗角蛋白阴性。结论:利用多次差速传代可从混合培养的原代细胞中获得纯化的牙囊细胞。     

Nitrite reduction in acidic solution at a GC/Eastman-AQ-Os(bpy)32+-PVP composite modified electrode

The negatively charged polymer polyester sulfonic acid (Eastman-AQ, abbreviated to AQ), positively charged polymer polyvinyl pyridine (PVP) and mediator Os(bpy)₃²⁺ were used to construct composite modified glassy carbon (GC) electrodes (abbreviated to GC/AQ-Os(bpy)₃²⁺-PVP). The reduction of NO₂^? in acidic solution was taken as a model reaction to explore the properties of the modified electrode. On the steady state polarization curve of NO₂^? reduction there were two well-developed waves with much enhanced plateau current densities and positively shifted half-wave potentials compared with bare GC electrodes. In 0.05 mol/l H₂SO₄ + 5 mmol/l NO₂^? the modified electrode exhibited plateau current densities of 723 and 1153 μA cm^?2 and half-wave potential shifts of 0.29 and 0.56 V for the first and second current wave, respectively, showing promising potential for nitrite detection. The catalytic activity for NO₂^? reduction did not decrease appreciably over 4 months. A number of relevant kinetic and thermodynamic parameters are estimated experimentally. NO₂^? reduction at the composite modified electrodes is suggested to follow the SR mechanism (pure kinetic conditions involving mutual compensation between a catalytic reaction and substrate diffusion in the film in addition to diffusion in the solution phase) according to the Savéant–Andrieux theory.     

变形链球菌表面蛋白和葡糖基转移酶基因疫苗防龋动物实验:Keyes龋齿计分研究

目的 :了解变形链球菌基因疫苗 pcDNA3 pac和 pcDNA3 gtfB的免疫防龋效果。 方法 :2 8d龄Wistar大鼠 3 6只 ,随机分为pcDNA3 pac组 (A组 )、pcDNA3 gtfB组 (B组 )、pcDNA3 pac联合 pcDNA3 gtfB组 (C组 )、变形链球菌灭活全菌组 (D组 )、pcDNA3空载体组 (E组 )和PBS液组 (F组 )进行 3次双侧颌下腺腺周注射免疫。建立定菌鼠模型 ,诱龋 3个月 ,根据Keyes经典评分方法从龋损范围及深度进行龋损综合评估和比较。结果 :龋损牙面计分在 pcDNA3与PBS组最高 ,其次为单基因疫苗免疫组 ,联合免疫和灭活全菌细胞最低 (P <0 .0 1或P <0 .0 5 ) ;窝沟龋各级计分 :E级龋在单基因疫苗组 ,联合疫苗组、灭活全菌细胞组无区别 (P >0 .0 5 ) ,而PBS组和 pcDNA3组则较低 (P <0 .0 1) ;Dm级、Ds级则是联合免疫组与灭活全菌细胞组最低 ,单基因疫苗免疫组较高而PBS和 pcDNA3组最高 (P <0 .0 1或P <0 .0 5 ) ;Dx级四个免疫组发生率很低或不发生 ,显著低于PBS组和pcDNA3组 (P <0 .0 1)。结论 :重组质粒pcDNA3 gtfB和pcDNA3 pac具显著有效的免疫防龋作用 ,以联合基因疫苗免疫最好 ,是理想的防龋决策之一。     

三种不同弓丝结扎方式的椅旁时间对比研究

目的通过测量三种不同弓丝结扎方式的椅旁时间,说明SPEED矫治系统自锁结扎能减少椅旁时间,提高工作效率.方法选取采用SPEED托槽自锁结扎、MBT托槽不锈钢丝结扎及MBT托槽橡皮圈结扎的患者各20例.测量患者上下颌的拆、结扎时间,并进行对比分析.结果SPEED自锁托槽弹簧夹的开闭合总时间平均为60.81s,MBT托槽不锈钢结扎丝的拆、扎总时平均为345.69s,MBT托槽橡皮圈的拆、扎总时平均为242.88s.经统计学分析,三者之间均有显著性差异(p＜0.001).结论SPEED矫治器能大大地提高医生的工作效率,很有必要在病人多,医生少的中国进行推广.