A simple and sensitive detection of diquat herbicide using a dental amalgam electrode A comparison using the chromatographic technique

This paper describes the use of a dental amalgam electrode (DAE) to evaluate the electrochemical behaviour and to develop an electroanalytical procedure for determination of diquat herbicide in natural water and potato samples. The work was based on the square wave voltammetry responses of diquat, which presented two well-defined and reversible reduction peaks, at -0.56 V (peak 1) and -1.00V (peak 2). The experimental and voltammetric parameters were optimised, and the analytical curves were constructed and compared to similar curves performed by high performance liquid chromatography coupled to ultraviolet-visible spectrophotometric detector (HPLC/UV-vis). The responses were directly proportional to diquat concentration in a large interval of concentration, and the calculated detection limits were very similar, around 10 mu g L(-1) (10 ppb) for voltammetric and chromatographic experiments. These values were lower than the maximum residue limit established for natural water by the Brazilian Environmental Agency. The recovery percentages in pure electrolyte, natural water and potato samples showed values from 70% to 130%, demonstrating that the voltammetric methodology proposed is suitable for determining any contamination by diquat in different samples, minimising the toxic residues due to the use of liquid mercury or the adsorptive process relative to use of other solid surfaces. (C) 2009 Published by Elsevier B.V.

Recovery of silver residues from dental amalgam

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evaluation of the dental structure loss produced during maintenance and replacement of occlusal amalgam restorations

The aim of this in vitro study was to evaluate four different approaches to the decision of changing or not defective amalgam restorations in first primary molar teeth concerning the loss of dental structure. Ditched amalgam restorations (n = 11) were submitted to four different treatments, as follows: Control group - polishing and finishing of the restorations were carried out; Amalgam group - the ditched amalgam restorations were replaced by new amalgam restorations; Composite resin group - the initial amalgam restorations were replaced by composite resin restorations; Flowable resin group - the ditching around the amalgam restorations was filled with flowable resin. Images of the sectioned teeth were made and the area of the cavities before and after the procedures was determined by image analysis software to assess structural loss. The data were submitted to ANOVA complemented by the Student Newman Keuls test (p < 0.05). The cavities in all the groups presented significantly greater areas after the procedures. However, the amalgam group showed more substantial dental loss. The other three groups presented no statistically significant difference in dental structure loss after the re-treatments. Thus, replacing ditched amalgam restorations by other similar restorations resulted in a significant dental structure loss while maintaining them or replacing them by resin restorations did not result in significant loss.

Validity and reliability of methods for the detection of secondary caries around amalgam restorations in primary teeth

Secondary caries has been reported as the main reason for restoration replacement. The aim of this in vitro study was to evaluate the performance of different methods - visual inspection, laser fluorescence (DIAGNOdent), radiography and tactile examination - for secondary caries detection in primary molars restored with amalgam. Fifty-four primary molars were photographed and 73 suspect sites adjacent to amalgam restorations were selected. Two examiners evaluated independently these sites using all methods. Agreement between examiners was assessed by the Kappa test. To validate the methods, a caries-detector dye was used after restoration removal. The best cut-off points for the sample were found by a Receiver Operator Characteristic (ROC) analysis, and the area under the ROC curve (Az), and the sensitivity, specificity and accuracy of the methods were calculated for enamel (D2) and dentine (D3) thresholds. These parameters were found for each method and then compared by the McNemar test. The tactile examination and visual inspection presented the highest inter-examiner agreement for the D2 and D3 thresholds, respectively. The visual inspection also showed better performance than the other methods for both thresholds (Az = 0.861 and Az = 0.841, respectively). In conclusion, the visual inspection presented the best performance for detecting enamel and dentin secondary caries in primary teeth restored with amalgam.

