Home About us Contact
|
Home About us Contact | ||
|
|
||
Amalgam
Kinds of Amalgam Terms modified by Amalgam Selected AbstractsThe Use of Silver Solid Amalgam Working Electrode for Determination of Nitrophenols by HPLC with Electrochemical DetectionELECTROANALYSIS, Issue 3-5 2009Ales Danhel Abstract The use of a silver solid amalgam working electrode for HPLC with electrochemical detection has been investigated. The thin-layer and wall-jet detectors based on this electrode were constructed and applied for the determination of a mixture of nitrophenols. The optimal separation and detection conditions for the determination of 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol and 2-methoxy-5-nitrophenol in mixture were found using RP-HPLC at Nova-Pack C18 column and amperometric detection with the above mentioned detectors. It has been proved that the silver solid amalgam electrode is a suitable working electrode for HPLC-ED and provides sufficient sensitivity for determination of tested nitrophenols. [source] Comparative radiopacity of tetracalcium phosphate and other root-end filling materialsINTERNATIONAL ENDODONTIC JOURNAL, Issue 4 2000C. D. Laghios Abstract Aim This study compared the radiopacity of tetracalcium phosphate (TTCP) and 11 root-end filling materials relative to human dentine. Methodology Specimens of 2 mm thickness and a graduated aluminium stepwedge were placed on dental X-ray films and exposed to an X-ray beam. The optical densities of the specimens and aluminium steps were measured. The optical densities of the specimens were correlated to the equivalent thickness of aluminium with a regression analysis equation. The equation was used to calculate the equivalent aluminium thickness of each of the specimens. Results Nine of the materials were found to be of acceptable radiopacity (at least 2 mm Al more radiopaque than dentine). TCCP and two of the glass-ionomer compounds were found to have insufficient radiopacity to be radiographically distinguishable from human dentine. Conclusions All the materials were found to be distinguishable radiographically from dentine, except for Vitrebond, TTCP and Ketac-Fil. Amalgam was the most radiopaque material and Ketac-Fil was the least radiopaque material tested. [source] The post-amalgam era: a selection of materials and their longevity in the primary and young permanent dentitionsINTERNATIONAL JOURNAL OF PAEDIATRIC DENTISTRY, Issue 3 2003H. Forss Summary. Objectives. During the last decade there has been a rapid change in the selection of dental restorative materials as the use of amalgam has decreased. The aim of this study was to obtain information on children's restorative dental care in Finland and to analyse the longevity of failed restorations. Design. A random sample of public dental health care centres was drawn from the registers and the dentists working there were asked to record information for each restoration they placed during a three-day period. The survey data comprised a total of 2186 restorations in patients younger than 17 years. Results. Of the children in need of restorative treatment, only a few had previous amalgam restorations. Primary caries was the main reason for restorative treatment in both primary and permanent dentitions (80% and 83%, respectively). In primary teeth, the most common restorative material was resin-modified glass ionomer cement (57·4%), whereas in permanent teeth, composite resin dominated (58·7%). Amalgam was not used at all in the primary dentition and in only 0·6% of permanent teeth. Eighteen per cent of treatments in primary and 12% in permanent teeth were replacements of previous fillings. The mean age of failed glass ionomer restorations was 2·8 years (n = 101) in the primary dentition, and 3·5 years (n = 54) in the permanent dentition. Conclusions. Until better restorative materials are developed, more attention should be paid to the prevention of dental caries as well as to the proper handling of alternative materials. [source] Effect of cavity varnish, amalgam liner or dentin bonding agents on the marginal leakage of amalgam restorationsJOURNAL OF ORAL REHABILITATION, Issue 5 2001S. Belli The purpose of this in vitro study was to compare marginal leakage of Class II amalgam restorations lined with different agents (two new generation dentin bonding systems, a cavity varnish and an amalgam liner). Forty freshly extracted human molar teeth were divided into five groups. Class II preparations were prepared in the mesial and distal surfaces of each molar. While the cavities in two groups were lined with two new generation bonding systems, the other two groups were treated with an amalgam lining material and a cavity varnish. Fifth group was used as control, without any lining. Amalgam* was hand-condensed into each preparation. Specimens were thermocycled, stained and sectioned. Microleakage was graded using a stereomicroscope. Mean microleakage scores for occlusal and cervical margins were calculated and analised. For the leakage values on occlusal margins, Kruskal,Wallis test indicated no significant difference in all groups. For the leakage values on cervical margins, Kruskal,Wallis test indicated significant difference in four groups when compared with controls (P < 0·001). On the other hand, there was no significant difference between the occlusal and cervical leakage values in each group. [source] Dental Amalgam and Multiple Sclerosis: A Systematic Review and Meta-AnalysisJOURNAL OF PUBLIC HEALTH DENTISTRY, Issue 1 2007Kevin K. Aminzadeh Bsc Pharm Abstract Objectives: