10.59987/ads/2010.3-4.14-21
This study aims to critically summarize the literature about bisphenol A (BPA), indicate whether and how those risks are real and emphasize how it is eventually possible to prevent them. With this in mind, we should consider nature, risks and control of BPA, as well as its presence and its role in sealants and composites. It is important to note that we will focus on literature exclusively written about the possible estrogenic activity (and not about the general toxicology profile) of BPA or its possible derivatives released from composites and sealants (without mentioning, or covering just briefly, similar activities performed by their components).
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 Estrogenicity of bisphenol A released from sealants and composites: a review of the literature
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 Estrogenicity of bisphenol A released from sealants and composites: a review of the literature
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0024 4 Estrogenicity_Eramo:-       10-02-2011      11:47     Pagina 14




               Estrogenicity of bisphenol A released from
               sealants and composites: a review of the literature




                                                                                                                   i
                                                                                                                 al
                                                                                                               on
               Stefano Eramo1, DDS                                             and composites. It is important to note that we will focus
               Giacomo Urbani1 MD, DDS                                         on literature exclusively written about the possible estro-
               Gian Luca Sfasciotti2 MD, DDS, PHD                              genic activity (and not about the general toxicology profile)
               Orlando Brugnoletti2 MD, DDS                                    of BPA or its possible derivatives released from compos-
               Maurizio Bossù2 DDS, PHD                                        ites and sealants (without mentioning, or covering just briefly,




                                                                                                             zi
               Antonella Polimeni2 MD, DDS                                     similar activities performed by their components).

               1University of Perugia, Italy




                                                                                            a
               2“Sapienza” University of Rome, Rome, Italy                     Bisphenol A
               Department of Odontostomatological and Maxillofacial
               Sciences (A. Polimeni)                                          Bisphenol A (BPA) is recorded in the CAS (Chemical Ab-




                                                                                         rn
               Paediatric Dentistry Unit                                       stract Service), number 00080-05-7 and its chemical name
                                                                               as used in Europe is 2,2-Bis (4-hydroxyphenyl) propane.
               Corresponding author:                                           There are a large number of synonyms, such as the fol-




                                                                               te
               Dott. Maurizio Bossù, Department of Odontostomatolog-           lowing most common: Bis(4-hydroxyphenyl)dimethyl
               ical and Maxillofacial Sciences                                 methane; 4,4’-dihydroxydiphenyl propane; 4,4’-dihydroxy-
               Paediatric Dentistry Unit                                       2,2-diphenyl propane; Diphenylolpropane; 4,4’-isopropy-
               “Sapienza” University of Rome                                   lidenediphenol (1).
               Via Caserta, 6 - 00161 Rome, Italy
               Phone: + 39 06 49976649
                                                                     In        BPA is produced by the condensation of phenol and ace-
                                                                               tone in the presence of catalysts and catalyst promoters
               E-mail: maurizio.bossu@uniroma1.it                              (2); its molecular formula is C15H16O2 and its structure is
                                                                               shown in Figure 1; the molecular mass is 228.29 g / mol
                                                                               and it exists at room temperature in the form of a white sol-
                                                        ni
               Summary
               Estrogenicity of bisphenol A released from sealants and         id with a mild “phenolic” odour.
               composites: a review of the literature.                         The main physico-chemical properties of BPA are shown
                                                                               in Table 1.
                                              io


               This study aims to critically summarize the literature          BPA is primarily used in the production of polycarbonate
               about bisphenol A (BPA), indicate whether and how               (PC), a plastic widely used to produce infant feeding bot-
               those risks are real and emphasize how it is eventually         tles, tableware, microwave ovenware and storage con-
                                     iz



               possible to prevent them. With this in mind, we should          tainers.
               consider nature, risks and control of BPA, as well as its       It is also widely used in the production of epoxy resins, used
               presence and its role in sealants and composites. It is         as an internal, protective lining for cans and metal lids and
               important to note that we will focus on literature exclu-       the inner layer of water tanks and wine vats (1). Small
                      Ed




               sively written about the possible estrogenic activity (and
               not about the general toxicology profile) of BPA or its
               possible derivatives released from composites and
               sealants (without mentioning, or covering just briefly,
               similar activities performed by their components).
         IC




               Key words: bisphenol A, composites, sealants.


               Introduction
                                                                               Figure 1 - Low level laser irradiation of tongue.
  C




               Bisphenol A (BPA) is, by definition, a major component of
               Bis-GMA (bisphenol A glycidylmethacrylate or “Bowen’s           Table 1 - Ideal bone substitute features.
               resin”), a molecule known to be at the basis of composites
               and sealants used in dentistry. In the international dental     PROPERTIES            VALUES
©




               literature articles regularly appear arguing that BPA and/or
               its derivatives might be released into the oral cavity from     Boiling point         220°C at 4 mmHg – 398°C at 760 mmHg
               composites and sealants in doses which can produce es-          Melting point         150-157°C
               trogenic effects. This study aims to critically summarize the   Specific gravity      1.060-1.195 g/mL at 20-25°C
                                                                               Solubility in water   120-300 mg/L at 20-25°C
               literature, indicate whether and how those risks are real and
                                                                               Vapour pressure       8.7 x 10-10 – 3.96 x 10-7 mmHg at 20-25°C
               emphasize how it is eventually possible to prevent them.
                                                                               LogKσw                2.20 – 3.82
               With this in mind, we should consider nature, risks and con-
                                                                               Henry’s constant      1.0 x 10-10 atm-m3/mol
               trol of BPA, as well as its presence and its role in sealants

               14                                                                                     Annali di Stomatologia 2010; I (3-4): 14-21
0024 4 Estrogenicity_Eramo:-        10-02-2011        11:47      Pagina 15




               Estrogenicity of bisphenol a released from sealants and composites: a review of the literature


               amounts of BPA can migrate from containers into foods and             Bisphenol A in composites and sealants
               beverages, therefore its use is regulated in the European
               Union under the Commission Directive 2002/72/EC of 6                  Bisphenol A plays an important role in almost all com-
               August 2002 relating to plastic materials and articles in-            posites and sealants, as it is an integral part of the mol-
               tended to come into contact with foodstuffs.                          ecule of Bis-GMA. It must, however, be specified (as was




                                                                                                                       i
               In the United States and in Japan its use is also author-             clearly emphasized by ADI, 2008) that in reality BPA can




                                                                                                                     al
               ized in contact with food. The European Commission’s Sci-             become part of these dental materials in three ways: a) as
               entific Committee on Food (SCF) published in 2002 an                  a direct ingredient, b) as a product of the degradation of
               opinion on BPA, defining a temporary TDI (Tolerable Dai-              other ingredients, c) as trace material derived from the man-
               ly Intake = the amount of a substance, expressed on a body            ufacture of other ingredients.




