不同灭菌法对齿科高速裂钻腐蚀的初步研究

目的研究齿科常用的灭菌方法：干热灭菌法、湿热灭菌法、化学浸泡灭菌法对高速裂钻腐蚀的影响。方法将100根全新高速裂钻随机分为10组,每组10根。第1组为对照组,不予以任何处理;另9组为实验组,分别用湿热灭菌法、干热灭菌法、化学浸泡法处理5、10、15次。采用称重法、扫描电镜观察及成分分析、表面显微硬度测量法对高速裂钻的腐蚀情况进行研究。结果湿热法处理5、10、15次组,干热法处理10、15次组以及化学浸泡法处理15次组与对照组相比,其重量增加均有统计学意义（ P<0.05）。电镜图片显示：湿热组形貌改变最为显著,出现明显腐蚀外观并与灭菌次数呈正相关;干热组最轻微。表面成分分析显示高速裂钻中的主要成分钨、铬、铁、钴、镍在灭菌处理前后其相对体积分数有所改变,其中钨以对照组、干热组、化学浸泡组、湿热组顺序依次增多;铁则以此顺序依次降低。与对照组相比,三种灭菌法均降低裂钻表面硬度（ P<0.05）,其中湿热组影响最大;干热组和化学浸泡组次之。随着灭菌次数的增加,湿热组和化学浸泡组裂钻表面硬度差异具有统计学意义（ P<0.05）,干热组硬度差异无统计学意义（ P>0.05）。结论不同灭菌处理对高速裂钻均产生一定的腐蚀,以湿热法最为明显。温度和湿度对高速裂钻的腐蚀有协同作用,干热灭菌对裂钻的腐蚀作用较轻。     

三种灭菌法对高速裂钻腐蚀和切削率的影响

目的:观察湿热灭菌法、干热灭菌法、化学浸泡灭菌法处理高速裂钻后其表面腐蚀情况,以及对高速裂钻切削率的影响。方法:100根新高速裂钻随机分成10组分别用3种灭菌方法处理5、10、15次,体视显微镜观察处理前后裂钻表面形态的变化,参考Siegel标准自制设备测试裂钻的垂直和侧向切削率,统计分析灭菌处理对切削率的影响。结果:3种灭菌方法中,湿热灭菌法引起的裂钻表面腐蚀最严重;干热法最轻;湿热灭菌法引起的裂钻切削率下降幅度最明显,化学浸泡法、干热法次之。灭菌次数与腐蚀程度、切削率的降低幅度成正比,处理15次后,裂钻的垂直和侧向切削率均有明显下降。结论:湿热灭菌法引起的裂钻腐蚀改变最明显、切削率降低幅度最大,化学浸泡法、干热法较轻,建议牙用高速裂钻类小器械采用玻璃珠灭菌器进行灭菌。     

金刚砂车针清洗消毒及灭菌方法的研究现状

金刚砂车针因其结构复杂、直接与患者口腔接触及需要重复使用的特点,因此关于该车针的清洗消毒灭菌方法一直受到人们的关注。常用的金刚砂车针清洗、消毒、灭菌的方法主要有人工清洗法、酶清洗法、超声震荡法、化学液浸泡法、干热灭菌法和湿热灭菌法。上述方法均存在优点和不足,本文综述了上述方法的适用范围和优缺点以及最新的研究进展。     

根管切削器械安全使用的探讨

目的探讨防止根管切削器械损耗的处理。方法抽取200枚后牙根管切削器械分成2组,将粘贴纸贴于器械柄部以记录使用的次数,分别进行干热灭菌和高压蒸汽灭菌,观察根管切削器械的形态。结果根管切削器械干热灭菌法与高压蒸汽灭菌法损耗率χ2检验P<0.05,有显著性差异。结论高压蒸汽灭菌效果优于干热灭菌法,建议根管切削器械处理使用高压蒸汽灭菌法。另外根据根管切削器械随着使用次数的增多,其损耗的机会相应增大,故通过粘贴纸记数方法,可杜绝根管切削器械无限制使用,从而使根管切削器械折断意外降到最低。     