Amalgam restorations have long been controversial due to their mercury content. Allegations that the mercury may be linked to nervous disorders such as Alzheimer's, chronic fatigue syndrome, and multiple sclerosis (MS) have fueled the calls for the removal of amalgam restorations from dentists' armamentarium. To explore and quantify the association between amalgam restorations and MS we have conducted a systematic review and meta-analysis of the literature. Methods: A systematic search in Medline (from 1966 to April 2006), EMBASE (2006, Week 16), and the Cochrane library (Issue 2, 2006) for English-language articles meeting specific definitions of MS and amalgam exposure was conducted. Studies were also identified using the references of retrieved articles. Studies were independently reviewed by two authors and disagreements were resolved by consensus. Studies were selected based on an a priori of defined criteria. Odds ratios (ORs) or relative risks were pooled using the random effects model. Heterogeneity was assessed using Q statistics. Results: The pooled OR for the risk of MS among amalgam users was consistent, with a slight, nonstatistically significant increase between amalgam use and risk of MS. Conclusion: Future studies that take into consideration the amalgam restoration size and surface area along with the duration of exposure are needed in order to definitively rule out any link between amalgam and MS. [source] Placement and replacement of restorations by selected practitionersAUSTRALIAN DENTAL JOURNAL, Issue 2 2005MJ Tyas Abstract Background: There are few Australian data on the reasons for placement and replacement of restorations, and the extent to which these are carried out in general practice. Methods: A survey was carried out of approximately 100 consecutive restorations placed by each of 28 general dental practitioners. The data were coded and statistically analyzed for various associations. Results: Resin composite was used twice as frequently as amalgam as a restorative material, and nearly four times as often as glass-ionomer cement. Secondary caries was the principal reason for replacing restorations, affecting predominantly amalgam restorations in Class I and Class V cavities. Teeth restored with amalgam fractured nearly twice as often as teeth restored with resin composite. The average ages of amalgam, resin composite and glass- ionomers at replacement were 13.6, 7.1 and 5.7 years respectively. Conclusions: Amalgam has the longest clinical service life, but is associated with more tooth fracture. Secondary caries is the main reason for replacing restorations. The anti-cariogenic effect of glass-ionomer cement is equivocal. [source] Replantation after extended dry storage of avulsed permanent incisors: report of a caseDENTAL TRAUMATOLOGY, Issue 4 2007Funda Kont Cobankara Abstract,,, A 15-year-old boy lost his maxillary right and left central incisor teeth in a bicycle accident. He was referred to our clinic 1 week after the injury. The crown-root integrities of both the teeth were not damaged. Although the teeth were stored under dry conditions for 1 week, reimplantation of the teeth was planned to retain the teeth in the mouth for as long a period as possible because of the patient's age. Following the debridement and sterilization of root surfaces in 2.5% NaOCl, root canals were prepared and filled with calcium hydroxide. Then, about 2 mm of the apexes were resected to ensure that the roots easily seated in the alveolar socket and the prepared cavities in root ends were obturated with the amalgam. The teeth were placed into their respective sockets and splinted temporarily. The root canal therapy was completed 5 weeks later. Ankylosis was observed radiographically after 10 months. The patient is now 23 years old and he is still able to use both the central incisors functionally. However, there is a pink appearance on the cervical buccal surface of left central incisor because of progressive replacement resorption. In this case, the new treatment plan is to perform a permanent restoration with dental implants following the extraction of both teeth. Even though the long-term prognosis is uncertain, this treatment technique has provided an advantage for the patient in his adolescent period by maintaining the height of alveolar bone and making the provision of an aesthetically acceptable permanent restoration at a later age possible. [source] Protective effect of Copalite surface coating on mercury release from dental amalgam following treatment with carbamide peroxideDENTAL TRAUMATOLOGY, Issue 3 2000I. Rotstein Abstract , The effect of Copalite coating on mercury release from dental amalgam following treatment with 10%, 20%, 30% and 40% carbamide peroxide was assessed in vitro, using a cold-vapour atomic absorption Mercury Analyzer System. Eighty samples of dental amalgam were automatically mixed in a dental amalgamator and condensed into silicon embedding molds. Forty amalgam samples were coated with three uniform layers of Copalite intermediary varnish and the other 40 samples were left uncoated. The coated and non-coated amalgam samples were exposed for 24 h to 10%, 20%, 30% or 40% carbamide peroxide preparations and compared with samples exposed to phosphate buffer. In the non-coated samples a significant increase of mercury concentration in solution was found following exposure to all carbamide peroxide preparations tested. Mercury concentration was directly related to carbamide peroxide concentration. In the Copalite-coated samples, significantly