                                                                                                                   on
               weight basis that can be ingested daily over a lifetime with-         a) As a direct ingredient, surprisingly, the BPA is rarely
               out appreciable risk) of 0.01 mg/kg bw (therefore, equal                  used as a formula ingredient in composites and
               to 10 g/Kg pc), that derived from No-Observed-                            sealants. In order to explain this apparent paradox, it
               Adverse-Effect Level (NOAEL) of 5 mg/kg bw/day, apply-                    is necessary to remember, together with Sodherolm




                                                                                                                 zi
               ing a 500-fold uncertainty factor. In 2006, in the light of the           and Mariotti, that Bowen described three methods for
               vast number of scientific articles published in the mean-                 the synthesis of the monomer BIS-GMA (3,4):
               time, the European Commission asked EFSA (European                        1. Reaction between two moles of glycidyl methacry-




                                                                                                 a
               Food Safety Authority) to review the safety of BPA for use                    late with one mole of bisphenol A. A tertiary amine
               in materials in contact with food.                                            was added to catalyze the addition of the pheno-
               The Panel of EFSA has issued an opinion in which the re-                      lic hydroxyl groups to the epoxide groups. This




                                                                                              rn
               evaluation of BPA focused particularly on effects of BPA                      method (preferred by Bowen) is the simplest one
               on reproduction and on the endocrine (hormonal) system                        and can lead to the maintenance of both gly-
               (1). A great scientific debate has taken place about the                      cidylmethacrylate and BPA as impurities in quan-
               aforementioned effects.Therefore, the Panel concluded that                    tities instrumentally identified.




                                                                                     te
               the NOAEL of 5 mg/kg bw/day remains valid. The Panel                      2. Condensation of sodium salt of bisphenol A with
               also concluded that endocrine-system related effects of low-                  an equivalent amount of the reaction product of gly-
               doses of BPA in rodents have not been demonstrated in                         cidyl methacrylate and anhydrous hydrochloric acid.
               a robust and reproducible way, as some studies indicat-
                                                                          In                 During this reaction, sodium chloride is formed as
               ed major species differences between rodents and humans                       a by-product that could be washed away. Residu-
               in the way that BPA is handled in the body: humans more                       als of the bisphenol A salt are left in the final prod-
               rapidly metabolise and eliminate BPA than rats do and, in                     uct if excess glycidylmethacrylate is used during
               addition, mice are particularly sensitive to estrogens. Giv-                  the reaction and if the reaction is not allowed to be
                                                             ni
               en, however, that BPA is a weak oestrogen, absence of ad-                     completed. These residuals may be in large quan-
               verse effects at doses of BPA equal or below 0.5 mg/kg                        tities, which may reach several g/g of substance
               bw/day derived from an important study on mice and two                        (able to induce estrogenic effects in vitro).
                                                 io

               generations of their offspring added further certainty for                3. Reaction of glacial methacrylic acid with the digly-
               risk assessment. According to available scientific evidence                   cidyl ether of a bisphenol and a tertiary amine was
               and because of remaining doubts, the Panel applied a 100-                     added to catalyze the above reaction. Therefore
               fold uncertainty factor to establish TDI, that is usually used,               methacrylate groups were attached to hydroxy glyc-
                                       iz



               and established for humans a full TDI of 0.05 mg / kg body                    eryl groups, which, in turn, were linked to phenoxy
               weight equal to 50 µg/kg body weight.                                         groups. This synthetic method excludes the use of
               Thus, a child of 36 kg weight can take, without risks, a dai-                 bisphenol A. Any molecule of bisphenol A possibly
                      Ed




               ly dose of BPA of 1800 g and an adult of 70 kg a dose of                      present in the final product comes from unreacted
               3500 g. It has been estimated that the human dietary lev-                     impurities from the synthesis of diglycidyl ether of
               el of BPA is below 50 mg/kg/day TDI, infants and children                     bisphenol A. Good quality control measures in this
               included (Table 2).                                                           reaction are sufficient to avoid the presence of these
               Furthermore, a recent publication of the American CERHR                       unreacted portions, and today the majority of
               (Centre for the Evaluation of Risks to Human Reproduc-                        manufacturers of dental composites prefer this syn-
         IC




               tion, 2007) agrees with the reassuring general conclusions                    thetic method as it leaves the fewest parts per mil-
               of the experts of the European Community.                                     lion of BPA free or released in the final product.
  C




               Table 2 - Ideal bone substitute features.

               Age of consumer                Food/Beverages consumed                       Dietary exposure to BPA based on conservative
                                                                                            migration value (microgram/kg bw/day)
©




               3 month-old infant             Breast milk only                              0.2
               3 month-old infant             Infant formula fed with glass bottle          2.3
               3 month-old infant             Infant formula fed with PC bottle             11
               6 month-old infant             Infant formula fed with PC bottle
                                              and commercial foods/beverages                13
               1.5 year-old                   2 kg commercial foods/beverages               5.3
               Adult                          3 kg commercial foods/beverages               1.5


               Annali di Stomatologia 2010; I (3-4): 14-21                                                                                       15
0024 4 Estrogenicity_Eramo:-        10-02-2011        11:47     Pagina 16




               S. Eramo et al.


               b) As a degradation product of other ingredients in the oral        Hamid and Hume in a study in vitro by HPLC did not iden-
                    cavity conditions, the BPA may come, particularly but          tify the presence of BPA in the eluate of seven dental
                    not exclusively, from products containing bisphenol A          sealants (Concise, Ultraseal, P & FS, Prisma Shield Com-
                    dimethacrylate (Bis-DMA), since the latter is exposed          pules, Helioseal F, Dentsply Delton and Delton J & J), but
                    in the oral cavity to the BPA degradation, especially by       stressed the release of TEGDME from Concise and He-




                                                                                                                     i
                    salivary esterases.                                            lioseal(8).




