Wear of prosthodontic materials—an in vivo study

The aim of this investigation was to study quantitative and qualitative aspects of the wear process of some prosthodontic materials in three different persons in vivo. The in vivo models combined two methods: removable double crowns and a replica technique. The wear resistance of gold (types III and IV), porcelain and a microfilled resin was studied opposing metal ceramic crowns and in one person when opposing all four materials. All three persons had earlier histories of occlusal wear of teeth and/or restorations. The wear rate of gold and porcelain showed equal values antagonizing metal ceramic crowns in all three persons. The microfilled resin had a wear rate three or four times higher in the same situations. No significant difference in wear resistance could be found between type III and type IV gold alloys. The wear mechanism seemed to be a fatigue type in porcelain, and in gold a combined fatigue and abrasive type of wear. The microfilled resin showed mainly a fatigue type of wear but some observations indicating a tribochemical reaction were also made.     

In vitro and in silico evaluations of resin-based dental restorative material toxicity

This study aims to evaluate the cytocompatibility of three provisional restoration materials and predict neurotoxic potential of their monomers. These mate     

In vitro and in vivo studies on the toxicity of dental resin components: a review

In vitro and in vivo studies have clearly identified that some components of restorative composite resins, adhesives, and resin-modified glass ionomer cements are toxic. The mechanisms of cytotoxicity are related firstly to the short-term release of free monomers occurring during the monomer–polymer conversion. Secondly, long-term release of leachable substances is generated by erosion and degradation over time. In addition, ion release and proliferation of bacteria located at the interface between the restorative material and dental tissues are also implicated in the tissue response. Molecular mechanisms involve glutathione depletion and reactive oxygen species (ROS) production as key factors leading to pulp or gingival cell apoptosis. Experimental animal approaches substantiate the occurrence of allergic reactions. There is a large gap between the results published by research laboratories and clinical reports.     

The release of mercury from dental amalgam and potential neurotoxicological effects

OBJECTIVES: The aim of this study was to estimate the amount of mercury released into both air and saliva from fresh and aged, abraded amalgam discs and then investigate neurotoxic effects of inorganic mercury upon sensory neuronal cultures. METHODS: An air-tight chamber was constructed to allow the combined estimation of mercury species released from amalgam pellets. The level released into air and saliva from both freshly packed and aged-abraded amalgam pellets was assessed. Dorsal root ganglia cultures from male CBA mice were exposed to 1 and 10 microM mercuric chloride concentrations. The effects of this were assessed by means of morphology, adhesion, size and immunocytochemistry. RESULTS: The mercury released into air from dry fresh amalgam was low and less than the recommended industrial exposure limit for mercury. However, covering the discs with saliva reduced air-mercury levels by 46-56% and there was a statistically significant difference in the air-mercury levels recorded (p=0.013-0.048). The mercury released into air from dry abraded amalgam was shown to be above the recommended industrial limit. Coating the abraded amalgam discs with saliva reduced the mercury by 66-72% with the levels recorded being significantly lower (p<0.001). The level of total mercury within the saliva was found to be highly variable. Little change was noted in the neuronal cultures treated with 1 microM mercuric chloride. However, the cultures exposed to high level (10 microM) mercuric chloride showed cells that became rounded and clumped together indicating pathological change.CONCLUSIONS: Amalgam placement appears to present minimal mercury exposure risk. To reduce the amount of mercury released into air, however, amalgam should be polished in a moist atmosphere with high volume aspiration. The neurotoxic effect of mercury appears to be related to concentration, as only in the cultures treated with 10 microM mercuric chloride showed striking qualitative and quantitative cellular changes.     

大鼠牙囊细胞多向分化潜能的体外研究

目的:体外研究用差速贴壁法和有限稀释法纯化的大鼠牙囊细胞(Dental foilicle cells,DF-Cs)的多向分化潜能,为用于口腔组织工程的种子细胞奠定基础。方法:体式显微镜下准确分离7 d龄SD大鼠第一磨牙牙囊组织,使用酶消化法、有限稀释法、差速贴壁法进行培养和纯化细胞,取第3代细胞分别进行以下检测:①流式细胞仪鉴定细胞表面抗原标记;②骨向诱导、成脂诱导、成神经诱导和相关检测。结果:①差速贴壁法和有限稀释法纯化培养的大鼠牙囊细胞大多呈长梭形,部分细胞呈三角形,细胞形态呈现异质性;②流式细胞仪检测结果显示所获得的牙囊干细胞表面标记CD29、CD90阳性率分别为95.6%、98.6%,而CD45的阳性率仅为4.2%;③成骨诱导后,茜素红染色呈阳性,ALP染色显示ALP表达增强明显;成脂诱导后细胞胞浆内可见明显脂滴,油红O染色呈阳性;神经细胞诱导后细胞形态发生明显改变,神经微管蛋白染色呈阳性。结论:体外培养的大鼠牙囊细胞具有较强的多向分化能力,可作为口腔组织工程理想的种子细胞。     

Fluoride release from dental cements and composites: a mechanistic study.