lower concentrations of mercury in solution were found as compared to the non-coated samples (P<0.01). In conclusion, exposure of amalgam restorations to 10%,40% carbamide peroxide-based bleaching agents increased the mercury release. Pre-coating of the external amalgam surfaces with Copalite significantly reduced the release of mercury. [source] The Use of Silver Solid Amalgam Working Electrode for Determination of Nitrophenols by HPLC with Electrochemical DetectionELECTROANALYSIS, Issue 3-5 2009Ales Danhel Abstract The use of a silver solid amalgam working electrode for HPLC with electrochemical detection has been investigated. The thin-layer and wall-jet detectors based on this electrode were constructed and applied for the determination of a mixture of nitrophenols. The optimal separation and detection conditions for the determination of 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol and 2-methoxy-5-nitrophenol in mixture were found using RP-HPLC at Nova-Pack C18 column and amperometric detection with the above mentioned detectors. It has been proved that the silver solid amalgam electrode is a suitable working electrode for HPLC-ED and provides sufficient sensitivity for determination of tested nitrophenols. [source] Working Electrodes from Amalgam Paste for Electrochemical MeasurementsELECTROANALYSIS, Issue 4 2008Bogdan Yosypchuk Abstract Paste electrode with paste amalgam as an active electrode material is described here for the first time. Designed electrode from silver paste amalgam (AgA-PE) is solely metallic and does not contain any organic binder. Mechanical surface regeneration of AgA-PE is performed in the same way as for classical carbon paste electrodes and reproducibility of such regeneration is about 10%. Electrochemical surface regeneration appeared very efficient for most measurements. In dependence on paste metal content, the electrode surface can be liquid (resembling a film) or rather solid. The hydrogen overvoltage on AgA-PE is high, and the electrode allows measurements at highly negative potentials. AgA-PE is well suited for study of reduction or oxidation processes without an accumulation step. Anodic stripping voltammetry of some metals tested on the electrode is influenced by formation of intermetallic compounds. The measurement based on cathodic stripping voltammetry (adenine, cysteine) and on catalytic processes from adsorbed state (complex of osmium tetroxide with 2,2,-bipyridine) can be performed on AgA-PE practically under the same conditions as found earlier for HMDE and for silver solid amalgam electrode. The working electrode from paste amalgam combines the advantages of paste and metal electrodes. [source] Amalgam Electrodes for ElectroanalysisELECTROANALYSIS, Issue 8 2003Øyvind Mikkelsen Abstract Liquid mercury is a unique material for the indicator electrode in voltammetry. One reason for this is the high overvoltage for hydrogen formation, thus extending the actual potential window. Diluted amalgams are important reaction products in voltammetric (polarographic) processes, however liquid amalgams are rarely used directly as electrode material for analytical purposes. Because of the fact that voltammetry is very suitable for field and remote monitoring, issues concerning the use of mercury electrodes in environmental analyses have led to considerable research effort aimed at finding alternative tools with acceptable performance. Solid electrodes are such alternatives. Different types of electrodes are reviewed. In particular, solid amalgam electrodes are very promising, with acceptable low toxicity to be used for field measurements. Solid amalgam electrodes are easy and cheap to construct and are stable over a reasonable time up to several weeks. Assessment of the toxicity risk and the long time stability for remote and unattended monitoring is discussed. The differences between solid dental amalgam electrodes, made by using techniques known from dental clinical practice, and mercury film or mercury layer electrodes on solid substrates are reviewed. In particular the dental technique for constructing solid amalgam electrodes gives advantage because it's fast and inexpensive. Also the technique for making dental amalgam has been explored and optimized over years by dentists, giving advantage when the same technique is used for constructing electrodes. Dental amalgam electrodes has been found to act similar to a silver electrodes, but with high overvoltage towards hydrogen. This make it possible to use the dental amalgam electrode for detection of zinc, cobalt and nickel in additions to other metals like lead, copper, thallium, cadmium, bismuth, iron etc. Also the use for reducible organic compounds is expected to be promising. [source] Students' clinical experience on outreach placementsEUROPEAN JOURNAL OF DENTAL EDUCATION, Issue 1 2010M. Smith Abstract Primary care outreach placements increasingly feature in UK undergraduate dental curricula. The profile of clinical work undertaken on placement may differ from traditional hospital-based programmes and between outreach settings. An appreciation of any differences could inform curriculum development. Objective:, To compare the profiles of clinical work experienced on a traditional hospital-based programme and outreach placements in different settings. Setting:, One dental hospital and eight existing primary care block placements in England. Subjects and methods:, Subjects were four cohorts of senior dental students in one UK dental school. Departmental records provided data on students' clinical