                                                                                                                   al
               c) As trace material, BPA can be used in the manufac-               Carrying out an in vitro analysis using high-performance
                    ture of other ingredients (bedsides Bis-GMA) in com-           liquid chromatography (HPLC) for seven sealants (Delton,
                    posites and sealants, therefore its residues may be            Concise, Helioseal, PrismaShield, Seal-Rite I, Rite II and
                    present in final products in case of poorly controlled         Defender Seal), Nathanson et al. found that none of them




                                                                                                                 on
                    reactions.                                                     had released BPA, even if the BPA dimethacrylate was de-
               Obviously it is necessary to note that the composites and           tected in the eluate of two commercial products (Delton
               sealants produced in Europe, Japan and in the U.S. must             and Defender) as well as the presence of various other mol-
               meet strict standards determining the maximum amount of             ecules (TEGDME, Bis-GMA, UDMA) (9).




                                                                                                               zi
               BPA released under the conditions of the oral cavity; fur-          In 1999 some important contributions worth being taken
               thermore these standards are based on toxicological as-             more carefully into consideration appear almost simulta-
               pects and not on those of estrogens (which require lower            neously.
               doses to act). According to our point of view the problem           Schafer et al., in an experimental work in vitro, confirm the




                                                                                               a
               has therefore to be focused on four questions, to which an-         potential estrogenicity of BPA and BPA dimethacrylate in
               swers will be given at the end of the review of the literature:     micromolar concentrations in vitro (at doses that are, how-




                                                                                            rn
               - is BPA released from composites and sealants?                     ever, 1,000 times higher than the estrogen reference, rep-
               - If yes, how much of it is released?                               resented by 17β-estradiol), both repeating the experiences
               - Might the released doses have estrogenic action?                  of Olea et al. and with the use of flow cytometry. They very
               - Is there a way to prevent the possible release?                   clearly stress that their conclusions are valid only “in vit-




                                                                                   te
                                                                                   ro“ and that “in vivo“ is necessary to investigate various con-
                                                                                   troversial aspects and, in particular:
               Analysis of literature                                              - how much the xenoestrogens are accumulated and

               Although it was known since the ‘30s that some diphenyl
                                                                         In             metabolized;
                                                                                   - what is the level of exposure of people to these com-
               compounds containing two hydroxyl groups in para posi-                   pounds;
               tion could show estrogenicity, only since the mid-90s, the          - what exactly are the levels sufficient to cause adverse
               research has dealt with the possible estrogenic effects of               reactions;
                                                           ni
               BPA. This was generally due to the increased number of              - how much the xenoestrogens have additive effects (10).
               studies on this compound, which is, as already noted, wide-         Soderholm and Mariotti (3), in a comprehensive and pre-
               ly used in the synthesis of substances forming the inner            cise review of the literature (already mentioned in this in-
               lining of many food containers and, in particular, to the in-       troduction), not only present the synthesis of experimen-
                                                io


               creasing use of resin-based sealants and composites (both           tal work that had appeared up until then on the release and
               for their intrinsic improvement and for their use in adhe-          possible estrogenic action of BPA from dental products, but
               sive systems) (3,5).                                                also explore for explanatory purposes three main areas:
                                       iz



               The first one addressing this issue in dentistry was a Span-        chemistry and clinical use of Bis-GMA, steroids’ action in
               ish group of the University of Granada along with re-               the body and in the oral cavity, the various theories about
               searchers at Tufts University of Boston: in this widely cit-        how bisphenol A–based resins may affect estrogen-sen-
                      Ed




               ed article the authors, studying the behaviour of three com-        sitive tissues in the body. These authors concluded that
               posites and a sealant, reported that the release and the            “based on existing research, we must accept that certain
               estrogenic activity of BPA and BPA dimethacrylate was only          impurities may be present in some Bis-GMA–based
               due to the sealant(6). In particular, the authors conclud-          resins, and these impurities, when released from restora-
               ed in a clinical trial on 18 subjects that the polymerized          tions, are potentially estrogenic” but added that “the
               sealant (Delton) was able to release high doses into sali-          amounts of bisphenol A that may be present as an impu-
               va (one hour period after treatment), ranging from 90 to            rity or produced as a degradation product from dental
         IC




               930 g of BPA and BPA dimethacrylate for 50 mg of com-               restorations, including sealants, are quite small and far be-
               pound. These doses were more than sufficient to induce              low the doses needed to affect the reproductive tract.
               estrogenic responses in a particular cell line. Authors con-        Lewis et al., in a study in vitro carried out to identify the
               cluded that “the use of bis-GMA-based resins in dentistry,          release of BPA and BPA dimethacrylate from 28 com-
  C




               and particularly the use of sealants in children, appears           mercial dental products (20 composites and 8 sealants,
               to contribute to human exposure to xenoestrogens”.                  see Table 1) using HPLC, found no measurable released
               By return mail, Habib and Kugel, in a letter to the editor          quantities of these compounds; the only exception was rep-
               of the magazine which had published the article by Olea             resented by a sealant (Delton II) able to release amounts
©




               et al. , criticized it, underlining in particular the need to un-   of bisphenol capable of producing estrogenic responses
               dertake scientific studies in order to define the presence          in vitro. The authors concluded, however, that “dental resins
               of risks and their possible gravity as well as the need to          in general do not represent a significant source of BPA or
               avoid “emotional aspects and hysteria”(7).                          BAD exposure” (11).
               In the following years, the problem posed by Spanish au-            Schmalz et al., in a trial in vitro conducted by HPLC on the
               thors does not seem to have raised, in fact, the said “hys-         release of BPA from sealant monomers under different hy-
               teria” in dentistry, and even the dental scientific analyses        drolytic conditions (variable pH values, esterase action,
               are rather reduced in number.                                       pooled saliva for up to 24 hours) stress the importance of

