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http://cro.sagepub.com/Critical Reviews in Oral Biology & Medicine

http://cro.sagepub.com/content/11/3/333The online version of this article can be found at:

 DOI: 10.1177/10454411000110030401

2000 11: 333CROBMW. Geurtsen

Biocompatibility of Resin-Modified Filling Materials  

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Page 2: resin obturation

BIOCOMPATIBILITY OF RESIN-MODIFIEDFILLING MATERIALS

W. GeurtsenDepartment of Conservative Dentistry & Periodontology, Medical University Hannover, Carl-Neuberg-Str. 1, D-30539 Hannover, Germany; [email protected]

ABSTRACT: Increasing numbers of resin-based dental restorations have been placed over the past decade. During this same

period, the public interest in the local and especially systemic adverse effects caused by dental materials has increased sig-

nificantly It has been found that each resin-based material releases several components into the oral environment. In partic-

ular, the comonomer, triethyleneglycol di-methacrylate (TEGDMA), and the 'hydrophilic' monomer, 2-hydroxy-ethyl-methacry-late (HEMA), are leached out from various composite resins and 'adhesive' materials (e.g., resin-modified glass-ionomercements IGICsl and dentin adhesives) in considerable amounts during the first 24 hours after polymerization. Numerousunbound resin components may leach into saliva during the initial phase after polymerization, and later, due to degradationor erosion of the resinous restoration. Those substances may be systemically distributed and could potentially cause adversesystemic effects in patients. In addition, absorption of organic substances from unpolymerized material, through unprotectedskin, due to manual contact may pose a special risk for dental personnel. This is borne out by the increasing numbers of den-

tal nurses, technicians, and aentists who present with allergic reactions to one or more resin components, like HEMA, glu-

taraldehyde, ethyleneglycol di-methacrylate (EGDMA), and dibenzoyl peroxide (DPO). However, it must be emphasized that,except for conventional composite resins, data reported on the release of substances from resin-based materials are scarce.There is very little reliable information with respect to the biological interactions between resin components and various tis-

sues. Those interactions may be either protective, like absorption to dentin, or detrimental, e.g., inflammatory reactions of soft

tissues. Microbial effects have also been observed which may contribute indirectly to caries and irritation of the pulp.

Therefore, it is critical, both for our patients and for the profession, that the biological effects of resin-based filling materialsbe clarified in the near future,

Key words. Resin-based materials, biocompatibility, leaching, adverse effects.

(I) IntroductionThe long-lasting, ongoing controversy on the hazards

for patients due to mercury exposure from amalgamhas also increased the public interest in possible adverseeffects caused by other dental restorative materials, likecomposite resins and resinous pit and fissure sealants.Therefore, a thorough scientific evaluation of the biologi-cal behavior of each of those materials must be per-formed. This analysis should be based upon detailed datareported on the release of components from these mate-rials and their local and systemic 'interactions with vari-ous tissues Schmalz and Arenholt--Bindslev, 1998).

It has been found that, due to degradation and/orcorrosion, several components are leached out from eachresin-IDased dental material into the oral environment.This, in turn. may cause adverse local and/or systemiceffects Geurtsen, 1998). In addition, direct interactions atthe interface between a restoration and the oral tissuesmay also influence biocompatibility. For example, it hasbeen reported that plaque and gingival indices as well asprobing depths adjacent to 5- to 6-year-old direct com-posite restorations were significantly higher comparedwith those at non -restored sites (Peumans et cl., 1998).

To begin with, this review article will focus on themost important parameters which characterize the bio-compatibility of a resin-based restorative material. Thiswill be followed by a critical evaluation of reports dealingwith the dispersal of substances from various resinousmaterials (resin composites, resin-modified GlCs, poly-acid-modified composite resins l'compomers'l, dentinadhesives, and pit and fissure sealants). Finally, the bio-logical effects of those materials and the substancesreleased by them will be examined, and possible clinicalconsequences will be discussed.

(11) Determination of Biocompatibilityof Resin-based Materials

Various factors determine the biocompatibility of aresin-based material, particularly the amount andnature of leachable components as well as surfacestructure of the final restoration. Several authors havereported a correlation between increased plaque accu-mulation and gingival irritation adjacent to resinrestorations and roughness and marginal adaptationof the filling (Sanchez-Sotres et al., 1969; Peumans et

al., 1998). In contrast to the local irritation caused by

3331111335~20 0 1 GRevOrl BolMe

Crit Rev Oral Biol MedI I 3) .3 3 3- 3 5 5 22000)

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Figure la. Human primary gingrival fibroblast monolayer, non-incubated control culture. Cells reveal normal morphology.Original magnification 40x.

Figure l b. 'Direct contact test' with a polymerized resin-modifiedGIC (lonosealTM). The non-cytotoxic material did not induce anycellular alteration. Cells have grown close to the specimen.Original magnification 40x.

Figure lc. 'Direct contact test' with a cured specimen of a resinmodified GIC (VitrebondTM). No viable cells are visible due to thehighly cytotoxic material. Original magnification 40x.

surface parameters, released substances can inducelocal effects in oral tissues (pulp, gingiva, oralmucosa) as well as adverse systemic reactions. Thenature of such responses is either allergic or toxic(Hume and Gerzina, 1996).

In general, two mechanisms may result in the segre-gation of components from resinous dental materials.After polymerization, unbound monomers and additivesare extracted by solvents, e.g., saliva and/or dietary sol-vents, especially during the first 24 hrs. Thus, monomer-polymer conversion is a very important aspect of the bio-compatibility of a resin restoration. But leachable sub-stances may also be generated by erosion and degrada-tion over time (Ferracane, 1994, 1995; Geurtsen, 1998).Resin degradation and erosion may be caused by photo,thermal, mechanical, or chemical influences. For exam-ple, it has been found that salivary esterases can degradethe surfaces of composite resins, which may then result inthe liberation of methacrylic substances (GCpferich,1996). The nature of the matrix monomer(s) can also sig-nificantly influence the release of components. It hasbeen reported that UDMA-based composite resin IUDMA= urethane di-methacrylate; 1,6-bis(methacrylyloxy-2-ethoxycarbonylamino)-trimethylhexaneI is less water-sol-uble than materials containing Bis-GMA ("Bowenmonomer", bisphenol-A-glycidyl methacrylate) (Pearsonand Longman, 1989).

Prior to clinical application, each resin-based restora-tive material must be thoroughly investigated for biocom-patibility by means of numerous standardized tests. Thisstructured approach was first addressed by Autian (1974),who suggested three consecutive steps or levels:

(I) screening tests (non-specific toxicity),(11) usage tests in animals (specific toxicity), and(111) clinical studies with humans.Today, a battery of in vitro and in vivo tests has been

recommended by the International StandardsOrganization for the 'Biological evaluation of medicaldevices' (ISO, Geneve, Switzerland, 1992-1997). Thosestandards include guidelines for sample preparation,tests for cytotoxicity, genotoxicity, carcinogenicity, andreproductive toxicity as well as tests to evaluate localreactions after implantation, irritation, sensitization, andsystemic toxicity. Furthermore, pre-clinical and clinicalevaluation as well as risk analysis and risk managementare defined (Schmalz, 1997).

(A) CYTOTOXICITY TESTS

Cell cultures derived from animals and humans havebeen used during the past 30 years for the determi-nation of cytotoxic effects caused by resin-basedrestorative materials Permanent cell lines and pri-mary cells, derived mainly from oral tissues, have

334 Cr0 Rev Orol Bid Med333 355 120001

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been used (Figs. 1-3) (Ratanasathien et al., 1995;Geurtsen et cil., 1998b, 1999a).

Generally, permanent cells which have been cul-tured for years show homogeneous morphology andphysiology In contrast, primary cell cultures whichmay originate from target tissues reveal a limited lifespan and are heterogeneous. Thus, an in vivo situationis generally better-simulated by primary cultures. Inaddition to the use of primary cells derived from oraltissues, artificial pulp chambers have been created.The rationale for the use of these devices is to repro-duce interactions (e.g., absorption) between releasedsubstances and dentin and to determine the signifi-cant toxic influences of those components on thepulp. These systems have, in common, dentin as a dif-fusion or adsorption barrier ('in vitro pulp chambertests') (Hanks et cil., 1988; Schmalz et al, 1999). At pres-ent, three-dimensional (3-D) cell cultures with one celltype or two different cell lines have been developed(Figs. 3a, 3b). Those cell cultures more closely resem-ble the various tissues with their complex organizationof extracellular matrix and different cell types.Therefore, interactions between resin substances andextracellular matrix may be better reproduced, in thefuture, by the application of 3-D cell cultures. On theother hand, it must be emphasized that the more com-plex In vivo-like reactions in such 3-D cell cultures maybe more difficult to interpret than responses observedin simple "2-D monolayer" cultures.

Various 'biological endpoints' are used for theinvestigation of cytotoxic effects due to solid speci-mens or extracts from polymerized samples, e.g.,

*evaluation of enzyme activity,*membrane integrity and cell metabolism (DNA-,RNA-, and protein synthesis),

*alteration of cell morphology and cytoskeleton bylight- and electron microscopy, and

*determination of cell growth inhibition and of ED90I= effective dose which causes a 50% reduction ofcell proliferation) (Geurtsen, 1988; Geurtsen andLeyhausen, 1997).

Substances liberated from resin-based dental materi-als can also interact chemically and osmotically withthe membranes of suspended erythrocytes and even-tually lead to the release of hemoglobin. The totalhemolytic activity due to segregated substances andsurface effects is assessed for evaluation of the cyto-toxicity of resin-based materials and various individ-ual substances, e.g., Bis-GMA (Fujisawa et cial, 1978,Stanford, 1980). In addition, interactions betweenhydrophobic resin components and liposomes havebeen investigated for determination of the detrimen-tal solubilizing effects on the lipid bilayer of cellmembranes (Fujisawa et cia, 1988).

Figure 2a. Sub-confluent human primary osteoblast-like cellsderived from alveolar bone, non-incubated control, cells withnormal morphology. Original magnification 40x.

Figure 2b. Osteoblast-like cells 24 hrs after incubation with theaqueous extract of a PMMA-bone cement (Palacos.m). The cyto-compatible eluate did not cause any cellular injuries. Originalmagnification 40x.

Figure 2c. Osteoblast-like cells 24 hrs after treatment with water elates of a resin-modified GIC (VitrebondTM). The eluate was extreme-ly cytotoxic; no viable cells are visible. Original magnification 40x.

I fl3j 333 355 120001 Cr0 Rev Orcil B!ol Med 3351 1(3):333-3 5 5 (2000) Crit Rev Orcal Biol Med 335 at BIOLOGICAL LABS LIBRARY on December 27, 2013 For personal use only. No other uses without permission.cro.sagepub.comDownloaded from

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Figure 3a. Primary human gingival fibroblasts after three-dimen-sional growth in a polyester mesh. The culture reveals a more 'tis-sue-like' structure rather than a monolayer (Fig. 1 a). HE staining.Original magnification 750x.

Figure 3b. 3-D culture of primary human gingival fibroblastsgrown for 4 wks (SEM). Fibroblasts grow between the meshfibers and exhibit a tissue-like organization. Original magnifica-tion 3000x. Bar, 100 ,m. (Figs. 3a and 3b courtesy of Dr.Hillmann, Hannover, Germany)

The application of various biological endpoints orthe evaluation of different parameters greatly influ-ences the results of cytotoxicity studies For this rea-son, it is difficult to compare the results from differ-ent investigations On the other hand, similar resultsobtained from a wide range of cell culture tests mayprovide a powerful tool for characterization of theeffects of resin components on host tissues.

(B) MICROBIAL TESTS

The purpose of microbial tests is to determine whether amaterial may inhibit or stimulate the growth of micro-organisms. Furthermore, studies have been undertakento evaluate whether bacteria may degrade resinousmaterials intra-orally. Micro-organisms originating fromthe oral cavity and other sites have been used. Mostauthors, however, have used cariogenic micro-organisms(e g, mutans streptococci like S. sobrinus, and lactobacil-li) for the evaluation of microbial effects of resin-basedmaterials (Updegraff et al., 1971; Orstavik and Hensten-Pettersen, 1978; Hansel et al., 1998).

(C) DETERMINATION OF GENOTOXICITY/MUTA-GENICITY AND CARCINOGENICITY

Genotoxicity and carcinogenicity are very importantparameters that can have an impact on the systemiccompatibility of a resin-based material. Genotoxicitymeans the presence of a DNA-reactive substance whichmay be mutagenic or carcinogenic (Leyhausen et al.,1995). Due to the extremely hazardous consequences,genotoxicity/mutagenicity and carcinogenicity are of veryhigh public interest. Therefore, each material must bethoroughly evaluated by several in vitro and in vivo tests,which are described in the OECD guidelines for the test-ing of chemicals (Heil et al., 1996).

