Back to Science mainpage

For those with small monitors
If you want to see this document in a
screen-wide separate window, then

toxicity of amalgams, alloys, and their elements and phases.
Kaga M; Seale NS; Hanawa T; Ferracane JL; Waite DE; Okabe T
Baylor College of Dentistry, Dallas, Texas.
Dent Mater, 1991 Jan, 7:1, 68-72
The purpose of this study was to compare the relative cytotoxicity of
amalgams, alloys, and their constituent elements and phases, by means of a
rapid and sensitive in vitro cell culture test. Pure copper and zinc showed
intensive cytotoxicity, significantly greater than that of pure silver and
mercury. Pure tin was non-cytotoxic. The gamma-one phase (Ag2Hg3) revealed
moderate cytotoxicity, which was significantly decreased by the addition of
1.5% and 5% Sn. However, the addition of 1.5% Zn to gamma 1 containing 1.5% 
Sn dramatically increased the cytotoxicity of gamma 1 to the same level as
that of pure zinc. Whenever zinc was present in amalgams, higher
cytotoxicity was revealed. High-copper amalgams showed the same
cytotoxicity as a zinc-free low-copper amalgam. The addition of selenium
did not reduce the cytotoxicity of amalgam. The cytotoxicity of amalgams
was reduced after 24 h. The results of this study suggest that the major
contributor to the cytotoxicity of alloy for amalgam is probably copper,
while that for amalgam is zinc.

Dental amalgam: the materials.
Marshall SJ; Marshall GW Jr
Department of Restorative Dentistry, University of California, San
Francisco 94143.
Adv Dent Res, 1992 Sep, 6:, 94-9
The goal of this presentation is to describe the material as it is used
clinically, explain why small quantities of Hg can be released, and suggest
ideas for amalgams that do not release mercury. A set amalgam is a dynamic
material that undergoes many microstructural changes during clinical use,
related to both the elevated temperature and corrosion-prone environment in
the mouth and mechanical forces applied to the restoration. Amalgams can be
roughly into two groups by their copper content: low Cu (traditional) and
high Cu. High-Cu amalgams generally perform better clinically, but all
amalgams corrode to some extent in the mouth. Some corrosion is deemed to
be a positive factor, because corrosion product deposition reduces leakage
at the margins of restorations; that is, the restorations are partly
self-sealing. One of the reasons cited for the improved clinical
performance of high-Cu amalgams over low-Cu amalgams is that the
corrosion-prone phase, gamma 2, is nearly
eliminated in high-Cu amalgams. Future research should involve improvements
in the clinical performance of dental amalgams, studies of the mercury
release from various types of amalgams and the toxic potential of this
exposure, and the development of new amalgam systems that reduce the
mercury exposure. Although the longevity of modern amalgams is impressive,
it is important for their stability to be increased both clinically and
microstructurally. An amalgam should be developed with a stable
microstructure that, once set, would not change during clinical use.
Microstructural changes lead to clinical deterioration. A stable system
would not corrode, and the matrix transformation gamma 1 to beta 1 would be

Interactions between dental amalgams and the oral environment.
Marek M
School of Materials Engineering, Georgia Institute of Technology, Atlanta
Adv Dent Res, 1992 Sep, 6:, 100-9
Dental amalgam fillings interact in a complex way with the environment in
the oral cavity as they are subjected to chemical, biological, mechanical,
and thermal forces. These forces change the restoration's appearance and
properties, while metal ions, amalgam debris, non-metallic corrosion
products, and mercury vapor are released into the oral cavity. The
phenomena and conditions that affect the amalgam/environment interaction
include the chemistry and biochemistry of the environment, formation of
biofilms on the amalgam
surfaces, existence of localized corrosion cells, galvanic contacts with
other metallic restorations, abrasion during mastication, and synergistic
effects of the different forces. Corrosion processes result in a
degradation of the functional amalgam properties, while tarnishing
reactions cause discoloration. Corrosion degradation of amalgam fillings is
due mainly to localized corrosion cells in pores and crevices. Corrosion on
occlusal surfaces is accelerated by abrasion during mastication, which
removes the protective surface films. The
average total amounts of metal species, including mercury, released per day
in  vivo from a restoration have not been determined. Much of the reported
indirect evidence for high mercury release rates is either unreliable or
controversial. A more detailed investigation is needed and will require the
development of more sophisticated techniques of sampling in vivo, as well
as both experimental and theoretical modeling in vitro.

