国产直丝陶瓷托槽摩擦力性能的研究

目的研究国产直丝陶瓷托槽的摩擦力性能。方法利用MTS Tytron250微力试验机测定我院与清华大学联合研制开发的下颌尖牙位直丝陶瓷托槽与0．016英寸不锈钢圆丝、0．016×0．022英寸不锈钢方丝、0．016英寸镍钛丝在不锈钢丝结扎方式下的摩擦力,并以一种进口陶瓷托槽作为对照组。结果国产直丝陶瓷托槽的最大静摩擦力与对照组陶瓷托槽相比差异无显著统计学意义,平均动摩擦力比对照组陶瓷托槽显著降低。结论国产直丝陶瓷托槽的摩擦性能可以满足临床需要。     

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目的对自锁托槽与传统托槽滑动阻力的大小及变化规律进行对比研究。方法本研究于2011年9—12月在山西医科大学口腔医院和太原理工大学应用力学与生物医学研究所共同完成。根据人体实际弹性模量比例制作含牙周膜的上颌仿真模型,测试自锁托槽和传统托槽分别与0．016英寸、0．018英寸的镍钛丝和0．017英寸×0．022英寸、0．018英寸×0．025英寸、0．019英寸x0．025英寸的不锈钢方丝匹配时的滑动阻力大小。结果使用同种弓丝时,滑动阻力由小到大排列：DamonQ被动自锁托槽〈Tomy主动自锁托槽〈传统金属托槽,两两比较差异有统计学意义（P〈0．05）。同一种托槽情况下,除0．019英寸×0．025英寸不锈钢方丝外,其余滑动阻力都随弓丝直径的增大而增大,且两两比较差异有统计学意义（P〈0．05）。结论临床实践中托槽类型与弓丝的匹配对滑动阻力的影响十分重要,从而实现牙齿的快速有效移动。     

唇舌侧托槽转矩控制性能的有限元对比分析

目的：分析唇舌侧托槽转矩控制性能的差异,同时探讨不同材质不同尺寸的弓丝对舌侧托槽转矩控制的影响规律。方法：建立左上尖牙到右上尖牙的唇舌侧托槽三维有限元模型,在弓丝尺寸及材质不同的情况下,模拟临床左上中切牙转矩加载±20°。结果：随着转矩角度的增大,唇舌侧托槽转矩值逐渐增大,舌侧托槽转矩值为唇侧托槽的3～5倍;0．48 mm ×0．64 mm 弓丝的转矩值大于0．43 mm ×0．64 mm;弓丝尺寸相同时,不锈钢丝（SS）,β－钛丝（TMA）,镍钛丝（NiTi）,转矩值依次减小。结论：唇舌侧托槽转矩均随着转矩角度和弓丝的弹性模量的增大而增大;在相同的转矩角度下,舌侧托槽产生的转矩值大于唇侧托槽;舌侧托槽的转矩值与弓丝尺寸及材质有关。     

弓丝与结扎方法对摩擦力影响的实验研究

目的:了解4种弓丝和2种结扎方法对托槽与弓丝摩擦力的影响。方法:在干燥条件下,按正交实验设计,使用LJ-500型拉力实验机的微型测力计,测试4种弓丝与6种直丝托槽组合及采用2种结扎法时在后牙段的动、静摩擦力。所得数据进行方差分析和二次响应回归分析。结果:在弓丝与所有托槽组合中,0.018英寸×0.025英寸(1in=2.54cm)的不锈钢方丝动、静摩擦力最小,0.019英寸×0.025英寸的不锈钢方丝动、静摩擦力最大,0.018与0.020英寸不锈钢圆丝介于两者之间,但0.018英寸圆丝的动摩擦力较大,0.020英寸圆丝的静摩擦力较大。动、静摩擦力平均百分比从小到大依次为:0.019英寸×0.025英寸方丝、0.020英寸圆丝、0.018英寸×0.025英寸方丝、0.018英寸的圆丝。弹力橡皮圈结扎的动、静摩擦力及动、静摩擦力平均百分比均大于不锈钢丝结扎。结论:0.018英寸的不锈钢圆丝不适宜滑动机制;在0.022英寸系统的直丝托槽中,用0.019英寸×0.025英寸不锈钢方丝关闭间隙,应尽可能加强支抗控制;干燥条件下弹力橡皮圈结扎不利于托槽、弓丝滑动。     

