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Amalgam -- Resurrection and Redemption Part 2:
The Medical Mythology of Anti-Amalgam
Michael J. Wahl, D.D.S.
Myth #10: There are no health concerns about the components
composite resins, glass ionomers, and other nonamalgam materials.
Fact #10: Although they appear safe
and effective, there are health concerns
warranting further study about the components of composite resins,
glass ionomers, and other nonamalgam materials.
Since many anti-amalgamists consider mercury released from
dental amalgams to be unsafe, they recommend the use of "nontoxic"
nonamalgam alternatives, most commonly composite resins. One group
of anti-amalgamists stated, "It would seem that now is the
time for dentistry to use composite (polymeric and ceramic) alternatives
and discard the metal alchemy bestowed on its profession from
a less enlightened era."  But Mackert stated:
A frequent claim by the anti-amalgamists is that "no
research has shown that dental amalgam is safe," yet the
same charge can be leveled against composites and other dental
materials. No material can ever be judged "safe" with
any kind of finality, because new biological evaluation techniques
are always being developed, and previously unanticipated adverse
effects are continually being discovered for all materials .
Just as amalgam fillings release mercury, so composite resin
restorations have been shown to leach between 14 and 22 separate
potentially hazardous compounds, including DL-camphorquinone;
4-dimethylaminobenzoic acid ethy ester, drometrizole; 1,7,7-trimethylbicyclo[2,2,1]heptane;
2,2-dimethoxy[1,2] diphenyletanone; ethyleneglycol dimethacrylate;
and triethyleneglycol dimethacrylate .
In a study of 35 identifiable dental resin composite monomers/additives
of commercial composite resin composites (Table 1), investigators
found nine severely or moderately cytotoxic components . Other
studies have also shown composite resin components to be cytotoxic
(causing damage or destruction of cells). [5-15] Several studies
have shown that dentin bonding agents and their components are
mutagenic (cause mutations in new generations). [16-19] Wataha
et al stated, "the components of resin composites are hazardous
in that they all cause significant toxicity in direct contact
with fibroblasts." 
Table 1. Components of Resin Composites
Bowen monomer, isopropyliden-bis (2-hydroxy-3-(4-phenoxy)-propylmethacrylate
Camphoric acid anhydride
4-Dimethylaminobenzoic acid ethyl ester
|Reprinted with permission of
Wiley-Liss, Inc., a subsidiary of John Wiley & Sons, Inc.
Adapted from Geurtsen W et al 
Resin composite components have been shown to cause immunosupression
or immunostimulation  and to inhibit DNA  and RNA synthesis
. Resin composite restorative material was shown to be more
cytotoxic than amalgam in a comparative in vitro study . Various
resin components of dentin bonding agents have been shown to suppress
the mitochondrial acitivty of macrophages . Various composite
restorative materials implanted into animals have been shown to
cause inflammatory responses, including an increase in lymphocytic
infiltration as well as fibroblasts and epithelioid cells .
There have been several reports of allergy to composite resins
and their ingredients [27-31]. It has been suggested that composite
resins may be a cause of hand eczema and skin symptoms in dentists
. Vinyl, latex, and modified latex gloves are permeable to
several resin composite materials . Some resin monomers have
been shown to encourage the growth of cariogenic microorganisms
Resin composites , sealants , and glass ionomers 
have been shown to release formaldehyde, a possible carcinogen
. One dentist, commenting on the fact that some anti-amalgamists
describe composite resins as "mercury-free fillings,"
has called amalgam restorations "formaldehyde-free restorations."
 Chemically cured composite resins contain the initiator benzoyl
peroxide , which has been shown to be carcinogenic in many
studies [41-43]. There is even concern that there may be environmental
harm from the waste in dental offices using composite resin filling
Glass ionomer cements have been shown to inhibit macromolecular
synthesis . In a review of the side-effects of dental ceramics,
Mackert reported that ceramic dental restorations may cause silica
granulomas and often contain radioactive fluorescing agents, both
of which may cause systemic effects . Even gold can be allergenic
. One study showed that the gold itself in gold foil restorations,
and not the condensation of the gold foil, caused hemorrhage,
destruction of odontoblasts, and inflammation of the pulp .
Most reviews have concluded that composite restorative materials
are safe [48-51], but there is far more knowledge about dental
amalgam than there is about composite resin and glass ionomer
filling materials . After extensively reviewing the toxicity
of non-amalgam filling materials, Schmalz concluded, "it
is not possible to rank dental filling materials in respect to
their biocompatibility, and it is evident that biocompatibility
must be considered to the same extent for both amalgams and commonly
used or recommended alternative fillings materials." 
