复合树脂直接粘接修复Ⅲ.复合树脂材料的选择与应用

按照材料组成及其聚合机制,直接粘接修复的主要材料包括复合树脂和玻璃离子水门汀两大类.取两类材料各自的优点,又出现了将其复合研制的复合体(compomer)、玻璃复合体(giomer)和光固化玻璃离子水门汀(light-cured glassionomer cements).复合树脂是目前临床应用最广的一类材料,具有和天然牙相似的色泽,并随着物理机械性能得以不断提高,已成为临床直接粘接修复的首要选择.大量临床实践证明,只要合理选择并使用得当,复合树脂可以获得令人满意的临床效果.     

一种复合体和四种树脂化玻璃离子水门汀的氟离子释放测定

目的 比较１种复合体和４种树脂化玻璃离子水门汀在水中释放氟离子的能力。方法 用氟离子选择电极，分别在第１、７、３０ｄ直径２５３ｄ，５种材料固化后标本浸泡训的氟离子浓度。结果 除复合体以外的所有材料，均显示了高的初期氟离子释入并急剧下降，然后缓慢下降。结论 复合体释放的氟离子比树脂化玻璃离子水门汀少。对于龋病高发的患者，选择高氟离子释放的树脂化玻璃离子水门汀材料较好。     

玻璃离子粘固剂及复合体氟离子体外释放的比较

目的:比较不同类型玻璃离子粘固剂(GIC)及复合体在体外释放氟离子的能力。方法:选择树脂改良型GIC(VITREBOND;FUJIⅡLC),传统型GIC(FUJIⅡ;国产GIC;GLASLONOMER)及复合体(DYRACT)作为实验对象。使用氟离子选择电极,连续14d测定各种材料固化后标本浸泡溶液中的氟离子浓度,采用光固化树脂(Z100)作为实验对照组。实验数据采用单因素方差分析和q检验法检验。结果:5种GIC均显现出较高的初期氟离子释放,2 d后氟离子释放趋于平稳;复合体显现出一种平缓的氟离子释放状态。树脂改良型GIC的累计氟离子释放量明显高于其他材料,其由高到低的顺序为:VITREBOND>FUJIⅡLC>国产GIC>DYRACT>FUJIⅡ>GLASLONO-MER(P<0.05)。结论:树脂改良型GIC较传统型GIC和复合体具有更好的氟离子释放能力,在预防继发龋上可能具有一定的优势。     

纳米Si3N4织布增强义齿基托机械性能的研究

目的研究纳米Si3N4纤维织布作为加强体对PMMA机械性能的影响。方法将预处理的纳米Si3N4纤维织布,经室温固化和加热固化制样各成三组Si3N4织布/PMMA复合试件,厚度分别为1.0 mm,1.5mm,2.0 mm。未添加织布的为对照组,通过万能试验机测定并比较分析不同厚度的织布增强树脂基托的挠曲强度和杨氏弹性模量。结果无论是常温固化还是加热固化条件下,添加织布的复合材料厚度为2.0mm时,其挠曲强度和弹性模量达到最大,机械性能达到最佳,与对照组相比差异具有统计学意义(P<0.01);相比于室温固化条件,纳米Si3N4纤维织布增强基托树脂机械性能的提高在加热固化条件下更易实现。结论合理添加纳米Si3N4纤维织布形成合适厚度的基托复合体材料,其挠曲强度和弹性模量可以得到大幅提高,当复合材料厚度为2.0mm,其机械性能达到最佳,尤以加热固化条件下明显。     

不同固化方式对封闭剂性能的影响

考察光固化、化学固化两种固化方式对封闭剂性能的影响。从粘结性能看，粘度值相近，树脂突长度无显著差异，但抗剪粘结强度光固化优于化学固化。在机械性能上，自制材料表面硬度、径向抗张强度光固化高于化学固化，在抗压强度上两者差异不大（Ｐ＞０．０５），但Ｃｏｎｃｉｓｅ材料结果与此相反，原因有待进一步研究，吸水性和磨耗率都是光固化小。总体评价，光固化实验室性能优于化学固化。     