In vitro assays for the evaluation of genotoxicity canbe differentiated into procaryotic and eucaryotic tests.Important bacterial tests are the classic Ames test andthe recently developed uvnu-test. Recommended eucary-otic tests are the chromosomal aberration test, thehypoxanthine-guanine phosphoribosyltransferase assay(HPRT), the sister chromatid exchange, and the DNA syn-thesis inhibition test (DIT) (Geurtsen and Leyhausen,1997, Stea et al., 1998, Schweikl and Schmalz, 1999). Sinceit is difficult to discriminate between bactericidal or cyto-toxic effects and genotoxicity, the procaryotic or eucary-otic test system cannot be the only basis for the deter-mination of DNA-damaging properties of an individualsubstance or a resin-based restorative material.Consequently, different test systems must be used for athorough monitoring of genotoxicity, e.g., procaryotic andeucaryotic tests supplemented by an in vivo assay.

A rapid and simple in vivo test for genotoxicity is theAlkaline Filter Elution assay (AFE) with viable freshwaterclams Dreissenci polymorpho and Corbicula fluminea. Thismethod allows for the quick determination of DNAstrand breaks induced by the exposure of the animals togenotoxic substances (Heil et al 1996).

(D) IMPLANTATION TESTS IN ANIMALS

Non-specific local histocompatibility of restorative resinmaterials is evaluated in vivo by means of implantation

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tests in animals, e.g., rabbits and rats. Pure specimensare implanted intramuscularly, suocutaneously, and intobones. Alternatively, fenestrated or non-fenestratedpolyethylene tubes which contain the test material areimplanted for the elimination of possible effects due todifferent surface structures of individual specimens.Tissue reactions are determined macro- and microscopi-cally as well as histochemically (Autian, 1970, 1974;Burpee et al, 1978; Wennberg et al., 1983; Henderson et al.,1987). Differences in how resin materials are used clini-cally is. the implantation of these materials into rodentsoft tissues must be consideredl when results fromimplant tests are evaluated.

(E) SYSTEMIC TOXICITYRodents are used mainly for the determination ofadverse systemic effects to resin-based restorative mate-rials. Various aspects can be investigated, includingacute oral toxicity (LD50 = lethal dose for 50% of the testanimals after oral uptake), acute inhalation toxicity,reproductive toxicity, alterations in systemic organs, andcardiovascular effects (Geurtsen, 1988). It should be rec-ognized that resin-based materials release componentsin relatively small amounts. Therefore, acute oral toxici-ty is of less value for the assessment of the biocompati-bility of resin-based dental materials.

(F) TESTS FOR EVALUATIONOF SENSITIZATION AND IRRITATION

According to ISO guidelines for the biological evaluationof medical devices applied in dentistry, resin-basedmaterials must also be tested for skin irritation and sen-sitization. For an evaluation of skin irritation, test mate-rials are applied to shaved dorsal skin. Final assessmentof skin reactions is performed 72 hrs after baseline. Forthe maximization method (sensitization), test solutionsare injected into skin adjacent to the neck (Clemmensen,1985; Altuna and Freeman, 1987; Katsuno et al., 1998).

(G) PULP STUDIES IN ANIMALS AND HUMANS

In contrast to implantation tests, pulp studies are per-formed for the determination of specific local reactions.Due to the specific application of the resinous material,these studies are referred to as "usage tests". Resin-based materials, as well as single components, havebeen investigated (Dalleske et al., 1978; Stanley et al.,1979). The experimental animals used in these investiga-tions include rats, dogs, pigs, and monkeys (Tyas andBrowne 1977;, McCluggage et al., 1980; Schmalz, 1981). Afew studies have been performed with human teeth,obtained from adolescents, which had to be extracted fororthodontic reasons (Plant and lones, 1976; Tyas andBrowne, 1977, Dalleske et al. 1978; Elbaum et al., 1992;Dejoux et al, 1993i! Due to ethical concerns about human

experiments, especially with children and adolescents,there are only a few pulp studies involving humans(Goracci et al., 1995).

It has been found that the in livo toxicity of theresinous test materials may be modified by various fac-tors. Toxic effects induced by released components canbe reduced by interaction with dentin. However, adversereactions induced by resin components can also beenhanced, e.g., by pre-existing caries lesions, acid-etch-ing of dentin ('total-etch technique'), or bacterial prolif-eration in the gap between the filling and the cavity wall(Fiore-Donno and Baume, 1966; Eriksen and Leidal,1979; Torstenson et al., 1982). Transferability of usagetests performed by various researchers or with differentspecies is limited due to technical, physiological, ormorphological factors, etc. For example, histologicaltechnique and subjective evaluation of the pulpal condi-tions may differ considerably among authors. In addi-tion, regenerative potential of the pulp or the numberand diameter of dentinal tubules may vary with differentspecies (Tyas and Browne, 1977, Geurtsen, 1988 Schilkeet al., 1999). These important factors must be consideredwhen results of various pulp studies, especially with dif-ferent species, are appraised or compared

(H) CLINICAL STUDIESClinical studies are necessary for the final assessment ofthe biological behavior of resin-based materials, espe-cially of their long-term biocompatibility. These clinicaltrials may be performed only with those materials whichhave revealed a sufficient biocompatibility in pre-clinicalscreening and usage tests. Various 'biological' parame-ters are evaluated in clinical investigations pulp reac-tions, compatibility with gingiva/periodontium! irritationof the oral mucosa, and plaque accumulation (Samaha,1982; Dunkin and Chambers, 1983; Geurtsen andSchoeler, 1997).

(111) Toxicity of Individual Resin Components(A) CYTOTOXICITY TESTS

Numerous individual ingredients of resin-based materi-als have been tested for cytotoxicity in various cell cul-ture systems with diverse biological endpoints. As a

result, it is difficult to compare data obtained in the var-ious reported studies. Ratanasathien et al. 11995)observed interactive effects-synergism, additive effects,and antagonism-of four important resin components in

Balb/c 3T3 cultures. In addition, increased exposure time

of the cells to the tested materials resulted in an

increased cytotoxicity I'toxic ranking' Bis-GMA > ure-

thane dimethacrylate (UDMA) > triethyleneglycol di-methacrylate (TEGDMA) >>> 2-hydroxy-ethyl-methacry-

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TABLE 1Substances Identified in Methanol Extracts and Aqueous Eluates (heavy-type) of Composite Resins,Polyacid-modified Composite Resins, Resin-modified Glass-ionomer Cements, and ED50 Concentrations(Geurtsen, 1998; Geurtsen et al., 1 998a,b, 1999; *according to 0ysaed et aL, 1988)

Abbr. M [u] ED50 [mM] Allergy Mut. Compound

(Co)monomersBis-GMABis-PMABis-EMABis-MAUDMA

UPGMAHEGDMAPEGDMATEGDMATEGMMATEGMAATEEGDMADEGDMAEGDMAGDMADDDMAHDMMAHDDMAPDDMABDDMAMBDDMA 1/2DBDDMA 1/2PRDMAHPMADMTCDDABEMASIMASYHEMA 1/2TMPTMAHEMAMMAMAA

InitiatorsCQBLDMBZDPICIDBPOBPE

512480452364470

96841837428621827233024219814231018625424022625838421214430417624816633813010086

166210256316242198

0.08-0.14n.d.0.21-0.780.10-0.160.06-0.47

n.d.n.d.n.d.0.12-0.26n.d.n.d.n.d.0.07-0.180.46-2.31n.d.> 5.0n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.1.93-4.10n.d.n.d.n.d.1.77-2.52> 5.0n.d.

2.17-2.400.68-2.020.24-0.340.04650.43-3.800.92-2.42

Yes

Yes

Yes

Yes

Yes2

Yes2

Yes3

Yes4

YesYes

No

YesYes

No

Yes'12

Yes2'3

Yes

"Bowen monomer"; bisphenol-A-glycidyl methacrylate"Propoxylated bisphenol-A-di-methacrylate""Ethoxylated bisphenol-A-di-methacrylate""Bisphenol-A-dimethacrylate"1 ,6-bis(methocryloyloxy-2-ethoxycarbonylamino)-2,4,4-trimethylhexane;urethane di-methacrylate"Urethane bisphenol-A-di-methacrylate"Hexaethyleneglycol di-methacrylatePentaethyleneglycol di-methacrylateTriethyleneglycol di-methacryloteTriethyleneglycol mono-methacrylateTriethyleneglycol methacrylate acrylateTetraethyleneglycol di-methacrylateDiethyleneglycol di-methacrylateEthyleneglycol di-methacrylateGlycidyl methacrylate1,1 0-Decanediol di-methacrylate1,6-Hexamethylene monomethacrylate1,6-Hexanediol di-methacrylate1,5-Pentanediol di-methacrylate1,,4-Butanediol di-methacrylateBDDMA-methanol-adduct 1/2BDDMA-auto-adduct 1/21,2-Propanediol di-methacrylateHydroxypropylmethacrylateBis(acryloxymethyl)tricyclo[5.2. 1 .02 6]decaneBenzyl methacrylate3-Trimethoxysilane propylmethacrylate1 /2-Cyclohexene methacrylateTrimethylolpropane tri-methacrylate2-Hydroxy-ethyl-methacrylateMethyl methacrylateMethacrylic acid

CamphoroquinoneBenzilDimethoxybenzoinDiphenyliodoniumchlorideDibenzoyl peroxideBenzoicacid phenylester

338 Crit Rev Oral Biol Med (2000)338 Crit Rev Oral Biol Med 1 1(3):333-355 (2000)

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Abbr.Co-initiatorsDMDDADMTDADIPATHADMPTDHEPTDCHADEAEDMAPECEMADMABEEDMABBEEDMABEHEDMAEMADEMAEEA

PhotostabilizerHMBPTINPTIN326TIN350TIN328

InhibitorsHQMEBHTMBPMBEP

PlasticizerDCHPDEHP

M [u]

213241177269135195181117165160193265277157313

228225315323351

124220312368

330390

Reaction/decomposition productsBME 136TEG 150EG 62DICH 168BEA 108MMMA 132FA* 30CA 182HC 1/2 168CIB 112BRB 156IB 204

ED50 [mM]

0.31-0.590.31-0.480.39-1.471.25-2.862.30-4.251.30-3.582.35-4.482.61-4.172.78 - > 5.00n.d.1.22-1.26n.d.n.d.n.d.n.d.

0.44-3.07n.d.n.d.n.d.n.d.

n.d.0.16-0.20n.d.n.d.

0.69-0.85n.d.

2.14-2.811.99-5.96n.d.1.83-3.491.74-3.17n.d.n.d.1.17-2.53n.dn.dn.d.n.d.

Allergy Mut.

Yes

Compound

Dimethyl-dodecylamineDimethyl-tetradecylamine

Yes2 2,6-Diisopropyl-anilineTrihexylamineDimethyl-p-toluidineDihydroxy-ethyl-p-toluidine

Yes' Dicyclo-hexylamineDiethyl-amino-ethanol

Yes' 2-(4-Dimethylaminophenol)ethanolN-(2-Cyanoethyl-)N-methylanilin4-N,N-Dimethylaminobenzoic acid ethyl ester4-N,N-Dimethylaminobenzoic acid butyl ethoxy ester4-N,N-Dimethylaminobenzoicacid 2-ethylhexyl esterN,N-Dimethyl aminoethyl methacrylateN,N-(Bisethylmethacrylate)-2-ethoxyethylamine

Yes2

2-Hydroxy-4-methoxy benzophenone2(2'-Hydroxy-5'-methylphenyl) benzotriazoleTinuvin 326Tinuvin 350Tinuvin 328

Hydroqu inone-monomethyl-ether2,6-Di-t-butyl-4-methyl phenol2,2'-Methylene-bis(6-t-butylphenol)2,2'-Methylene-bis(6-t butyl-4-ethylphenol)

Dicyclohexyl-phthalateBis(2-ethylhexyl) phthalate

YesYes'2

7?

Benzoic-acid-methylesterTriethylene-glycolEthylene-glycol1,6-Diisocyanato-hexaneBenzyl alcoholMethyl-methacrylate-methanol adductFormaldehyde (0ysaed et al., 1988)Camphoric anhydride2(3)-endo-HydroxyepicamphorChlorine benzene (from DPICI)Bromine benzene (from DPICI)iodine benzene (from DPICI)

ContaminantsTPP 262 0.32-0.45 Triphenyl-phosphaneTPSb 352 0.09-0.10 Yes23 Triphenyl-stibane

Mut. = results from genotoxicity/mutagenicity studies (data from 1umu test, 2DIT, 3AFE assay; Heil et al., 1996; 4HPRT assay; Schweikl and Schmalz, 1999). Allergy =

resin components which may cause hypersensitivity/allergy in humans (Jordan et aL, 1979; Kanerva et al., 1 994b, 1995; Richter and Geier, 1996; Richter, 1996)

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Biomass production of L. acidophilus after incubationwith Bis4GMA and UDMA for 40 h

0ow00

A

120

100

-

I I

go

40 -J

20 I0 r

IN a

0011c a I I_ :L 'J*IBis-GMA UDMA

Biomass production of L. aiophilus after incubationwith EGDMA and TEGDMA for 40 h

00a

v

140

120

in0

600 .