experience in different settings and their achievement of placement learning objectives. Descriptive statistics for groups were compared. Main outcome measures:, (1) Counts of patients encountered and of clinical procedures completed in the following categories: simple plastic restorations, endodontics, cast restorations, dentures, extractions and children's dentistry. (2) Student perceptions of placement learning reported via Likert scales. Results:, Outreach students encountered twice as many patients and typically completed about three times as much clinical work as students in the hospital, e.g. 44 cf 16 simple plastic restorations, seven cf two endodontic procedures. There were variations in profiles by setting. For example, amalgam being more likely to be used on outreach especially in the General Dental Service; more children's dentistry in community services and more extractions in Dental Access Centres. Students reported learning outcomes generally being achieved (average 94%) although with some variation by setting. Conclusion:, Dental outreach training greatly increases the quantity of students' clinical experience in everyday dentistry compared to a hospital-based programme. Placements also increase awareness of service delivery and develop clinical skills. There are appreciable variations between outreach settings possibly reflecting their purposes. Multiple contrasting outreach placements for each student might increase the uniformity of learning experiences. [source] Contribution to the Reactivity of N,N, -Diaryl-1,4-diazabutadienes Aryl,N=CH,CH=N,Aryl (Aryl = 2,6-Dimethylphenyl; 2,4,6-Trimethylphenyl) Towards Boron TrichlorideEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2006Lothar Weber Abstract The reaction of Aryl,N=CH,CH=N,Aryl (3a: Aryl = 2,6-Me2C6H3; 3b: Aryl = 2,4,6-Me3C6H2) with 2 equiv. BCl3 in a toluene/hexane mixture at ,50 °C led to an inseparable mixture of borolium salts [Aryl,Na=CH,CH=N(Aryl)BCl2(Na,B)]+BCl4, (4a: Aryl = 2,6-Me2C6H3; 9a: Aryl = 2,4,6-Me3C6H2) and [Aryl,Na=CH,C(Cl)=N(Aryl)BCl2(Na,B)]+BCl4, (4b: Aryl = 2,6-Me2C6H3; 9b: Aryl = 2,4,6-Me3C6H2) and the bicyclic species [HCa=N(Aryl)BCl2N(Aryl),Cb=(Ca,Cb)]2 (5: Aryl = 2,6-Me2C6H3; 10: Aryl = 2,4,6-Me3C6H2). Sodium amalgam reduction of borolium salts 4a,b and 9a,b afforded inseparable mixtures of the diazaboroles 2,6-Me2C6H3NaCH=CR,Nb(2,6-Me2C6H3)BCl(Na,B) (1: R = H; 6: R = Cl) and 2,4,6-Me3C6H2NaCH=CR,Nb(2,4,6-Me3C6H2)BCl(Na,B) (2: R = H; 11: R = Cl). In order to obtain pure 1 and 2, diazabutadienes 3a and 3b were slowly combined with 2 equiv. BCl3 in the same solvents at ,78 °C. The acyclic adducts Cl3BN(Aryl)=CH,CH=N(Aryl)BCl3 (7a: Aryl = 2,6-Me2C6H3; 7b: Aryl = 2,4,6-Me3C6H2) were reduced with sodium amalgam to furnish the aminoboranes Cl2BN(Aryl)CH=CH,N(Aryl)BCl2 (8: Aryl = 2,6-Me2C6H3; 12: Aryl = 2,4,6-Me3C6H2). Stirring solutions of 8 and 12 in the presence of CaH2 cleanly gave the diazaboroles 1 and 2, respectively. The novel compounds were characterized by elemental analyses and 1H-, 11B-, 13C NMR and mass spectra. The molecular structures of 1, 4a, 5 and 8 were elucidated by single X-ray diffraction analyses. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Synthetic, Structural, and Electrochemical Studies of 2-Ferrocenyl- and2-Cymantrenyl-Functionalized 2,3-Dihydro-1H -1,3,2-diazaboroles and1,3,2-DiazaborolidenesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2005Lothar Weber Abstract Reaction of (dibromoboryl)ferrocene (1) with 1 equiv. of the diazabutadiene tBuN=CH,CH=NtBu, and subsequent reduction of the obtained borolium salt 2 with sodium amalgam, affords the first ferrocenyl-functionalized 1,3,2-diazaborole (3). Similarly, 1,1,-bis(dibromoboryl)ferrocene (4) can be transformed into compound 6, which contains two diazaborolyl substituents at the ferrocene core. Treatment of precursors 1 and 4 with 1,2-bis(tert -butylamino)ethane in the presence of Et3N gives rise to the formation of the diazaborolidine derivatives 13 and 14. 1-Dibromoboryl-3-methylcymantrene (7) was also treated with tBuN=CH,CH=NtBu to give the borolium salt 8, which was subsequently reduced to the 2-cymantrenyl-diazaborole 9. Treatment of 7 with tBuN(H)CH2CH2N(H)tBu in the presence of Et3N furnished the corresponding 2-cymantrenyl-diazaborolidine 15. The novel compounds were characterized by elemental analyses and various spectroscopic techniques (IR; 1H, 13C, and 11B NMR; MS). The molecular structures of 3, 6, and 15 were elucidated by X-ray diffraction analyses. Cyclovoltammetric studies of the ferrocene derivatives at high scan rates show features of a quasireversible oxidation at the iron center. The heterocyclic groups serve as electron donors, considerably lowering the oxidation potential of the central iron atoms when compared to the parent compound ferrocene. