Dental Amalgam

To evaluate the effect of an 8% arginine-calcium carbonate fluoride-free desensitizing paste on the surface roughness of resin composite, porcelain, amalgam, gold, and human dental enamel both prior to and following simulated toothbrushing. A resin composite (Filtek Supreme), a commercial porcelain (IPS Empress), an amalgam (Dispersalloy), gold (JIF-PF) and human dental enamel were used, as well as commercial finishing and polishing instruments. Eight two-sided samples were fabricated for each group. The composite and amalgam samples were stored at 100% relative humidity and 37 degrees C for 48 hours prior to measuring the surface roughness and completing the subsequent finishing and polishing procedures. Enamel blocks were cut from human lesion-free teeth and embedded in acrylic. The blocks were then polished flat with high polishing pastes. For gold and porcelain, the same size was used and the materials processed by a professional dental laboratory. Following storage, each surfac...

Amalgam, composite resin and compomer are frequently used in operative dentistry today. Earlier studies have shown the periodontal consequences induced by these materials if they have intracrevicular restorative margins. This study was performed on dogs where Class V cavities with apical margin located at the alveolar bone crest were prepared and restored with these materials. Three months later, the experimental and control sites were prepared for histological analysis. Mean bone loss was significant only with compomer. The mean length of the supracrestal connective tissue was almost the same with the three fillings. The length of epithelial attachment was the highest with composites. There was a decrease in the length of the biologic width from Day 0 to Day 90.

More than five hundred million direct dental restorations are placed each year worldwide. In about 55% of the cases, resin composites or compomers are used, and in 45% amalgam. The longevity of posterior resin restorations is well documented. However, data on resin composites that are placed without enamel/dentin conditioning and resin composites placed with self-etching adhesive systems are missing. The database SCOPUS was searched for clinical trials on posterior resin composites without restricting the search to the year of publication. The inclusion criteria were: (1) prospective clinical trial with at least 2 years of observation; (2) minimum number of restorations at last recall = 20; (3) report on dropout rate; (4) report of operative technique and materials used; (5) utilization of Ryge or modified Ryge evaluation criteria. For amalgam, only those studies were included that directly compared composite resin restorations with amalgam. For the statistical analysis, a linear mi...

The goal of this presentation is to describe the material as it is used clinically, explain why small quantities of Hg can be released, and suggest ideas for amalgams that do not release mercury. A set amalgam is a dynamic material that undergoes many microstructural changes during clinical use, related to both the elevated temperature and corrosion-prone environment in the mouth and mechanical forces applied to the restoration. Amalgams can be divided roughly into two groups by their copper content: low Cu (traditional) and high Cu. High-Cu amalgams generally perform better clinically, but all amalgams corrode to some extent in the mouth. Some corrosion is deemed to be a positive factor, because corrosion product deposition reduces leakage at the margins of restorations; that is, the restorations are partly self-sealing. One of the reasons cited for the improved clinical performance of high-Cu amalgams over low-Cu amalgams is that the corrosion-prone phase, gamma 2, is nearly elimi...

The microleakage of four retrograde filling materials was compared in vitro. Fifty-three single rooted teeth were instrumentated and root filled with resin chloroform and gutta-percha. The gutta-percha cones were left extruding from the access opening. All teeth were apicected and retrograde fillings placed. The materials used were a non γ2 amalgam (Amalcap), a glass ionomer cement (ChemFil II), threaded titanium pins cemented with a glass ionomer cement (ChemFil II) and identical titanium pins cemented with a silicone material (Adheseal). After removal of the gutta-percha with tweezers, a radioactive isotope solution was placed in the teeth. Extraradicular samples were taken at 3, 7, 28, 77 and 104 days. All retrograde fillings showed some microleakage. The group with titanium pins cemented with silicone showed the least leakage: significantly less than the teeth with glass ionomer cement (P < 0.01) and with amalgam (P < 0.01). No significant differences were found between other groups.

Biomaterials and their applications in medicine and dentistry have been recognized in regular clinical practice. In recent years lot of research is being done on its application in the field of medicine and particularly in restorative dentistry. These materials found to be successful for restoration of teeth in esthetic, function and to maintain the integrity of masticatory muscles. Some of the dental materials, the biocompatibility and application has been discussed and reviewed.

The amount of mercury in the wastewater of three dental clinics from United Arab Emirates over a period of 3 to 17 days was quantified using cold vapour-atomic absorption spectrometry technique. The total Hg concentration in the wastewater of these clinics ranged from 25 to 146 μg d-1. The Hg concentration in the wastewater samples collected from the outlets of the dental
chairs after dental treatments varies depending on the type of dental treatment: the average Hg concentration in the samples of only amalgam restoration is 39 μg per sample (std. dev. 37, range 4-142); for samples with amalgam restoration plus other types of dental treatment is 24 μg per sample (std. dev. 24, range <MDL-77); and for sample with no amalgam restoration is 18 μg per sample (std. dev. 16, range <MDL-33).