B EGDMA TEGDMA

Figure 4a. Bis-GMA and UDMA significantly inhibited growth ofL. acidophilus (Hansel et al., 1998).Figure 4b. In contrast to base monomers, the relativelyhydrophilic comonomers EGDMA and TEGDMA significantlypromoted proliferation of L. acidophilus (Hansel et al., 1998).

late (HEMA)I. These authors concluded that exposuretime as well as interactions between and among variousreleased substances significantly influence biocompati-bility. The high cytotoxicity of the monomers Bis-GMA,UDMA, and TEGDMA was corroborated by other studies(Hanks et al., 1991; Lehmann et al., 1993; Yoshii, 1997). Ithas been reported that TEGDMA can induce lipid peroxi-dation of microsomes. Furthermore, this comonomeralso exhibited surfactant-like potency which may causedetrimental solubilization of the lipid bilayer of cellmembranes (Terakado et al., 1984; Fujisawa et al., 1988).

Geurtsen et al. ( 1998a) investigated cytotoxic effectsof 35 single monomers and additives of compositeresins in permanent 3T3 cells and three primary humanoral fibroblast cultures (Table 1). ED50 values varied sig-nificantly, from 0.0465 mM to > 5 mM. The testedinhibitor 2,6-di-t-butyl-4-methyl phenol (BHT), thephotostabilizer 2-hydroxy-4-methoxy benzophenone(HMBP), the initiator diphenyliodonium chloride

(DPICL), and the contaminant triphenyl-stibane (TPSb)exhibited severe cytotoxic effects. Within the groups of(co)monomers and (co)initiators, high or moderatecytotoxic reactions were observed, whereas the evaluat-ed decomposition/reaction products caused only mod-erate or slight effects (Table 1). The most importantphoto-initiator, camphoroquinone, which was found insignificant amounts in aqueous extracts from resin-based materials, revealed moderate cytotoxic effects.This was confirmed by Atsumi et al. (1998) with perma-nent human submandibular-duct cells.

Analysis of the data from various reports, takentogether, indicates that, for most of the severely cytotox-ic resin components, less toxic alternatives are available.In particular, the cytotoxicity of TEGDMA may be of greatclinical interest. This relatively hydrophilic comonomeris released from many resin-based materials in consider-able amounts (Spahl and Budzikiewicz, 1994; Geurtsen,

Blomass production of S. sobrinus after incubationwith BIs.GMA and UDMA for 10 h

e-W00

0

A BIs4MA UDMA

Biomass production of S. sobrinus after incubationwith EGDMA and TEGDMA for 10 h

I0

Il

140

100..................i........., .. ........

o0 .- ........

40-!

20 I011 IiI0 I IiId, J." I

B EGDMA TEGDMAFigure 5a. In contrast to L. acidophilus, proliferation of S. sobrinuswas not affected by Bis-GMA (Hansel et al., 1998).Figure 5b. EGDMA and TEGDMA also enhanced growth of S.sobrinus (Hansel et al., 1998).

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1998; Spahi et al., 1998). Due to its high cytotoxic poten-cy, this substance may significantly contribute to adverselocal and systemic effects. The liberation of TEGDMAfrom resin restorations, therefore, should be minimizedor prevented Furthermore, it must be emphasized thatthere is no cell line which is consistently more sensitivecompared with others (Geurtsen et al., 1998a; MacDougallet al, 1998). Thus, each substance must be comprehen-sively screened for cytotoxicity by rneans of different per-manent and primary cell cultures. The application of anIi vitro pulp chamber device (dentin barrier assay) mayhelp to simulate complex intra-oral interaction whichcan significantly modify cytotoxic effects in vivo

(B) MICROBIAL EFFECTS

There is currently a great controversy over whether pul-pal irritation due to a resin restoration is mainly causedby bacteria proliferating between the cavity wall and thefilling lBrannstrbm and Vojinovic, 1976; Qvist, 1993).Solid- as well as liquid-phase systems have been used todetect whether single-resin components can influencemicrobial growth (Updegraff et al., 1971; Hansel et cl.,1998). Proliferation of mutans streptoccoci (S. sobrinus)and lactobacilli (L. acidophilus) was either inhibited, pro-moted, or not influenced in a dose-dependent manner bythe substance that was tested. Bis-GMA did not altergrowth of S. sobrinus, whereas proliferation of L. acidophiluswas significantly inhibited. UDMA reduced proliferationof both cariogenic pathogens. Generally, only very smallamounts of these hydrophobic substances are releasedinto an aqueous environment. Taken together, thoselarge base monomers should not have microbial effects.

The water-soluble comonomers EGDMA (ethyleneglycol di-methacrylate) and TEGDM\AA, however, promo-ted proliferation of S. sobrinus and L acidophilus (Figs. 4a,4b, 5a 5b) iHansel et al., 1998). Analysis of these dataclearly shows that the severely cytotoxic comonomersEGDMA and TEGDMA, which are present in considerableamounts in aqueous extracts of numerous resin-basedmaterials, may significantly promote growth of cario-genic pathogens (Spahl et al 1998). Thus, cytotoxic prop-erties and m icrobial growth promotion of thesecomon .mers may contribute to pulpal injury.

(C) In ViVO STUDIES

The LD,o concentrations (acute oral toxicity) of severalsubstances have been evaluated in experimental animalstudies The LD50 (per I kg body weight) was 950 mg fordibenzoyl-peroxide and 8400 mg for methyl-methacrylate(Deichmann. 941 1 Geurtsen, 1988). Due to the relativelylow concentrations of components released from poly-merized resin restorations in the oral cavity, acute oral(systemic) toxicity is not of great value in the assessment

of the biocompatibility of those materials.It has been reported that methyl methacrylate

(MMA) may be teratogenic and can cause adverse car-diovascular effects in animals (Phillips et al., 1971, Singhet al., 1972; Karlsson et al., 1995). In addition, subcuta-neous polymethyl-methacrlylate implants inducedmalignant tumors in rodents (Oppenheimer et al., 1955).

Very few experiments have been performed to assessthe acute local (pulp) toxicity of individual resin sub-stances. It was found that the degree of pulpal alter-ations induced by those components correlates withcavity depth (Stanley, 1992). Two substances (dibenzoylperoxide, 2-hydroxy-4-methoxy-benzophenone) causedpulpal inflammation in teeth of monkeys when appliedto cavities without a protective lining (Stanley et a)., 1979)-

(IV) Conventional and Polyacid-modifiedComposite Resins

(A) COMPOSITION AND LEACHING OF COMPONENTSConventional composite resins contain a polymerizableorganic matrix, inorganic reinforcing fillers, and a silanecoupling agent which bridges the organic and inorganiccomponents (Ferracane, 1995). The organic matrix con-sists of several (co)monomers, e.g., Bis-GMA, UDMA, eth-yleneglycol di-methacrylate compounds ( EGDMA,D/TEGDMA, etc.), and various additives ((co)initiators,stabilizer, inhibitorl (Table 1). In general, all organicingredients of a composite resin are extractable byorganic solvents, like methanol, after polymerization. Afew components, however, are also leached into an aque-ous medium. In particular, considerable amounts ofTEGDMA may be released by polymerized compositeresin into water. Bis-GMA, UDMA, EGDMA DEGDMA1,6-hexanediol di-methacrylate, methyl methacrylate,camphorquinone, 4-N,N-dimethylamino-benzoic acidethyl ester, and various other substances have beenidentified in minor concentrations in aqueous extracts(Geurtsen, 1998; Spahl et al., 1998).

Several composite resins liberated formaldehydeinto water over a long time period (11 5 days) Thisdegradation product was especially noted in extractsfrom specimens with an unpolymerized oxygen-inhib-ited surface layer. The amount of extracted formalde-hyde was partly in the order of magnitude which wasfound to cause local allergic reactions (Oysaed andRuyter, 1988; Koch and Staehle, 1997). Inorganic sub-stances (ions) like silicon, boron, sodium, and bariumare also released from filler particles in trace amounts

(0ysed et a)., 1988).'Compomers' (polyacid-modified composite resins)

have been developed to combine the fluoride release ofglass-ionomer cements (GICs) with the mechanical prop-

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erties of composite resins. Thus, these materials arecomposed of an ion-releasing glass, mainly calcium-alu-minum-fluoro-silicate glass, and a polymerizable organ-ic matrix. The fillers are partially silanized to couple theglass with the polymer network. In addition to conven-tional monomers (Bis-GMA, UDMA), the organic matrixof compomers contains bi-functional monomers withtwo carboxylic groups and two double-bond functions,e.g., TCB (tetracarboxylic butyl methacrylate), which issynthesized from butane-tetracarboxylic acid and 2-hydroxyethyl methacrylate (HEMA) (Attin and Buchalla,1998; Meyer et al., 1998). The bi-functional monomers canreact with methacrylates by radical polymerization andby acid-base reaction to bring about release of ions fromthe glass in the presence of water. However, compomersdo not contain water. Thus, no significant acid-base neu-tralization occurs during polymerization. Those materi-als, therefore, are much closer to composite resins thanto glass-ionomer cements (Meyer et al., 1998).

There are very few data on the release of substancesfrom 'compomers'. The aqueous eluates of polyacid-modified composite resins were analyzed by gas chro-matography/mass spectrometry (GC/MS) and high-per-formance liquid chromatography (HPLC). Ethylene gly-col compounds (comonomers) and the hydrophilicmonomer HEMA were the chief constituents identified inthese aqueous extracts (Geurtsen et at., 1998b; Hamid etal., 1998). In addition, the following decomposition prod-ucts of base monomers and several co-initiators werefound: N-(2-cyanoethyl)-N-methylaniline (CEMA), 4-N,N-dimethyl amino benzoic acid ethylester (DMABEE),and N,N-dimethyl amino ethyl methacrylate (DMAEMA)(Geurtsen et al., 1998b). Due to the ion-leaching glassfillers, compomers may also release fluoride, especiallyduring the first few days after polymerization. But it mustbe emphasized that those materials leach out consider-ably smaller amounts of fluoride than do conventionaland resin-modified glass-ionomer cements (Attin andBuchalla, 1998; Geurtsen et at., 1998c, 1999b).

(B) CYTOTOXICITYSolid specimens and extracts of polymerized samples ofcomposite resins have been tested in various cell cul-tures. The results of those studies have varied signifi-cantly, depending on the product tested (Lampert andHeidemann, 1980; Tronstadt and Wennberg, 1980). It wasreported that polymerized specimens of one hybrid-typecomposite resin were moderately cytotoxic during a four-year period in permanent and primary human oral cellcultures. Non-polymerized samples of this product, how-ever, were severely cytotoxic and revealed genotoxiceffects (Geurtsen, 1987a, 1988). Aqueous eluates of sev-eral hybrid-type composite resins induced only moder-ate cytotoxic reactions (Geurtsen, 1987b).

Nakamura et al. (1985) tested various consecutiveextracts of light-curing products over six weeks in HeLacells. The first eluates caused moderate to severe cellularalterations which were not observed with later extracts. Incontrast, set material of light-cured and chemically curedcomposite resins revealed slight or no toxic effects whentested in an artificial pulp chamber made up of dentinslices placed between the materials and the cell cultures(Hanks et al., 1988). Polymerized composite resin separat-ed from the extraction medium by etched dentin hadtoxic potency higher than that of specimens placed onunetched dentin (Hume, 1985). This observation indi-cates that the application of the 'total-etch technique'may be associated with a higher risk for pulp irritationdue to composite resin restorations, even in combinationwith dentin bonding (Gerzina and Hume, 1996).

Mohsen et al. (1998) investigated the influence of var-ious parameters on the cytotoxic potential of severallight-curable UDMA-based composite resins. Cytotoxicitydecreased with increasing curing time and higher agingtime. A reduction of cytotoxicity was also observed whenpolished samples without an oxygen-inhibited surfacelayer were tested. Furthermore, cell viability increasedwhen specimens were extracted with water, ethanol, orother organic solvents prior to cell culture experiments(Mohsen et al., 1998; Rathbun et al., 1991).

The cytotoxic potency of polyacid-modified compos-ite resins varied considerably depending on the producttested (Pertot et al., 1997; Geurtsen et al., 1998b). Aqueouseluates of two polyacid-modified composite resinsinduced moderate injuries in permanent 3T3 fibroblastcultures, whereas one product (DyractTM Cem, De TreyDentsply) caused severe cytotoxic effects. The severelytoxic extract contained a very high concentration ofTEGDMA, whereas the two moderately cytotoxic compos-ite resins released only small amounts of comonomers,like HEMA, and various ethylene glycol compounds.