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Estimating Background and Threshold Nitrate Concentrations Using Probability GraphsGROUND WATER, Issue 5 2006S.V. Panno Because of the ubiquitous nature of anthropogenic nitrate () in many parts of the world, determining background concentrations of in shallow ground water from natural sources is probably impossible in most environments. Present-day background must now include diffuse sources of such as disruption of soils and oxidation of organic matter, and atmospheric inputs from products of combustion and evaporation of ammonia from fertilizer and livestock waste. Anomalies can be defined as derived from nitrogen (N) inputs to the environment from anthropogenic activities, including synthetic fertilizers, livestock waste, and septic effluent. Cumulative probability graphs were used to identify threshold concentrations separating background and anomalous NO3 -N concentrations and to assist in the determination of sources of N contamination for 232 spring water samples and 200 well water samples from karst aquifers. Thresholds were 0.4, 2.5, and 6.7 mg/L for spring water samples, and 0.1, 2.1, and 17 mg/L for well water samples. The 0.4 and 0.1 mg/L values are assumed to represent thresholds for present-day precipitation. Thresholds at 2.5 and 2.1 mg/L are interpreted to represent present-day background concentrations of NO3 -N. The population of spring water samples with concentrations between 2.5 and 6.7 mg/L represents an amalgam of all sources of in the ground water basins that feed each spring; concentrations >6.7 mg/L were typically samples collected soon after springtime application of synthetic fertilizer. The 17 mg/L threshold (adjusted to 15 mg/L) for well water samples is interpreted as the level above which livestock wastes dominate the N sources. [source] New tin(IV) complexes with sterically hindered o -iminobenzoquinone ligand: Synthesis and structureHETEROATOM CHEMISTRY, Issue 6 2009Alexandr V. Piskunov The reduction of 4,6-di-tert-butyl-N-(2, 6-di-iso-propylphenyl)-o-iminobenzoquinone (imQ) by tin amalgam in hexane solution leads to new six-coordinated o-iminoquinonato tin(IV) complex (iSQ)2SnAP (1) (where iSQ and AP are o-iminosemiquinolate and dianion o-amidophenolate, respectively). Variable temperature magnetic susceptibility measurements of 1 have shown that this complex possesses a weak ferromagnetic exchange between o-iminosemiquinonate ligands. The oxidation of 1 with air oxygen produces new o-iminoquinonolate tin(IV) derivatives [(iSQ)Sn(AP)]2O (2) and (iSQ)2Sn(OH)2 (3) containing ,-oxo- and hydroxo-ligands, respectively. The electronic structure of 1 was examined by DFT analysis. Complexes 1,3 have been investigated using single-crystal X-ray diffraction. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:332,340, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20555 [source] The effect of mineral trioxide aggregate on the apexification and periapical healing of teeth with incomplete root formationINTERNATIONAL ENDODONTIC JOURNAL, Issue 1 2006W. T. Felippe Abstract Aim, To evaluate the influence of mineral trioxide aggregate (MTA) on apexification and periapical healing of teeth in dogs with incomplete root formation and previously contaminated canals and to verify the necessity of employing calcium hydroxide paste before using MTA. Methodology, Twenty premolars from two 6-month old dogs were used. After access to the root canals and complete removal of the pulp, the canal systems remained exposed to the oral environment for 2 weeks. Canal preparation was then carried out using Hedström files, under irrigation with 1% sodium hypochlorite, 1 mm short of the radiographic apex. After drying, the canals of two premolars in each dog were left empty (control group). The other eight teeth in each animal were divided into two experimental groups. The apical thirds of the canals of group 1 were filled with MTA. In the teeth of group 2, the canals were dressed with a calcium hydroxide,propylene glycol paste. After 1 week, the paste was removed and the apical third was filled with MTA. All teeth were restored with reinforced zinc oxide cement (IRM) and amalgam. The animals were killed 5 months later, and blocks of the teeth and surrounding tissues were submitted to histological processing. The sections were studied to evaluate seven parameters: formation of an apical calcified tissue barrier, level of barrier formation, inflammatory reaction, bone and root resorption, MTA extrusion, and microorganisms. Results of experimental groups were analysed by Wilcoxon's nonparametric tests and by the test of proportions. The critical value of statistical significance was 5%. Results, Significant differences (P < 0.05) were found in relation to the position of barrier formation and MTA extrusion. The barrier was formed in the interior of the canal in 69.2% of roots from MTA group only. In group 2, it was formed beyond the limits of the canal walls in 75% of the roots. MTA extrusion occurred mainly in roots from group 2. There was similarity between the groups for the other parameters. Conclusions, Mineral trioxide aggregate used after root canal preparation favoured the occurrence of the apexification and periapical healing. The initial use of calcium hydroxide paste was not necessary for apexification to occur, and has shown to be strongly related to the extrusion of MTA and formation of barriers beyond the limits of the root canal walls. [source] The effect of the renewal of calcium hydroxide paste on the apexification and periapical healing of teeth with incomplete root formationINTERNATIONAL ENDODONTIC JOURNAL, Issue 7 2005M. C. S. Felippe Abstract Aim, To evaluate the influence of renewing calcium hydroxide paste on apexification and periapical healing of teeth in dogs with incomplete root formation and previously contaminated canals. Methodology, Forty premolars from four 6-month-old dogs were used. After access to the root canals and complete removal of the pulp, the canal systems remained exposed to the oral environment for 2 weeks. Canal preparation was then carried out using Hedströem files, under irrigation with 1% sodium hypochlorite, 1 mm short of the radiographic apex. After drying, the canals of one premolar in each dog