               16                                                                                       Annali di Stomatologia 2010; I (3-4): 14-21
0024 4 Estrogenicity_Eramo:-        10-02-2011        11:47    Pagina 17




               Estrogenicity of bisphenol a released from sealants and composites: a review of the literature


               the conversion under these conditions of BPA into BPA           action is probably linked to BPA dimethacrylate” and that
               dimethacrylate as well as how the majority of commercial        “the possibilities of the BPA eluted from dental resin-based
               products did not contain any compounds (12). Authors con-       materials mimicking natural steroid hormones are negli-
               cluded that the results reported by Olea et al. (6) may be      gible” (15).
               attributed to the BPA-dimethacrylate content of Delton, but,    Fung et al. have carried out an in vivo test on 40 adult vol-




                                                                                                                 i
               on the other hand, no BPA release is expected under phys-       unteers collecting saliva and blood samples at various in-




                                                                                                               al
               iological conditions from fissure sealants based on Bis-        tervals (1h, 3h, 1 day, 3 days and 5 days) after sealant (Del-
               GMA if pure-base monomers are used.                             ton) placement and using HPLC to determine BPA con-
               The same research group, Arenholt-Bindslev et al., then         centration; 18 patients constituted the low-dose group, re-
               conducted an in vivo analysis, placing two different types      ceiving a single 8-mg dental sealant dose on one surface,




                                                                                                             on
               of fissure sealants (Delton and Visioseal) in 8 volunteers.     while 22 patients constituted the high-dose group, receiving
               5 ml of saliva were collected immediately, 1 hour and 24        a total dosage of 32 mg of sealant on four surfaces. This
               hours after placement of the fissure sealant. The saliva        experience frankly seemed rather questionable in some
               samples analysis by HPLC found that small quantities of         respects, from a dental point of view, because the authors




                                                                                                           zi
               BPA (0.3-2.8 ppm i.e. 0.3 to 2.8 mg/L, as the sample col-       did not used a dental dam (as most of the other authors
               lected of 5 ml, the total quantity was 1.5-14 g) were de-       cited did), did not immediately make a collection of fluid,
               tected in saliva samples collected only immediately after       touched up the areas of sealant with rotary instruments,
               placement of Delton sealant; furthermore, in a recombi-         and collected fluids in plastic containers (which can react




                                                                                           a
               nant yeast cell assay, significantly increased estrogenic ac-   with BPA). However, the authors, despite detected low con-
               tivity was found in saliva samples collected immediately        centrations of BPA in saliva specimens collected at both




                                                                                        rn
               after placement of Delton. The authors concluded that “BPA      one and three hours immediately after sealant placement
               can be found in saliva samples collected immediately af-        in saliva (from 5.8 to 105.6 parts per billion, i.e. g/L), and
               ter placement of Delton”, however, it is “considerably low-     relying on the continued absence of measurements in blood
               er than the amount reported by other sealants. No de-           and saliva samples after 24 hours, state that “that BPA re-




                                                                               te
               tectable amounts of BPA nor estrogenic activity were de-        leased orally from a dental sealant may not be absorbed
               tected 1 hour after Delton treatment (13).                      or may be present in non-detectable amounts in systemic
               In 2000, the Olea group revived interest in research in this    circulation, therefore, “the concern about potential estro-
                                                                      In
               field, showing that, despite the reassuring findings of pre-
               vious literature, BPA was released not only from the “usu-
                                                                               genicity of a sealant may be unfounded” (16).
                                                                               Manabe et al., using in vitro an original method of selec-
               al” Delton, but also from 7 others commercial composites        tive extraction in combination with gas chromatography-
               currently used in dentistry (Pekalux, Charisma, SILUX plus,     mass spectrometry, revealed that the composites and
               Z100, Tetric, Brilliant, Polofil). Using HPLC and gas chro-     sealants examined released up to 91.4 ng of bisphenol-
                                                             ni
               matography/mass spectrometry, the authors studied               A/g material into a buffered saline solution, when poly-
               biphenolic molecules eluted from in vitro polymerized com-      merized, during a 24-hour incubation. The authors con-
               mercial composites, with particular reference to BPA, and       cluded that bisphenol-A can be released from dental ma-
                                                 io

               found values of up to 1.8 g/g of polymerized materials.         terials, however the leachable amount would be less than
               Such concentrations, underlined the authors, may have “bi-      1/1000 of the reported dose (2 g/kg body weight/day) re-
               ological effects, as have been demonstrated in in vivo ex-      quired for xenoestrogenisity in vivo (17).
               perimental models (14).                                         Al-Hiyasat et al., in an in vivo study, investigated the effect
                                       iz



               Tarumi et al., by means of the Reporter Gene Assay, in-         of leached substances from dental composites on the fer-
               vestigated the endocrine response to three sealants             tility of male mice. Using Z 100, the authors prepared 50 poly-
               (Delton, Defender and Teethmate) and 4 adhesive resins          merized discs (for a weight of 3.9 g), immersed them in
                      Ed




               (Linerbond, Scotchbond, Optibond Solo and AllBond). Two         ethanol for 24 hours and sonicated them for 30 minutes. The
               of these sealants (Delton and Defender) were confirmed          eluate evaporated the at 80°C. The obtained sediment was
               to have estrogenic activity, although none of the tested ma-    dissolved in distilled water and intragastrically administered
               terials contained BPA. They concluded that “endocrine-like      to 20 male mice. The procedure was repeated for 28 days


               Table 3 - Commercial dental products (from ref. 11).
         IC




               1.    Bisfil P Bisco, A                                          15.   Prisma APH Caulk/Dentsply A
               2.    Brilliant Dentin Coltene/Whaledent A                       16.   Prisma TPH Caulk/Dentsply A
               3.    Charisma Kulzer, A                                         17.   Prodigy Kerr A
  C




