Understanding the mercury reduction issue: the impact of mercury on the environment and human health

Mercury has been used in both medicine and dentistry for centuries. Recent media attention regarding the increased levels of mercury in dietary fish, high levels of mercury in air emissions, and conjecture that certain diseases may be caused by mercury exposure has increased public awareness of the potential adverse health effects of high doses of mercury. Dentistry has been criticized for its continued use of mercury in dental amalgam for both public health and environmental reasons. To address these concerns, dental professionals should understand the impact of the various levels and types of mercury on the environment and human health. Mercury is unique in its ability to form amalgams with other metals. Dental amalgam--consisting of silver, copper, tin, and mercury--has been used as a safe, stable, and cost-effective restorative material for more than 150 years. As a result of this use, the dental profession has been confronted by the public on two separate health issues concerning the mercury content in amalgam. The first issue is whether the mercury amalgamated with the various metals to create dental restorations poses a health issue for patients. The second is whether the scraps associated with amalgam placement and the removal of amalgam restorations poses environmental hazards which may eventually have an impact on human health. Despite the lack of scientific evidence for such hazards, there is growing pressure for the dental profession to address these health issues. In this article, the toxicology of mercury will be reviewed and the impact of amalgam on health and the environment will be examined.     

Improving the oral health status of all Americans: roles and responsibilities of academic dental institutions: the report of the ADEA President's Commission

Academic dental institutions are the fundamental underpinning of the nation's oral health. Education, research, and patient care are the cornerstones of academic dentistry that form the foundation upon which the dental profession rises to provide care to the public. The oral health status of Americans has improved dramatically over the past twenty-five to thirty years. In his 2000 report on oral health, the Surgeon General acknowledges the success of the dental profession in improving the oral health status of Americans over the past twenty-five years, but he also juxtaposes this success to profound and consequential disparities in the oral health of Americans. In 2002, the American Dental Education Association brought together an ADEA President's Commission of national experts to explore the roles and responsibilities of academic dental institutions in improving the oral health status of all Americans. They have issued this report and made a variety of policy recommendations, including a Statement of Position, to the 2003 ADEA House of Delegates. The commission's work will help guide ADEA in such areas as: identifying barriers to oral health care, providing guiding principles for academic dental institutions, anticipating workforce needs, and improving access through a diverse workforce and the types of oral health providers, including full utilization of allied dental professionals and collaborations with colleagues from medicine.     

Contamination of tooth-colored mineral trioxide aggregate used as a root-end filling material: a bacterial leakage study

This experiment investigated the ability of tooth-colored mineral trioxide aggregate (MTA) to maintain an apical seal in the presence of bacteria when contaminated with blood, saline or saliva. Ninety extracted human teeth with single canals were randomly placed into six groups of 15. Canals were prepared to size 50. The apical 3 mm of each root was removed and 3 mm root-end preparations were made with a #329 bur. Root-end preparations in groups 1 through 3 were filled with MTA after contamination with blood, saline, or saliva, respectively. In group 4, uncontaminated root-end preparations were filled with MTA. Groups 5 and 6 served as negative and positive controls. A tube/tooth assembly was utilized to suspend each root end in Trypticase Soy Broth (TSB). The access chambers were filled with Staphylococcus epidermidis. Positive growth over thirty days was demonstrated by turbidity of the TSB. Vitek analysis was used to confirm the presence of S. epidermidis in the positive samples. Data evaluation consisted of a chi(2) analysis (p < 0.05). Although all experimental groups demonstrated leakage, tooth-colored MTA contaminated with saliva (group 3) leaked significantly more than the uncontaminated tooth-colored MTA (group 4) (p = 0.028).     

Dimensional Accuracy of 7 Die Materials

PURPOSE: The purpose of this study was to compare the linear dimensional accuracy and the handling characteristics of 7 die materials. MATERIALS AND METHODS: A master die analogous to a complete veneer crown preparation was machined from medical grade stainless steel, and 3 measurements (1: vertical; 2 and 3: horizontal) were made from 3 scribed reference lines. Individual polyvinylsiloxane impressions were made (n = 10) for each of the specimens. The fabricated dies were measured (50x) to the nearest 0.0001 mm. Data were subject to ANOVA/Duncan tests at significance level 0.05 and pairwise comparisons. RESULTS: Type IV resin-impregnated dental stone and copper-plated dies most closely approximated the dimensions of the master die, and were not significantly different from each other in any of the pairwise comparisons. Conventional Types IV and V dental stone dies exhibited setting expansion within the range appropriate for gypsum. Epoxy resin die materials demonstrated shrinkage comparable to the expansion of the Types IV and V dies. Polyurethane dies displayed a combination of linear expansion and shrinkage. Bis-acryl composite resin dies had excessive shrinkage. CONCLUSIONS: Type IV resin-impregnated dental stone and copper-plated dies were more dimensionally accurate than the other die materials tested.     