were left empty (group 4-control), and those of the other nine teeth in each animal were filled with a calcium hydroxide-propylene glycol paste. All teeth were restored with reinforced zinc oxide cement (IRM) or IRM and amalgam (group 4). The paste was renewed and the teeth restored again 1 week later. Then, the nine teeth in each animal were divided into three experimental groups: group 1 , paste not changed; group 2 , paste renewed every 4 weeks for 5 months; and group 3 , paste renewed after 3 months had elapsed. The teeth were restored with IRM and amalgam (groups 1 and 3) or IRM (group 2). The animals were killed 5 months later, and blocks of the teeth and surrounding tissues were submitted to histological processing. The sections were studied to evaluate six parameters: apical calcified tissue barrier, inflammatory reaction, bone and root resorption, paste extrusion and microorganisms. Results of experimental groups were analysed by Kruskal,Wallis nonparametric tests and by the test of proportions. The critical value of statistical significance was 5%. Results, Significant differences (P < 0.05) were found in relation to the presence of bone resorption and paste in the periradicular area, the formation of a calcified tissue barrier at the apex, and the intensity of the apical inflammatory reaction. Bone resorption was more evident in group 1 (medicament not changed), and the presence of paste in the periodontal tissues was more common in groups 2 and 3. Renewal of the paste reduced the intensity of the inflammatory reaction (groups 2 and 3), but the formation of apical calcified tissue was more noticeable in the teeth where the paste had not been renewed. Conclusions, Replacement of calcium hydroxide paste was not necessary for apexification to occur, however, it did reduce significantly the intensity of the inflammatory process. Monthly renewal of calcium hydroxide paste reduced significantly the occurrence of apexification. [source] The comparison of the effects of three types of piezoelectric ultrasonic tips and air polishing system on the filling materials: an in vitro studyINTERNATIONAL JOURNAL OF DENTAL HYGIENE, Issue 4 2007T Arabaci Abstract:, Aim:, The aim of this study was to evaluate the effect of air polishing and different ultrasonic scaler inserts on dental fillings, such as amalgam, composite and porcelain. Materials and methods:, This study was performed on amalgam, composite and porcelain samples. The surfaces of the samples were exposed to different type of piezoelectric ultrasonic scaler inserts and air-abrasive unit. The scaler inserts were Instrument A, Instrument PS and PI. The roughness of the surfaces of each sample were measured with a profilometer and observed by stereomicroscope. Results:, The stereomicroscopic images and profilometric values showed that Instrument A and PS resulted in rough surfaces, such as chips, nicks and scratches on the amalgam, composite and porcelain surfaces. The Instrument PI roughened the amalgam surface, but it did not roughen the porcelain or composite surfaces. The profilometric measurements (Ra) showed that the roughness of the surfaces depending on air polishing was less than the ultrasonically scaled surfaces. Conclusion:, The wrong tip applications during dental scaling procedure cause roughness, such as scratches, nicks or chips, not only on the teeth surfaces but also on the filling materials. Thus, dental scaling procedure on the restorations should be performed carefully and the roughness sites on the restorations have to be re-polished after scaling to prevent plaque accumulation. [source] Marketing networks as a form of strategic alliance among craft enterprisesINTERNATIONAL JOURNAL OF NONPROFIT & VOLUNTARY SECTOR MARKETING, Issue 3 2002Ann M. Torres Craft enterprises are a unique form of small and medium-sized enterprise (SME) and represent an amalgam between the manufacture of products and the fulfilment of artistic vision. Craft enterprises typically have insufficient resources, inadequate access to specialised expertise and limited opportunities to make an impact on the marketplace. One way to redress these limitations and to improve the competitive position of craft enterprises is by forming networks, or cooperative alliances. The case study of ,Homethrown', a successful marketing network for potters, provides insight into the advantages and limitations of this type of strategic alliance, as well as guidelines for fostering cooperation and moderating conflict. Copyright © 2002 Henry Stewart Publications [source] The ancient inhabitants of Jebel Moya redux: measures of population affinity based on dental morphologyINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 2 2007J. D. Irish Abstract This paper reexamines some of the methods and craniometric findings in the classic volume The Ancient Inhabitants of Jebel Moya (Sudan) (1955) by Mukherjee, Rao & Trevor, in light of recent archaeological data and relative to a new dental morphological study. Archaeological evidence characterises these inhabitants as having been heavily influenced by outside sources; yet they managed to establish and maintain their own distinctive culture as seen in the site features and surviving artefact collections. The dental study, modelled after the original craniometric-based investigation and using the same or similar comparative samples, detected complementary indications of outside biological influence. In the study, up to 36 dental traits were recorded in a total of 19 African samples. The most influential traits in driving