Dyract flow流动复合体和光固化窝沟封闭剂3年效果评价

目的 :评价Dyractflow流动复合体用于窝沟封闭剂的临床应用价值及其效果。 方法 :对 3 60例 6～10岁患者的 72 0个上、下颌第一恒磨牙用Dyractflow流动复合体进行窝沟封闭术 ,并采用可见光固化窝沟封闭剂自身对照的研究方法评价效果。结果 :随诊 3年后发现Dyractflow流动复合体组在术 1、2、3年的涂膜保留率均比可见光固化组高 (P <0 .0 1)。但龋病患病率无显著性差异 (P >0 .0 5 )。结论 :Dyractflow流动复合体是一种可靠的窝沟封闭剂 ,值得临床推广应用     

义齿软衬材料的理化性能

义齿软衬材料为一种固化后具有一定弹性的衬垫材料。其具有分散咀嚼力,减轻义齿对支持组织的局部压力,改善义齿固位的功能。义齿软衬临床应用及功能的发挥与其理化性能密切相关。本文就软衬的粘结强度、吸水性和溶解性、粘弹性、润湿性、微生物粘附、抗老化等几方面主要性能及有关影响因素作一综述。     

各种聚合方法对复合树脂抗压强度及硬度的影响

本研究采用化学催化、可见光照射、加热、加热同时加一定压力、激光辐照等五种聚合固化方法,制备复合树脂。通过测定其抗压强度和表面硬度,研究聚合方法对材料某些机械性能的影响,实验结果证明:不同聚合方法所获得的复合树脂,其抗压强度及硬度值有差异。其基本规律是按化学催化→可见光固化→热固化的顺序而增加。这与以往一些学者的研究结果相符。激光固化,因采用二氧化碳红外激光辐照。热效应起主要作用,故材料性能达到或接近热固化水平。研究采用激光固化方法,不但具有化学固化和可见光固化操作简便的优点,而且还有热固化方法所得材料较高的机械性能,并有可能在口腔条件下应用的前景,值得进一步深入研究。     

光固化复合体修复楔状缺损疗效观察

目的 评价光固化复合体修复楔状缺损的临床疗效。方法 将１９５例计６２４颗牙随机分成治疗组和对照组,治疗组用光固化复合体修复,对照组用光固化复合树脂修复。结果 结果显示光固化复合体与牙面的粘接性强,对牙髓的刺激性小。１２个月后复查显示,治疗组成功率达９５．６％,对照组成功率为８０．１％,两组有显著差异（Ｐ〈０．０１）。结论 可以认为光固化复合体是一种修复楔状撄损的新型理想材料。     

光敏材料修复楔状缺损的固位研究

目的 减少楔状缺损充填体的脱落率。方法 对２０６人中１０２９颗牙的楔状缺损用光固化树脂或复合体两种材料充填,随访一年。并对１２０颗有楔状缺损离体牙分别用上述途中事作破坏性试验。结果 临床组和实验组结果均显示：同材料窄深型缺损比宽浅型缺损固位好;光固化树脂比复合体固位好。结论建议临床上楔状缺损宽浅型用光固化树脂充填,窄深型二种材料均可。     

不同聚合方法对义齿基托树脂吸水性和溶解性的影响

目的 研究不同聚合方法对义齿基托树脂吸水性和溶解性的影响。方法 选择两种常用热凝义齿基托树脂材料,分别采用传统水浴法和电热聚合法制作样本,测量各样本的吸水值和溶解值。结果 日进水浴组、日进电热组、贺利氏水浴组、贺利氏电热组的吸水值依次为（25.48±3.04) μg/mm、（22.96±4.6) μg/mm、（22.65±5.44) μg/mm（18.21±5.19) μg/mm,以上各组的溶解值依次为（0.62±0.17) μg/mm、（0.54±0.18) μg/mm、（0.56±0.10) μg/mm、（0.51±0.11) μg/mm。日进水浴组的吸水值稍高,差别有统计学意义,其余各组比较均无差别。结论 不同聚合方法对义齿基托树脂吸水性和溶解性并无显著影响,所制作样本均符合国家标准。     

Microbicidal efficacy of ozonated water against Candida albicans adhering to acrylic denture plates

Background/aims:  Ozone is known to act as a strong antimicrobial agent against bacteria, fungi, and viruses. We examined the effect of ozonated water on Candida albicans on acrylic denture plate.
Methods:  The heat-cured acrylic resins were cultured with C. albicans . After treatment of flowing ozonated water, the number of attached C. albicans was counted. In some experiments, the test samples were treated with ozonated water in combination with ultrasonication.
Results:  After exposure to flowing ozonated water (2 or 4 mg/l) for 1 min, viable C. albicans cells were nearly nonexistent. The combination of ozonated water and ultrasonication had a strong effect on the viability of C. albicans adhering to the acrylic resin plates. There were no significant differences in antimicrobial activity against C. albicans between plates immersed in ozonated water with ultrasonication and those treated with commercially available denture cleaners. In addition, electron microscopic analysis revealed that small amounts of C. albicans remained on the plate after exposure to flowing ozonated water or immersion in ozonated water with ultrasonication.
Conclusion:  Our results suggest that application of ozonated water may be useful in reducing the number of C. albicans on denture plates.     