OBJECTIVES: The purpose of this study was (1) to compare the fluoride release profile of an experimental composite to commercial GICs, resin-modified GICs, and composite resins; (2) to assess the fluoride release process. METHODS: Commercial materials (n = 3) were prepared according to manufacturers' directions. The experimental composite (n = 3) consisted of 78 wt% filler and 22 wt% resin. The resin consisted of 19 wt% BisGMA, 38 wt% UDMA, 19 wt% TEGDMA, and 24 wt% HEMA. Disc specimens were placed into 25 ml of deionized water in sealed polyethylene vials and shaked at 1.4 Hz at 37 degrees C. Fluoride release was measured using a fluoride-ion specific electrode at different time intervals up to 284 days. RESULTS: The fluoride release rate of the experimental composite demonstrated the highest rate of release within the first day (p = 0.05), but decreased significantly by day 7. Release rates of the commercial glass-ionomer cements and resin-modified glass-ionomer cements thereafter were significantly higher than the experimental and commercial composites at p = 0.05. Among the materials studied, cumulative fluoride release is adequately described by a two-term equation consisting of an initial fluoride release via a rapid dissolution process followed by a long-term diffusive release. SIGNIFICANCE: An increase in the hydrophilicity of the polymer matrix through the introduction of HEMA improved the fluoride release over the short term during which dissolution occurs. Such a release behavior could be beneficial if it results in a fluoride reservoir that could be maintained by a prolonged slower release thereafter.     

Mercury release from amalgam: a study in vitro and in vivo

Total mercury release from a high-copper and a low-copper amalgam was measured in a study in vitro using atomic absorption spectrophotometry. Conditions of mechanical agitation and sealant coverage were evaluated over time. Mercury release was found under agitation and no-agitation conditions to increase shortly after preparation and then to level off after 24 to 48 hours. No difference in mercury release was observed for either amalgam type. Sealant coverage of amalgam significantly reduced mercury release under agitation conditions. In an experiment in vivo mercury vapor was measured at different times for patients receiving their first amalgam restoration. Sealant coverage was found to significantly reduce mercury vapor after chewing on this restoration compared to a nonsealant-covered amalgam.     

rhBMP-2-mPEG-PLA纳米缓释微球缓释凝胶的制备及体外释放实验研究

目的制备一种改性后的rhBMP-2聚乳酸缓释纳米微球(rhBMP-2-mPEG-PLA-Ns),并研究其理化性能和体外释放研究,以用于将来的骨创伤修复。方法运用复乳法制备mPEG-PLA缓释微球,利用透射电子显微镜观察微球表面形态,激光粒度分布测试仪测试纳米微球粒径。采用ELISA法测定微球包封率及载药量,并选择动态透析释药法测定其体外释放率。结果微球表面光滑、圆整,纳米球体粒径均匀。纳米微球的粒径在45⁵0 nm,粒径分布范围较窄。包封率和载药量分别为(78.2±1.81)%和((2.24±0.24)×10-5)%,体外释放试验中,没有发现突释现象,24 h释放率为23.47%,微球在21 d后释放度达78.56%。结论 rhBMP-2-mPEG-PLA缓释纳米微球具备良好的理化特性和缓释效果,为后续药物在口腔方面的应用打下良好的基础。     

A method for the in vitro toxicity testing of dental restorative materials.

An vitro method of toxicity testing of dental restorative materials is described in which their clinical usage is closely simulated. The test material was separated from the cells by either a synthetic filter or dentine slice. Toxic effects were quantiated by determining changes in enzyme activity by scanning and integrating microdensitometry.     

An in vitro microleakage study of a new multi-purpose dental adhesive system

summary Despite the advances made in the field of adhesive dentistry, microleakage still remains an area of concern, as a secure seal to dentine and cementum still cannot be achieved with certainty. This project compared the effectiveness of a new adhesive, Scotchbond Multi-Purpose Dental Adhesive System® (SBMP) with an established product, Gluma Bonding System® (Gluma) in preventing microleakage and the influence of storage, thermal and load cycling on microleakage patterns. In uncycled specimens, Gluma Bonding System had significantly less leakage (P < 001) at both occlusal and cervical margins. Thermocycling of composite restorations utilizing SBMP resulted in a significant decrease (P < 005) at the occlusal margins but had no effects on cervical leakage. Mechanical loading had no influence on leakage patterns either cervically or occlusally. Three months' storage and combined treatment resulted in a significant decrease in leakage (P < 005) at the occlusal margins.     