In summary, then, cytotoxicity of composite resinsvaries depending on the product tested and especiallyupon the quantity of leachable components. An opti-mum polymerization, therefore, is of high importance forthe cytocompatibility of those materials. Furthermore,extractable amounts of components should be reduced,e.g., by the use of less-water-soluble components.Severely cytotoxic substances should be replaced by lesstoxic alternatives, if available.

(C) MICROBIAL EFFECTS

Fresh specimens of several composite resins inhibitedmicrobial growth (0rstavik and Hensten-Pettersen,1978). But other authors found no significant influenceon the proliferation of micro-organisms (Updegraff et al.,1971). Recently, it was reported that the water extract ofa hybrid-type composite resin promoted the growth of

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the caries pathogen L. acidophilus. It was found that thiseluate contained a high amount of TEGDMA. Aqueousextracts of another composite resin with a low concen-tration of TEGDMA, however, inhibited growth of thismicro-organism. Thus, the release of high concentrationsof TEGDMA may stimulate proliferation of cariogenicbacteria within marginal gaps which then may contributeto recurrent caries and pulpal irritation (Figs. 4a, 4b, 5a,5b, 6a, 6b). Release of microbial growth-stimulating sub-stances, therefore, should be minimized or prevented(Hansel et al., 1998). Alternatively, antibacterialmonomers (like methacryloyloxydodecylpyridinium bro-mide, MDPB) or fillers, e.g., ApacideriM, based on apatitecontaining silver and zinc, have been added to compos-ite resins. These experimental materials significantlyinhibited proliferation of cariogenic bacteria (Syafiuddinet al., 1997. Imazato et a)., 1998c).

(D) In ViVO STUDIES

Local, non-specific toxicity of polymerized compositeresins was determined after implantation into varioustissues, e.g, muscle and bone. Generally, compositeresins caused only slight to moderate tissue alterationswhich decreased over time (Chan et a)., 1972; Howdenand Silver, 1980, Wennberg et al., 1983).

Numerous pulp studies have been performed for theevaluation of local specific reactions. The results of theseusage tests have yielded contradictory results. Anabsence of or only slight pulp irritations were reportedby Retief et al. ( 1973) and Suzuki et al. ( 1995). Other inves-tigators, however, observed moderate to severe reactions(Tronstadt and Spangberg, 1974; Valcke et al., 1980).

It has been observed that several co-factors influ-ence the pulp toxicity of composite resins. A protectivecavity lining coupled with an increased thickness inremaining dentin reduced the risk of pulpal inflamma-tion (Quist, 1975; Dalleske et al., 1978) On the otherhand, previous damage to the pulp due to deep carieslesions and acid-etching of dentin on the cavity floorenhanced toxicity (Fiore-Donno and Baume, 1966;Stanley et a)., 1 975; Eriksen and Leidal, 1979).

Several authors have noted a correlation betweenpulpal irritations of resin-restored teeth and bacteria(and their by-products), whereas material toxicity per sewas of no significance (Brannstrom and Vojinovic, 1976;Torstenson et a/., 1982; Cox, 1992, Cox and Suzuki, 1994).It should be recognized, however, that comonomersreleased from a resin filling into marginal clefts maystimulate microbial growth and consequently may, atleast indirectly, contribute to pulpal irritation caused bythose bacteria (Hansel et a)., 1998). However, pulpalinflammation was also found in resin-restored teethwithout bacterial microleakage, especially when low-vis-cous bonding agents had been applied to thin acid-pre-

treated dentin layers (Horsted ct al), 1986; Quist et al.,1989, Fujitani et at., 1992). When one considers the per-meability of dentin, especially after acid pre-treatment,and the release of cytotoxic and hydrophilic

A

B

Figure 6a. This is a 20-year-old patient presenting with an upperright first molar with an occlusal amalgam restoration and a com-posite resin filling. The amalgam restoration reveals marginalgaps; the resin filing shows only a slight marginal discoloration.

Figure 6b. The restorations were removed without excavation ofcarious dentin. The amalgam cavity is caries-free, whereasextensive recurrent caries is visible beneath the compositerestoration. This caries recurrence may have been caused by thegrowth of cariogenic micro-organisms due to release ofcomonomers, e.g., EGDMA or TEGDMA (Hansel et a/., 1998).

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(co)monomers from polymerized composite resin, it isreasonable to suggest that those substances can con-tribute significantly to pulp injuries (Hume, 1985;Hamid et al., 1996; Eick et al., 1997; Marshall et al., 1997;Abou Hashieh et al., 1998; Gale and Darvell, 1999). Onthe other hand, it must be emphasized that the barrierfunction of dentin may protect the pulp from toxic influ-ences. Thus, for example, diffusion of monomersdecreases significantly with thicker dentin, and the pen-etration of bacterial by-products is also reduced bydentin (Pissiotis and Spangberg, 1992; Hamid et al.,1996; Hamid and Hume, 1997a).

Several retrospective and prospective studies on theclinical long-term performance of composite resins havebeen reported (Mjbr et al., 1990; Wilder et al., 1991;Roberts et al., 1992). In general, evaluation of the fillingsincluded determination of pulpal conditions. A four-yearclinical study with 1209 Class I and Class 11 restorationsrevealed long-lasting post-operative pain or pulpitis asa cause for failure in only four cases. Glass-ionomercement was applied as a base in all cavities.Additionally, areas with thin dentin were covered with acalcium hydroxide cement (Geurtsen and Schoeler,1997). A meta-analysis of 16 long-term clinical studies ofposterior composite resin fillings also indicated noincreased risk of pulpal irritation (El-Mowafy et alc., 1994).

In summary, there is sufficient evidence that vari-ous factors associated with composite resin restora-tions possess tissue-damaging potency. Furthermore,pulp inflammation/necrosis as a consequence of a com-posite resin filling is probably due to the interaction ofseveral tissue-irritating parameters rather than to a sin-gle detrimental factor. Usage tests as well as long-termclinical studies indicate that composite resins do notpose a special risk for the dental pulp if they are prop-erly applied.

(V) Resin-based Pit and Fissure Sealants

(A) COMPOSITION AND RELEASE OF SUBSTANCESResinous pit and fissure sealants consist of an unfilled orfilled organic matrix. Like composite resins, the matrix ofdental sealants is composed of a mixture of various(co)monomers (mainly Bis-GMA, UDMA, and TEGDMA)and additives. Some sealants also contain fluoride-releasing components. Either clear, tinted, or opaqueauto-polymerizing and visible-light-curable products areavailable (Waggoner and Siegal, 1996).

Public concern about the safety of resin sealants wasgreatly increased by the report of Olea et al. (1996). Usingthe HPLC technique, these authors reported that thepotentially estrogenic substance bisphenol-A wasreleased from fissure sealants in vivo. It must be empha-sized that this observation was mainly based on one

female patient who had received fissure sealants twoyears earlier. Bisphenol A, however, is rapidly releasedfrom polymerized sealants and is quickly excreted(Ashby, 1997). Thus, it is more than unlikely that dentalsealants can serve as a long-term intra-oral source forthe leaching of bisphenol A. Olea et al. (1996) also report-ed that resin oligomers may liberate bisphenol-A afterstorage in alkaline (pH 13) or acidic (pH 1) media at100°C for 30 min. But these conditions do not exist invivo. In contrast to the findings by Olea et al. (I1996), usingHPLC or GC/MS methodology, a number of authorsreported that the product investigated by Olea et al.(1996), and other sealants as well, did not releasebisphenol-A into water or ethanol. TEGDMA, however,was released from several sealants (Hamid and Hume,1997b; Nathanson et al., 1997; Geurtsen et al., 1999a).Interestingly, TEGDMA was not identified by Olea et al. intheir analysis. This strongly suggests that Olea et al.(1996) may have misinterpreted TEGDMA peaks asindicative of bisphenol-A. Due to different mass spectraand retention times, bisphenol-A and TEGDMA can beeasily distinguished from each other by GC/MS.Accordingly, no bisphenol-A was found with GC/MS(Geurtsen et al., 1999a).

In addition to TEGDMA, monomers (like Bis-GMA,UDMA), comonomers (mainly ethylene glycol com-pounds), and additives [e.g., camphorquinone andDMABEE (4-N,N-Dimethylaminobenzoic acid ethylester)l leach out from sealants in minor quantities(Hamid and Hume, 1997b; Nathanson et al., 1997; Spahlet al., 1998; Geurtsen et al., 1999a).

(B) BIOCOMPATIBILITYFew in vitro studies have been published about the cyto-toxicity of resinous pit and fissure sealants. There are noin vivo data available except for one case report of anallergic reaction to the sealants (see below) (Hallstrbm,1993). Water extracts of two sealants were investigated inhuman embryonic lung fibroblast cultures. It wasobserved that both materials were more cytotoxic thanPMMA (polymethyl methacrylate) acrylic controls (Rawlset al., 1992). Aqueous eluates of four sealants causedmoderate-to-severe inhibition of cell growth in 3T3 cul-tures. Considerable cytotoxic effects in permanent 3T3fibroblasts were caused by one product which leachedhigh amounts of TEGDMA into de-ionized water(Geurtsen et al., 1999a).

In general, only sparse results on biocompatibilityand release of substances from these materials are avail-able. These limited data as well as the similarities incomposition and degradation compounds indicate thatleaching and biological behavior of resin-based pit andfissure sealants should be comparable with that of com-posite resins.

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(VI) Dentin Adhesives

(A) COMPOSITION AND RELEASE OF SUBSTANCES

Members of the group of dentin adhesives differ con-siderably in their chemical composition, mode ofaction, and clinical handling. Dentin adhesives aremainly used to improve the bonding between dentinand composite resins. In addition, dentin bondingagents are applied as cavity liners and for treatment ofhypersensitive teeth with exposed root surfaces (Coxand Suzuki, 1994; lain et al., 1997; Schuckar andGeurtsen, 1997)

Depending on the product, dentin adhesives mayconsist of one to three components ('bottles').Conditioners (etchants) containing acid (e.g., phosphor-ic acid, maleic acid) or EDTA are used for partial or totalremoval of the dentin smear layer and for the structuralmodification of the binding substrate (Eick et al., 1997).The dissolved smear layer and conditioner are removedby thorough rinsing with water. This results in the open-ing of most orifices of the dentinal tubules. Primersconsist of a 'hydrophilic' monomer (e.g., HEMA) or amixture of monomers dissolved in solvents like water,ethanol, or acetone. Primers are applied to expand orre-expand the conditioned demineralized collagen net-work and to increase the wettability of the hydrophilicsubstrate for the hydrophobic components of the bond-ing agent. Furthermore, some dentin primers (e.g.,SyntaciM) contain glutaraldehyde for stabilization ofdemineralized collagen fibers. B3onding agents aremainly unfilled mixtures of various hydrophobic and/orhydrophilic co)monomers (e.g., Bis-GMA, UDMA,TEGDMA, HEMA) and additives. They are used to bindthe conditioned and/or primed dentin surface withcomposite resin. Several moderr products combineconditioner and primer ('self-conditioning primers') orprimer and bonding agent into one bottle.

Very little is known about the release of compo-nents from dentin adhesives. Nor-polymerized speci-mens of various dentin bonding agents were extractedby acetone. Gas chromatography/mass spectrometry(GC/MS) analysis revealed that the eluates predomi-nantly contained ethylene-glycol methacrylates, suchas EGDMA and D/TEGDMA, as well as smalleramounts of H-EIMA and MMA (methyl methacrylate)(Kanerva et al., 1994a). Geurtsen et al. ( 1999c) analyzedaqueous extracts of five modern dentin adhesives byGC/MS The adhesives analyzed released several sub-stances, predominantly EGDMA, TEGDMA, and HEMA,into de-ionized water. All materials released cam-

phoroquinone Additionally, four adhesives alsoreleased other (co)initiators, e ., 4-N,N -dimethy-laminobenzoic acid ethyl ester (DMABEE) anddiphenyliodoniumchloride (DPICI).

(B) BIOCOMPATIBILITY OF DENTIN ADHESIVES

(1) In vitro studies

Rakich et al. (1998) investigated the effects of four com-ponents of dentin bonding agents on the mitochondrialactivity (MTT assay) of macrophages which are importantin wound healing and inflammatory reactions. HEMA, 4-methacryloxyethyl-trimellitic anhydride 14-META), Bis-GMA, and UDMA were evaluated. The cytocompatibilityvaried significantly: HEMA (best compatibility) > 4-META >>> Bis-GMA > UDMA. A similar ranking of toxic-ity was found in experiments with Balb/c 3T3 mousefibroblasts (Ratanasathien et al., 1995). Aqueous extractsof five adhesives were tested in 3T3 fibroblast cultures.The cytotoxic potency of those products varied consider-ably. The most toxic material, which almost completelyinhibited cell growth, released TEGDMA in highamounts. Two materials released high concentrations ofHEMA and reduced cell proliferation considerably.Additionally, two products liberated small quantities of(co)monomers (EGDMA, TEGDMA, or HEMA) that affect-ed cell growth only slightly (Geurtsen et l., 1999c).