唇舌侧弓丝力学性能差异的三维有限元分析

目的 根据三托槽弯曲实验原理,应用三维有限元方法研究唇舌侧弓丝力学性能的差异。方法 建立槽沟均为0.022英寸的上颌切牙水平槽沟的Discovery唇侧托槽、垂直槽沟的第7代Kurz舌侧托槽共3颗,以及相应弓丝、结扎丝的三维有限元模型,分析不同弓丝材质、尺寸以及托槽间距下的唇舌侧弓丝的力学性能。结果 唇舌侧弓丝的载荷形变曲线图变化规律一致,主要由弓丝性质决定。弓丝材质对载荷的影响大于尺寸的影响,但小于两者的协同作用：舌侧弓丝载荷值随弓丝尺寸增大而增加（0.019×0.025 英寸不锈钢丝载荷值约为同材质0.017×0.025 英寸弓丝的 1.46倍）,但是该变化小于弓丝材质引起的变化（不锈钢丝载荷值约为同尺寸镍钛丝的2.73倍）,更小于弓丝尺寸与材质共同改变所引起的变化（0.019×0.025英寸不锈钢丝的载荷值较0.017×0.025 英寸镍钛丝增大约3.5倍）。在相同条件下,舌侧弓丝载荷值大于唇侧。随着托槽间距的增加,唇舌侧弓丝载荷值均减小（10 mm处加载时约为16 mm处的2.42倍,12、14 mm处分别为16 mm处的1.59倍及1.33倍）,前期变化幅度较大,后期趋于稳定。结论 在相同条件下,舌侧弓丝载荷值大于唇侧,提示应当选择比唇侧弓丝直径更小、刚度更低的弓丝作为舌侧矫治弓丝。临床上在选择弓丝时,首先应考虑弓丝的材质,其次为尺寸,并注意两者的协同作用,注意托槽间距对弓丝性能的影响。     

自锁托槽及弓丝材质对转矩效能的影响

目的探讨自锁托槽系统与不同弓丝组合的转矩效能的差异及变化规律。方法分别测试2种被动自锁托槽系统（Damon3、SmartClip）、2种主动自锁托槽系统（Time2、OPA—K）与2种弓丝（0．019×0．025英寸镍钛方丝、0．019×0．025英寸不锈钢方丝）组合的转矩效能。结果（1）除了SmartCliD与Damon3自锁托槽（P=1．000）、OPA—K与Time2自锁托槽（P=0．999）的转矩效能间差异无统计学意义外．其他自锁托槽间的转矩效能的差异均有统计学意义（P〈0．001）;（2）0．019×0．025英寸镍钛方丝、0．019×0．025英寸不锈钢方丝相同自锁托槽组间转矩效能的差异有统计学意义（P〈0．001）。结论被动自锁托槽的转矩效能明显低于主动自锁托槽,不同弓丝转矩效能的差异与边缘斜面有关。     

超滑结扎橡皮圈和常规结扎橡皮圈对摩擦力影响的对比研究

目的：探讨和比较超滑结扎橡皮圈和常规结扎橡皮圈在干燥和自然唾液条件下对摩擦力的影响。方法：选用超滑结扎橡皮圈和常规结扎橡皮圈、2种弓丝（0．019×0．025英寸方丝,0．018英寸圆丝）、MBT^TM直丝托槽组,模拟弓丝在后牙段在干燥和自然唾液条件下滑动,测量各组合的静、动摩擦力。结果：在于燥的条件下,无论在方丝组合还是圆丝组合,2种结扎橡皮圈静动摩擦力都无显著性差异。超滑结扎橡皮圈在自然唾液1h的条件下,与常规结扎橡皮圈结扎相比,在方丝组合,静摩擦力降低31.18％,动摩擦力降低21．66％;在圆丝组合,静摩擦力降低31．98％,动摩擦力降低28．67％。结论：超滑结扎橡皮圈在干燥条件下对静动摩擦力无显著影响。在自然唾液浸润1h的条件下,无论在方丝组合还是圆丝组合,超滑结扎橡皮圈能起到降低静动摩擦力的作用。     