inter-sample variation were then identified, and phenetic affinities were calculated using the Mahalanobis D2 statistic for non-metric traits. If phenetic similarity provides an estimate of genetic relatedness, these affinities, like the original craniometric findings, suggest that the Jebel Moyans exhibited a mosaic of features that are reminiscent of, yet distinct from, both sub-Saharan and North African peoples. Together, these different lines of evidence correspond to portray the Jebel Moya populace as a uniform, although distinct, biocultural amalgam. Copyright © 2006 John Wiley & Sons, Ltd. [source] Propofol intravenous conscious sedation for anxious children in a specialist paediatric dentistry unitINTERNATIONAL JOURNAL OF PAEDIATRIC DENTISTRY, Issue 1 2004M. T. Hosey Summary. Objectives., To report on both the use and dosage of propofol, as a new intravenous (IV) conscious sedative agent, for anxious children referred to a specialist paediatric dentistry service. Setting., Paediatric Dentistry Unit, Glasgow Dental Hospital and School. Sample., Thirty-four children, 25 females and 9 males, mean age 12 years 10 months, with a mean weight of 54·6 kg (range 30,110 kg). Methods., Report from 34 patients receiving intravenous sedation for the first time in respect of weight dose and amount of treatment completed. Results., Thirty-two children successfully accepted operative dental care on their first visit, they received a mean total dose of 146·25 mg of propofol (range 10 mg to 356 mg); in relation to body weight, the mean was 2·5 mg/kg (range 0·2,5·4 mg/kg). The treatment that they received included fissure sealants, amalgam and adhesive restorations, root canal therapy and single and multiple extractions. Their sedation and recovery were uneventful. Conclusions., Sub-anaesthetic doses of propofol used for IV conscious sedation infusion facilitated operative dental treatment in anxious children. [source] The post-amalgam era: a selection of materials and their longevity in the primary and young permanent dentitionsINTERNATIONAL JOURNAL OF PAEDIATRIC DENTISTRY, Issue 3 2003H. Forss Summary. Objectives. During the last decade there has been a rapid change in the selection of dental restorative materials as the use of amalgam has decreased. The aim of this study was to obtain information on children's restorative dental care in Finland and to analyse the longevity of failed restorations. Design. A random sample of public dental health care centres was drawn from the registers and the dentists working there were asked to record information for each restoration they placed during a three-day period. The survey data comprised a total of 2186 restorations in patients younger than 17 years. Results. Of the children in need of restorative treatment, only a few had previous amalgam restorations. Primary caries was the main reason for restorative treatment in both primary and permanent dentitions (80% and 83%, respectively). In primary teeth, the most common restorative material was resin-modified glass ionomer cement (57·4%), whereas in permanent teeth, composite resin dominated (58·7%). Amalgam was not used at all in the primary dentition and in only 0·6% of permanent teeth. Eighteen per cent of treatments in primary and 12% in permanent teeth were replacements of previous fillings. The mean age of failed glass ionomer restorations was 2·8 years (n = 101) in the primary dentition, and 3·5 years (n = 54) in the permanent dentition. Conclusions. Until better restorative materials are developed, more attention should be paid to the prevention of dental caries as well as to the proper handling of alternative materials. [source] British Society of Paediatric Dentistry: a policy document on the use of amalgam in paediatric dentistryINTERNATIONAL JOURNAL OF PAEDIATRIC DENTISTRY, Issue 3 2001Article first published online: 3 SEP 200 First page of article [source] The distinctive dynamics of exurban tourismINTERNATIONAL JOURNAL OF TOURISM RESEARCH, Issue 1 2005David Weaver Abstract The distinctiveness of the urban,rural fringe as a tourism venue, which merits recognition of exurban tourism as a distinct subfield, is based on a unique product amalgam that includes theme parks, tourist shopping villages, near-urban protected areas, factory outlet malls, golf courses and touring. In addition, the market is characterised by blurred tourist/non-tourist distinctions, a weak accommodation sector and extremely high visitation levels at some sites. It is argued that the urban,rural fringe is an inherently unstable area characterised by a variant of the standard destination life cycle confined to the late involvement, development and consolidations stages, and paralleling comparable volatile stages within the broader urban life cycle. Copyright © 2005 John Wiley & Sons, Ltd. [source] Greening of the Tooth,Amalgam Interface during Extended 10% Carbamide Peroxide Bleaching of Tetracycline-Stained Teeth: A Case ReportJOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 1 2002VAN B. HAYWOOD DMD ABSTRACT At-home bleaching with 10% carbamide peroxide in a custom-fitted tray has been shown to have some minor effects on certain brands of amalgam, pertaining to mercury release, but generally, effects on amalgam are not considered clinically significant. However, in this case report, a greening of the tooth structure in certain areas immediately adjacent to amalgam restorations in the maxillary and mandibular first molars occurred during tooth whitening. Other amalgam restorations in mandibular and maxillary