不同膨胀系数石膏模型材料对基托树脂力学性能的影响

目的研究不同膨胀系数石膏模型材料对基托树脂力学性能的影响。方法采用高、中、低3种不同膨胀系数的石膏模型材料包埋型盒,分别制作树脂基托试件,通过测量试件的冲击强度,弯曲强度,弹性模量和硬度,分析树脂试件的力学性能,用扫描电镜观察试件的表面及横断面结构。结果 1高、中、低膨胀系数石膏模型材料制作试样的冲击强度分别为:(5.79±0.90)KJ·m-2、(7.21±0.16)KJ·m-2和(8.89±0.58)KJ·m-2;弯曲强度分别为:(71.03±2.23)MPa、(85.18±5.32)MPa和(110.06±4.06)MPa;弯曲模量分别为:(2797±83)MPa、(2512±88)MPa和(2088±42)MPa;硬度(洛氏)分别为:16.30±0.35,20.50±0.38,26.80±0.14,各组数据之间的差异具有显著的统计学意义(P<0.01)。扫描电镜观察发现:高膨胀系数石膏制作的试样表面颗粒排列紊乱、孔隙较多,横断面气泡较多,结构疏松;低膨胀系数组的树脂试样表面颗粒排列整齐,孔隙较少,横断面气泡明显减少,结构致密;中膨胀系数组的表现介于两者之间。结论低膨胀系数石膏模型材料制作的树脂基托力学性能最佳。     

口腔用石膏的固化形变及影响因素

石膏作为重要的辅助材料在口腔修复的众多环节中发挥着不可替代的作用，本文着重介绍了石膏固化形变理论及固化形变中的各种相关影响因素，为临床应用提供参考。     

CGF—1型复合体的物理机械性能

目的：评价研制的新型光固化复合体ＣＧＦ－１与Ｄｙｒａｃｔ复合体、ＣＯ－１和ＦＵＪＩⅡ玻璃离子水门汀的物理机械性能。方法：按照有关实验方法分别测试研制复合体与对照材料的压缩强度、径向拉伸强度、挠曲强度、表面硬度。结果：ＣＧＦ－１的ＣＳ、ＤＴＳ、ＦＳ值都明显高于ＣＯ－１、ＦＵＪＩⅡ，接近Ｄｙｒａｃｔ。结论：ＣＧＦ－１型复合体的机械强度明显高于玻璃离子，可用作直接充填修复材料     

加强Ⅳ型石膏弯曲强度的实验研究

目的 研究不同直径的不锈钢丝能否加强Ⅳ型石膏模型的弯曲强度.方法 选用超硬石膏和硬石膏灌模,在模型中央分别放入4种不同直径0.5 mm、0.7 mm、0.9 mm和1.2 mm不锈钢丝进行加强,与对照组比较,测量每个样本的弯曲强度.数据采用单因素方差分析和Dunnett t检验.结果 超硬石膏组的F值为3.351,P值为0.017.0.9 mm直径组和1.2 mm直径组比较对照组有统计学意义(P＜0.05).硬石膏各组的F值为4.1,P值为0.006.1.2 mm直径组比较对照组有统计学意义(P＜0.05).结论 硬石膏模型中埋入不锈钢丝能加强其弯曲强度,且随着不锈钢丝的直径增大而增强,到1.2 mm直径时达到最高.     

铸造支架用石膏模型倒凹的填补方法

随着口腔修复技术的不断发展,整体支架也逐渐被广泛应用到临床修复中。在整体铸造中,影响支架就位的因素很多,其中以倒凹对支架就位带来的困难多见。而且,倒凹的超填也会影响支架的固位及密合度,所以合理填补倒凹尤为重要。本文介绍一种新的填补方法——观测仪引导蜡...     

微波与空气干燥石膏模型抗压强度的比较

微波在口腔修复领域中广泛应用于消毒、聚合塑料、模型除蜡、缩短基托塑料的面团期，而临床上用来干燥石膏模型，以节省义齿制作时间，提高工作效率，亦被同行们所关注。石膏的分类是根据它们的用途、不同成份的物理性能来决定的。资料证明：石膏的抗压强度是与水/粉比例、混合时间、混合体积、化学成份、相对湿度、储存温度及何时脱模等密切相关。刚脱模的石膏模型因处在初凝状态，表面硬度不足，需经28-48小时的空气干燥，以去除过多的水分，获得足够的表面硬度，以便在进行操作时不被破坏。本文研究的目的是，检测微波干燥2个不同时间的…     

