Dental amalgam. Designs for research in human populations

Attitudes of dentists and interns in Riyadh to the use of dental amalgam

Background

Studies investigating the attitudes of Saudi dentists to the use of amalgam for restorations are relatively rare. Considering the goals set forth by the Minamata Convention on Mercury, it appears prudent to investigate the attitudes of experienced dentists and fresh dental graduates to the use of amalgam. The aim of this study was to assess the attitudes of Saudi dentists and interns working in Riyadh, Saudi Arabia to the use of amalgam. Using a convenience sampling methodology, a total of 400 Saudi dentists and interns were contacted to request their participation in this cross-sectional questionnaire-based study. The questionnaire consisted of socio-demographic and practice characteristics such as gender, type of practice, as well as their service sector and questions related to the use of dental amalgam. The data obtained was analyzed using Chi square tests to compare differences in distribution between groups. P values of less than 0.05 were considered statistically significant.

Results

The overall response rate was 84% (336 of 400 potential participants). The majority of the participants (80.7%) did not use dental amalgam for restorations in their clinical practice frequently. A significantly higher number of participants working in private sector did not use amalgam frequently (P = 0.004), agreed on replacing good amalgam restoration with composite resin (P < 0.000) and on stopping the use of amalgam as a final restoration (P = 0.017) compared to participants working in public sector. A significantly higher number of interns did not use amalgam in their clinical practice frequently (P < 0.000), agreed on replacing good amalgam restoration with composite resin (P = 0.002) and on stopping the use of amalgam as a final restoration (P < 0.000) compared to dentists.

Conclusions

Within the limitations of this study, dental amalgam seems to be less frequently used among the surveyed Saudi dentists and interns working in Riyadh. Fresh dental graduates used amalgam less frequently compared to experienced dentists. Furthermore, private dental practitioners showed a propensity to replace existing well-placed amalgam restorations with resin composite which reinforces their market-oriented attitude reported in earlier studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-016-2294-x) contains supplementary material, which is available to authorized users.

Stiffness comparison of mushroom and straight SS and TMA lingual archwires

Background

The aim of this study is to investigate the relative stiffness of straight and mushroom lingual archwires of different diameters, cross sections and alloys, plotting their load/deflection graphs and using a modified three-point bending test.

Methods

Fujita’s mushroom archwires and straight lingual archwires of different diameters, cross sections and alloys were derived by a virtual set-up of an equal malocclusion and were cut at their straight distal portion. These distal portions were tested using a modified three-point bending test by an Instron 4467 dynamometer and the forces, were exerted at 1-mm deflection and were compared on each resulting load/deflection curve by means of ANOVA (p < 0.05).

Results

All upper lingual mushroom wires exerted significantly lower forces than the straight wire. Lower mushroom archwires were stiffer than their upper counterparts, which were longer and featured inset bends. In the lower arch, similar levels of forces were recorded for the two types of wire. Load-deflection curves were higher for the straight wires, and stiffness increased proportionally with their diameter.

Conclusions

The stiffness of an archwire is a function of its diameter, length and the alloy it is made from. In lower lingual wires, there is little difference in stiffness between mushroom and straight wires, but in upper wires, the straight version is considerably stiffer. The greater bearing effect exhibited by the straight wire in the working and finishing phases makes it less susceptible to bowing effect and therefore preferable for sliding mechanics during en masse retraction, particularly in the upper arch.

Evaluation of environmental and occupational exposure to mercury among Iranian dentists

The purpose of the study was to evaluate the environmental and occupational exposure to mercury (Hg), and to examine the various parameters, which contribute to high levels of mercury of Iranian dentists in Tehran. One-hundred hair and nail samples were collected from dentists. In addition, fifty samples from a control group and twenty-five additional samples from dental nurses were taken for comparison. The survey included a structured questionnaire designed to provide information about the parameters that influenced their occupational and environmental exposure to Hg. Overall mean concentrations in the hair and nails of the dentists was 2.84+/-0.47 and 3.56+/-0.53 mg/kg dry wt respectively. The equivalent values were 0.61+/-0.07 mg/kg in hair and 0.39+/-0.06 mg/kg in nails for the control group. In addition, mean concentrations in the dental nurses were 0.92+/-0.23 and 1.77+/-0.51 mg/kg in hair and nails respectively. The study showed that use of masks had a significant effect on Hg levels (p=0.02 for hair and p=0.03 for nails) and use of gloves only had significant effect on nails Hg (p=0.05). Hg concentrations in nails were significantly lower among the dentists who always used gloves and masks. Also, fish consumption and number of patients visited per day had a significant effect on hair (p=0.02 and p=0.02 respectively) and nails (p=0.03 and p=0.02 respectively) Hg. On the other hand, there was a significant effect of age in relation to Hg concentration in the hair and nails of the dentists (p=0.006 for hair and p=0.01 for nails). Multiple regressions were computed between hair Hg and the various assessed variables. The only positive results were between Hg concentration and masks for the dentists (p=0.03), and Hg concentration and the number of fish meals for the control group (p=0.009).