second molars in the same mouth did not demonstrate any green discoloration of the teeth. Upon removal of the affected amalgam restorations, recurrent decay was present in the areas of tooth greening but not in other areas adjacent to the restoration. The teeth were restored with posterior composite restorations. Whether the green discoloration was a result of some loss of material from a particular brand of amalgam, indicating leakage, or indicative of original or recurrent tooth decay is unclear in this single-patient situation. Other patients in the same study did not demonstrate this occurrence. Dentists should be ready to replace amalgam restorations should this green discoloration in adjacent tooth structure occur during bleaching, in case decay is present. CLINICAL SIGNIFICANCE The unusual discoloration cited suggests that amalgam restorations in potentially esthetic areas, including the lingual of anterior teeth, should be replaced prior to bleaching, to avoid the problem of difficult stain removal or translucency allowing restoration visibility following bleaching. [source] High-resolution sonography of sublingual spaceJOURNAL OF MEDICAL IMAGING AND RADIATION ONCOLOGY, Issue 2 2008P Jain Summary Ultrasound examination of the sublingual region is a non-invasive, safe, inexpensive and widely available procedure, unaffected by the amalgam in teeth which is a source of considerable artefact on CT and MRI images. With a little practice and good understanding of the anatomy, ultrasound can be a very helpful primary examination. If the lesion is clearly seen, no further imaging may be required. [source] Corrosion behaviour of high copper dental amalgamsJOURNAL OF ORAL REHABILITATION, Issue 6 2004A. U. J. Yap summary, This study evaluated the corrosion behaviour of two high copper dental amalgam alloys [Dispersalloy (Dentsply-Caulk) and Tytin (Kerr)] in different electrolytes. Amalgam specimens were prepared, coupled to a copper wire, cemented into glass tubes and polished to a 600-grit finish. A corrosion cell was prepared using a carbon counter-electrode, a standard calomel electrode as the reference and amalgam as the working electrode. The alloys were tested in the following mediums at 37 °C: (i) artificial saliva based on Fusayama's solution (FS), (ii) artificial saliva with citric acid adjusted to pH 4·0 (FC) and (iii) 1% sodium chloride solution (SC). Corrosion potentials (Ecorr) and corrosion rates (Icorr) were determined using potentiostatic and impedance spectroscopy methods. Data was subjected to anova/Scheffe's post hoc test at 0·05 significance level. For both alloys, the corrosion potential in FS was significantly greater than in SC. Corrosion potential of Tytin in FS and SC was also significantly greater than in FC. The corrosion rate of Dispersalloy in FC was significantly greater than in FS and SC. For Tytin, corrosion rate in SC was significantly greater than in FS and FC. Although no significant difference in corrosion potential/rate was observed between the alloys when tested in FS, significant differences were observed when electrochemical testing was carried out in FC and SC. The corrosion behaviour of high copper amalgam alloys are both material and environment dependent. Certain food substances may increase the corrosion of high copper amalgams. [source] Adherence of Streptococcus mutans to various restorative materials in a continuous flow systemJOURNAL OF ORAL REHABILITATION, Issue 3 2004S. Eick summary, A continuous flow system was developed to evaluate the adhesion of Streptococcus mutans ATCC 25175 to filling materials (Ariston, Tetric, Dyract, Compoglass, Vitremer, Aqua Ionofil, Ketac Fil, amalgam, Galloy and ceramics as controls). Streptococcus mutans was added to saliva-coated test specimens, and a nutrient broth permanently supplied over a time period of 48 h and then the weight of plaque, the number and viability of the bacteria adhering to the materials were determined. The weights of artificial plaque on all filling materials tested were higher than those on ceramics, the highest values were measured on the glass,ionomers. The amount of plaque correlates with the surface roughness, whereas there was no correlation of the surface roughness with the number of colony-forming units (CFU) of S. mutans. The CFU of adhering S. mutans also depends on the viability of the bacteria. The plaque on Ketac Fil contained a high number of viable bacteria. The fluorides of glass,ionomers do not efficiently prevent the attachment and the viability of S. mutans. [source] In vitro evaluation of the effect of a current bleaching agent on the electrochemical corrosion of dental alloysJOURNAL OF ORAL REHABILITATION, Issue 10 2002enay Canay summary, The nightguard bleaching of discoloured teeth is currently performed by using % 10 carbamide peroxide. While the material is effective on the bleaching of natural teeth, it may deteriorate crowns, bridges and amalgam restorations placed in the mouth. The purpose of the present study was to investigate the effect of 10% carbamide peroxide on the electrochemical corrosion of various dental casting alloys used for fixed partial dentures and dental amalgam. Tafel extrapolation curves were obtained by the corrosion cell that facilitated simulation of the oral enviroment and comparison of the corrosion rates of alloys and amalgam was accomplished. The results revealed that unpolished amalgam and nickel-chromium alloy samples had the most and noble alloys had the least corrosion rate. [source] | |||||||||||||||||||||||||||||||||||||