Water sorption and desorption on experimental composite resins

The water sorption and desorption, and the diffusion coefficients of the water sorption and desorption were studied on the experimental composite resins with various filler contents in both chemically-cured and light-cured type. As the filler content increased, the rate of the water sorption and desorption on the composites decreased. And these properties associated with the prediction obtained from the law of mixture. The filler did not absorb water, so the effect of the filler content on the diffusion coefficients of the water sorption was to be associated with of the law of mixture. However, in the diffusion coefficients of the water desorption the effect of filler content could not be proved to be associated with the law of mixture. The diffusion coefficients of the water desorption were over 2 times larger than the those of the water sorption.     

Corrosion behavior of dental alloys in various types of electrolyzed water

The corrosion behavior of dental alloys was examined in electrolyzed strong acid water, weak acid water and neutral water using a 7-day immersion test. The precious metal alloys, gold alloy. Au-Ag-Pd alloy and silver alloy showed the greatest surface color change and dissolution of constituents in the strong acid water and the smallest in the neutral water. The release of Au from gold alloy was especially marked in the strong acid water. Co-Cr alloy showed greater corrosion and tarnish resistance in the strong acid water rather than in the weak acid water and the neutral water. X-ray microanalysis revealed that the corrosion products on the precious metal alloys were silver chloride crystals and the thin brown products on Co-Cr alloy were cobalt and chromium oxides. Ti was sound in all three types of electrolyzed water. The neutral water appeared the least corrosive to metals among the three types showing equivalent bactericidal activity.     

The effect of water purification systems on fluoride content of drinking water

Objective: The purpose of the present study was to determine the effect of different water purification systems on the fluoride content of drinking water and to compare the efficacy of these water purification systems in reducing the fluoride content. Materials and Methods: Five different water purification systems were tested in this study. They were reverse osmosis, distillation, activated carbon, Reviva (R) , and candle filter. The water samples in the study were of two types, viz, borewell water and tap water, these being commonly used by the people of Davangere City, Karnataka. The samples were collected before and after purification, and fluoride analysis was done using fluoride ion-specific electrode. Results: The results showed that the systems based on reverse osmosis, viz, reverse osmosis system and Reviva (R) showed maximum reduction in fluoride levels, the former proving to be more effective than the latter; followed by distillation and the activated carbon system, with the least reduction being brought about by candle filter. The amount of fluoride removed by the purification system varied between the system and from one source of water to the other. Interpretation and Conclusion: Considering the beneficial effects of fluoride on caries prevention; when drinking water is subjected to water purification systems that reduce fluoride significantly below the optimal level, fluoride supplementation may be necessary. The efficacy of systems based on reverse osmosis in reducing the fluoride content of water indicates their potential for use as defluoridation devices.     

Water sorption and flexural properties of a composite resin cement

PURPOSE: The aim of this study was to assess the water sorption and determine the influence of water on flexural properties of a composite resin cement of 2 different viscosities. MATERIALS AND METHODS: A dual-cured composite resin cement of 2 different viscosities was tested according to International Standards Organization standards for dental composite materials. The samples tested for water sorption were stored in distilled water for 7 or 60 days. The samples tested for flexural properties were divided into 2 groups and stored either wet in distilled water or dry for 1, 7, or 60 days. After storage, a flexural test was performed with 3-point bending equipment. RESULTS: A significant increase in water sorption for both viscosities was registered as the storage time increased, but no significant difference between the 2 viscosities was recorded. Significantly lower strength and modulus were found for specimens that were wet stored for 60 days compared with the dry-stored ones, and significant changes in deflection at break were also registered. There were no differences in flexural properties between the 2 viscosities. Because of the lubricant and plasticizing effect of water on composite resin materials, the secant modulus and deflection at break seem to be valid methods to describe the complete deflection behavior. CONCLUSION: Water has an important effect on the flexural properties of composite resin cement after 60 days of storage time. No significant differences in water sorption and flexural properties were found between the high and low viscosities of the composite resin cement studied.     

