Dental workplace exposure and effect on fertility.
OBJECTIVES: This study assessed occupational exposure in dental surgeries on the basis of the reported use of dental materials and techniques and applied waiting-time-to-pregnancy methodology to study fertility in relation to the occupational exposure. METHODS: Data were collected retrospectively using a self-administered postal questionnaire addressing the occupational and reproductive history of the participants. The study groups consisted of 558 female dental surgeons and 450 high school teachers that had given birth in Norway to at least 1 living child. The present study comprised data from a total of 1408 pregnancies. The effects of practicing dentistry and of the given workplace exposure on fertility were analyzed with the discrete proportional hazard regression method. RESULTS: Most of the female dental surgeons were using amalgam for fillings during the period they tried to conceive, and 1/3 placed more than 50 fillings a week. Tooth-colored fillings were in limited use. Prior to 75% of the pregnancies, the dental surgeons reported handling chloroform-based root canal sealers. Forty percent of the dental surgeons were daily exposed to disinfectants containing ethanol and benzene. No difference was found in fertility between the dental surgeons and the high school teachers. Exposure to mercury, chloroform, and benzene was not associated with decreased fertility, except for a possible effect of mercury in the last pregnancy of multiparous dental surgeons. CONCLUSIONS: Occupational exposures had no clear adverse effects on fertility among the female dental surgeons studied. (+info)
Cadmium, mercury, and lead in kidney cortex of the general Swedish population: a study of biopsies from living kidney donors.
Cadmium, mercury, and lead concentrations were determined in deep-frozen kidney cortex biopsies taken from 36 living, healthy Swedish kidney donors (18 males and 18 females), who were 30-71 (mean 53) years of age. Information about occupation, smoking, the presence of dental amalgam, and fish consumption could be obtained for 27 of the donors. The samples (median dry weight 0.74 mg) were analyzed using inductively coupled plasma mass spectrometry, and the results were transformed to wet-weight concentrations. The median kidney Cd was 17 micrograms/g (95% confidence interval, 14-23 micrograms/g), which was similar in males and females. In 10 active smokers, the median kidney Cd was 24 micrograms/g, and in 12 who never smoked, it was 17 micrograms/g. The median kidney Hg was 0.29 micrograms/g, with higher levels in females (median 0.54 micrograms/g) than in males (median 0.16 micrograms/g). Subjects with amalgam fillings had higher kidney Hg (median 0.47 micrograms/g, n = 20) than those without dental amalgam (median 0.15 micrograms;g/g, n = 6), but kidney Hg was below the detection limit in some samples. Nearly half of the samples had kidney Pb below the detection limit. The median kidney Pb was estimated as 0. 14 micrograms/g. This is the first study of heavy metals in kidney cortex of living, healthy subjects, and the results are relatively similar to those of a few previous autopsy studies, indicating that results from autopsy cases are not seriously biased in relation to kidney metal concentrations in the general population. Cd concentrations in those who never smoked were relatively high, indicating considerable Cd intake from the diet in Sweden. The effect of dental amalgam on kidney Hg was as expected, although the reason for the difference in Hg levels between males and females is unclear. (+info)
Resistance to mercury and antimicrobial agents in Streptococcus mutans isolates from human subjects in relation to exposure to dental amalgam fillings.
Resistance to cefuroxime, penicillin, tetracycline, and mercury is reported for 839 Streptococcus mutans isolates from 209 human study subjects. The MICs of these drugs did not differ for isolates from one dental amalgam group and two nonamalgam subsets: a group with no known exposure to amalgam and a group whose members had their amalgam fillings removed. (+info)
Strength and microstructure of gallium alloys.
This study investigated the physical and mechanical properties and the microstructure of four different gallium alloys. For all gallium alloys, the compressive strengths measured at one hour (86-223 MPa) and 24 hours (265-286 MPa) after specimen preparation were found to be well within the range exhibited by many high-copper amalgams. The creep values and dimensional change of the gallium alloys were comparable to those of leading amalgams, except for the dimensional change value of one alloy. The set gallium alloys consisted of a multi-phase structure including beta-Sn, CuGa2, In4Ag9, Ag72Ga28, and Ga5Pd (except for one product that did not contain Pd) that was more complicated than the structure of dental amalgams. Although the gallium alloys had physical and mechanical properties comparable to those of high-copper amalgams, the microstructure, coupled with the instability of the element gallium itself, could make these materials more prone to corrosive attack compared to amalgams. (+info)
Management of extensive carious lesions in permanent molars of a child with nonmetallic bonded restorations--a case report.
