Contaminação por mercúrio na Odontologia: a utilidade da análise quantitativa em ambiente de prática restauradora com amálgama / Mercury contamination in Dentistry: the utility of quantitative analysis in environment with amalgam restorative practice

Objetivo - Verificar o uso e aplicação de um medidor portátil de análise quantitativa de vapores de mercúrio. Os locais de escolha foram a Clínica Odontológica e o Laboratório Multidisciplinar 104 da Faculdade de Odontologia das Faculdades São José, Rio de Janeiro-RJ, Brasil. Nesses locais ocorrem muitas atividades restauradoras com amálgama dentário realizadas por alunos, tornando-se importante a verificação da possível contaminação por vapores tóxicos de mercúrio existente naqueles ambientes. Métodos - Para a medição foi utilizado um aparelho analisador Zeeman quantitativo avançado de mercúrio portátil da marca Lumex modelo RA-915+. O aparelho foi acionado no final da tubulação de rejeito das cuspideiras das cadeiras A, C, D, E, F, J, H e ar do amalgamador recém-acionado. No Laboratório Multidisciplinar 104 foram inspecionados: ar/ambiente e em manequim usado para treino. Foram feitas também inspeções no ar em ambiente onde não se usa amálgama a fim de verificação do teor zero. Resultados - Na Clínica Odontológica as cadeiras C, E, F e H foram as que apresentaram os maiores índices de contaminação, dentre estas a cadeira H destacou-se com 26.140 ngHg/m³. Os locais onde não se manipula amálgama o índice foi 0ngHg/m³. Conclusões - Os altos índices de vapores de mercúrio nas tubulações das cadeiras indicam que as medidas seguras de descartes de resíduos não estão sendo realizadas adequadamente. Este sistema de medição quantitativa direta mostrou-se simples no manuseio e extremamente útil no monitoramento de ambientes sujeitos à contaminação por vapores tóxicos de mercúrio.

Objective - To examine the use and application of a portable meter for quantitative analysis of mercury vapors. The places of choice were the Dental Clinic and Laboratory Training 104 of the School of Dentistry of São José College, Rio de Janeiro-RJ, Brazil. In these places many activities occur restorative dental amalgam made by students, making it important to check the possible contamination by toxics vapors mercury existing in those environments. Methods - For the measurement we used an advanced device analyzer Zeeman quantitative mercury brand laptop Lumex model RA-915+. The device was fired at the end of the waste pipe spitting chairs A, C, D, E, F, J, H and air amalgamator newly activated. In the Laboratory Training 104 were inspected: air/environment and dummy used for training. Inspections were performed also on air at ambient where amalgam is not used to check content zero. Results - In Dental Clinic chairs C, E, F and H were the ones that showed the highest levels of contamination, among these the seat H stood out with 26.140 ngHg / m³. Places where no handles amalgam index was 0ngHg/m³. Conclusions - The high levels of mercury vapor in the pipes of the chairs indicate that measures of safe waste disposal are not being carried out properly. This direct quantitative measurement system proved simple in handling and extremely useful in monitoring environments subject to contamination by toxic mercury vapors.

Preliminary study of the forces developed by practitioners during amalgam condensation.

The aim of this preliminary study was to analyze, in vitro, the forces developed by practitioners during amalgam condensation. Standardized Class II cavities were drilled into 40 freshly extracted teeth. The forces exerted during condensation were then measured by means of a new device, the Endographe, and plotted online or offline as a function of time on Endogrammes. The work techniques of the different practitioners revealed similarities. The mean values of the vertical forces (+/- SEM) were: 15 +/- 2 N for manual compaction of capsule amalgam; 8 +/- 3 N for manual compaction of amalgam with a higher mercury-to-alloy ratio; 6 +/- 4 N for mechanical compaction of encapsulated amalgam; and 4 +/- 2 N for mechanical compaction of the modified amalgam. For the horizontal components, the forces were, respectively, 5 +/- 2 N, 0.1 +/- 0.05 N, 3 +/- 1 N, and 0.7 +/- 0.2 N. The mean values of condensation time were 20 +/- 15 s for each incremental application, with a great variation in durations between the beginning and end of condensation. By visually depicting forces as a function of time, the Endographe can be used to analyze the process of amalgam insertion and condensation. Future research will study the relationship between the forces developed during condensation and the adaptation of the amalgam to the walls of the cavity.