A comparative quantitative histological investigation of atrophic changes in the major salivary glands of liquid-fed rats.

Adult male rats were maintained on a wholly liquid diet for 9 days. The three pairs of major glands were removed, weighed, histologically sectioned and examined by stereological and morphometric techniques. The results were compared with the same glands from control rats maintained on normal hard diet and water, and the extent of the differences was compared between the three different types of gland. Up to 50% of the serous acinar volume in the parotid glands, but only 15% in the submandibular glands, was lost after liquid feeding. There was no loss of the mucous acinar tissue in the sublingual gland. Mean acinar diameters were reduced by 33% in parotids and 15% in submandibular glands after liquid feeding, whereas the mucous acini of the sublingual gland remained unaltered. The results point to varying levels of susceptibility to the loss of masticatory reflexes between the parotid serous acini and the submandibular serous acini, and show that the morphology of the sublingual mucous acini is independent of masticatory reflex stimulation. The reductions in acinar diameters suggest that most of the glandular atrophy after liquid feeding is due to acinar cell shrinkage rather than to losses of acinar cell numbers in both parotid and submandibular glands.     

A comparison of prosthetic ear models created from data captured by computerized tomography, magnetic resonance imaging, and laser scanning

PURPOSE: To compare the dimensional measurements and surface topography of stereolithographic models generated from computerized tomography (CT), magnetic resonance imaging (MRI), and laser scanning (LS) data with the same subjects' natural ears and ear casts. MATERIALS AND METHODS: Stereolithographic models were manufactured from images of the subjects' ears and ear casts recorded by CT, MRI, and LS, and dimensional measurements were compared. In the second part of the study, all stereolithographic models were CT scanned and reconstructed in an STL file format. A comparison of the surface topography of the CT, MRI, and LS model ears was made. RESULTS: Intraclass correlation coefficients indicated that dimensions could be reliably measured on the CT, MRI, and LS stereolithographic models. A 2-way analysis of variance revealed no statistical differences between the various sources of data (P = .991). The smallest differences of surface topography were observed on the MRI/CT superimpositions. CONCLUSION: The dimensional measurements on the stereolithographic models were similar to those from the original source. Only small differences were apparent between the surface topography of the CT, MRI, and LS models. MRI may be particularly appropriate to fabricate a prosthesis because it involves no radiation for the patient and internal form can be reproduced. The use of this technique in clinical practice requires further study.     

Development of a stereophotogrammetry technique to assess facial change following surgery for head and neck cancer

A stereophotogrammetry technique is described that can be used to map the face following surgery for head and neck cancer. It enables the effects of obturators on facial form to be assessed and may have a wide variety of applications. Int J Prosthodont 2011;24:342-344.     

Adult Dental Visits in California: Successes and Challenges

OBJECTIVES: This study sought to estimate and characterize the proportion of California adults who visited a dentist in the preceding year and to identify reasons for not going. METHODS: In 1995, 4,029 adults were interviewed by telephone as part of the California Behavioral Risk Factor Surveillance System. Items included recentness of a dental visit, dental insurance status, and number of teeth lost due to disease. Persons who had not seen a dentist within the preceding year were asked the main reason they had not gone. RESULTS: In 1995, 65.9% of adults reported visiting a dentist in the preceding twelve months. Use of dental services was greater among persons aged 35 years or older (70.4%) than among those aged 18-34 years (58.4%) and among those with dental insurance (74.9%) than those without (54.4%). Dental visits were less likely among adults living at or below 200 percent of the federal poverty level, those with less than a high school education, and the edentulous. Reasons most commonly cited for not seeing a dentist were no perceived reason to go (37.2%), cost (30.7%), and fear (9.2%). CONCLUSION: Substantial variation in use of dental services exists among California's adults. Achieving equity in access and opportunity for disease prevention in this state may require expanded dental insurance coverage and serious efforts in oral health promotion.     

Defining new paradigms for assessment of implant receptor sites. The use of CT/CBCT and interactive virtual treatment planning for congenitally missing lateral incisors

An emerging technology that encompasses computed tomography, cone-beam computed tomography, and interactive software applications has slowly progressed and evolved into a necessary tool for diagnosis, treatment planning, and delivery of dental implant and associated restorative and surgical procedures. The integration of these innovative tools is helping to define new methods for appreciating anatomy, improving accuracy, and enhancing presurgical prosthetic planning to achieve true restorative-driven implant dentistry. This article will demonstrate how computed tomography combined with interactive virtual treatment-planning software applications can empower clinicians with enhanced diagnostic capabilities for implant receptor-site assessment, generating new paradigms that eventually may supersede older methods of presurgical planning for dental implant reconstruction.