Lock-loose托槽与传统托槽摩擦力特性的比较研究

目的 在干燥和人工唾液环境中测量Lock-loose托槽结扎中间翼和结扎全翼时与弓丝之间滑动摩擦力和静摩擦力的大小,并与传统四翼托槽和自锁托槽进行对比。方法 应用原子力显微镜观察不锈钢弓丝与不同托槽摩擦前后的表观形貌。选用Lock-loose托槽、传统四翼托槽和自锁托槽,分别与0.406 4 mm、0.457 2 mm不锈钢圆丝和0.457 2 mm×0.634 9 mm、0.482 6 mm×0.634 9 mm不锈钢方丝组合,其中Lock-loose托槽使用结扎中间翼和结扎全翼两种结扎方式。使用电子万能力学实验机测量干燥和人工唾液两种环境下弓丝在托槽内滑动的动、静摩擦力。结果 不同尺寸弓丝与不同托槽摩擦前后的表面粗糙度无明显差异（P>0.05）;Lock-loose托槽结扎中间翼与4种弓丝组合的动、静摩擦力均接近于0,与传统四翼托槽有明显差异（P<0.05）;与0.457 2 mm×0.634 9 mm不锈钢方丝组合时,Lock-loose托槽结扎全翼可以获得最大动、静摩擦力,与传统四翼托槽和自锁托槽的差异有统计学意义（P<0.05）;人工唾液环境中的摩擦力小于干燥环境中的摩擦力（P<0.05）。结论 Lock-loose托槽可以通过不同的结扎方式调节并获得临床所需的摩擦力,有效解决了低摩擦力与强支抗控制的矛盾问题。     

脱落托槽热处理后对摩擦力影响的实验研究

目的测试热处理对托槽与弓丝间最大静摩擦力的影响。方法在干燥条件下,选取0.022×0.028英寸上颌尖牙不锈钢直丝托槽36枚,弓丝为0.019×0.025英寸不锈钢方丝。将36枚托槽随机分成三组,每组12枚,第一组不做任何处理,第二组、第三组托槽背板粘一薄层京津釉质粘结剂,热处理后用探针去除粘结剂,第三组托槽再进行超声清洗5分钟,分别测试这三组托槽与弓丝间最大静摩擦力。结果测得未经处理的上颌尖牙托槽与0.019×0.025英寸弓丝间最大静摩擦力值为74.67±12.73g;热处理及热处理后经超声清洗的托槽与弓丝间最大静摩擦力值分别是66.31±12.44g、61.97±13.47g。结论热处理及热处理后经超声清洗的托槽与弓丝间产生的最大静摩擦力值较未经任何处理的托槽与弓丝间产生的最大静摩擦力值明显减小。     

人工唾液中直丝弓托槽与弓丝静摩擦力的实验研究

目的探讨人工唾液条件下,不同时间,几种直丝托槽与弓丝在后牙段的静摩擦力特点。方法在人工唾液条件下,4个时间段,测试4种直丝托槽与4种弓丝组合在后牙段的静摩擦力。结果0.46mm不锈钢圆丝的静摩擦力最小,0.48mm×0.64mm不锈钢方丝的静摩擦力最大。弓丝、托槽组合在人工唾液条件下作用15d静摩擦力最大、30d静摩擦力最小。结论0.46mm不锈钢圆丝的静摩擦力最小;人工唾液作用30d静摩擦力最小。     

Long-term monitoring of microleakage of different amalgams with different liners

STATEMENT OF PROBLEM: Microleakage is a major factor contributing to the occurrence of secondary caries around amalgam restorations. Purpose The purpose of this study was to evaluate the effect of amalgam type, liner type, and storage period on microleakage. MATERIAL AND METHODS: Two hundred seventy bovine incisors were divided into 18 groups (n = 15). Two high-copper amalgam alloys (admixed and spherical type) and 3 liner options (no liner, varnish, and adhesive) were used to restore Class V preparations. After placement of restorations, the teeth were stored for 3 different periods (1 day, 1 week, and 12 months) in saline solution, After storage, the specimens were immersed in 0.5% methylene blue for 24 hours, sectioned, and then mean depth of dye penetration was measured separately for the incisal and cervical areas with the use of a binocular microscope (x200). Scores were assigned to a millimeter scale (+/- 0.2 mm). The data were analyzed with a 3-way analysis of variance and the Tukey Honestly Significant Different test (alpha = .05). RESULTS: The 3-way interaction was significant (P < .001 for the cervical and occlusal margins). After short-term storage (1 day and 1 week), the admixed alloy showed significantly lower leakage values than the spherical alloy only in cervical margins (1.45 and 1.56 for the admixed and 1.62 and 1.50 for the spherical alloy at the cervical [P = .034] and incisal margins [P = .702]), respectively. After 12 months, values decreased significantly for both amalgams, which were similar and lower than for the short-term storage period (short-term values of 1.62 and 1.39 for the admixed and 1.69 and 1.46 for the spherical alloy at the cervical and incisal margins, respectively; long-term values of 0.22 and 0.20 for the admixed and 0.33 and 0.36 for the spherical alloy at the cervical and incisal margins, respectively [P < .019]). When the adhesive was used, significantly superior sealing was observed for both amalgams. For the no liner and cavity varnish groups, the admixed alloy showed superior performance compared to the spherical alloy (with no liner, 1.11 and 0.98 for the admixed and 0.83 and 1.08 for the spherical alloy at the cervical and incisal margins, respectively; with varnish, 1.19 and 1.22 for the admixed and 1.63 and 1.34 for the spherical alloy, at the cervical and incisal margins, respectively [P < .037]). CONCLUSION: In the short-term, the lowest degree of leakage was found when adhesive was used. After 1 year, no differences were detected, regardless of the amalgam type and liner used.     