应用新型体外实验系统对牙科修复材料抗磨损性的研究

目的：评价牙科复合树脂材料的抗磨损性。方法：应用程控多功能口腔模拟机和三维图像激光测试仪对４种牙科复合树脂进行抗磨损性的实验研究。结果：材料磨损坑体积大小的顺序为：牙釉质〈Ｔａｒｇｉｓ Ｄｅｎｔｉｎ〈Ｄｅｎｔａｃｏｌｏｒ〈Ａｒｔｇｌａｓｓ〈Ｖｉｔａ Ｚｅｔａ。磨损坑最深点大小的顺序为：牙釉质〈Ｔａｒｇｉｓ Ｄｅｎｔｉｎ〈Ａｒｔｇｌａｓｓ〈Ｄｅｎｔａｃｏｌｏｒ〈Ｖｉｔａ Ｚｅｔａ。结论：Ｔａｒｇｉｓ     

Fluoride release from NaF- and AmF-impregnated toothpicks and dental flosses in vitro and in vivo

The aim of this study was to determine the fluoride release from toothpicks and dental flosses in vitro and in vivo, and to evaluate various approximal administration methods. In vitro, a total of 23 commercially available toothpicks and dental flosses and 3 prototypes impregnated with sodium fluoride (NaF), amine fluoride (AmF) or a combination of these two were tested. Fluoride release was determined for up to 24 h using an ion-specific electrode. A large variation was found between the products; most fluoride being released after 30 min. Generally speaking, toothpicks produced higher values than flosses. In vivo, the fluoride concentration in both treated and non-treated approximal areas was evaluated after using 2 different types of toothpicks and 4 dental flosses and after different application methods--such as a fluoride gel and fluoride solution. The mean fluoride concentration in oral fluid was up to 10 times higher at the treated sites than at the non-treated sites. Use of a fresh toothpick or a fresh piece of dental floss in each approximal space resulted in higher values compared with using one and the same toothpick/floss for the whole dentition. An interdental brush dipped in 0.2% NaF gel and a mouthrinse with 0.2% NaF resulted in elevated fluoride concentrations at the same level as when multiple toothpicks were used. To conclude, there are large variations in the fluoride release from various brands of fluoridated toothpicks and dental flosses. Treatment with a fluoridated toothpick or a dental floss can be expected to give elevated fluoride concentrations in the approximal area up to 60 min. Another interesting method for administering fluoride in the approximal area is to use an interdental brush dipped in fluoride gel.     

The release of mercury from dental amalgam: the mechanism and in vitro testing

Dissolution of mercury from the Ag-Hg matrix phase of dental amalgam is distilled water and synthetic saliva, and the mercury evaporation from the solutions, were studied in vitro. The main objectives of the study were to evaluate the factors that affect the results of the mercury release tests, and to consider the possible mechanisms of the release in vivo. Specimens were exposed to the liquids in open or closed bottles, and the changes in the mercury concentration were determined by cold-vapor Atomic Absorption Spectrophotometry. Concentration vs. time tests showed the dissolution rate decreasing with time. Tests involving sequences of short and long exposures with solution changes showed higher average rates for short-term dissolution into the fresh solution than for the longer preceding exposures. The differences were attributed to a stifling effect of the concentration of elemental mercury on the dissolution. It is believed that mercury dissolved mainly in the elemental form and that a continuous increase in the concentration was made possible by oxidation in the solution. In open cells, some of the mercury was lost by evaporation. The analysis showed that the results of mercury dissolution tests depend on many test variables, such as time, solution volume, oxidation and evaporation conditions, etc. Evaporation, dissolution, and evaporation/dissolution mechanisms of the mercury release in vivo were considered. It was concluded that the dissolution/evaporation model best described the mercury release from dental amalgam restorations.     