               4.    Clearfil PhotoPosterior Kuraray A                          18.   Silux Plus 3 M Dental Prod. A
               5.    Heliomolar Vivadent A                                      19.   Tetric Vivadent, A
               6.    Herculite XRV Kerr/Sybron A                                20.   Z100 3 M Dental Products A
               7.    Lite-Fil II Shofu Dental A                                 21.   Delton Base Dentsply/Ash, B
©




               8.    Occlusin GC-America A                                      22.   Delton Catalyst Dentsply/Ash, B
               9.    P-50 3 M Dental Products A                                 23.   Delton LC Ash/Dentsply, B
               10.   Palfique Estilite Paste Tokuyama A                         24.   FluoroShield Caulk/Dentsply B
               11.   Pekafil NF Bayer Dental, Germany A                         25.   PermaSeal Ultradent Products B
               12.   Pekalux Bayer Dental, Germany A                            26.   Prisma•Shield Caulk/Dentsply B
               13.   Pertac-Hybrid ESPE A                                       27.   Concise Opaque 3 M Dental Prod. B
               14.   PhotoClearfil Kuraray A                                    28.   UltraSeal XT Ultradent Products B



               Annali di Stomatologia 2010; I (3-4): 14-21                                                                                 17
0024 4 Estrogenicity_Eramo:-       10-02-2011        11:47     Pagina 18




               S. Eramo et al.


               (while keeping the same 50 discs). The study of these var-        Table 4 - Ideal bone substitute features.
               ious fertility tests enabled the authors to conclude that the
               components released from the composite under the above-           Composites               Manufacturer             Estrogenic
               mentioned conditions “have an adverse effect on the fertil-                                                       activity in vitro
               ity and reproductive system of male mice” (18).
                                                                                 Charisma                 Heraeus Kulzer                 X




                                                                                                                     i
               Atkinson et al. conducted an in vitro investigation into the
                                                                                 Flowline*                Heraeus Kulzer                 X




                                                                                                                   al
               stability of compounds usually found in dental sealants, us-
                                                                                 Esthet X                 Dentsply/Caulk                 X
               ing gas chromatography/mass spectrophotometry and
                                                                                 Surefil                  Dentsply/Caulk                 X
               HPLC. Subsequently, standard BPA molecules BPA
                                                                                 Spectrum                 Dentsply/DeTrey                X
               dimethacrylate and TEGDMA (triethylene-glycol




                                                                                                                 on
                                                                                 Herculite                Kerr
               dimethacrylate) were added to saliva. The authors found           Prodigy                  Kerr
               that free BPA in saliva is stable while the BPA dimethacry-       Revolution*              Kerr                           X
               late is rapidly converted to BPA which can slow this process.     Clearfil APX             Kuraray
               This process is significantly influenced by decreasing sali-      Clearfil ST              Kuraray




                                                                                                               zi
               vary pH and temperature (19).                                     Palfique Estelite        Tokuyama
               In an interesting article, Kostoryz et al. studied in vitro the   Palfique Toughwell       Tokuyama
               cytotoxic, mutagenic and estrogenic effects of hydroxylated       Palfique Estelite LV*    Tokuyama
               metabolites of BisGMA and BFDGE (bisphenol F diglycidyl           Litefil IIA              SHOFU




                                                                                             a
               ether, a molecule found in many oxirane composites), re-          Beautifil                SHOFU
               spectively represented by Bisphenol A bis (2,3-dihydrox-          Unifil F                 GC




                                                                                          rn
               ypropyl) ether and bisphenol F bis (2,3-dihydroxypropyl)          Z250                     3M
               ether. The study showed that they neither have estrogenic         Filtek Flow*             3M
               effects nor are mutagenic, and presented a lower cyto-            Glacier                  SDI
               toxicity. They were non-mutagenic, non-estrogenic, and pre-       Wave*                    SDI




                                                                                 te
               sented minor cytotoxicity (20).                                   Heliomolar               Vivadent
                                                                                 Tetric Ceram             Vivadent
               Using a reporter gene assay, Nomura et al. tested in vit-
                                                                                 Tetric Flow*             Vivadent
               ro for estrogenic activity three monomers (Bis-GMA,
                                                                                 Progress                 Kanebo
               UDMA and TEGDME) and five polymerization initiators
               (camphorquinone (CQ), benzoyl peroxide (BPO), di-
                                                                       In
                                                                                 * Flowable composites.
               methyl-para-toluidine (DMPT), 2-dimethylamino-ethyl-
               methacrylate (DMAEMA), and 1-allyl-2-thiourea (ATU)). Two
               of the products (BPO and DMPT) even showed reduced
                                                                                 effects of composites is necessary, although the release
                                                         ni
               estrogenic activity in vitro (21).
               Al-Hiyasat et al., in a similar article to the one already men-   of estrogenic compounds from composites is basically un-
               tioned (Al-Hiyasat et al., 2002) (18), suggested that             desirable“.
               leached components from a resin-based dental compos-              Sasaki et al., in an in vivo study using the ELISA system,
                                               io


               ite (Z-100) “have adverse effects on the fertility and re-        investigated the changes in the BPA concentration in the
               productive system of female mice”(22). The same Jordanian         saliva of 21 volunteers after restoration with composite
               group made up by Darmani et al., no longer studying the           resins (of constant weight of 0.1 grams). Nine commercially
                                      iz



               composite eluate but directly the BPA dimethacrylate ad-          available products were used in this study: (Z100,
               ministered intragastrically in doses ranging from 5 to 100        Progress, Palfique, Metafile Flo, UNIFIL S, Beautifil,
               µg /µg body weight, showed significant adverse effects on         Xeno CFII, Prodigy, Clearfil ST). Thanks to this method,
                      Ed