Mechanical behavior and microstructural characterization of different zirconia polycrystals in different thicknesses

PURPOSETo characterize the microstructure of three yttria partially stabilized zirconia ceramics and to compare their hardness, indentation fracture resistance (IFR), biaxial flexural strength (BFS), and fatigue flexural strength.MATERIALS AND METHODSDisc-shaped specimens were obtained from 3Y-TZP (Vita YZ HT), 4Y-PSZ (Vita YZ ST) and 5Y-PSZ (Vita YZ XT), following the ISO 6872/2015 guidelines for BFS testing (final dimensions of 12 mm in diameter, 0.7 and 1.2 ± 0.1 mm in thicknesses). Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were performed, and mechanical properties were assessed by Vickers hardness, IFR, quasi-static BFS and fatigue tests.RESULTSAll ceramics showed similar chemical compositions, but mainly differed in the amount of yttria, which was higher as the amount of cubic phase in the diffractogram (5Y-PSZ > 4Y-PSZ > 3Y-TZP). The 4Y- and 5Y-PSZ specimens showed surface defects under SEM, while 3Y-TZP exhibited greater grain uniformity on the surface. 5Y-PSZ and 3Y-TZP presented the highest hardness values, while 3Y-TZP was higher than 4Y- and 5Y-PSZ with regard to the IFR. The 5Y-PSZ specimen (0.7 and 1.2 mm) showed the worst mechanical performance (fatigue BFS and cycles until failure), while 3Y-TZP and 4Y-PSZ presented statistically similar values, higher than 5Y-PSZ for both thicknesses (0.7 and 1.2 mm). Moreover, 3Y-TZP showed the highest (1.2 mm group) and the lowest (0.7 mm group) degradation percentage, and 5Y-PSZ had higher strength degradation than 4Y-PSZ group.CONCLUSIONDespite the microstructural differences, 4Y-PSZ and 3Y-TZP had similar fatigue behavior regardless of thickness. 5Y-PSZ had the lowest mechanical performance.     

2种光固化灯固化对3种不同复合树脂聚合收缩的影响

目的:比较2种光固化灯对3种复合树脂聚合收缩的影响。方法:相移投影栅形貌测量仪测量Z100、Z250、AP-X等3种复合树脂在卤素灯和发光二极管固化灯开始固化后50s及开始固化后400s的树脂聚合收缩量。使用SPSS12.0软件包对QTH及LED固化组聚合收缩量进行单因素方差分析。结果:在开始固化后50s和400s,QTH固化灯和LED固化灯固化Z100、Z250树脂产生的聚合收缩量有显著差异,QTH固化灯固化Z100、Z250树脂产生的聚合收缩量显著大于LED固化灯(P<0.05),QTH和LED固化灯固化AP-X树脂产生的聚合收缩量则无统计学差异(P>0.05)。结论:LED及QTH固化灯固化Z100、Z250树脂产生的聚合收缩影响有显著差异(P<0.05),LED及QTH固化灯固化AP-X产生的聚合收缩无显著差异(P>0.05)。     