表面接枝技术对纤维加强树脂基桩力学性能的影响

目的探讨石英纤维表面接枝技术对纤维增强光固化树脂复合材料(FRC)桩力学性能的影响。方法将石英纤维随机分成5组分别进行以下表面处理:A组,10%H_2O_2浸泡20 min;B组,10%H_2O_2浸泡20 min+γ-MPS处理;C组,10%H_2O_2浸泡20 min+γ-MPS处理+Bis-GMA接枝1 h;D组,10%H_2O_2浸泡20 min+γ-MPS处理+Bis-GMA接枝3 h;E组,10%H_2O_2浸泡20min+γ-MPS处理+Bis-GMA接枝7 h。将处理好的石英纤维按相同体积比浸入光固化树脂基质中制成纤维增强树脂桩。测试试样的弯曲模量、弯曲强度、弯曲载荷,SEM观察断面的显微结构。结果不同接枝时间的石英纤维对FRC桩的力学性能有影响,其中E组力学性能明显提高,弯曲模量(24.65±2.20)GPa,弯曲强度(696.24±12.85)MPa,弯曲载荷(185.67±3.43)N,与其余组有显著差异(P<0.05)。结论纤维表面接枝技术能提高树脂基纤维桩材料的力学性能。     

不同热凝义齿基托树脂对基托表面亲水性及力学性能的影响

目的 研究不同热凝义齿基托树脂对基托表面亲水性及力学性能的影响,以提高义齿基托的表面特性及弯曲特性的新思路和新方法。方法 选择平均分子量及平均粒径不同的4种粉剂：D-100M(甲基丙烯酸甲酯聚合物粉）,聚甲基丙烯酸甲酯聚合(D-250M）,聚甲基丙烯酸甲酯/丙烯酸乙酯共聚物(D-300）,聚甲基丙烯酸乙酯聚合物(D-250E）,作为研究对象,将各组粉剂和4种单体(MMA,i-BMA,EHMA,HEMA）分别配对聚合成15种不同材料的试件,进行周期性浸泡,随后置于恒温干燥箱0、14、30、90、180、360天后,测定表面接触角及弯曲性能。结果 浸泡前各组试件之间的差异有统计学意义(P<0.05）。浸泡后各材料之间的接触角变化显著不同;弯曲强度及弯曲弹性模量的差异有统计学意义(P<0.05）。随着时间推移,甲基丙烯酸甲酯组(MMA）的弯曲强度显著高于其他组(P<0.05）;单体MMA和EHMA+HEMA组浸泡至360天时弯曲强度无显著变化;其余组的样本浸泡至30天后弯曲强度明显上升。结论 适当组成成分的搭配对热凝义齿基托的表面亲水性、弯曲强度及弯曲弹性模量有很大影响,恰当的组合能改进热凝义齿基托的表面特性及力学性能。     

两种消毒方法对牙科手机灭菌效果的评价

目的 :比较含氯消毒剂浸泡法和环氧乙烷气体灭菌法对牙科手机的灭菌效果。方法 :利用枯草杆菌黑色变种芽孢和乙肝表面抗原阳性血清污染牙科手机 ,消毒后进行定量杀菌实验 ,用酶联免疫吸附实验 (ELISA)法检测HBsAg 结果 :牙科手机浸泡在有效氯含量为 30 0 0× 10 -6的消毒剂中 30分钟 ,细菌杀灭率及乙肝表面抗原的抗原灭活率均未达到 10 0 % ,而环氧乙烷灭菌法可达到 10 0 %。结论 :环氧乙烷灭菌牙科手机效果可靠。     

T-ZnOw树脂基托在不同pH值浸泡液中物理性能的变化

目的研究T-ZnOw树脂基托在不同pH值浸泡液中的物理性能。方法按质量比将5%的T-ZnOw添加到树脂基托中,37℃条件下,分别放入pH值=7的去离子水、pH值=6的人工唾液及pH值=5的醋酸溶液中浸泡,每24h更换浸泡液。分别在浸泡前、浸泡2周、4周、8周后取出试件,进行冲击强度、弯曲强度、硬度的检测。结果添加和未添加T-ZnOw的基托,浸泡2周后在不同浸泡液中,人工唾液组、醋酸溶液组和去离子水组的冲击强度与硬度无显著差异（P〉0.05）;人工唾液组的弯曲强度和弹性模量大于醋酸组,小于去离子水组,而醋酸组的弯曲强度与弹性模量小于去离子水组。浸泡4周、8周后,人工唾液组和醋酸溶液组的冲击强度、弯曲强度和弯曲弹性模量、硬度有不同程度降低,去离子水组物理性能无明显变化（P〉0.05）。在同一种浸泡液中,浸泡相同时间,添加T-ZnOw的基托的物理性能优于未添加者。结论 3种浸泡液中,去离子水浸泡对T-ZnOw树脂基托材料物理性能无明显影响。添加T-ZnOw的基托的物理性能优于未添加者。     