Initial mercury evaporation from amalgams made with in-containing commercial alloys.

This study examined the Hg evaporation behavior during the early setting of amalgams that contain In in the alloy powders. Two different types of commercially available In-containing alloys were tested: an In-particle admixed powder (Indisperse, D) and an In-containing single-composition powder (Indiloy, S). Mercury evaporation from specimens (4 mm in dia, 8 mm tall) was monitored 10 min after trituration to 180 min using a mercury vapor analyzer according to the methods used in a previous study. The amounts released from 10 min to 180 min were compared with the results of our previous study on a single-composition amalgam (Tytin, T) with pure Hg and with Hg-In liquids (5 or 10%). Amalgam S and In-containing T terminated Hg evaporation within 180 min. There was no significant (p > 0.05) difference in the amount released between T amalgam made using pure mercury and D, and between T amalgam made with 5% In-containing mercury and S amalgam. Mercury release from amalgam D was significantly (p < 0.05) higher than from S or both types of In-containing T amalgam. Adding In to mercury or alloying In into the alloy particles appeared to be more effective in reducing the mercury vapor than admixing pure In particles into the amalgam.

[Evaluation of amalgam separators]. / Une évaluation des séparateurs d'amalgame.

There is an increased awareness about environmental protection and reduction of toxic waste. This applies also to the dental profession. One of the main concerns in dentistry is the reduction of amalgam slurry, which contains mercury, being drained by dental plants. The largest pieces of amalgam are stopped by the coarse filter. For eliminating the amalgam silt out of the sewage, amalgam separators have been developed. This paper presents an evaluation of seven separators, mounted in a preclinic set-up. The average particle size of the amalgam waste was determined. The flow-velocity of the separators differed very much between the different separators. One apparatus produced an inferior separation capacity compared to the others. Apparently not one was capable to purify the effluent to 0.05 mg/l during peak supplies of amalgam slurry. Other measures such as the reduction of the need for restoring, the use of alternative materials and modified preparation techniques, will further reduce the drain of amalgam silt by dental installations.

Properties of amalgams made from lathe-cut, high Cu amalgam alloys.

Two alloys for dental amalgams made from lathe-cut powder with high Cu content have been developed. The alloys have been characterized with respect to physical properties and microstructure. The strongest amalgam exhibited minimal dimensional changes during setting and had low flow and creep values. It had the highest Cu content of the two amalgams investigated and no gamma 2 phase. The epsilon and eta' phases may dispersion-strenthen the amalgam which in compressive strength was comparable to the strongest amalgams available. A new mechanism for gamma 2 disappearance is suggested where Cu replaces Hg directly in the gamma 2 phase thus forming the eta' phase.

The effect of the cooling rate of dental alloys on their amalgamation properties.

Silver-tin alloys of various compositions (60-80 atomic % Ag) have been prepared from the melt using cooling rates from about 50 degrees C/hr to about 10(6) degrees C/sec. Structural differences due to the different cooling rates were shown by metallographic and x-ray diffraction techniques. From each composition and cooling rate, powders were then prepared and amalgamated. The amalgams were tested for Hg content, dimensional change during setting, and tensile strength. Changes in cooling rates had some effect on the relative amounts of phases present but primarily affected the grain sizes. In general, the faster the cooling rate, the smaller the grain size; the smaller the grain size, the faster and more uniform the amalgamation; the more uniform the amalgamation, the stronger the amalgam. Storage of the alloy powders at room temperatures slowed their amalgamation rates, destroyed their uniformity,and resulted in weaker amalgams. However, no phase changes were observed by x-ray diffraction in the freshly comminuted alloys after aging at room temperature for two months.

On the solubility of zinc in the gamma-phase of the silver-mercury system.

By measuring lattice constants of a number of Ag-Hg-Zn alloys with gamma-phase structure, it has been shown that apart from a possible two-phase field there exists a continuous solid solution between gamma (Ag-Hg) and gamma (Ag-Zn). A correlation between the Zn-content in the gamma 1 phase in set dental silver amalgam and the Zn-content in the corresponding alloy has been determined.