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PubMed2005

Mercury (II) alters mitochondrial activity of monocytes at sublethal doses via oxidative stress mechanisms.

The perennial controversy about the safety of mercury in dental amalgams has adversely affected the availability and the quality of dental care. Chronic Hg(II) blood concentrations above 300 nM are known to alter function of the nervous system and the kidney. However, the effects of blood concentrations of 10 to 75 nM, far more common in the general population, are not clear and mechanisms of any effects are not known. The monocyte is an important potential target of Hg(II) because of its critical role in directing inflammatory and immune responses. In the current study we tested the hypothesis that concentrations of Hg(II) of 10 to 300 nM alter monocyte activity via a redox-dependent mechanism. Mitochondrial activity was used to establish inhibitory concentrations of Hg(II) following 6 to 72 h of exposures to THP1 human monocytic cells. Then subinhibitory concentrations were applied, and total glutathione levels and reactive oxygen species (ROS) were measured. Antioxidants [N-acetyl cysteine, (NAC); Na2SeO3, (Se)] and a pro-oxidant (tert-butylhydroquinone, tBHQ) were used to support the hypothesis that Hg(II) effects were redox-mediated. After 72 h of exposure, 20 microM of Hg(II) inhibited monocytic mitochondrial activity by 50%. NAC mitigated Hg(II)-induced mitochondrial suppression only at concentrations of greater than 10 microM, but Se had few effects on Hg-induced mitochondrial responses. tBHQ significantly enhanced mitochondrial suppression at higher Hg(II) concentrations. Hg(II) concentrations of 75 and 300 nM (0.075 and 0.30 microM, respectively) significantly increased total glutathione levels, and NAC mitigated these increases. Se plus Hg(II) significantly elevated Hg-induced total cellular glutathione levels. Increased ROS levels were not detected in monocytes exposed to mercury. Hg(II) acts in monocytic cells, at least in part, through redox-mediated mechanisms at concentrations below those commonly associated with chronic mercury toxicity, but commonly occurring in the blood of some dental patients.

Biocompatible Materials↗
PubMed1996

[Influence of chewing gum consumption and dental contact of amalgam fillings to different metal restorations on urine mercury content].

It had been shown previously by various authors that contact of amalgam fillings to metal fillings of different type can increase the electrochemically caused amalgam corrosion in vitro thus leading to an elevated release of mercury. So it was recommended to renounce of a dental contact of amalgam to metal fillings of other type. One aim of the present study was to evaluate possible influences of this contact in vivo on the urinary mercury contents in human volunteers. Neither approximal nor occlusal contacts had any influence on the urinary mercury excretion in comparison to a reference group with similar amalgam status. Furthermore, the influence of gum chewing on urinary mercury levels was taken into account. It could be shown that the consumption of chewing gum resulted in a significantly higher mean urinary mercury content in probands with amalgam fillings in comparison to people with similar amalgam status (gum chewers: 1.36 Hg/24 h vs. non-chewers 0.70 microgram Hg/24 h). Thus, gum chewing has to be considered as important parameter of influence on the urinary mercury levels of people with amalgam fillings.

Adult↗
PubMed1999

A clinical study of adhesive amalgam in pediatric dental practice.

This clinical study and 3-year follow-up evaluated the efficacy of adhesive amalgam restorations for pediatric dental practice. The original goal of the study was to determine when bonding of amalgam restorations should be performed. After the initial set of study restorations were placed, it appeared that the bonding should always be performed and that the study should concentrate on the modes of restoration failure.

Calcium Hydroxide↗
PubMed2004

Assessment of waste amalgam management in dental clinics in Ramallah and al-Bireh cities in Palestine.

The behavior of dental health personnel was examined with regard to the handling and proper disposal of wastes generated at common dental clinics, and some of the amounts of waste they produce were estimated. In January 2002, a random sample of 37 dental clinics was chosen in the cities of Ramallah and al-Bireh. The visited clinics were distributed between 31 private practices and six public/NGO dental clinics. The dentists were asked about the methods they follow in disposing and discarding of amalgam wastes. An average dentist is estimated to place two small, seven medium and nine large amalgam restorations releasing 22.6 grams of mercury each week. The majority of amalgam wastes ended up in trash or drain.

Dental Amalgam↗
PubMed1988

Stability of the mandible following advancement: a comparison of three postsurgical fixation techniques.