Amalgam restorations release small quantities of mercury, but
apparently not enough to cause systemic health problems. Mercury
from dental amalgam fillings cannot be linked to kidney damage,
Alzheimer's disease, multiple sclerosis, other central nervous
system diseases, "amalgam disease," mental disorders,
damage to the immune system, increases in antibiotic resistance,
or harmful reproductive effects. Dentists occupationally exposed
to mercury from the placement and/or removal of amalgam fillings
have not been shown to have harmful reproductive or other systemic
health effects, provided proper mercury hygiene is used. Just
as with amalgam, although they appear safe, there have been health
concerns raised about alternative filling materials, including
about composite resin. Dentists, physicians, dental assistants,
and patients can be confident that based on the available scientific
evidence, amalgam remains a safe and effective filling material.
- Lorscheider FL, Vimy MJ, Summers AO. Mercury exposure from
"silver" tooth fillings: emerging evidence questions
a traditional dental paradigm. FASEB J 1998;9:504-8.
- Mackert JR. Dental amalgam and mercury. JADA 1991;122(8):54-61.
- Lygre H, Høl PJ, Solheim E, Moe G. Organic leachables
from polymer-based dental filling materials. Eur J Oral Sci 1999;107:378-83.
- Geurtsen W, Lehmann F, Spahl W, Leyhausen G. Cytotoxicity
of 35 dental resin composite monomoers/additives in permanent
3T3 and three human primary fibroblast cultures. J Biomend Mater
- Leyhausen G, Lehmann F, Geurtsen. Cytocompatibility of 38
composite monomers/additives in human oral primary cell cultures.
J Dent Res 1997;76 (Spec Issue):382 [Abstract 2945].
- Arenholt-Bindslev D, Ebbehöj, Hörsted-Bindslev.
Cytotoxicity of conditioners and bonding agents. J Dent Res 1994;73
(Spec Issue):952 [Abstract 111].
- Bouillaguet S, Wataha JC, Hanks CT, et al. In vitro cytotoxicity
and dentin permeabililty of HEMA. J Endodon 1996;22:244-8.
- Wataha JC, Rueggeberg FA, Lapp CA, et al. In vitro cyto-toxicity
of resin-containing restorative materials after aging in artificial
saliva. Clin Oral Invest 1999;3:144-149.
- Itota T, Toni Y, Sogawa N, Sogawa C, Inoue K. Cyto-toxicity
of a trial resin composite liner containing TiK2F6 on rat dental
pulp cells. Dent Mater J 1999;18:271-277.
- Sletten GBG, DahI JE. Cytotoxic effects of extracts of compomers.
Acta Odontol Scan 1999;57:316-322.
- Hikage S, Sato A, Suzuki 5, Cox CF, Sakaguchi K. Cytotoxicity
of dental resin monomers in the presence of S9 mix enzymes. Dent
Mater J 1999;18:76-86.
- Costa CAS, Vaerten MA, Edwards CA, Hanks CT. Cytotoxic effects
of current dental adhesive systems on im-mortalized odontoblast
cell line MDPC-23. Dent Mater 1999;15:434-441
- Costa CAS, Teixeira HM, Nascimento ABL, Hebling J. Biocompatibility
of two current adhesive resins. J Endodon 2000;26:512-516.
- Imazato S, Tarumi H, Ebi N, Ebisu S. Cytotoxic effects of
composite restorations employing self-etching primers or experimental
antibacterial primers. J Dent 2000;28:61-67.
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- Schweikl H, Schmalz G. Glutaraldehyde-containing dentin bonding
agents are mutagens in mammalian cells in vitro. J Biomed
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of various dentine bonding agents. Biomater 1996;17:1451-6.
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agents. J Biomed Mater Res 1994;28:1061-7.
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of resins and other dental resotrative materials. J Oral Rehabil
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unpolymerized resin components on the function of accessory cells
derived from the rat incisor pulp. J Dent Res 1995;74:1162-7.
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of resin components on cultured mammalian fibroblasts. J Dent
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materials. Eur J Oral Sci 1998;106:713-20.
- Mackert JR, Jr. Side-effects of dental ceramics. Adv Dent
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with unusual features. Br J Dermatol 1973;88:505-8.
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of posterior restorative materials. CDA J 1996;24(9):17-31.
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are they safe? JADA 1999;130:201-8.
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Dr. Wahl practices dentistry in Wilmington, Delaware. This
article was originally published in Quintessence International
32:696-710, 2001, and is reproduced here with the kind permission
permission of Quintessence
Publishing Co. The author thanks Drs. J. Rodway Mackert, Ivar
A. Mjör, and Fred Eichmiller for reading the manuscript and
offering several helpful suggestions.
Part 1: Intro
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Part 2: Intro
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