The influence of dentin on the cytotoxicity of fourdentin adhesives was evaluated with L 929 fibroblasts.Each product was tested using dentin slices with highand low hydraulic conductance. Generally, all adhesiveswere significantly more cytotoxic when slices with highhydraulic conductance were applied (Abou-Hashieh et al.,1998). These observations confirm that the nature andquantity of released substances, as well as the barrierfunction of dentin, decisively influence the cytotoxicpotential of dentin adhesives. Some products releasehigh quantities of (co)monomers (TEGDMA, HEMA)which may cause pulpal alterations, especially whenapplied in areas with a thin dentin layer. Thus, only goodcytocompatible dentin adhesives are recommended as apulp protective cavity lining on thicker dentin layers.

(2) Microbial effects

Several micro-organisms are associated with carieslesions, especially mutans streptococci (S. mutans Ssobrinus) and lactobacilli (Emilson and Krasse, 1985).Bacteria and their by-products may also cause pulpalirritation. Therefore, dentin adhesives with antimicrobialproperties would be of great clinical advantage for pro-phylaxis of recurrent caries as well as for prevention ofpulpal alterations due to microbial effects.

The experimental incorporation of the monomer,methacryloyloxy dodecylpyridinium bromide, into a self-etching primer significantly increased the antimicrobialpotency, even after polymerization (Imazato et al., 1998a,b).A screening of seven adhesives revealed antimicrobialeffects of conditioners/etchants (EDTA, phosphoric acid).Antibacterial properties were also observed with primers

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containing maleic acid or glutaraldehyde. The other primersand most bonding agents, however, did not show anyantimicrobial property (Emilson and Bergenholtz, 1993).Similar observations with other self-conditioning primershave been reported (Imazato et al., 1998c). A polymerizingdentin adhesive containing glutaraldehyde (SyntacTM) hada strong antibacterial effect when tested on eight microbialcultures. But set and aged materials were not tested (Fragaet al., 1996). It can be concluded that most dentin adhesivesexhibit antimicrobial effects only in the initial phase afterapplication. Thus, generally speaking, no anti-cariogenicand pulp-protecting effect due to long-term antimicrobialpotency of dentin adhesives can be expected.

(3) In vivo studiesDentin bonding agents may irritate the dental pulp bythree mechanisms: (I) by the conditioner/etchant, (11)direct cytotoxic effects due to released substances, and(111) by bacteria or microbial by-products. Additionally, itmust be appreciated that dentin conditioning/etching('total-etch technique') can significantly increase trans-port of released organic substances through dentin.Thinner dentin layers may enhance pulpward diffusion ofmonomers as well as the total leaching of substancesfrom polymerized dentin adhesive (Hamid et al., 1996;Hamid and Hume, 1997a). Interestingly, it was observedthat diffusion of HEMA and TEGDMA, in particular,through dentin is not prevented by positive hydrostaticpressure (Gerzina and Hume, 1995). The application of aHEMA-containing bonding resin in combination with acomposite resin reduced TEGDMA diffusion throughdentin only slightly in comparison with a composite resinthat was used without an adhesive. But the dentin adhe-sive-composite resin combination resulted in additionalpulpward diffusion of considerable quantities of releasedHEMA. Thus, dentin adhesives that leach high amountsof the cytotoxic (co)monomer may cause pulp alteration,especially when the 'total-etch technique' is used. Nopulp-protective effects due to reduced diffusion ofTEGDMA leached from composite resin can be expected.

Several studies on the response of the pulp to dentinadhesives have been performed. The results of thesestudies are not easily comparable because of the differ-ences in the composition of the adhesives and the tech-niques used. The application of a three-component prod-uct, according to the principles of the total-etch tech-nique, did not cause significant pulpal irritation of mon-key teeth over a 90-day period (Inokoshi et al., 1998).Similar observations were made by White et al. (1994) inadult rhesus monkeys. Evidence was presented that irre-versible pulpal inflammation is not induced when dentinadhesives are applied in cavities with a thick dentin layer,particularly in caries-free dentin preparations extendingjust inside the dento-enamel junction (Goracci et al.,

1995; Pameijer and Stanley, 1995; Gilpatrick et al., 1996).Several investigators have compared the reactions of

exposed and non-exposed pulps after the application ofdentin adhesives in combination with dentin acid-etching.No differences were found between exposed or non-exposed pulps and between the adhesives and theCa(OH)2 group, which generally served as a control(Akimoto et al., 1998; Cox et al., 1998; Tarim et al., 1998). Butdetrimental effects of the total-etch technique with dentinadhesives in vital-pulp-capping of monkey teeth werereported by Pameijer and Stanley (1998). Interestingly,these authors also observed that micro-organisms werepresent in a large percentage of vital and non-vital teeth.Thus, bacteria had no significant influence on the reactionof the pulps after application of dentin adhesives.Additionally, it was found that pulps directly capped withdentin adhesive may develop a sub-acute foreign bodyresponse due to impacted resin particles. The authors con-cluded that the long-term effect of resin particles in pulpaltissue needs further clarification (Gwinnett and Tay, 1998).

These contradictory results clearly show that thereare insufficient data for a reasonable conclusion on theeffects of dentin adhesives on the pulp. In particular, itmust be noted that the abovementioned histologicalpulp studies covered a period of only about threemonths. Consequently, the long-term, in vivo, biologicaleffects are not known. Although dentin adhesives may beof benefit to reduce marginal microleakage and to pre-vent pulpal hypersensitivity in cavities with a relativelythick dentin layer, dentin in deep cavities should be cov-ered by a cavity liner for pulp protection. This is corrob-orated by in vitro observations indicating that HEMA andTEGDMA may cross dentin even under positive hydro-static pressure. Exposed pulps should be directly cappedwith Ca(OH-)2 until there is enough scientific evidence insupport of the long-term clinical efficiency and biocom-patibility of various dentin adhesives.

(VII) Resin-modified Glass-ionomer Cements

(A) COMPOSITION AND LEACHING OF SUBSTANCES

Resin-modified glass-ionomer cements (rmGIC) containion-releasing glass particles, water-soluble polyacrylicacids, light-curable monomers (e.g., HEMA), and addi-tives. Various products are composed of photo-curableside-chains linked to water-soluble polymeric acids. Incontrast to polyacid-modified composite resins (com-pomers), rmGICs contain water and thus exhibit an acid-base reaction with salt formation and a free-radical poly-merization (Kakaboura et al., 1996; Nicholson, 1998). Dueto their ease of application in comparison with conven-tional GICs, resin-modified systems are being increas-ingly used clinically, especially in pediatric dentistry

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(Vaikuntam, 1997).Several investigators evaluated the release of fluo-

ride from rmGlCs )Forss, 1993; Ulukapi et al., 1996; Friedlet al., 1997; Geurtsen et al., 1998c). The release of fluoridevaried significantly, depending on the product tested andthe extraction medium. In general, less fluoride leachedfrom rmGlCs than from conventional GICs (Geurtsen,1998). Leaching of organic components from variousrmGICs into distilled water was investigated by Hamid etal. 11998). HEMA was the only compound detected in thewater extracts by HPLC. Aqueous eluates of two rmGlCswere analyzed with GC/MS (Geurtsen et al., 1998b). Bothproducts released HEMA into de-ionized water. In addi-tion, one material (Vitrebond'IMm) released the initiator,diphenyliodoniumchloride (DPICI), which was also pres-ent in one dentin adhesive (SyntaciM) (Geurtsen et al.,1999c). DPICI was identified by its GC-decompositionproducts chlorine-, iodine- and bromine benzene. Itmight be possible, however, that these highly toxic sub-stances are generated during polymerization and arethereafter released into an aqueous environment.

Our knowledge about the quality and amount ofleachable components from rmGlCs is insufficient.Besides (co)monomers, (co)initiators, etc., reaction ordegradation products, e.g., benzenes, are released whichmay then cause adverse local and/or systemic effects.These leachable reaction or degradation products, there-fore, should be identified as soon as possible.

(B) BIOCOMPATIBILITY OF RESIN-MODIFIED GICs

The cytocompatibility of various conventional and resin-modified GICs was evaluated in cultures of primaryhuman osteoblasts. All materials, except for one prod-uct, exhibited good cytocompatibility. Viable osteoblastsgrew inito contact with the specimens. One resin-modi-fied GIC (Vitremer"'Nl), however, was very cytotoxic. Theauthors concluded that these adverse reactions might bedue to release of high amounts of HEMA (Oliva et a).,1996). Comparable observations were reported byConsiglio et il, ('1998). Two rmGlCs (VitrebondiM andVitremeri\'( reduced protein synthesis of human gingivalfibroblasts by 00°o, whereas the four tested convention-al GlCs caused significantly less inhibition of proteinsynthesis. Severe cytotoxicity of Vitremert'N in permanent 3T3 fibroblasts was also found by Kan et al. (1997).The other rmGIC (Fu'ji 11 LCiSII caused no or only slightcellulal alterations. Finally, the detrimental cellulareffects of Vitrebond'%- and the mild cytotoxicity of Fuji 11LCI' were corroborated in monolayers of 3T3 fibroblasts,primary human gingival fibroblasts, human peripherallymphocytes, and in dentin barrier tests with fibroblasts(Leyhaulsen et al., 1998, Geurtsen et al., 1998c; Stea et a).,1998, Schmalz tot a)., 1999) (Figs. Ia-c, 2a-c). It appears

that the deleterious effects of Vitrebond'im may be partlydue to the release of the highly cytotoxic initiator,diphenyliodoniumchloride, and/or its decompositionproducts (Ceurtsen et a)., 1998c). It is noteworthy that theabovementioned in vitro studies produced fairly similarresults, even though different cell types and biologicalendpoints were used.

Besides its cytotoxic effect, fresh Vitremeri\i' alsorevealed moderate to strong antibacterial effects in cul-tures of mutans streptoccoci and lactobacilli (Fraga etal., 1996, Fried) et al., 1997). Direct and indirect genotox-ic reactions were caused by Vitrebond"'5' in procaryoticand eucaryotic in vitro assays, whereas other resin-modi-fied and conventional GICs induced only questionableindirect genotoxicity or no such effect. These in vitroresults were confirmed by in vivo assays (Heil eta), 1996;Stea etal., 1998).

Taken together, there is strong evidence that someresin-modified GICs may be genotoxic and severely cyto-toxic due to release of various substances, e.g., HEMAand DPICI. Consequently, rmClCs may cause adverselocal and/or systemic effects. Thus, leaching of thosecomponents must be minimized or prevented.

(VIII) Allergic Reactions Causedby Resin-modified Filling Materials

The allergic or sensitizing potential of resin materialsand components was evaluated in various in vivo studies,e.g., maximization tests with guinea pigs. A marked aller-gic potential was exhibited by impurities of the matrixmonomer Bis-GMA (B)jrkner et al. 1984; B)brkner,1984b). Aliphatic urethane (meth)acrylates, for dentalapplication, were more potent sensitizers than aromaticurethane acrylates and (meth)acrylated aliphatic ure-thane (Bj6rkner, 1984a). HEMA also revealed a markedallergic effect. From 60 to 100% of tested guinea pigsreacted to high concentrations of this monomer in themaximization test (Clemmensen, 1985). In addition,mutual cross-sensitivity to methacrylates was found.Guinea pigs sensitized to various methacrylates alsoresponded strongly to methacrylates which had notbeen used for sensitization (Chung and Giles, 1977).Similar observations have also been made in humans(Kanerva et al., 1992b; Richter and Geier, 1996). Skinreactions were provoked by some bonding systems inguinea pigs and Macaca mulatta monkeys (Altuna andFreeman, 1987; Katsuno et al., 1998).

Patients, and especially dental personnel, areincreasingly exhibiting local and systemic allergic reac-tions to components of resinous dental materials(Kanerva et al., 1994a,b; Richter and Geier, 1996;Tschernitschek et al., 1998). It must be emphasized, how-ever, that the number of individuals allergic to resin-

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based dental materials is still low. In addition, etiologicfactors other than dental materials may also induceintra-oral contact allergy, e.g., ingredients in food, bever-ages, and oral hygiene products (De Rossi andGreenberg, 1998).

Kallus and Mjor (1991) investigated the incidence ofadverse reactions to dental materials. Two verified long-standing effects to resin-based materials (dentures) werefound in 13,325 patients. Only eight patients out of atotal number of 31 1 persons who had been referred to adental hospital for possible allergic reactions to dentalmaterials suffered from a verified allergy to methacry-lates (Tschernitschek et al., 1998).