口腔石膏模型细菌污染情况的调查

人的口腔中存在着多种微生物,翻制的义齿石膏模型常带有患者口腔内存在的多种细菌,如不进行彻底消毒,极易造成医院内交叉感染。为了解未消毒的义齿石膏模型细菌污染情况,笔者对某义齿加工厂的口腔石膏模型微生物污染状况进行了调查,为医院制定感染措施提供依据。一、资料和方法菌株来源:2006年5月～2007年2月间,对某义齿加工厂106副口腔石膏模型进行细菌采样并培养分析。试剂:法国梅里埃公司出品的API10s,API20NE,API20strep板条鉴定。细菌学监测采样、培养及鉴定:根据卫生部《消毒技术规范》(2002年版)进行采样监测。用无菌棉拭子蘸取…     

使用FUS-invest锆系牙科纯钛包埋料提高铸件的物理机械性能及精度

目的:评价自制FUS-invest锆系牙科纯钛包埋料铸造的纯钛铸件的物理机械性能及标准化单冠的精度.方法:制备7个厚度为0.8 mm的纯钛比例铸件.经伺服液压动态实验系统、断口扫描电镜观察及能谱分析,评价其物理机械性能.制备38个标准化单冠,实验组(FUS-invest锆系包埋料)、对照组(磷酸盐系包埋料)各19个,测量显微镜测标准化单冠边缘差异值d和铸件内壁与工作模的距离,进行铸件精度评价.采用SPSS17.0软件包对数据进行统计学分析.结果:①纯钛铸件的弹性模量为(123.5±14.2)GPa,屈服强度为(569.3±16.5) MPa,抗拉强度为(668.4±16.1) MPa,延伸率为(4.5±0.2)％;断口EDS分析除钛元素外,不同深度处可发现少量不同含量的Si元素和Fe元素,但未检测出Zr元素.②精度实验中,单因素方差分析及两独立样本t检验显示,组内标准化单冠边缘4个标记点处的测量值无显著差异(P＞0.05);实验组和对照组相比亦无显著差异(P＞0.05).2组内部测量值无显著差异(P＞0.05),而组内内部不同标记点间差异显著(P＜0.01).结论:虽然FUS-invest锆系包埋料铸造获得铸件的延伸率略低,但各项物理机械性能均达到临床要求.无论边缘适合性还是内部适合性,2组均无显著差异且均在临床可接受范围,2组边缘差异均值约为46 μm,内部近咬合面的差异均值约为56 μm,内部轴壁处的差异均值约为0.     

聚醚醚酮物理特性改善的研究进展

聚醚醚酮(polyetheretherketone, PEEK)具有优异的力学特性、耐磨性、射线透射性及良好生物相容性,是生物医学领域最具有前景的高分子材料之一。然而,PEEK的机械强度仍与人骨相比仍具有一定的差异,其材料表面的生物惰性,还会导致的骨结合不良、感染等的问题,这些缺点限制着PEEK的应用。本文将总结改善PEEK物理特性研究的最新进展,就改善PEEK机械性能、表面结构和表面微观形貌进行综述,分析不同改性策略的优缺点,并对今后的研究的方向进行展望。     

物理方法加速正畸牙移动的研究进展

近年来,国内外学者在加速正畸牙齿移动方面做了许多研究,以期减少疗程长的不良反应,同时提高效率。目前,加速牙齿移动的方法较多,而其中对于物理治疗的研究尚未完善。文章从电磁场、弱激光、低强度脉冲超声、周期性力装置、电流等5个方面对目前已证实能加快正畸牙移动的物理方法进行综述。     

Study of the physical properties of type IV gypsum, resin-containing, and epoxy die materials

STATEMENT OF PROBLEM: Little published information is available comparing the properties of recently developed resin-modified gypsum and epoxy resin die materials, which are claimed to be superior to conventional type IV gypsum die materials. PURPOSE: This study compared the properties of 3 new die materials and 2 conventional type IV gypsum products. METHODS AND MATERIAL: The linear dimensional change, detail reproduction, surface hardness, abrasion resistance, and transverse strength of 2 recently introduced, resin-modified gypsum die materials (Resinrock and Milestone), a new epoxy resin die material (Epoxy-Die), and 2 conventional type IV gypsum die materials (Silky-Rock and Die-Stone) were studied. RESULTS: All gypsum products expanded, whereas the epoxy resin material contracted during setting. The epoxy resin exhibited much better detail reproduction, abrasion resistance, and transverse strength than the gypsum materials, which were similar in these properties. A conventional type IV gypsum exhibited the highest surface hardness, whereas the epoxy resin had the lowest value. CONCLUSION: The resin-modified gypsum products were not significantly superior to the conventional type IV gypsum die materials. In general, the epoxy resin exhibited the best properties of the materials studied; however, its setting shrinkage may necessitate alterations in technique to achieve well-adapted castings.     

