Soderholm 201-209

BIS-GMA–BASED RESINS IN DENTISTRY: ARE THEY SAFE? KARL-JOHAN SÖDERHOLM, D.D.S., M.PHIL., ODONT.DR.; ANGELO MARIOTTI, D.D.S., PH.D.
Background. The authors critically surveyed
that short-term administration of BIS-GMA and/or research dealing with the release of resin components bisphenol A in animals or cell cultures can induce from dental composites and the potential of these changes in estrogen-sensitive organs or cells.
agents to mimic or disrupt estrogenic cell responses.
However, considering the dosages and routes of ad- Types of Studies Reviewed. The
ministration and the modest response of estrogen- studies reviewed included those on synthetic methods sensitive target organs, the authors conclude that the used to make bisphenol A glycidyl methacrylate, or short-term risk of estrogenic effects from treatments BIS-GMA, and the biological effects of this resin in using bisphenol A–based resins is insignificant.
cell culture and animals. The estrogenic effect of Long-term effects need to be investigated further.
bisphenol A was targeted because bisphenol A is Clinical Implications. Commonly used
present as an impurity in some resins (BIS-GMA) dental resins should not be of concern to the general and as a degradation product from other resins public; however, pharmacological evaluation of den- (bisphenol A dimethacrylate, or BIS-DMA).
tal materials is needed to ensure biologically safe and Results. The outcomes of this review revealed
therapeutically effective substances.
“If we had a reliable way to label our toys good and bad, it would be easy to regulate technology wise- ly. But we can rarely see far enough ahead to know which road leads to damnation. Whoever concernshimself with big technology, either to push it forward or to stop it, is gambling in human lives.” —Freeman Dyson, “Disturbing the Universe,” 1979
During World War II, German researchers de- polymerization process of the epoxy resin. To veloped a chemical process that could be used to overcome this problem, Bowen attached methyl cure dental methacrylates at room temperature.1,2 methacrylate groups to the end groups of the Despite initial successes, the clinical results re- epoxy resin, thereby converting the epoxy resin to ported during the mid-1950s showed that chemi- a dimethacrylate.9,10 The experimental outcome cally cured methacrylate restorations were asso- was successful and resulted in a new resin called ciated with increases in discoloration, recurrent bisphenol A glycidyl methacrylate, or BIS-GMA, tooth decay and pulp reactions.3-5 These initial side effects were attributed to polymerization Bowen’s resin had some important advantages, including reduced shrinkage during polymeriza- tion and the ability to form cross-links (which are searchers added inert filler particles to the self- stronger than linear polymers) during polymer- curing methacrylate resin.6,7 To improve strength ization. However, the higher viscosity of BIS- and adhesiveness of the resinous restorations, GMA made it more difficult to add filler to the Bowen8 explored the possibility of using epoxy monomer and to mix the chemically cured com- resins (diglycidyl ether of bisphenol A) mixed with posite. To solve this problem, different monomers silica particles. The in vitro results were promis- with lower viscosities (for example, triethylene- ing, but the presence of moisture inhibited the glycol dimethacrylate, or TEGDMA) were added Copyright 1998-2001 American Dental Association. All rights reserved.
Figure 1. The bisphenol A molecule (top) is estrogenic. Under clinical conditions, esterase present in salivacan break ester linkages (arrows). If the bisphenol A glycidyl methacrylate, or BIS-GMA, molecule (center) isattacked by esterase, no bisphenol A will form. However, if the ester linkages of the bisphenol A dimethacry-late, or BIS-DMA, molecule (bottom) are attacked, bisphenol A can form.
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CREATING BIS-GMA
Inhibitory
Protein Complex
Transcription-
Activating
Hormone-
Binding
pounds containing two hydroxygroups in para positions. Onesuch derivative, bearing two Hinge Region
DN A-Binding Domain
bisphenol A, has been used bysome manufacturers during syn-thesis of BIS-GMA.10 Because ofthe estrogenic effect of bisphenolA, it seemed reasonable to sus- GMA–containing materials,bisphenol A molecules could bepresent that could cause an es-trogenic response.
Release of Inhibitory
Protein Complex
DN A-Binding Site Exposed
bisphenol A groups present inthe BIS-GMA molecule are ster-ically hindered and if themonomer is pure and does notcontain any impurities from the Figure 2. The unbound or free hormone enters the cell by diffusion and binds to macromolecules called receptors. When binding occurs, the re- ceptor releases an inhibitory protein complex, and the DNA-binding siteof the receptor becomes exposed and ready to bond to the DNA.
derstand the potential risks as-sociated with BIS-GMA, we Chemistry. In 1965, Bowen
Copyright 1998-2001 American Dental Association. All rights reserved.
Problems. From a biological
THE ESTROGEN FAMILY
AND HOW IT WORKS
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Cell culture experiments.
BIS-GMA EPISTEMOLOGY
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In situ experiments.
Absorption, metabolism
and excretion: pharmacoki-
netics. Questions remain
Copyright 1998-2001 American Dental Association. All rights reserved.
Copyright 1998-2001 American Dental Association. All rights reserved.
CONCLUSION
Herstellung von Zahnersatzteilen, insbeson- Tokes L, Feldman D. Bisphenol-A: an estro- genic substance is released from polycarbon- ate flasks during autoclaving. Endocrinology Patentschr German patent 760351: 1940.
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