               the fertility and reproductive systems of male and female         the authors found BPA concentrations ranging from 15 to
               mice (23).                                                        100 ng/ml of saliva (in other words in 1 ml of saliva, a re-
               Takahashi et al. demonstrated that the release of BPA from        leased amount equal to 0.15-1 g/g of substance was pres-
               polycarbonate crowns also demonstrated that the hTERT             ent). It is interesting to find that sufficient gargling, if car-
               (human telomerase catalytic subunit mRNA) is a possible           ried out immediately after polymerization, can quickly re-
               target test to evaluate the estrogenicity of the PBA (24).        move BPA completely from the oral cavity (26).
               Also of great interest is the article by Wada et al., published   Joskow et al. conducted a study in vivo on the release of
         IC




               in the well known Journal of Dental Research in which the         BPA from two sealants (Delton and Helioseal): after
               Japanese authors tested the hypothesis that commercial            sealant placement in 14 volunteers they measured BPA in
               composites, which contain various monomers and addi-              saliva and urine samples collected at prescribed intervals
               tives, may exhibit estrogenic activity in vitro. The estrogenic   immediately after, after an hour and after 24 hours. The
  C




               activity of eluates obtained from 24 resin composites placed      sealants were tested using a gas chromatograph-high res-
               into a steel mould (5 mm diameter and 1.5 mm high), and           olution mass spectrometer. The authors detected differences
               18 chemicals with concentration equal to 100 nmol/L iden-         between the salivary BPA concentrations of Delton (large
               tified from the composites tested, were examined with the         amounts, also present one hour later in the urine) and He-
©




               use of the reporter gene assay (25).                              lioseal-treated patients one hour after sealant placement.
               They revealed estrogenic activity in vitro for six of the 24      This conclusion of this article is particularly interesting as
               composites (Table 4, active composites are shown with X),         the authors (hosted by the ADA official journal) stated that
               and three of the 18 constituents: a photostabilizer (HMBP),       “Dental sealants may be a point source for low-level BPA
               a photoinitiator (DMPA) and an inhibitor (BHT) (Table 5).         exposure at levels that show health effects in rodents. Fur-
               The authors wisely concluded that “the clinical relevance         ther research is required to determine whether human ex-
               of the results of the present in vitro study remains unclear“     posure to BPA at these levels causes adverse effects” (27).
               and that “further investigation into the in vivo estrogenic       Eliades et al. did not discover release of BPA by HPLC from

               18                                                                                        Annali di Stomatologia 2010; I (3-4): 14-21
0024 4 Estrogenicity_Eramo:-         10-02-2011       11:47       Pagina 19




               Estrogenicity of bisphenol a released from sealants and composites: a review of the literature


               Table 5 - Ideal bone substitute features.

               Formula                                                                    Abbreviations                 Estrogenicity

               Monomers
               2,2-bis[4-(3-methacryloxy-2-hydroxypropoxy)-phenyl]-propane                Bis-GMA




                                                                                                                    i
               Urethane dimethacrylate                                                    UDMA




                                                                                                                  al
               Triethyleneglycol dimethacrylate                                           TEGDMA
               Diethyleneglycol dimethacrylate                                            DEGDMA
               Ethyleneglycol dimethacrylate                                              EGDMA




                                                                                                                on
               Initiators
               Camphorquinone                                                             CQ
               2,2-dimethoxy-2-phenylacetophenone                                         DMPA                                X




                                                                                                              zi
               Photostabilizers
               2-hydroxy-4-methoxybenzophenone                                            HMBP                                X
               2-(2-benzotriazolyl)-p-cresol                                              TIN-P
               2-(2'-hydroxy-5'-tert-octylphenyl) benzotriazole                           TIN 320




                                                                                               a
               Inhibitors




                                                                                            rn
               2,6-di-tert-butyl-p-cresol                                                 BHT                                 X
               4-methoxyphenol                                                            HQME

               Co-initiators




                                                                                   te
               4-dimethylaminobenzoic acid ethyl ester                                    DMABEE
               4-dimethylaminobenzoic acid 2-n-butoxyethyl ester                          DMABBEE
               4-dimethylaminobenzoic acid 2-ethylhexyl ester                             DMABEHE
               2-(dimethylamino) ethyl methacrylate                                       DMAEMA
               N,N-dimethyl-p-toluidine
                                                                         In               DMPT
               N-(2-cyanoethyl)-N-methylaniline                                           CEMA
                                                             ni

               two types of composite (Rely-a-bond and Reliance) in-               be performed in dentistry in order to avoid the absorption
               tended for the fitting of an orthodontic bracket. (28,29)           by the patient of the monomers and, in particular, the re-
               In a selective review of the literature, Azarpazhooh and            lease of BPA from sealants and composites.
                                                 io


               Main, working on the assumption that the “release of den-           Rueggeberg et al. conducted research to examine the ef-
               tal sealant components such as BPA has the potential to             fectiveness of 5 treatments (carried out for 20 seconds) in
               bind the estrogen receptors of relevant cells at sub-toxic          eliminating the residual monomer amount of the surface
                                        iz



               concentrations“, instead investigated whether the place-            of freshly polymerized sealants. They found that the use
               ment of pit- and fissure-sealant materials causes toxicity,         of pumice in cup eliminates on average 95%, while
               and thus harms patients (30).                                       pumice on cotton ball 93%, dry cotton 89%, wet cotton
                       Ed




               Having identified 377 articles in the literature related to this    86%, and an air/water spray removed 68%. The authors
               topic, the authors chose 11 of them, under strict exclusion         concluded that it appears that the most effective method
               criteria, to be investigated (though 15 studies have been           of removing the air-inhibited layer from sealants after their
               assessed). From the comparison of these studies, the au-            placement is to apply a mild abrasive (pumice) in combi-
               thors concluded that “that patients are not at risk for ex-         nation with some sort of mechanical energy (a hand scrub
               posure to BPA from the use of dental sealants”, however,            with a cotton roll or an air-driven prophylaxis cup) (32).
               “to reduce the potential for BPA toxicity from sealants, den-       Schafer et al. emphasize the possibility of treating the sur-
         IC




               tal providers should use simple clinical procedures.                face of freshly polymerized sealants with mild abrasive and
               Gioka et al. examined the structure, composition and es-            by means of a prophylaxis cup to remove residual free
               trogenic effects in vitro of particles obtained from the drilling   monomer (33).
               of two types of orthodontic composite (System 1 + and Blu-          Sasaki et al., as we mentioned before, noticed in their ex-
  C