Comparison between physical properties of resin materials and those of gypsum materials for dental models and dies (author's transl)]

Setting time, water sorption, solubility, dimensional change, hardness, tensile strength, compressive strength, bending strength, and Young's modulus of resin model materials and gypsum model materials were determined. These results are following: 1) Setting time of Goldex is in general the same as that of dental plaster, and setting time of Alpha-Die and that of Dicodur are the same as densite type stone. But setting time of Rock Model is very long, that is, ten times as long as that of densite type stone. 2) Water sorption and solubility of gypsum model materials are larger than those of resin model materials. Solubility of Dicodur is larger in comparison with the other resin model materials. 3) During setting, all of gypsum model materials expand but all of resin model materials contract. The absolute values of dimensional change of Rock Model and of densite type stones are the same, but smaller compared with those of other materials. 4) The value of knoop hardness of resin model materials is between that of plaster of Paris and that of hydrocal type stones. 5) In comparison with densite type stone, resin model materials are 2.5 to 5.0 times in tensile strength, the same in compressive strength, and 1.5 to 2.3 times in bending strength. 6) Young's modulus of resin model materials is 1/3 to 1/5 as much as that of densite type stones.     

Changes in physical properties of joined gypsum fragments.

(1) The dimensional change in joined fragments of gypsum models was small. The highest percentage occurred with zinc phosphate cement. (2) The cyanoacrylate cements produced the strongest bonds. Mendent Formula VI and the epoxy cement were least effective. (3) The bond strength was generally greater after 24 hours. The exceptions were Mendent Formula VI and zinc phosphate cement. (4) Different gypsum products responded differently to bonding agents. Some are superior for plaster of Paris; others for artificial dental stone.     

Comparative evaluation of mechanical and physical properties of a new bulk-fill alkasite with conventional restorative materials

PurposeThe physical and mechanical performance of a newly commercialized dental restorative material (alkasite) was compared with glass ionomer cement (GIC) and nano-hybrid composite.MethodologyHuman extracted premolars were used to investigate the shear bond strength. Restorative materials were placed on the dentine surface and were aged in deionized water for 14 days. The 3-D surface roughness was evaluated before and after chewing simulation cycles (50,000). The samples were fatigued mechanically using a chewing simulator and investigated with a scanning electron microscope (SEM).ResultsFor shear bond strength, alkasite showed significantly high values than GIC, whereas non-significant difference was observed between alkasite and nano-hybrid composite. After the chewing simulation (50,000 cycles), non-significant difference was found between GIC and nano-hybrid composite, where surface roughness values were highest for GIC and lowest for alkasite.ConclusionThe newly developed restorative material (alkasite) has shown better results than existing restorative materials.     

Selected mechanical properties of fluoride-releasing restorative materials

Mechanical properties, diametral tensile strength (DTS) and flexural strength (FS) of six fluoride releasing materials were measured and compared. The samples were prepared and tested according to ISO specifications. The materials included a glass ionomer (Fuji IX), a resin-modified glass ionomer (Photac-Fil), two compomers (F 2000; Dyract AP) and two composites (Solitaire; Tetric Ceram). The tests were performed after the materials were stored in distilled water (DTS) and phosphate buffered saline solution (FS) at 37 degrees C for 24 hours and one week. Fluoride-releasing composite resin had the highest flexural and diametral tensile strengths and were statistically stronger than compomers, followed by resin-modified glass ionomer and conventional glass ionomer. However, a notable exception to this general trend was Solitaire, a fluoride-releasing composite resin.     

Mineralization and mechanical properties of the canine mandible distraction wound following acute molding

To investigate the influence of an acute single step callus manipulation immediately after distraction on mechanical properties and mineralization of the regenerate, custom made distraction devices were bilaterally placed in the mandibular angle of 15 beagle dogs, allowing to simultaneously compress and stretch the regenerate after completed linear distraction. The animals were divided in three groups (n=5): Group 1 and 2 underwent manipulation of the regenerate, group 3 remained in a linear position. After 42 (group1) and 90 (group 2 and 3) days of consolidation the animals were sacrificed. The mechanical properties were assessed in an Instron testframe and bone density quantified by quantitative computed tomography and three- dimensionally assessed (Scion Image processing and analysis software). After 6 weeks of consolidation 25% of the specimens reached a stiffness which was >/=90% of the mean values of the unoperated reference hemi-mandibles. After a 13 week consolidation period, 62.5% were as stiff as the referenced specimens. Manipulated regenerates, allowed to heal under stable conditions for 13 weeks, had the same mechanical properties as specimens that underwent pure linear distraction. A temporary but not significant delay of osseous healing had to be postulated for the stretched zone after 6 weeks, indicating this area to be more critical than the compressed area.