Eighteen cadavers from routine autopsy casework were subject to a study of tissue levels of total mercury in brain, thyroid, and kidney samples by atomic absorption. On these same cadavers, all dental amalgam fillings (the most important source of inorganic mercury exposure in the general population, according to the World Health Organization (WHO) were charted. Total mercury levels were significantly higher in subjects with a greater number of occlusal amalgam surfaces (&gt;12) compared with those with fewer occlusal amalgams (0-3) in all types of tissue (all P &lt; or = 0.04). Mercury levels were significantly higher in brain tissues compared with thyroid and kidney tissues in subjects with more than 12 occlusal amalgam fillings (all P &lt; or = 0.01) but not in subjects with 3 or less occlusal amalgams (all P &gt; or = 0.07).

It is well known that when Thomas Johann Seebeck first detected a magnetic effect in the vicinity of a bi-metallic circuit by maintaining a temperature difference between its contact-points, his first attempts at explaining the phenomenon were not accurate.

Fortunately for Seebeck, the Danish scientist Hans Christian Oersted soon heard about his results, and he immediately recognised a similarity between Seebeck's findings and those from his own pioneering work in electricity and magnetism.

Oersted had already established that when an electric current was made to flow in a circuit, it produced exactly the same type of magnetic effect as reported by Seebeck. He therefore deduced that the temperature imbalance applied across Seebeck's bi-metallic circuits must be causing a current to circulate in those too, a fact which until then had not been apparent to Seebeck.

However, it is perhaps not so well known that Oersted continued to show a very keen interest in Seebeck's work, and that between 1823 and 1830 he presented several papers of his own describing the latest developments in thermoelectricity
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In 1998 a collection of Oersted's scientific papers, translated into English from the original Danish manuscripts by Karen Jelven, Andrew D. Jackson and Ole Knudsen, were published in a volume entitled, "Selected Scientific Works of Hans Christian Oersted".

These translations offer a fascinating insight into some of the earliest discoveries in thermoelectric science, not least among them the verification in a paper of 1830 that a purely thermoelectric device could cause convulsions in frog's legs similar to those reported in experiments carried out by Alessandro Volta and Luigi Galvani a few decades earlier.

On the 240th anniversary of his birth, this 40-minute presentation celebrates Hans Christian Oersted's contributions to the advancement of knowledge and understanding in the early days of thermoelectric science, and it may also serve as an inspiration for further reflection on how thermoelectric phenomena are perceived today.

At the University of British Columbia, we introduced an ePortfolio assignment in the operative dentistry clinical simulation module and conducted a pilot study to explore the usefulness of ePortfolios as a learning tool for dental students. Qualitative assessments included student self-reflections on the ePortfolio experience. In the quantitative evaluation, ePortfolio learning was hypothesized as a multidimensional experience with four dimensions: 1) an ePortfolio experience is valuable for learning operative dentistry; 2) an ePortfolio is time-consuming, but overall a useful experience; 3) ePortfolio learning requires technical skills that are manageable; and 4) ePortfolio experience may be beneficial for lifelong learning. Overall, both quantitative and qualitative assessments demonstrated that students valued ePortfolio learning as a positive experience. In multivariate analyses (confirmatory factor analysis), the four-dimensional model of ePortfolio learning was confirmed. Futu...

Aim: This study aims to compare the fracture strength, fracture pattern, types of fracture involved, and areas of fractured restoration among endodontically treated permanent lower premolars restored with different restorative materials. Materials and Methods: Sixty-nine mature human permanent lower premolars recently extracted for orthodontic, periodontal, or other reasons were selected and divided into three groups (n = 23). Groups 1 and 2 were endodontically treated. Standardized mesio-occlusal distal cavities were then prepared in both Groups 1 and 2. Groups 1 and 2 were restored with amalgam using Nayyar's core technique and glass fiber post with composite resin core, respectively. Group 3 consisted of intact teeth which acted as control group. All teeth were tested under constant occlusal load until fracture occurred using a Universal Testing Machine. Data analysis was carried out using Kruskal–Wallis test complemented by Mann–Whitney test. Results: The mean values of fracture strength were 388.05 N (± 158.09) for Group 1, 588.90 N (± 151.33) for Group 2, and 803.05 N (± 182.23) for Group 3. Kruskal–Wallis test showed significant differences among all three groups in terms of fracture strength. The mean load required to fracture intact teeth in Group 3 was significantly highest, followed by Group 2 (P < 0.01) and finally Group 1 (P < 0.01). Most fractures occurred within the coronal structure and were considered favorable pattern. Besides, majority of the fractures occurred on restorations and particularly at the distal side. Conclusions: Teeth restored with fiber post and composite core resulted in higher fracture resistance than teeth restored with Nayyar's core amalgam restoration.

Keywords: Fracture pattern, fracture resistance, glass fiber post, Nayyar's core, post and core technique

Purpose: To compile a survey of the longevity and reasons for failure of stainless steel crowns, amalgam, glass-ionomer, composite and compomer restorations in stress-bearing cavities of primary molars. Methods: This work reviewed the dental literature of 1971 up to July 2003 for longitudinal, controlled clinical studies and retrospective cross-sectional studies. Only studies investigating the clinical performance of restorations in primary