Vapor phase adsorption of water on hydroxyapatite.

Water vapor adsorption isotherms were determined gravimetrically on three hydroxyapatite sampel differing in preparation and with surface areas of 70.4, 22.5, and 3.0 M2/gm, respectively. Heats of adsorption for the first layer of water were found to be 13.3, 13.2, and 13.9 kcal/mole on these hydroxypatites. From repeated thermal desorption and adsorption cycles of water, stepwise adsorption was observed which diminished with each outgassing cycle until it disappeared after the fourth cycle. Cross-sectional area of adsorbed water molecule on hydroxyapatite surface was estimated at 11.5 A2. Standard free energies, isosteric heats, changes in enthalpy, and entropy of adsorption of water on HAP samples outgassed at 300 C were determined.     

Effects of a small electric current on sterilization of a dental unit water line

In the present study, water was circulated in a simulated dental unit water line with electrifying a small current. The morphology of the biofilm developed on inner surface of the water line and the number of heterotrophic bacteria were investigated to elucidate the effect of a low level electric current on the biofilms formation associated with bacteria reproduction. Destruction and malconformation of biofilms by electrification was observed using SEM, in addition to deformation and hypertrophy of the bacteria. By naked eye observation, small pieces, which were possibly exfoliated biofilms, were detected in electrified water. While an adherent, yellow gel was demonstrated on the inner surface of the water line without electrification. With electrification, the number of bacteria decreased during the first week, however the bacteria increased gradually after that. The number of bacteria without electrification was consistently greater than that with electrification and the difference was statistically significant (P<0.05). The predominant bacteria were identified as Sphingomonas paucimobilis. The excess chlorine levels decreased to a minimum value within one week. The small current appeared to have effects on biofilm formation of heterotrophic bacteria that resulted in enhanced chlorine sterilization of dental unit water. Thus, electrification has considerable potential for the extermination of bacterial biofilms in dental unit water lines.     

Efficacy of ozone on survival and permeability of oral microorganisms

In the present study, we examined the effect of ozonated water on oral microorganisms and dental plaque. Almost no microorganisms were detected after being treated with ozonated water (4 mg/l) for 10 s. To estimate the ozonated water-treated Streptococcus mutans, bacterial cells were stained with LIVE/DEAD BacLight Bacterial Viability Kit. Fluorescence microscopic analysis revealed that S. mutans cells were killed instantaneously in ozonated water. Some breakage of ozonated water-treated S. mutans was found by electron microscopy. When the experimental dental plaque was exposed to ozonated water, the number of viable S. mutans remarkably decreased. Ozonated water strongly inhibited the accumulation of experimental dental plaque in vitro. After the dental plaque samples from human subjects were exposed to ozonated water in vitro, almost no viable bacterial cells were detected. These results suggest that ozonated water should be useful in reducing the infections caused by oral microorganisms in dental plaque.     

Attitudes of Irish and European dentists to water quality of dental unit water systems

BACKGROUND: Dental unit water systems (DUWS) are used in dental practices to provide water to irrigate the oral cavity. Dental surgeries across the European Union (EU) use DUWS that may be prone to microbial contamination. OBJECTIVES: To determine Irish dental practitioners' attitudes to perceived risk from working with DUWS and their protocols for the management of biofilm in their DUWS and compare these with other European dentists. DESIGN: A questionnaire was used to determine DUWS types in use, practitioners' attitudes to risks associated with using DUWS and their DUWS management protocols. RESULTS: There were six different types of DUWS, 40 per cent of which were > 5 years old, 42 per cent of DUWS were fed by purified or distilled water. Only four per cent of practitioners carried out microbiological analysis on their water, but 38 per cent indicated that they cleaned or disinfected their DUWS. One-hundred per cent of practitioners were not aware of national/international guidelines for microbial contamination of DUWS but 77 per cent were concerned about DUWS water quality. CONCLUSIONS: The majority of practitioners were working with equipment that is < 5 years old. The majority of DUWS were not treated but practitioners were concerned about dental unit water quality and would welcome regular microbiological water tests and clear advice on cleaning/disinfection of the water supply in their dental units. Practitioner attitudes and behaviours were broadly similar in the other European countries studied.