Prevalence of smoking among dentists in Catalonia - Spain (2006). Literature review of smoking cessation practices in the dental office

Objective: The objective of this study was to collect data on the prevalence of smokers among Catalonian dentists (by age and sex) and compare them with existing data on the general population, doctors, registered nurses and pharmacists. The overall prevalence of smokers in Catalonia (2006) was 34.5% of men and 24.3% of women. Data available on the prevalence of smoking among doctors (26.3% men and 22.1% women), pharmacists (19.8% men and 20.6% women) and registered nurses (34.1% men and 35.3% women) relates to the year 2002. Study design: In September 2006, Catalonian dentists (n=3,799) were asked about their habits in relation to tobacco in a self-administered questionnaire, on use and opinions with respect to dental amalgam. Five hundred and seventynine questionnaires were received, of which 538 answered the question on smoking (14.2% of the sample universe). Results: The prevalence of smokers among dentists is lower (24.9% of men and 18.4% of women) than in the general population and other healthcare professionals. In dentists in the age group between 25 and 34 years, the prevalence was 26.1% in men and 14.9% in women, while the prevalence in this age group in the general population was 43.6% and 37.1%, respectively. Conclusion: Catalonian dentists have a much lower prevalence of tobacco use than the general population and lower even than other healthcare professionals. Given that non-smoking healthcare professionals have better awareness for providing recommendations for smoking prevention and cessation, Catalonian dentists may be a valid group for performing this task for which there is scientific evidence.

A study of the microstructural characteristics of dental amalgams

Metallographic studies by scanning electron microscopy and energy dispersive spectroscopy carried out for two types of dental amalgam showing a porous multiphase material. Surface analysis shows that the structure of the Dispersalloy amalgam consists of gamma-Ag3Sn, gamma(1)-Ag2Hg3, eta'-Cu6Sn5, epsilon-Cu3Sn and eutectic Ag-Cu phases. while Velvalloy amalgam consists mainly of gamma, gamma(1) and gamma(2)-Sn7-8Hg phases. The latter phase presents an uniform distribution often associated with voids.

Inhibition of demineralization in vitro around amalgam restorations

Objective: The purpose of this in vitro study was to evaluate some forms of preventing or avoiding demineralization within enamel cavity walls adjacent to amalgam restorations. Method and materials: Third molar teeth were sectioned to obtain 72 specimens, divided into one control and five experimental groups: amalgam only; varnish plus amalgam; acidulated phosphate fluoride plus amalgam; adhesive amalgam; glass-ionomer cement plus amalgam; control (amalgam only, not subjected to a demineralization challenge). The experimental groups were subjected to pH and thermal cycling and then submitted to enamel hardness determinations. Results: Significant differences between the treatment groups revealed that the bonded amalgam technique offered the best resistance to demineralization. The use of cavity varnish resulted in greater mineral loss than amalgam placed alone. Conclusion: The use of an adhesive system, glass-ionomer cement, or acidulated phosphate fluoride under amalgam restorations may interfere with development of secondary caries.

Microleakage in primary teeth restored by conventional or bonded amalgam technique.

The aim of this in vitro study was to evaluate marginal leakage in class V restorations in primary teeth restored with amalgam, using three different techniques. Thirty maxillary anterior primary teeth, clinically sound and naturally exfoliated, were used. In group 1 (n = 10), two thin layers of a copal varnish (Cavitine) were applied. In group 2 (n = 10), Scotchbond Multi-Purpose Plus, a dual adhesive system, was used according to manufacturer instructions. In group 3 (n = 10), One-Step adhesive system in combination with a low-viscosity resin (Resinomer) were used according to manufacturer instructions. All samples were restored with a high-copper dental amalgam alloy (GS 80, SDI). After restoration, the samples were stored in normal saline at 37 degrees C for 72 h. The specimens were polished, thermocycled (500 cycles, 5 degrees and 55 degrees C, 30-s dwell time) and impermeabilized with fingernail polish to within 1.0 mm of the restoration margins. The teeth were then placed in 0.5% methylene blue for 4 h. Finally, the samples were sectioned and evaluated for marginal leakage. The Kruskal-Wallis test showed that the filled adhesive resin (group 3) had the least microleakage. There was no significant difference between groups 1 and 2.

Restorative treatment on class I and II restorations in primary molars: A survey of Brazilian dental schools

A survey was sent to 70 Brazilian dental schools evaluating techniques and restorative materials being taught for Class I and II preparation in posterior primary teeth by Pediatric Dentistry courses. After a 54% response rate, marked teaching diversity was found among Brazilian dental schools. Amalgam continues to be taught, but a tendency of preference towards more esthetic-like materials was observed.

Indicators of the risk mechanics for Class-I and Class-II amalgam and composite resin restorations

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Is there difference of Streptococcus mutans count and adherence on amalgam and resin occlusal restorations? A blind clinical study

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)