               gloo). In particular, they investigated the estrogenicity of        periments that 30 seconds’ gargling with warm water was
               the eluate obtained after one months’ immersion, carried            sufficient to almost completely remove the BPA released
               out by grinding in saline solution in contact with an estro-        from tested composites (26).
               gen-responsive cell line (MCF-7). Both the adhesives                At the end of their review of the literature, Azarpazhooh
©




               showed estrogenic effects in vitro, and proliferation rates         and Main recommended that dental providers avoid the po-
               of MCF-7 cells increased by 160% and 128%, compared                 tential for BPA toxicity from the dental sealants by treat-
               to the control. The authors concluded that, apart from the          ing their polymerized surface layer using one of the fol-
               potentially hazardous action of adhesive aerosol particu-           lowing procedures:
               late produced by grinding, composite resin particulates may         • using a mild abrasive, such as pumice, either on a cot-
               act as “endocrinological disruptors“ (31).                               ton applicator or with a prophylaxis cup
               The last bibliographic consideration is the limited number          • having older children and adolescents gargle with tepid
               of articles that dealt with the preventive activities that can           water for 30 seconds

               Annali di Stomatologia 2010; I (3-4): 14-21                                                                                   19
0024 4 Estrogenicity_Eramo:-        10-02-2011        11:47     Pagina 20




               S. Eramo et al.


               •    washing the surface of the sealant for 30 seconds with               1996 104: 808.
                    an air-water syringe while using suction to remove flu-        8.    Hamid A, Hume WR. A study of component release from
                    ids and debris from a child’s mouth (30).                            resin pit and fissure sealants in vitro. Dent Mater 1997
                                                                                         13(2):98–102.
                                                                                   9.    Nathanson D, Lertpitayakun P, Lamkin MS, Edalatpour M
                                                                                         and Chou LL In vitro elution of leachable components from




                                                                                                                       i
               Conclusion
                                                                                         dental sealants. J Am Dent Assoc 1997 128;1517-1523.




                                                                                                                     al
               Regarding the four initial questions, the conclusions that          10.   Schafer TE, Lapp CA, Hanes CM, Lewis JB, Wataha JC,
                                                                                         Schuster GS. Estrogenicity of bisphenol A and bisphenol A
               we can draw from analysis of the literature are the following:
                                                                                         dimethacrylate in vitro. J Biomed Mater Res 1999 45:192-
               - BPA can be effectively released from composites and




                                                                                                                   on
                                                                                         197.
               sealants.
                                                                                   11.   Lewis JB, Rueggeberg FA, Lapp CA, Ergle JW e Schuster
               - In the literature, released doses vary greatly between                  GS. Identification and characterization of estrogen-like com-
                   composites (very low releases of between 0 and 1-2                    ponents in commercial resin-based dental restorative ma-
                    g) and sealants. In the first investigation on this sub-             terials. Clin Oral Invest 1999 3:107–113.




                                                                                                                 zi
                   ject, the amount released reached a maximum of 930              12.   Schmalz G, Preiss A, Arenholt-Bindslev D. Bisphenol-A
                    g per dose of 50 mg sealant. This amount was nev-                    content of resin monomers and related degradation prod-
                   er reached in subsequent researches which never re-                   ucts. Clin Oral Invest 1999 3:114–9.
                   vealed releases or, if there were any, the doses were




                                                                                                a
                                                                                   13.   Arenholt-Bindslev D, Breinholt V, Preiss A, Schmalz G.
                   from 10 to 100 times lower (1-10 g).                                  Time-related bisphenol-A content and estrogenic activity in
               - The maximum doses that may be released may ac-                          saliva samples collected in relation to placement of fissure




                                                                                             rn
                   tually have estrogenic action in vitro (i.e., on “sensitized”         sealants. Clin Oral Invest 1999 3:120–125.
                   cells), but it is necessary to note that, compared to a         14.   Pulgar R, Olea-Serrano MF, Novillo-Fertrell A, Rivas A,
                   maximum release of 930 micrograms of BPA from the                     Pazos P, Pedraza V, Navajas J M and Olea N. Determination
                   “worst” sealant, under the European regulations a child               of Bisphenol A and Related Aromatic Compounds Re-




                                                                                   te
                   of 36 kg can tolerate a daily dose of over 1800 g BPA                 leased from Bis-GMA-Based Composites and Sealants by
                   without any risks, while a teenager of 50 kg can tol-                 High Performance Liquid Chromatography. Environ Health
                   erate a dose of 2500 g. It should be emphasized that                  Perspect 2000 108:21-27.
                                                                                   15.   Tarumi H, Imazato S, Narimatsu M, Matsuo M, Ebisu S. Es-
                   uted, up to a maximum of four times.
                                                                         In
                   any acute dose of sealant is usually single or distrib-
                                                                                         trogenicity of fissure sealants and adhesive resins deter-
               - It is impossible to prevent release, but it is possible to              mined by reporter gene assay. J Dent Res 2000
                                                                                         79:1838–1843.
                   prevent the absorption of BPA by the patient. In this re-
                                                                                   16.   Fung EY, Ewoldsen NO, St Germain HA, Marx DB, Miaw
                   gard, we would suggest not only employing one or
                                                                                         CL, Siew C, Chou HN, Gruninger SE, Meyer DM Pharma-
                                                           ni
                   more of the mechanical methods proposed by differ-
                                                                                         cokinetics of bisphenol A released from a dental sealant.
                   ent authors, but especially (and perhaps these authors                J Am Dent Assoc 2000 131(1):51-8.
                   implied this) the use of a dental dam.                          17.   Manabe A, Kaneko S, Numazawa S, Itoh K, Inoue M,
               Finally, here below is a statement from the ADA (2008):
                                                io