Adverse reactions to a Bis-GMA-based fissure sealantin a six-year-old girl have been described by Hallstrom(1993). One day after application of the material, thepatient developed multiple allergic reactions: asthma,blisters on the gingiva adjacent to the resin sealants,swellings, and rashes on various areas of the body (arms,palms, legs, lips, ears). The symptoms completely disap-peared within nine days after removal of the sealants. Averified extra-oral hypersensitivity to composite resin wasobserved in one patient (Nathanson and Lockhart, 1979).Other patients revealed an allergic contact dermatitis tocomposite resin. The reactions were caused by Bis-GMAand benzoyl peroxide (Carmichael et al., 1997; Kanerva etal., 1989). Seventeen oral lichenoid lesions on the mucosain contact with composite resin restorations weredescribed by Lind (1998). Total remission of the lichenoidreactions was observed after replacement of the resin fill-ings in four cases and partial remission in another fivepatients. The author suggested that contact of the oralmucosa with formaldehyde derived from the resinrestoration may have been the main etiologic factor inthese cases. There are several reports in the medical anddental literature regarding hypersensitivity or allergicreaction of patients to MMA (Kaaber, 1990; Richter andGeier, 1996; Hochman and Zalkind, 1997) (Table 1).

Dental personnel often have manual contact withresinous materials. Many acrylates rapidly penetratelatex or vinyl gloves (Kanerva et al., 1993). Monomervapors can be inhaled through face masks. Thus, deviceslike gloves and face masks provide only incomplete pro-tection. Taken together, the incidence of allergy to resin-based materials in dental professionals (dentists, nur-ses, dental technicians) has increased. Lonnroth andShahnavaz (1998b) found that 16-17% of the dental per-sonnel in their study were hypersensitive to dental mate-rials, in comparison with 0.5%-2% in the control group.Hand dermatitis and symptoms on the fingers were sig-nificantly more frequent among dental professionalsthan in the control group (Lonnroth and Shahnavaz,1998a). There are some resin components which areespecially important with respect to allergic reactions in

dental personnel. Dental nurses showed a high incidenceof allergic reactions to glutaraldehyde and benzoyl per-oxide, whereas dental technicians were frequently hyper-sensitive to HEMA, EGDMA, MMA, benzoyl peroxide,TEGDMA, and dihydroxy-ethyl-p-toluidine (Schnuch andGeier, 1994). Other investigators have reported that den-tal nurses and dentists developed allergic contact der-matitis to HEMA caused by handling of dentin adhesives(Kanerva et al., 1992a, 1994a). Six nurses and one dentisthad positive patch tests to composite resins. Four ofthose individuals were hypersensitive to Bis-GMA, andthree reacted to TEGDMA; two patients were also hyper-sensitive to MMA. All of these dental nurses had to stopthe practice of their profession (Kanerva et al., 1989).

It is very likely that the use of resin-based materialsin dentistry will significantly increase in the future.Concomitantly, the incidence of allergies to dental resincomponents will probably also increase considerably,among patients and especially among dental personnel.The proper handling of those products, therefore, is ofconsiderable importance. Specifically, contact withunpolymerized material must be avoided. In addition,adequate ventilation of rooms for processing of resin-based materials is recommended, to minimize the con-centration of monomer vapors in the air.

(IX) Genotoxicity of Resin-based Restorative Materials

There is little information on the genotoxic effects ofindividual resin components. Hensten-Pettersen et al.(1978) screened single ingredients of composite resins(initiators, inhibitors, UV-absorbers) in the classic Amestest. None of the tested components revealed mutagenicactivity. Miller et al. (1986), however, found weak muta-genic reactions due to one co-initiator. No mutagenicitywas observed with Bis-GMA and UDMA in the Ames test(Geurtsen, 1988). Fourteen mono-substances were inves-tigated by means of the umu test (procaryotic, in vitro), theDIT (DNA-synthesis inhibition test; eucaryotic, in vitro),and the AFE assay (in vivo) (Table 1) (Heil et al., 1996).Interestingly, almost all tested resin components weregenotoxic in at least one test system. The effects rangedfrom 'borderline' to 'strong positive'. No positive resultswere observed with the monomers BEMA (benzylmethacrylate) and HEMA, whereas Bis-GMA (umu, AFE)and UDMA (AFE) were genotoxic in one or two assays.

Recently, it has been reported that TEGDMA inducedlarge DNA sequence deletions in the hprt gene of V79cells. The authors concluded that the induction of suchDNA sequence deletions might be common for acrylatesand methacrylates (Schweikl and Schmalz, 1999).

Mutagenic effects in the Salmonella typhimuriummutagenicity test system ('Ames test') were producedby glutaraldehyde as well as by dimethyl sulfoxide

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(DMSO) and physiologic saline eluates of a dentinadhesive. Two other products exhibited no mutagenici-ty. It was concluded that the mutagenic effects of one ofthose dentin adhesives (SyntacFmv) were induced by thegenotoxic ingredient, glutaraldehyde (Schweikl et al.,1994). Dose-dependent mutagenicity was found inAmes tests with unpolymerized rnaterial of two dentinadhesives. Genotoxic effects were also caused bymonomeric solutions used in orthodontics for cemen-tation. However, no specific component was identifiedas the causative agent in those studies (Athas et al.,1979; Li et al., 1990).

Scarce data are available about the genotoxicity ofcomposite resins. DMSO and cell culture mediumextracts of two hybrid-type composite resins were investi-gated in various assays. Genotoxic effects were producedby the DMSO eluates of one composite resin (Sono-Cem]N1) in the eucaryotic DIT (Heil et al., 1996) (Table 2).

A resin-modified glass-ionomer cement (Vitrebond[M)exhibited strong genotoxic action. Extracts of this rmGlCinduced sister chromatid exchange in human peripherallymphocytes in vitro. Genotoxicity was verified by three dif-ferent in vitro and in vivo assays: the procaryotic umu test,the eucaryotic DIT, and the in vivo NFE assay. Analysis ofwater extracts of this GIC indicates that leaching of the ini-tiator, DPIGI, may contribute to this strong genotoxicaction (Heil et al 1996; Stea et al., 1998) (Table 2).

Taken together, it is clear that there are insufficientdata documenting the genotoxicity of resin-based dentalmaterials. In light of the evidence of the genotoxic poten-tial of some of these materials, it is important that theresearch in this area be given sericus consideration.

(X) Conclusions and SummaryThe biocompatibility of a resin-based dental restorativematerial is predominantly determined by the amountand nature of released organic substances. The cytotoxicpotential of these components varies significantly.

TABLE 2Mutagenicity of Aqueous Eluatesand DMSO Extracts from Two CompositeResins (cr) and Two Resin-modifiedGlass-ionomer Cements (GIC)

Product Aqueous Extract DMSO Extract

HerculiteTM (cr) No NoSono-CeMTM (cr) No Yes2lonosea ITM (GIC) No n.d.4VitrebondTM (GIC) Yes'-3 Yes'

Results from umu test, IDIT, 3AFE assay IHeil et al., 1996); 4not determined.

Additionally, interactive effects of secreted organicand/or inorganic substances may occur, e.g., synergism,additive effects, and antagonism.

Resin-based restorations release several (co)monomers(like ethylene glycol compounds, HEMA) and additives(mainly initiating substances) into the oral cavity which maycause adverse local and systemic effects in patients, e.g.,lichenoid reactions of the oral mucosa or allergic reactions.There are sufficient data demonstrating that the liberatedsubstances may diffuse pulpward through dentin in highquantities (TEGDMA HEMA), particularly through thindentin layers or after acid-etching of dentin. It appears thathigh quantities of these components may result in pulpalinflammation.

Although it is of considerable significance, it is notknown if substances leached from resinous materialsenter the blood stream, and whether they are trans-formed in the liver and/or accumulate in other tissues.

Manual contact between organic components andunprotected skin during application of resin-based materi-als poses an increased risk for allergic reactions in dentalpersonnel. There is strong evidence that some ingredients ofresin-based materials (e.g., glutaraldehyde), as well as aque-ous extracts of various products, are genotoxic in vitro and invivo. Thus, a high priority should be given to clear identifica-tion of the genotoxic components in resin-based materials.

Taken together, one can conclude that resin-basedrestorations may cause adverse local and systemiceffects. Therefore, a careful handling of resin-based den-tal materials is critical in order to minimize adverseeffects, e.g., optimum polymerization, cavity lining inareas with deep dentin, and no direct skin contact.

The increasing usage of tooth-colored fillings in theposterior region as well as the development and clinicalapplication of new adhesive techniques (ceramic inlaysand crowns, etc.) indicate that the use of resinous mate-rials will significantly increase in the future. This, in turn,will very likely increase the incidence of local and sys-temic side-effects. The following aspects, therefore,should be primary aims of future research

*Development of in vitro biocompatibility testswhich better simulate in vivo conditions

*Determination of those chemical-biological inter-actions which are critical for the biocompatibilityof resinous materials

*Investigation of the systemic distribution, metab-olism, and/or accumulation of leached compo-nents in the human body

*Identification of severely cytotoxic and/or geno-toxic compounds and replacement of these sub-stances by better biocompatible components*Development of resinous materials with highmonomer-polymer conversion and low amountsof leachable substances

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REFERENCES

Abou Hashieh 1, Franquin IC, Cosset A, Dejou J, Camps I(1998). Relationship between dentine hydraulic con-ductance and the cytotoxicity of four dentine bondingresins in vitro. I Dent 26:473-477.

Akimoto N, Momoi Y, Kohno A, Suzuki S, Otsuki M,Suzuki S, et al. (1998). Biocompatibility of ClearfilLiner Bond 2 and Clearfil AP-X system on nonex-posed and exposed primate teeth. Quintessence Int29:177-188.

Altuna G, Freeman E (1987). The reaction of skin toprimers used in the "single-step" bonding systems.Am I Orthod Dentofac Orthop 91:105-1 10.

Ashby 1 (1997). Bisphenol-A dental sealants: the inap-propriateness of continued reference to a singlefemale patient. Env Health Persp 105:362.

Athas WF, Gutzke GE, Kubinski ZO, Kubinski H (1979). Invitro studies on the carcinogenic potential of ortho-dontic bonding materials. Ecotox Environm 3:401-410.

Atsumi T, Murata I, Kamiyanagi 1, Fujisawa S, Ueha T(1998). Cytotoxicity of photosensitizers cam-phorquinone and 9-fluorenone with visible light irra-diation on a human submandibular-duct cell line invitro. Arch Oral Biol 43:73-81.

Attin T, Buchalla W (1998). Material-specific and clini-cal assessment of compomers. Dtsch Zahnirztl Z53:766-774.

Autian 1 (1970). The use of rabbit implants and tissue cellculture tests for the evaluation of dental material. IntDent 1 20:481-490.

Autian J (1974). General toxicity and screening tests fordental materials. Int Dent 1 24:235-250.

Bjorkner B (1984a). Sensitizing potential of urethane(meth)acrylates in the guinea pig. Contact Dermatitis11:115-119.

Bjorkner B (1984b). The sensitizing capacity of multifunc-tional acrylates in the guinea pig. Contact Dermatitis11:236-246.

Bjorkner B, Niklasson B, Persson K (1984). The sensiti-zing potential of di-(meth) acrylates based on bisphe-nol A or epoxy resin in the guinea pig. ContactDermatitis 10:236-304.

Brannstrbm M, Vojinovic 0 (1976). Response of the den-tal pulp to invasion of bacteria around three fillingmaterials. J Dent Child 43:83-89.

Burpee VF, Hackenberg RW, Hillegass DV, Arconti RJ,Sharp WV (1978). Acid phosphatase activity as enzy-matic assay of biomedical compatibility of polymers.I Biomed Mater Res 12:767-771.

Carmichael Al, Gibson IJ, Walls AWG (1997). Allergic con-tact dermatitis to bisphenol-A-glycidyldimethacrylate(BIS-GMA) dental resin associated with sensitivity toepoxy resin. Br Dent 1 8:297-298.

Chan KC, Soni NM, Khowassah MAF (1972). Tissuereactions to two composite resins. 1 Prosthet Dent27:176-180.

Chung CW, Giles A (1977). Sensitization potentials ofmethyl, ethyl, and n-butyl methacrylates and mutu-al cross-sensitivity in guinea pigs. I Invest Derm68:187-190.

Clemmensen S (1985). Sensitizing potential of 2-hydroxy-ethylmethacrylate. Contact Dermatitis 12:203-208.

Consiglio R, Rengo S, Liguoro D, Riccitiello F, FormisanoS, Palumbo G, et al. (1998). Inhibition by glass-ionomer cements of protein synthesis by human gin-gival fibroblasts in continuous culture. Arch Oral Biol43:65-71.

Cox CF (1992). Effects of adhesive resins and variousdental cements on the pulp. Oper Dent 5:165-176.

Cox CF, Suzuki S (1994). Re-evaluating pulp protection:calcium hydroxide liners vs. cohesive hybridization. JAm Dent Assoc 125:823-831.