A validated cold vapour-AAS method for determining mercury in human red blood cells

A cold vapour-atomic absorption spectrometry (CV-AAS) method for determining mercury in dental students and clinical teaching staff red blood cells at a dental school using amalgam as a restorative material has been validated. A number of blood samples (n = 122) from dental students in years I to V, clinical teachers in restorative dentistry and controls were collected and analysed. Accuracy, linearity, precision (repeatability and reproducibility) and robustness of the method have been determined, and detection and quantification limits have been calculated. Linearity of response was verified for concentrations ranging from 5 to 40 microgL(-1) of mercury. Correlation coefficient of the calibration straight lines was always >/=0.99. Intra-day precision of the method gave coefficient of variation (CV) of 5.51%. Inter-day precision of the method calculated after analysis of five different concentrations of mercury standard solutions by the same analyst in different days and by two different analysts in different days gave coefficient of variation 4.89 and 5.44%, respectively. The accuracy of the method was calculated a CRM NIST 966 (toxic metals in bovine blood) total amount of mercury was found a concentration of 28.83 +/- 2.2 microgL(-1). Recovery was 89.27%. Robustness of the method evaluated by changing different experimental conditions under which analyses performed, fractional factorial design was done for assessing robustness of the method. Root mean square error was found out as 1.56. Limits of detection and quantification were 1.84 and 4.03 microg of Hg per litre of sample, respectively. Results show the suitability of the method for direct measurement of mercury in red blood cells and the importance of the working conditions for people dealing with amalgam at a dental school.

Blood mercury levels of dental students and dentists at a dental school

OBJECTIVE

To determine the blood mercury levels in dental students and clinical teaching staff in a dental school using amalgam as a restorative material.

SETTING

A dental school in Ege University, Turkey surveyed during one academic year.

SUBJECTS AND METHODS

Cross-sectional study of groups of dental students (n=92) in years I to V, clinical teachers in restorative dentistry (n=16) and controls (n=14). Mercury concentration was estimated in venous blood samples using a cold vapour atomic absorption method at the commencement and end of the academic year. Daily air mercury levels were determined in clinical and teaching areas by measuring the darkening of palladium chloride discs using spectrophotometry.

RESULTS

There were statistically significant increases (p<0.001) in plasma mercury concentration between measurements in all groups at the end of the academic year. Red cell mercury levels were also consistently elevated. Although the highest levels of mercury were recorded in persons working with amalgam, increased levels were also found in subjects working in the teaching classrooms but not with amalgam (controls and first year students).

CONCLUSION

Increased mercury levels appeared to be due to background exposure from spillage of mercury and amalgam residues on floors. Increased mercury hygiene and regular control of working atmosphere should be implemented to prevent mercury exposure in the dental pre-clinical laboratory.

Mercury in dental amalgam--a public health concern?

Dental amalgam has been the subject of intermittent controversy since it was introduced into dental practice approximately 150 years ago. The controversy has centered on the use of mercury in dental amalgam and the potential health implications to dental patients and dental health professionals from mercury exposure. In recent years the debate over the use of dental amalgam has intensified due to several articles in professional journals and media coverage by television and the press. This paper reviews the recent literature regarding dental amalgam, describes the activities of the antiamalgamists, examines the alternatives to dental amalgam, and reviews the recommendations for additional research. The existing scientific evidence does not demonstrate that mercury in dental amalgam poses a public health hazard. However, researchers on both sides of the controversy agree that much remains to be examined about the health implications of dental amalgam and that the subject merits continued research.

Report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

The committee screened several hundred articles, citing 518 published papers. Some are present quality in research, others provide clinical interest, and some are identified as misleading. New techniques in pulp physiology and pathology are reported. Laser use and techniques in prevention, restorative dentistry, and materials use are reported. Epidemiology of selected diseases and the results of various formulations for treatment are cited. Diagnosis of craniomandibular dysfunction is well represented as well as references to literature reviews and other sophisticated scientific investigation. Research on adhesives is presented in respect to bonding agents for dentin and enamel. Several clinical studies are included, along with customary laboratory reports on several materials.