粉末冶金制作钛合金试件的力学性能试验

目的 研究真空烧结粉末冶金法制作钛合金试件的力学性能。方法 采用真空烧结粉末冶金法制作钛合金试件,测试钛合金试件的抗压强度和弯曲强度。结果 在100－300MPa范围内,烧结体的抗压强度为111－921MPa随着成形压力的增大,烧结体的抗压强度增大;采用的3种钛粉末粒度对烧结体的力学性能没有影响;钛粉镀铜镀锡组结体的抗压强度较其它粉末配方组大。在150－250MPa范围内,烧结体的三点弯曲强度为102－183MPa,弯曲弹性模量为12193－26630;不同配方组的烧结体弯曲强度有差异（P＜0．05）;而弯曲弹性模量无差异（P＞0．05）。结论 钛基金属粉末的配方及成形压力对烧结体的力学性能有影响,对钛粉进行化学镀铜镀锡处理是改善钛粉的压制性能、烧结性能、提高烧结体力学性能的理想方法。     

聚乙烯纤维加强聚甲基丙烯酸甲酯的机械性能测试

目的　观察聚乙烯纤维对聚甲基丙烯酸甲酯是否有加强作用。方法　采用自制模具,制作化学固化聚甲基丙烯酸甲酯(PMMA)组、化学固化PMMA加0·25 mm结扎丝组、化学固化PMMA加Ribbond聚乙烯纤维组3组试样,共28个。用万能材料实验机进行三点弯曲实验,记录试样的弯曲强度和弹性模量值,并进行统计分析。结果　化学固化PMMA组的弯曲强度为(51·383±2·761)MPa,弹性模量为(179 1·2±113·760)MPa。化学固化PMMA加 0·25 mm结扎丝组的弯曲强度为(58·725±1·218)MPa,弹性模量为(209 2·76±120·280)MPa。Ribbond聚乙烯纤维加强组的弯曲强度为(80·975±2·580)MPa,弹性模量为(286 6·53±107·510)MPa。经单因素方差分析各组之间皆有显著性差异(P<0·001)。Newman-Keuls法检测各组之间均有显著性差异(P<0·05)。结论　Ribbond聚乙烯纤维加强能显著提高聚甲基丙烯酸甲酯的弯曲强度和弹性模量。     

Cutting effectiveness of diamond instruments subjected to cyclic sterilization methods

The effect of repeated sterilization on the cutting effectiveness of one brand of rotary dental diamond cutting instruments was measured. Four groups of five diamond burs were sterilized by four methods: (1) sterilization with a chemical agent (Sporicidin); (2) steam under pressure (autoclave); (3) dry heat (Dri-Clave); or (4) chemical vapor (Chemiclave). Each group of diamond instruments made a timed cut in a ceramic block. This cut and all subsequent cuts were measured and were used to determine a baseline cutting effectiveness. Each group of diamond burs was then ultrasonically cleaned, sterilized, and another cut was made. At the end of 10 cycles there was no difference in cutting efficiency of the dental diamond instruments. However, there are differences in the cutting efficiency of individual diamond instruments. The SEM evaluation made prior to cutting and at the end of the 10 cycles of sterilization demonstrated that diamond wear was similar in all groups and that little diamond particle loss occurred in any group.     

Effects of sterilization on the mechanical properties and the surface topography of nickel-titanium arch wires

The effects of sterilization on the mechanical properties and the surface topography were determined on 0.017 x 0.025-inch Nitinol and Titanal arch wires. Three approved heat sterilization methods were used: dry heat, formaldehyde-alcohol vapor, and steam autoclave. Elastic moduli were obtained on 1-inch segments in 3-point bending. Laser scans of flatwise wire surfaces were conducted to detect surface alterations--whether they were caused by tarnish, corrosion, or pitting. Tensile properties were determined on 7-inch lengths: the 0.1% yield strength, the ultimate tensile strength, and the percent elongation at break. Within the confines of the present sterilization experiments, no detrimental changes were observed for either the selected mechanical properties or the surface topography. When the mean values of the two products were compared, Nitinol was less compliant but stronger than Titanal. Laser spectroscopy showed that Titanal possessed at least three times more specular reflectivity than Nitinol.     

高温高压灭菌对口腔医学模型精准度影响的研究

目的：观察高温高压灭菌对常用三种模型材料制作的模型形变影响。方法：应用牙科用普通石膏、硬石膏、超硬石膏各制作口腔医学模型30个,共90个。分别测出三组模型在高温高压灭菌前后的长度与体积改变,通过统计学与率差分析,了解该方法处理后模型长度与体积的改变。结果：三组模型在灭菌前后长度与体积的改变经统计学比较,均未出现显著性差异。各组模型均未发现统计学与率差同时存在差异情况。结论：高温高压灭菌处理口腔医学模型,灭菌效果可靠,不会使模型变形,对人体与环境无害,是一种良好的使模型灭菌的方法。     

The effect of sterilization on bending and torsional properties of K-files manufactured with different metallic alloys