Cox CF, Hafez AA, Akimoto N, Otsuki M, Suzuki S, TarimB (1998). Biocompatibility of primer, adhesive andresin composite systems on non-exposed andexposed pulps of non-human primate teeth. Am I DentI0:S55-S63.

Dalleske RL, Stanley HR, Heyde lB (1978). Human pulpresponse to a new composite system. Vytol compos-ite restorative and bonding agent. Oral Surg Oral MedOral Pathol 46:418-426.

De Rossi SS, Greenberg MS (1998). Intraoral contactallergy: a literature review and case reports. I Am DentAssoc 129:1435-1441.

Deichmann W (1941). Toxicity of methyl, ethyl and n-butyl methacrylate. I Indust Hyg Toxicol 23:343-351.

Dejoux J, Remusat M, Franquin IC (1993).Biocompatibility testing of restorative materials influ-encing dentin and pulp. I Biomed Mater Res 27:877-884.

Dunkin RT, Chambers DW (1983). Gingival response toclass V composite resin restorations. I Am Dent Assoc106:482-484.

Eick JD, Gwinnett AJ, Pashley DH, Robinson SI (1997).Current concepts on adhesion to dentin. Crit Rev OralBiol Med 8:306-335.

El-Mowafy OM, Lewis DW, Benmergui C, Levinton C(1994). Meta-analysis on long-term clinical perfor-mance of posterior composite restorations. J Dent22:33-43.

Elbaum R, Remusat M, Brouillet IL (1992).Biocompatibility of an enamel-dentin adhesive.Quintessence Int 23:173-182.

Emilson CG, Bergenholtz G (1993). Antibacterial activityof dentinal bonding agents. Quintessence Int 24:511-515.

Emilson CG, Krasse B (1985). Support for and implica-tions of the specific plaque hypothesis. Scand I DentRes 93:96-104.

350 Crit Rev Oral Biol Med 11(3) 333-355 (2000)

11(3):333-355 (2000)350 Crit Rev Oral Biol Med

at BIOLOGICAL LABS LIBRARY on December 27, 2013 For personal use only. No other uses without permission.cro.sagepub.comDownloaded from

Page 20: resin obturation

Eriksen HM, Leidal TI (1979). Monkey pulpal response tocomposite restorations in cavities treated with vari-ous cleansing agents. Scand I Dent Res 87:309-317.

Ferracane IL (1994). Elution of leachable componentsfrom composites. J Oral Rehabil 21:441-452.

Ferracane IL 11995). Current trends in dental composites.Crit Rev, Oral Biol Med 6.302-318.

Fiore-Donno G, Baume LI (1966). Etude histologique dela reaction pulpaire a l'gard dlu nouveau materiauxd'obturation 3M Addent. Schweiz Mschr Zahnheilk76 877-887.

Forss H 11993). Release of fluoride and other elementsfrom light-cured glass ionomers in neutral and acidicconditions, J Dent Res 72:1257-1262.

Fraga RC, Siqueira IF, de Uzeda M (1996). In vitro evalua-tion of antibacterial effects of photo-cured glassionomer liners and dentin bonding agents during set-ting. Prosthet Dent 76:483-486.

Friedl KH, Schmalz G, Hiller KA, Shams M (1997). Resin-modified glass ionomer cements: fluoride release andinfluence on Streptococcus mutans growth. Eur J Oral Sci105:81-85.

Fujisawa SrImai Y, Kojima K, Masuhara E (1978). Studieson hemolytic activity of bisphenol A diglycidylmethacrylate (Bis-GMA). J Dent Res 57:98-102.

Fujisawa S, Kadoma Y, Kadoma Y (1988). IH and '3C NMRstudies of the interaction of eugenol, phenol, and tri-ethyleneglycol dimethacrylate with phospholipidliposomes as a model system lor odontoblast mem-branes. Dent Res 67:1438- 1441.

Fujitani M, Inokoshi S, Hosoda H (1992). Effect of acidetching on the dental pulp ir adhesive compositerestorations. Int Dent J 42 3-11.

Gale MS, Darvell BW (1999). Dentine permeability andtracer tests. Dent 27 1 -11.

Gerzina TM, Hume WR (1995). Effect of hydrostatic pres-sure on the diffusion of monomers through dentin in0itro. Dent Res 74 369-373.

Gerzina TM, Hume WR (1996). Diffusion of monomersfrom bonding resin-resin composite combinationsthrough dentine in vitro. J Dent 24:125-128.

Geurtsen W 1987a) .Subcellular damage caused by theunfillecd component systems of a composite. DtschZahntirztl Z 42 580-583.

Geurtsen W (1987b). Studies on the cellular tolerance ofposterior composites. Dtsch Zahndrztl Z 42:960-963.

Geurtsen W 11988). Die zellulare Vertraglichkeit zah-narztlicher Komposite ICellular compatibility of den-tal composite resinsl. Munich, Germany Carl HanserPubl. Comp., ISBN 3-446-15058-7.

Geurtsen W (1998). Substances released from dentalresin composites and glass ionomer cements. Eur JOral Sci 106:687-695.

Geurtsen \V Iehausen G (1997). Biological aspects of

root canal filling materials-histocompatibility, cyto-toxicity, and mutagenicity. Clin Oral Invest 1:5-11.

Geurtsen W, Schoeler 1 (1997). A 4-year retrospectiveclinical study of class I and 11 composite fillings. Dent25:229-232.

Geurtsen W, Lehmann F, Spahl W, Leyhausen G (1998a).Cytotoxicity of 35 dental resin compositemonomers/additives in permanent 3T3 and threehuman primary fibroblast cultures. J Biomed Mater Res41:474-480.

Geurtsen W, Spahl W, Leyhausen G (1998b). Residualmonomer/additive release and variability in cytotoxi-city of light-curing glass-ionomer cements and com-

pomers. I Dent Res 77:2012-2019.Geurtsen W, Bubeck P, Leyhausen G, Garcia-Godoy F

(1998c). Effects of extraction media upon fluoriderelease from a resin-modified glass-ionomer cement.Clin Oral Invest 2:143-146.

Geurtsen W, Spahl W, Leyhausen G (1999a). Variability ofcytotoxicity and leaching of substances from fourlight-curing pit and fissure sealants. Biorned Mater Res44:73-77.

Geurtsen W, Leyhausen G, Garcia-Godoy F (I1999b). Effectof storage media on the fluoride release and surfacemicrostructure of four polyacid-modified compositeresins ("compomers"). Dent Mater 415 196-201.

Geurtsen W, Spahl W, Muller K, Leyhausen G (1999c).Variability of cytotoxicity and leaching of substancesfrom five dentin adhesives. J Biomned Mater Res 48 772-777.

Gilpatrick RO, Johnson W, Moore D, Turner 1 (1996).Pulpal response to dentin etched with 10% phosphor-ic acid. Am I Dent 9:125- 129.

Gopferich A (1996). Mechanisms of polymer degradationand erosion. Biomaterials 17:103-114.

Goracci G, Mori G, Bazzucchi M (1995). Marginal seal andbiocompatibility of a fourth-generation bondingagent. Dent Mater 11:343-347.

Gwinnett AJ, Tay FR (1998). Early and intermediate timeresponse of the dental pulp to an acid etch techniquein vivo. Am J Dent 10:S35-S44.

Hallstrbm U (1993). Adverse reaction to a fissure sealant:report of case. Dent Child 60: 143-146.

Hamid A, Hume R (1997a). The effect of dentin thicknesson diffusion of resin monomers in vitro Oral Rehabil24:20-25.

Hamid A, Hume WR (1997b). A study of componentrelease from resin pit and fissure sealants in vitro. DentMater 13:98-102.

Hamid A, Sutton W, Hume WR (1996). Variation inphosphoric acid concentration and treatment timeand HEMA diffusion through dentin. Am Dent9:211-214.

Hamid A, Okamoto A, lwaku M, Hume WR (1998).Component release from light-activated glass

1113133335S20001 Crit Rev Oral Biol 351I I( 3):333-355 000) Crit Rev Oral Biol Med 35 1

at BIOLOGICAL LABS LIBRARY on December 27, 2013 For personal use only. No other uses without permission.cro.sagepub.comDownloaded from

Page 21: resin obturation

ionomer and compomer cements. I Oral Rehabil25:94-99.

Hanks CT, Craig RG, Diehl ML, Pashley DH (1988).Cytotoxicity of dental composites and other materialsin a new in vitro device. I Oral Pathol 17:396-403.

Hanks CT, Strawn SE, Wataha IC, Craig RG (1991).Cytotoxic effects of resin components on culturedmammalian fibroblasts. J Dent Res 70:1450-1455.

Hansel C, Leyhausen G, Mai UEH, Geurtsen W (1998).Effects of various resin composite (co)monomers andextracts on two caries-associated micro-organisms invitro. I Dent Res 77:60-67.

Henderson ID, Mullarky RH, Ryan DE (1987). Tissue bio-compatibility of kevlar aramid fibers and polymethyl-methacrylate composites in rabbits. J Biomed Mater Res21:59-64.

Heil J, Reifferscheid G, Waldmann P, Leyhausen G,Geurtsen W (1996). Genotoxicity of dental materials.Mutat Res 368:181-194.

Hensten-Pettersen A, Jacobsen N, lansen 1 (1978).Mutagenic potential and influence on cell growth ofsingle components of dental polymers (abstract). IDent Res 57(Spec Iss):297.

Hochman N, Zalkind M (1997). Hypersensitivity tomethyl methacrylate: mode of treatment. J ProsthetDent 77:93-96.

Horsted P, Simonsen AM, Larsen MI (1986). Monkey pulpreactions to restorative materials. Scand I Dent Res94:154-163.

Howden GF, Silver IA (1980). The use of an improved rab-bit ear chamber technique for the study of dentalmaterials. Int Endodont J 13:3-16.

Hume WR (1985). A new technique for screening chemi-cal toxicity to the pulp from dental restorative mate-rials and procedures. l Dent Res 64:1322-1325.

Hume WR, Gerzina TM (1996). Bioavailability of compo-nents of resin-based materials which are applied toteeth. Crit Rev Oral Biol Med 7:172-179.

Imazato S, Ehara A, Torii M, Ebisu S (1998a).Antibacterial activity of dentine primer containingMDPB after curing. J Dent 26:267-271.

Imazato S, Imai T, Ebisu S (1998b). Antibacterial activity ofproprietary self-etching primers. Am J Dent 11: 106-108.

Imazato S, Imai T, Russell RRB, Torii M, Ebisu S (1998c).Antibacterial activity of cured dental resin incorpo-rating the antibacterial monomer MDPB and anadhesion-promoting monomer. J Biomed Mater Res39:511-515.

Inokoshi S, Fujitani M, Otsuki M, Sonoda H, Kitasako Y,Shimada Y, et al. (1998). Monkey pulpal responses toconventional and adhesive luting cements. Oper Dent23:21-29.

lain P, Vargas MA, Denehy GE, Boyer DB (1997). Dentindesensitizing agents: SEM and x-ray microanalysis

assessment. Am I Dent 10:21-27.Jordan WP, Sherman WI, King SE (1979). Threshold

responses in formaldehyde-sensitive subjects. J AmAcad Dermatol 1:44-48.

Kaaber S (1990). Allergy to dental materials with specialreference to the use of amalgam and polymethyl-methacrylate. Int Dent 1 40:359-365.

Kakaboura A, Eliades G, Palaghias G (1996). An F1TRstudy on the setting mechanism of resin-modifiedglass-ionomer restoratives. Dent Mater 12:173-178.

Kallus T, Mjir I (1991). Incidence of adverse effects ofdental materials. Scand I Dent Res 99:236-240.

Kan KC, Messer LB, Messer HH (1997). Variability in cyto-toxicity and fluoride release of resin-modified glass-ionomer cements. J Dent Res 76:1502-1507.

Kanerva L, Estlander T, Jolanki R (1989). Allergic contactdermatitis from dental composite resins due to aro-matic epoxy acrylates and aliphatic acrylates. ContactDermatitis 20:201-211.

Kanerva L, Estlander T, Jolanki R (1992a). Active sensitiza-tion caused by 2-hydroxyethyl methacrylate, 2-hydroxy-propyl methacrylate, ethyleneglycol dimethacrylate andN,N-dimethylaminoethyl methacrylate. J Eur Acad DermVenereol 1: 165-169.

Kanerva L, Estlander T, Jolanki R (1992b). Double activesensitization caused by acrylics. Am I Contact Dermatitis3:23-26.

Kanerva L, lolanki R, Estlander T (1993). Dentist's occu-pational allergic contact dermatitis caused bycoconut diethanolamide, N-ethyl-4-toluene sulfon-amide and 4-tolyldiethanolamine. Acta Derm Venereol73:126-129.