This study examines short-term stability of the mandible following mandibular advancement surgery by means of three standard techniques of postsurgical fixation. Twenty-two adult female rhesus monkeys (Macaca mulatta) underwent sagittal ramus advancement osteotomy of approximately 4 to 6 mm. Six animals had dental maxillomandibular fixation alone. Six animals had dental plus skeletal maxillomandibular fixation with circummandibular wires connected to pyriform aperture wires. Ten animals had rigid internal fixation with bicortical bone screws between the proximal and distal segments without maxillomandibular fixation. Radiographic cephalograms with the aid of tantalum bone markers and dental amalgams were analyzed during the first 6 postoperative weeks to evaluate skeletal and dental stability. Rigid internal fixation and the use of dental plus skeletal maxillomandibular fixation were both equally effective in the prevention of postsurgical relapse. However, in the animals in which only dental maxillomandibular fixation was used, statistically significant changes (relapse) occurred when compared with either of the other groups.

Animals↗
PubMed1999

Packable composites: overview and technical considerations.

OBJECTIVE: New composites, called packable or condensable composites, are being promoted as amalgam alternatives. The purposes of this review article are to identify these products, define new terminology associated with them, summarize the advertised properties for the materials, discuss the ideal properties for packable composites, review the properties of the major products, and critically evaluate the proposed handling procedures for these materials. REVIEW: The term packable is preferable to condensable for describing this new class of materials. All materials should be considered amalgam alternatives, not amalgam substitutes. The compositions and physical properties reported by manufacturers reveal that none of the materials represents a remarkable improvement over the properties of more traditional universal composites. The designs of Solitaire (Heraeus Kulzer), ALERT (Jeneric-Pentron), and SureFil (Dentsply/Caulk) are discussed in detail. The distinguishing characteristics of all packable compositions are less stickiness or stiffer viscosity than conventional composites, which allow them to be placed in a manner that somewhat resembles amalgam placement. CONCLUSIONS: Packable composites may allow more convenient placement in posterior sites and may offer some technique advantages over conventional composites. However, there is no evidence that their clinical properties are consistently better than those of conventional universal composites. CLINICAL SIGNIFICANCE: Packable composites may be selected as alternatives to amalgam or conventional universal composites, but they are not equal to or better than dental amalgam in all respects. Also, in most cases, mechanical properties of packable composites are not substantially better than those of most conventional universal composites.

Composite Resins↗
PubMed1992

Electron microscopic X-ray microanalysis of metals deposited in oral mucosa.

A 35-year-old woman exhibited bluish-brown discoloration of her buccal mucosa suggesting malignant melanoma. Histopathological examination revealed that the pigment was not melanin but caused by metal deposits. Electron microscopically, metallic particles were located on the lamina densa of basal laminae at mucosal epithelium, nerve fibers, and blood vessels and on the microfilaments of elastic fibers as well as in macrophages and fibroblasts. Electron microscopic point X-ray microanalysis revealed that these metallic particles were composed of Ag, Se, Fe, Co, Cu, and S. Analysis suggests that these metals were derived from dental amalgam and that the discoloration was caused by amalgam tattoo.

Adult↗
PubMed2003

Cases of mercury exposure, bioavailability, and absorption.

Mercury is a unique element that, unlike many metals, has no essential biological function. It is liquid at room temperature and is 13.6 times heavier than water. Its unique physical properties have been exploited for a variety of uses such as in mercury switches, thermostats, thermometers, and other instruments. Its ability to amalgamate with gold and silver are used in mining these precious metals and as a dental restorative. Its toxic properties have been exploited for medications, preservatives, antiseptics, and pesticides. For these reasons there have been many industrial uses of mercury, and occupational exposures of workers and industrial emissions and effluents contaminating air, water, soil, and ultimately food chains have long been a matter of great public health concern. This paper examines briefly six cases representing various forms of exposure to different species of mercury, and indicates the methodological issues in estimating exposure, bioavailability and absorption; these cases include Minamata disease in Japan, organic mercury poisoning in Iraq, methylmercury (MeHg) exposure in the Amazon, dimethylmercury (PMM) in the laboratory, an elemental mercury spill in Cajamarca, Peru, and a mercury-contaminated building in Hoboken, NJ, USA. Other scenarios that are not described include occupational exposure to mercury salts, mercurial preservatives in vaccines, cultural and ritualistic uses of mercury, and mercury in dental amalgams.

Absorption↗