The purpose of this study was to assess the effect of dry-heat or autoclave sterilization on the resistance to fracture in torque and angular deflection and the resistance to bending of K-type files made of nickel-titanium (Nitiflex, Naviflex), titanium (Microtitane) or stainless steel (Flexofile, Flex-R).
Ten K-type files of each sort, from size 25 to 40, were tested, according to ANSI/ADA specification 28 (1988) and ISO specification 3630 (1992). Sterilization with dry heat and autoclave slightly decreased the flexibility of files made of stainless steel and nickel-titanium for most of the sizes, although the values obtained satisfied ISO specifications. The files made of titanium showed an increased flexibility after sterilization with autoclave (sizes 30 and 35) and dry heat (sizes 30, 35 and 40). Resistance to fracture varied amongst the five groups of files tested as follows: it decreased in some sizes of stainless-steel instruments, decreased in all sizes of titanium files assessed by the torsional moment, and either increased or decreased in some sizes of nickel-titanium files. All files tested, however, satisfied relevant standards for angular deflection after being subjected to sterilization with an autoclave or dry heat.     

Effect of sterilization on the strength and cutting efficiency of twist drills

Retentive-pin twist drills were subjected to four methods of sterilization and then examined to determine possible effects on resistance to fracture, cutting efficiency, and surface condition. Sterilization methods included steam autoclave, chemical vapor autoclave, dry heat, and immersion in glutaraldehyde. Although the steam and chemical vapor groups had lower mean fracture strengths after sterilization, there was no statistically significant difference among the groups. Only the steam autoclave group showed a statistically significant loss of cutting efficiency. Scanning electron microscopic evaluation revealed that only drills sterilized by steam autoclave showed changes in the surface condition or cutting edges.     

INFLUENCE OF MICROWAVE STERILIZATION ON THE CUTTING CAPACITY OF CARBIDE BURS

Objective:

This study compared the cutting capacity of carbide burs sterilized with microwaves and traditional sterilization methods.

Material and Methods:

Sixty burs were divided into 5 groups according to the sterilization methods: dry heat (G1), autoclave (G2), microwave irradiation (G3), glutaraldehyde (G4) or control – no sterilization (G5). The burs were used to cut glass plates in a cutting machine set for twelve 2.5-min periods and, after each period, they were sterilized (except G5) following the protocol established for each group. The cutting capacity of the burs was determined by a weight-loss method. Data were analyzed statistically by Kruskal-Wallis and Dunn''s test.

Results:

The means of the cutting amount performed by each group after the 12 periods were G1 = 0.2167 ± 0.0627 g; G2 = 0.2077 ± 0.0231 g; G3 = 0.1980 ± 0.0326 g; G4 = 0.1203 ± 0.0459 g; G5 = 0.2642 ± 0.0359 g. There were statistically significant differences among the groups (p<0.05); only dry heat sterilization was similar to the control.

Conclusion:

Sterilization by dry heat was the method that least affected the cutting capacity of the carbide burs and microwave sterilization was not better than traditional sterilization methods.     

Sterilization beneath rings on dental instruments.

This study determined the effectiveness of standard methods of instrument sterilization beneath instrument rings. Sets of three types of dental instruments were contaminated with known amounts of bacterial spores (Bacillus stearothermophilus or Bacillus subtilis). Instrument rings were placed over the contamination and the instruments processed through standard cycles in a steam autoclave, an unsaturated chemical vapor sterilizer, a standard dry heat sterilizer, an ethylene oxide gas sterilizer or a 2.0% alkaline glutaraldehyde solution. Controls consisted of spore-contaminated instruments without rings that were not processed through any sterilizing method and that were processed through each sterilizing method. All instruments and their associated rings were cultured for the presence of live spores. The results indicate that the reliability of sterilization beneath the instrument rings used is greatest if the ringed instruments are processed through a steam autoclave or an unsaturated chemical vapor sterilizer.     

Effect of three sterilization techniques on finger pluggers.

The effects of different sterilization methods on the fatigue life of finger pluggers were investigated. Ninety finger pluggers for each of four sizes (A, B, C, and D) were subdivided into subgroups of 10. Each subgroup was subjected to 1, 8, or 15 cycles of steam autoclave, dry heat, or bead sterilization. Ten control pluggers for each size were not sterilized. After sterilization, experimental and control finger pluggers were subjected to cyclic bending until fracture. Only the A finger pluggers autoclaved for eight cycles had a significantly lower number of cycles to failure compared with that of the controls. Nine subgroups had significantly greater number of cycles before failure than did the control. Because all but one sterilized group had fatigue lifetimes statistically equal to or greater than nonsterilized controls, clinicians generally can use any of the three sterilization methods without fear of plugger failure.