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目的 评价不同牙根暴露量的牙冠延长术对不同牙位的疗效.方法 选择2007年1月至2011年1月沈阳市口腔医院拟行牙冠延长术的患者122例,共148颗患牙(前牙68颗、前磨牙48颗和磨牙32颗).各牙位根据牙冠延长术中牙根暴露量(3或4 mm)随机等分.检查术前及术后1个月、6个月和1年的出血指数、牙齿松动度、牙周袋深度和附着丧失,并进行比较.结果 牙冠延长术中牙根暴露量为3 mm时,术后各患牙均未出现松动,在术后1个月时均出现牙龈出血,术后6个月和1年牙龈出血得到改善；牙根暴露量为4 mm时,术后1个月前牙出现松动,在术后6个月及1年恢复稳定,前磨牙和磨牙在术后均未出现松动.所有患牙的牙周袋深度和附着丧失在治疗后均有较明显的改善.结论 术中牙根暴露3 mm和4mm远期疗效均满意；为了获得更多的临床牙冠实现更好的修复条件,暴露牙根最好在4mm左右；而考虑到前牙美观问题,建议在前牙区术中牙根暴露量最好控制在3 mm以内.     

不同间隔时间预备不同桩核系统对桩核微渗漏的影响

目的：研究不同间隔时间预备不同桩核系统对微渗漏的影响.方法：收集因正畸需要拔除的132颗下颌单根前磨牙,进行根管治疗、根管预备和桩核制作及粘结.132颗牙随机分为4组,分别在桩核粘固后5 min、15 min、30 min、24 h,阴性对照组进行牙体预备,每组内再随机分为铸造桩核磷酸锌粘固、铸造桩核聚羧酸锌粘固和玻璃纤维桩核树脂粘固亚组.每一标本进行染色法评价微渗漏情况.结果：相同的桩核系统中,渗漏值随着桩核粘固间隔时间的延长而降低;相同的间隔时间下,5 min、15 min和24 h时,纤维桩核系统的渗漏值最小,与其它两组比较均有统计学意义（P＜0.05）,30 min时铸造桩核磷酸锌粘固组与纤维桩核系统组无统计学意义（P＞0.05）.结论：不同间隔时间预备不同桩核系统对桩核微渗漏值有影响,为了桩核的稳固,应尽量在桩核粘固24 h后进行牙体预备.     

不同抛光工具对不同类型复合树脂表面微观结构的影响

目的：探讨抛光工具对树脂表面微观结构的影响并与离体天然牙釉质表面进行比较。方法：将5种树脂试件（n＝9）随机各分为3组（n＝3）：Astropol抛光（A）组、Sof-Lex抛光（B）组、Super-snap抛光（C）组,分别进行抛光,对照（D）组为离体牙釉质表面。原子力显微镜测试试件表面粗糙度和微观结构。结果：抛光后A组的Ra值低于B组（P＝0．015）;Z350 XT树脂抛光后获得的Ra值最低（P＜0．05）;用3种不同的抛光工具抛光5种不同的树脂与对照组的Ra值比较无统计学差异（P＞0．05）。结论：Astropol抛光工具效果优于Sof-Lex;Z350 XT与其它4种树脂相比有更好的抛光性能;3种抛光工具对5种树脂抛光均有效。     

Microhardness of different thicknesses of resin composite polymerized by conventional photocuring at different distances

This in vitro study sought to evaluate the influence of photocuring modes and polymerization time on the microhardness of a hybrid composite resin. Sixty composite resin specimens were prepared at random and divided into 12 experimental groups (n=5), consisting of four curing tip distances (2.0 mm, 4.0 mm, 6.0 mm, and 8.0 mm) and three sample thicknesses (0.5 mm, 1.0 mm, and 2.0 mm). All samples were polymerized with a continuous output at 550 mW/cm2. After 24 hours, Knoop microhardness measurements were obtained on top and bottom surfaces of the sample, with a load of 25 g for 10 seconds. Five indentations were made on each surface of each sample. Subdivided parcels ANOVA test and Tukey test were performed (p = 0.05). There were no statistical differences among the experimental groups for the top surface. On the bottom surface, 0.5 mm and 1.0 mm sample thicknesses showed significantly higher hardness means for all photocuring tip distances when compared with the 2.0 mm sample thickness. In terms of the photocuring tip distance, the 2.0 mm and 4.0 mm distances showed significantly higher hardness means for all sample thicknesses when compared with the 8.0 mm distance. For all experimental conditions, the top surface showed higher hardness than the bottom surface. It was concluded that the resin composite increments should be decreased to improve the polymerization of the resin composite bottom surface in deep cavities.