                                                                                         Hisamitsu H, Sasa R,Yoshida T. Detection of bisphenol-A in
               “There is also evidence that some dental sealants, and to                 dental materials by gas chromatography-mass spectrome-
               a lesser extent dental composites, may contribute to very                 try. Dent Mater J. 2000 19(1):75-86.
               low-level BPA exposure. The ADA fully supports contin-              18.   Al-Hiyasat AS, Darmani H, Elbetieha AM. Effects of resin
                                       iz



               ued research into the safety of BPA but, based on current                 based dental composites on fertility of male mice. Eur J Oral
               evidence, the ADA does not believe there is a basis for                   Sci 2002 110(1):44–7.
               health concerns relative to BPA exposure from any den-              19.   Atkinson JC, Diamond F, Eichmiller F, Selwitz R, Jones G.
                       Ed




               tal material“.                                                            Stability of bisphenolA, triethylene-glycol dimethacrylate,
                                                                                         and bisphenol A dimethacrylate in whole saliva. Dent Mater
                                                                                         2002 18(2):128–35.
               References                                                          20.   Kostoryz EL, Eick JD, Glaros AG, Judy BM, Welshons WV,
                                                                                         Burmaster S e Yourtee DM. Biocompatibility of Hydroxylated
               1.   EFSA (European Food Safety Authority). Bisphenol A for use           Metabolites of BISGMA and BFDGE. J Dent Res 2003
                    in food contact materials EFSA Journal 2006; 428: 10-75.             82(5):367-371.
         IC




               2.   Staples C.A., Dorn P.B., Klecka G.M., O’Block S.T. and Har-    21.   Nomura Y, Ishibashi H, Miyahara M, Shinohara R, Shiraishi
                    ris L.R. A review of the environmental fate, effects and ex-         F, Arizono K. Effects of dental resin metabolites on estro-
                    posures of bisfenol A Chemosphere 1998 36(10):                       genic activity in vitro. J Mater Sci Mater Med 2003
                    2149-2173.                                                           14(4):307–10.
  C




               3.   Soderholm KJ and Mariotti A. BisGMA based resins in den-       22.   Al-Hiyasat AS, Darmani H, Elbetieha AM. Leached compo-
                    tistry: Are they safe? J Am Dent Assoc 1999 130:201-209.             nents from dental composites and their effects on fertility of
               4.   Bowen RL, inventor. Method of preparing a monomer hav-               female mice. Eur J Oral Sci 2004 112(3):267–72.
                    ing phenoxy and methacrylate groups linked by hydroxy          23.   Darmani H, AS. Al-Hiyasat. Reproductive toxic effect of
                    glycerol groups. U.S. patent 1965 3179623. April.                    bisphenol A dimethacrylate in Mice. J Biomed Mater Res
©




               5.   Dodds EC, Lawson W. Synthetic estrogenic agents without              2004 69A: 637–643.
                    the phenanthrene nucleus. Nature 1936 137:996.                 24.   Takahashi A, Higashino F, Aoyagi M, Kyo S, Nakata T, Noda
               6.   Olea N, Pulgar R, Perez P, Olea-Serrano F, Rivas A, Novillo-         M, Shindoh M, Kohgo T and Sano H. Bisphenol A from Den-
                    Fertrell A, Padranza V, Soto AM, Sonnenschein C. Estro-              tal Polycarbonate Crown Upregulates the Expression of
                    genicity of resin-based composites and sealants used in              hTERT. J Biomed Mater Res 2004 71B: 214–221.
                    dentistry. Environ Health Perspect 1996 104:298-305.           25.   Wada H, Tarumi H, Imazato S, Narimatsu M and Ebisu S. In
               7.   Habib CM and Kugel G. Estrogenicity of Resin-based Com-              vitro Estrogenicity of Resin Composites. J Dent Res 2004
                    posites and Sealants in Dentistry. Environ Health Perspect           83 (3):,222-226.


               20                                                                                         Annali di Stomatologia 2010; I (3-4): 14-21
0024 4 Estrogenicity_Eramo:-        10-02-2011        11:47    Pagina 21




               Estrogenicity of bisphenol a released from sealants and composites: a review of the literature


               26. Sasaki N, Okuda K, Kato T, Kakishima H, Okuma H, Abe K.        30. Azarpazhooh A and Main PA. Is There a Risk of Harm or
                   Salivary bisphenol-A levels detected by ELISA after restora-       Toxicity in the Placement of Pit and Fissure Sealant Mate-
                   tion with composite resin. J Mater Sci Mater Med 2005              rials? A Systematic Review. J Can Dent Assoc 2008 74 (2):
                   16(4):297–300.                                                     179- 183.
               27. Joskow R, Barr DB, Barr JR, Calafat AM, Needham LL,            31. Gioka C, Eliades T, Zinelis S, Pratsinis H, Athanasiou AE,
                   Rubin C. Exposure to bisphenol A from bis-glycidyl                 Eliades G, Kletsas D. Characterization and in vitro estro-




                                                                                                                    i
                   dimethacrylate-based dental sealants. J Am Dent Assoc;             genicity of orthodontic adhesive particulates produced by




                                                                                                                  al
                   2006 137(3):353–62.                                                simulated debonding. Dent Mater 2009 25: 376–382.
               28. Eliades T, Hiskia A, Eliades G, Athanasiou AE. Assessment      32. Rueggeberg FA, Dlugokinski M, Ergle JW. Minimizing pa-
                   of bisphenol-A release from orthodontic adhesives. Am J            tients’ exposure to uncured components in a dental sealant.




                                                                                                                on
                   Orthod Dentofacial Orthop; 2007a 131:72–5.                         J Am Dent Assoc 1999 130(12):1751–7.
               29. Eliades T, Gioni V, Kletsas D, Athanasiou AE, Eliades G.       33. Schafer TE, Lapp CA, Hanes CM, Lewis JB. What parents
                   Oestrogenicity of orthodontic adhesive resins. Eur J Orthod;       should know about estrogen-like compounds in dental ma-
                   2007b 29:404–7.                                                    terials. Pediatr Dent 2000 22(1):75–6.




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                                                 io
                                       iz
                      Ed
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©




               Annali di Stomatologia 2010; I (3-4): 14-21                                                                                    21