The prevalence of sensitivity to constituents of dental alloys.
Namikoshi T; Yoshimatsu T; Suga K; Fujii H; Yasuda K
Department of Removable Prosthodontics, Nagasaki University School of
Dentistry, Japan.
J Oral Rehabil, 1990 Jul, 17:4, 377-81
Ninety-five participants were epicutaneous patch tested in order to
determine the prevalence of sensitivity to components of dental alloys.
Seventeen individuals (17.9%) developed allergic reactions, which were
caused by mercury (10.5%), copper (2.1%), nickel, cobalt, tin, gold and
zinc (1.1%). Eight of 17 allergic responders had a history of dermatitis
from metal contact. The results show that there is a need for careful
immunological considerations during the selection of suitable alloys,
particularly in the case of patients with lesions
suspected of being caused by dental alloys.

Placental transfer of heavy metals in normal pregnant Japanese women.
Tsuchiya H; Mitani K; Kodama K; Nakata T
Arch Environ Health, 1984 Jan, 39:1, 11-7
To investigate the interrelation of heavy metals and the influence on next
generation, total mercury and methylmercury, lead, cadmium, manganese,
copper, zinc, and iron were determined in the maternal blood, placenta,
umbilical cord, and umbilical cord blood. Samples were collected at
delivery from 231 pregnant women who were living in the city of Nagoya,
located in the central district of Japan, during 1974 and 1978. Total
mercury and methylmercury, cadmium, and iron were higher in cord blood than
in maternal blood, whereas copper and zinc were lower. Significant positive
correlations were observed between maternal and cord blood with regard to
total mercury and methylmercury, lead, cadmium, and manganese contents.
Significant correlations were also observed between many pairs of metals,
particularly in umbilical cord and its blood.

Concentrations of heavy metals in maternal and umbilical cord blood.
Ong CN; Chia SE; Foo SC; Ong HY; Tsakok M; Liouw P
Department of Community Medicine, National University of Singapore.
Biometals, 1993 Spr, 6:1, 61-6
Concentrations of lead, cadmium, methylmercury and total mercury were
measured in maternal and umbilical cord blood using graphite atomic
absorption spectrometry. Two essential metals, copper and zinc, were also
determined using ion chromatography. Lead, copper and zinc were found to be
lower in the cord blood whereas methylmercury and total mercury were higher
in cord blood than in maternal blood. Little differences were noted for
cadmium in maternal and cord blood. Significant positive correlations were
observed between the concentrations in maternal and cord blood with regard
to lead (correlation
coefficient, r = 0.44), copper (r = 0.34), zinc (r = 0.29), methylmercury
(r = 0.44) and total mercury (r = 0.58). These results suggest that, like
essential metals, most heavy metals can move rather freely across the human
placenta. The potential health effects of heavy metal transfer from mothers
to young infants cannot be discounted.

Reference intervals for trace elements in blood: 
significance of risk factors.
Grandjean P; Nielsen GD; Jırgensen PJ; Hırder M
Institute of Community Health, Odense University, Denmark.
Scand J Clin Lab Invest, 1992 Jun, 52:4, 321-37
A random sample of 100 men and 100 women was examined for whole-blood
concentrations of mercury, lead, cadmium and selenium, and the serum
concentrations of selenium, nickel, fluoride, aluminium, zinc and copper.
Major predictors were sex, hormonal factors (pregnancy, menopause, use of
oral contraceptives), age, tobacco smoking and alcohol drinking. Among
notable associations, increased blood-mercury was related to the presence
of more than four amalgam fillings in the teeth. Blood-mercury correlated
blood-selenium, but a relation to fish intake could only be demonstrated
for the former parameter. In women, blood-lead appeared to increase with
age, with the highest levels seen after the menopause. Serum-nickel was
slightly lower in patients with nickel-related contact eczema. Only the
selenium concentrations showed a slight increase in individuals taking
mineral supplements. Serum-zinc concentrations decreased considerably
during the day. Thus, due to the substantial influence of physiological and
environmental factors, individual
results must be interpreted in the light of the known predictors for the
trace element concentration. However, population-based reference intervals
for trace elements in blood are useful to explore geographic and temporal