The badly decayed molar teeth of a 12-year-old were restored using resin composite and ceramic restorations. The maxillary first left permanent molar, which had an extensive carious lesion that had destroyed most of the coronal hard tissues of the tooth, was restored to shape and function with a heat-treated resin composite onlay restoration. The restoration was followed up for two years. The mandibular right first molar had a failing large amalgam restoration with extensive recurrent caries. After a three-month period of pulp-capping, the tooth was restored with a bonded ceramic onlay restoration. A nine-month follow-up of this restoration is provided. The maxillary right first molar, which also had a failing large amalgam/resin composite restoration, was restored with a direct resin composite restoration. Under traditional treatment regimens, these extensive cavities would have been treated using more invasive procedures such as pin-retained restorations or elective root canal therapy, post placement, core build-up and crowning. Bonded non-metallic restorations avoid the trauma, time and cost that accompany such extensive procedures and offer a more conservative approach. (+info)
Mercury evaporation from amalgams with varied mercury contents.
This study examined the relationship between mercury content and mercury evaporation from amalgams during setting. Two different types of commercial high-copper amalgams (single composition and admixed types) were used. Cylindrical specimens of each amalgam were prepared with five different mercury contents according to ADA Specification No.1. Specimens were also prepared by hand condensation. Mercury evaporation from amalgam specimens maintained at 37 degrees C was measured using a gold film mercury analyzer from 10 min after the end of trituration until the mercury concentration in air reached an undetectable level. The mercury content more clearly influenced the mercury evaporation from the admixed type amalgam specimens when the mercury content decreased below the manufacturers' recommended trituration conditions. Triturating with less mercury than the manufacturers' recommended amount cannot lower the evaporation of mercury from freshly made amalgam. Proper condensing procedures can minimize the mercury evaporation from the amalgam surface. (+info)
Biological monitoring and exposure to mercury.
Occupational health professionals' interest in controlling mercury (Hg) exposure, and the use of biological monitoring in this context, has been ongoing for a number of years. Evidence from urinary Hg results in a number of UK firms who have undertaken some form of biological monitoring or occupational health surveillance suggest that exposure has decreased over the last 10-15 years. This decrease precedes the establishment in the UK of an advisory biological monitoring guidance value (HGV) for urinary Hg and the production of updated medical guidance from the Health & Safety Executive on Hg exposure (MS12 1996). This latter document recommends a urinary sampling interval for urinary Hg of between 1 and 3 months, which is consistent with the reported toxicokinetics of Hg excretion, but we highlight that urinary Hg represents integrated exposure over many previous months. Mercury is a recognized nephrotoxin and MS12 1996 mentions the use of regular dipstick protein estimations. We review our experience of investigating proteinuria and enzymuria in a large-scale cross-sectional occupational study. The incidence of Hg-induced renal disease is probably very rare at current exposure levels. Therefore acceptance of a high false-positive rate of proteinuria not related to Hg exposure needs to be considered in any urinary protein testing regime of Hg workers. The establishment of an HGV for urinary Hg has raised questions about the uncertainty associated with a urinary Hg result, including factors such as diurnal variation, whether urine correction by creatinine or specific gravity is preferable and the possibility of non-occupational sources of Hg contributing significantly towards breaching the HGV. Correction of urinary Hg results by creatinine or specific gravity and the use of a fixed sampling time, such as the beginning or end of the day, substantially reduce the uncertainty in a urinary Hg measurement. But even with good laboratory precision, an individual with a true urinary Hg excretion of 20 nmol/mmol creatinine could supply urine samples of between 14 and 26 nmol/mmol creatinine. The influence of dietary sources in the UK contributing to urinary Hg values approaching or exceeding the HGV is unlikely. The use of tribal or ethnic cosmetics and remedies needs to be considered if a urinary Hg result looks inappropriately high, as some such preparations have been found to contain Hg and can be absorbed through the skin. The ability of excessive chewers or teeth grinders who have a large number of dental amalgam fillings to breach the urinary HGV in the absence of substantial occupational Hg exposure has been reported in a few Scandanavian studies. We report here a likely case of this phenomenon. Since the establishment of the HGV, our biological monitoring Hg data from a number of industry sectors using inorganic or metallic Hg have suggested that a minority of samples (13%) are still greater than the HGV. (+info)
HLA-association in patients with intolerance to mercury and other metals in dental materials.
A group of selected 25 patients with serious intolerance to heavy metals used for dental restoration were examined for HLA antigens. A significant increase for HLA -- B37, B47 and DR4 was found. The value of the relative risk is not significant after correction for the number of antigens tested and therefore further studies of more patients are needed. (+info)