氟化物涂膜体外释氟情况研究

作者研究氟化物涂膜在体外使用后氟化物的释放情况，发现涂膜对于其中的氟化物有一定的缓释作用，但这种缓释作用的速度并不均匀，以开始一分钟的释放速度最快，以后释放速度明显减２４小时涂膜释氟量约占其总含量３０％，由于这种缓释作用，可使局部环境中氟化物保持一定浓度，延长氟化物与釉质对接触时间，阻止羟磷灰玫瑰溶解，促进脱矿釉质的再矿化。     

An estimation of fluoride release from various dental restorative materials at different pH: In vitro study

Background: In the mid of 1980s, the cariostatic effect of fluoride ions on enamel caries had been demonstrated in many studies. The use of fluoride releasing dental restorative materials has seen increasing from many years for the specific purpose of leaching of fluoride into the surrounding tissues to inhibit secondary dental caries as well as prevention of caries in the newly erupted tooth. In the dental caries, acidic environment causes the demineralization of tooth structure and also affect the restorative margins of dental restoration. Aim: various restorative materials show different behavior in different pH conditions of oral cavity. Thus, the aim of this study was to evaluate the fluoride release of the various restorative materials at different pH. Design: In this in vitro study, 30 samples of each dental restorative material were prepared and grouped into five with six samples in each group as per the pH of the solution 4.3, 4.6, 5.0, 5.5, and 6.2. All the samples were subjected to alternate cycling of the demineralizing solution (6 h) and remineralizing solution (18 h) for 15 days. Results: the fluoride release was measured by using fluoride ion specific electrode and digital ion analyzer. The result showed that the fluoride release rate was significantly higher in first day and reduced after third day to nearly constant level. At pH 4.3, the fluoride release was highest and lowest at pH 6.2. Conclusion: the Amalgomer CR showed the highest fluoride release among all the experimental dental restorative materials.     

Short-term reactions of human dental pulp to formocresol and its components – a clinical-experimental study

Abstract – Pulps of 58 human premolars were amputated under standardized conditions, and standardized amounts of dressings containing 4 or 19% formaldehyde solutions, 35% cresol or formocresol, were applied to the wound surface. Tissue reactions were studied after 4, 8 or 16 d using enzyme histochermical and routine histologic techniques. The results showed that formaldehyde fixed the tissue in vivo , the extent of fixation being dependent on the concentration of formaldehyde. Fixation did not reach the apical foramen. Formaldehyde also caused vascular changes at varying distances from the fixed tissue, indicating transport of formaldehyde via the vessels, Cresol caused necrosis and vascular changes limited mainly to the upper portion of the root pulp. Application of formocresol resulted in devitalization of the whole or almost the whole of the root pulp within 4 d, accompanied by complex vascular changes, depending mainly on the formaldehyde component. Root pulp exposed to formocresol for 5 min only showed partial devitalization due to compromised blood flow, while practically no fixation occurred. The inflammatory response to formocresol and its components was remarkably limited.     

The potential for dental plaque to protect against erosion using an in vivo-in vitro model--a pilot study

BACKGROUND: Tooth erosion is a problem for professional wine tasters (exogenous erosion from frequent exposure to wine acids) and for people with gastro oesophageal reflux disease (GORD) and bulimia who experience frequent reflux of gastric contents into the mouth (endogenous erosion from mainly HCl). The objective in this study was to determine whether plaque/pellicle could provide teeth with any protection from two common erosive acids, using an in vivo-in vitro technique. METHODS: Tiles of human tooth enamel and root surfaces were prepared from six extracted, unerupted third molar teeth and sterilized. Mandibular stents were prepared for six volunteer subjects and the tiles bonded to the buccal flanges of these stents. They were worn initially for three days to permit a layer of pellicle and plaque to form over the tile surfaces, and for a further 10 days of experimentation. Following cleaning of the plaque/ pellicle layer from the tiles on the right side flange, all the tiles were submerged in either 0.06M HCl or white wine for an accumulated time of 600 and 1500 minutes, respectively. Depths of erosion were determined using light microscopy of sections of the enamel and root tiles. SEM of the lesion surfaces was carried out to investigate the nature of erosive damage and of plaque/pellicle remnants. RESULTS: Retained plaque was found to significantly inhibit dental erosion on enamel, from contact with both HCl and wine, compared with that resulting following its removal. However, it was found to provide no significant protection on root surfaces. SEM analysis of the tile surfaces revealed marked etching of enamel on the cleaned surfaces, and considerable alteration to the appearance of remaining plaque and pellicle on most surfaces. CONCLUSION: Within the limitations of numbers of specimens, dental plaque/pellicle provided a significant level of protection to tooth enamel against dental erosion from simulated gastric acids and from white wine, using an in vivo-in vitro model. It was unable to provide any significant protection to root surfaces from these erosive agents. Possible reasons for this difference are explored.