Kanerva L, Henriks-Eckermann ML, Estlander T, JolankiR, Tarvainen K (1994a). Occupational allergic contactdermatitis and composition of acrylates in dentalbonding systems. I EurAcad Derm Venereol 3:157-168.

Kanerva L, Estlander T, lolanki R (1994b). Occupationalskin allergy in the dental profession. Dermatol Clinics12:517-532.

Kanerva L, Jolanki R, Leino T, Estlander T (1995).Occupational allergic contact dermatitis from 2-hydroxyethyl methacrylate and ethylene glycoldimethacrylate in a modified acrylic structural adhe-sive. Contact Dermatitis 33:84-89.

Karlsson J, Wendling W, Chen D, Zelinsky J, JeevanandamV, Hellman S, et al. (1995). Methylmethacrylatemonomer produces direct relaxation of vascularsmooth muscle in vitro. Am Anaesthesiol Scand 39:685-689.

Katsuno K, Manabe A, Kurihara A, Itoh K, Hisamitsu H,Wakumoto S, et al. (I1998). The adverse effect of com-mercial dentine-bonding systems on the skin ofguinea pigs. I Oral Rehabil 25:180-184.

Koch Mi, Staehle Hl (1997). Formaldehyde release fromdental materials. Dtsch Zahnarztl Z 5 2:778-782.

352 Crit Rev Oral Biol Med 1 l(3):333-355 (2000)352 Crit Rev Oral Biol Med 1 1(3):333-355 (2000) at BIOLOGICAL LABS LIBRARY on December 27, 2013 For personal use only. No other uses without permission.cro.sagepub.comDownloaded from

Page 22: resin obturation

Lampert F, Heidemann D 11980). Composite filling mate-rials in cell cultures. Dtsch Zahnarztl Z 35:483-485.

Lehmann F, Levhausen G, Spahl W, Geurtsen W (1993).Comparative cell culture studies of the cytotoxicity ofcomposite resin components. Dtsch Zahndrztl Z48:651 -653.

Leyhausen G, Heil 1, Reifferscheid G, Geurtsen W (1995).The genotoxic potential of composite components.Dtsch Zahinrztl Z 50: 134-136.

Leyhausen G, Abtahi M, Karbakhsch M, Sapotnick A,Geurtsen W (1998). Biocompatibility of various light-curing and one conventional glass-ionomer cement.Bionmaterials 19:559-564.

Li Y, Noblitt TW, Dunipace Al, Stookey GK (1990).Evaluation of mutagenicity af restorative dentalmaterials using the Ames salmonella/microsometest. J Dent Res 69 1188-1192.

Lind PO (1998). Oral lichenoid reactions related to com-posite restorations. Acta Odontol Scand 46:63-65.

Lbnnroth EC Shahnavaz H (1 998a). Hand dermatitis andsymptoms from the fingers among Swedish dentalpersonnel. Swed Dent J 22:23-32.

Lbnnroth EC, Shahnavaz H (1998b). Adverse health reac-tions in skin, eyes, and respiratory tract among dentalpersonnel in Sweden. Swed Dent J 22:33-45.

MacDougall M, Selden (K, Nydegger JR, Carnes DL1998). Immortalized mouse odontoblast cell lineMO6-G3 application for in vitro biocompatibility test-ing. Am Dent lO:SII -S16.

Marshall GW Ir, Marshall SJ, Kinney JH, Balooch M (1997).The dentin substrate: structure and properties relatedto bonding J Dent 25:441 -458.

McCluggage SG, Holmstedt OV, Malloy RB (1980). An invivo model for evaluating the response of pulp to var-ious biomaterials. J Bionied Mater Res 14:63 1-639.

Meyer IM. Cattani-Lorente MA, Dupuis V (1998).Compomers between glass-ionomer cements andcomrposites. Bliomaterials 19529- 539.

Miller EGO Washington VH, Bowles WH, Zimmermann ER(1986). Mutagenic potential of some chemical com-ponents of dental materials. Dent Mater 2: 163-165.

M'jr IA, Iokstadt A, Ovist V (1990). Longevity of posteri-or restorations. Int Dent J 40:11-17.

Mohsen NM, Craig RG, Hanks CT 11998). Cytotoxicity ofurethane dimethacrylate composites before and afteraging and leaching. I Biomed Mater Res 39:252-260.

Nakamura M. Imai K, Oshima H, Kudo T, Yoshioka S,Kawahara fH (1985). Biocompatibility test of light-cured composites in vitro. Dent Mater 1 4:231-237.

Nathanson D. Lockhart P (1979). Delayed extraoralhypersensitivity to dental composite material. OralSurc Oral Med Oral Pathol 47:329-333.

Nathanson D, Lerpitayakun P, Lamkin MS, Edalatpour M,Chou t L 11997)1 In vitro elution of leachable components

from dental sealants. I Am Dent Assoc 128:151 7-1523.Nicholson JW (1998). Chemistry of glass-ionomer

cements: a review. Biomaterials 19:484-494.Olea N, Pulpgar R, Perez P, Olea-Serrano F, Rivas A,

Novillo-Fertrell A, et al. (1996). Estrogenicity of resin-based composites and sealants used in dentistry. EnvHealth Persp 104:298-305.

Oliva A, Della Ragione F, Salerno A, Riccio V, Tartaro G,Cozzolino A, et al. (1996). Biocompatibility studies onglass ionomer cements by primary cultures of humanosteoblasts. Biomaterials 17:1351- 1356.

Oppenheimer BS, Oppenheimer ET, Danishefsky AP, StoutAP, Eirich FR (1955). Further studies of polymers as car-cinogenic agents in animals. Cancer Res 15:333-340

Orstavik D, Hensten-Pettersen A (1978). Antibacterialactivity of tooth-colored dental restorative materials.I Dent Res 57:171 174.

0ysaed H, Ruyter IE (1986). Water sorption and fillercharacteristics of composites for use in posteriorteeth. I Dent Res 65:1315-1318.

0ysaed H, Ruyter IE, Kleven S (1988). Release offormaldehyde from dental composites. Dent Res67:1289- 1294.

Pameijer CH, Stanley HR (1995). Pulp reaction to adentin bonding agent. Am I Dent 8 140-144.

Pameijer CH, Stanley HR (1998). The disastrous effects ofthe "total etch" technique in vital pulp capping in pri-mates. Am J Dent 11 :S45-S54.

Pearson GJ, Longman CM (1989). Water sorption and sol-ubility of resin-based materials following inadequatepolymerization by a visible-light curing system. I OralRehabil 16:57-61.

Pertot WJ, Stephan G, Tardieu C, Proust IP (1997).Comparison of the intraosseous biocompatibility ofDyract and Super EBA. J Endodont 23:315-319.

Peumans M, Van Meerbeek B, Lambrechts P, Vanherle G,Quirynen M (1998). The influence of direct compositeadditions for the correction of tooth form and/or posi-tion on periodontal health. A retrospective study.Periodontol 69:422-427.

Phillips H, Cole PV, Lettin AW (1971). Cardiovasculareffects of implanted acrylic bone cement. Br Med J3(772):460-461.

Pissiotis E, Spangberg L (1992). Dentin as inhibitor ofbacterial toxicity on pulpal cells in vitro. Endod18:166- 171.

Plant CG, Jones DW (1976). The damaging effects ofrestorative materials. Br Dent 1 140:406-412.

Quist V (1975). Pulpal reactions in human teeth to toothcoloured filling materials. Scand J Dent Res 83:54-66.

Ovist V (1993). Resin restorations leakage, bacteria,pulp Endodont Dent Traumatol 9 127- 152.

Quist V, Stoltze K, Quist (1989). Human pulp reactionsto resin restorations performed with different acid-

Crit Rev Oral Biol Med 3531 1(3).-333-355 0000)

at BIOLOGICAL LABS LIBRARY on December 27, 2013 For personal use only. No other uses without permission.cro.sagepub.comDownloaded from

Page 23: resin obturation

etch restorative procedures. Acta Odontol Scand47:253-267.

Rakich DR, Wataha IC, Lefebvre CA, Weller RN (1998).Effects of bonding agents on macrophage mitochon-drial activity. I Endod 24:528-533.

Ratanasathien S, Wataha JC, Hanks CT, Dennison lB(1995). Cytotoxic interactive effects of dentin bond-ing components on mouse fibroblasts. J Dent Res74:1602-1606.

Rathbun MA, Craig CT, Hanks CT, Filisko FE (1991).Cytotoxicity of a Bis-GMA dental composite beforeand after leaching in organic solvents. I Biomed MaterRes 25:443-457.

Rawls HR, Marshall MV, Cardenas HL, Bhagat HR,Cabasso 1 (1992). Cytotoxicity evaluation of a newradiopaque resin additive-Triphenyl bismuth. DentMater 8:54-59.

Retief DH, Cleaton-Jones PE, Austin J (1973). Pulpalresponse to a new composite dental restorative mate-rial. i Oral Pathol 2:215-221.

Richter G (1996). Dental materials-a problem in allergydiagnosis? Part II: Patch testing and relevance evalu-ation in selected groups of dental materials. Hautarzt47:844-849.

Richter G, Geier J (1996). Dental materials-a problem inallergy diagnosis? Part I: Analysis of patch testresults in patients with oral mucosal complaints orproblems possibly related to denture materials.Hautarzt 47:839-843.

Roberts MW, Folio J, Moffa JP, Guckes AD (1992). Clinicalevaluation of a composite resin system with a dentinbonding agent for restoration of permanent posteriorteeth: a 3-year study. I Prosthet Dent 67:301-306.

Samaha NS (1982). Effect of different composites andamalgam on the gingiva. Dtsch Zahndrztl Z 37:339-343.

Sanchez-Sotres L, Van Huysen G, Gilmore HW (1969). Ahistologic study of gingival tissue response to amal-gam, silicate and resin restorations. I Periodontol40:543-546.

Schilke R, Bauf3 0, Lisson IA, Schuckar M, Geurtsen W(1999). Bovine dentin as a substitute for humandentin in shear bond strength measurements. Am JDent 12:93-96.

Schmalz G (1981). Biological proof of filling materials inthe Gotting miniature pig-a pilot study. Dtsch ZahnarztlZ 36:357-360.

Schmalz G (1997). Concepts in biocompatibility testing ofdental restorative materials. Clin Oral Invest 1:154-162.

Schmalz G, Arenholt-Bindslev D (1998). Dental fillingmaterials-hazards to patients and to environment-Introduction. Eur I Oral Sci 106:677.

Schmalz G, Schuster U, Nuetzel K, Schweikl H (1999). Anin vitro pulp chamber with three-dimensional cell cul-tures. J Endodont 25:24-29.

Schnuch A, Geier 1 (1994). Kontaktallergene beiDentalberufen. Dermantosen 42:253-255.

Schuckar M, Geurtsen W (1997). Proximo-cervical adap-tation of Class 1I-composite-restorations after ther-mocycling-a quantitative and qualitative study. J OralRehabil 24:766-775.

Schweikl H, Schmalz G (1999). Triethylene glycoldimethacrylate induces large deletions in the hprtgene of V79 cells. Mutat Res 438:71-78.

Schweikl H, Schmalz G, Bey B (1994). Mutagenicity ofdentin bonding agents. J Biomed Mater Res 28:1061-1067.

Singh AR, Lawrence WH, Autian J (1972). Embryonic-fetaltoxicity and teratogenic effects of a group ofmethacrylate esters in rats. Dent Res 5 1:1632-1638.

Spahl W, Budzikiewicz H (1994). Qualitative analysis by gasand liquid chromatography/mass spectrometry of den-tal resin composites. Fresenius J Anal Chem 350:684-691.

Spahl W, Budzikiewicz H, Geurtsen W (1998).Determination of leachable components from fourcommercial dental composites by gas and liquid chro-matography/mass spectrometry. I Dent 26:137-145.

Stanford JW (1980). Recommended standard practicesfor biological evaluation of dental materials. Int Dent I30:140-188.

Stanley HR (1992). Local and systemic responses to dentalcomposites and glass ionomers. Adv Dent Res 6:55-64.

Stanley HR, Going HR, Chauncey HH (1975). Humanpulp response to acid pretreatment of dentin and tocomposite restorations. I Am Dent Assoc 91:817-825.

Stanley HR, Bowen RL, Folio J (1979). Compatibility ofvarious materials with oral tissues. Il. Pulp responsesto composite ingredients. I Dent Res 58:1507-1517.

Stea S, Visentin M, Cervellati M, Verri E, Cenni E,Savarino L, et al. (1998). In vitro sister chromatidexchange induced by glass ionomer cements. J BiomedMater Res 40:545-550.

Suzuki S, Cox CF, Leinfelder KF, Snuggs HM, Powell CS(1995). A new copolymerized composite resin system:a multiphased evaluation. Int I Periodont Rest Dent15:483-495.

Syafiuddin T, Hisamitsu H, Toko T, Igarashi T, Goto N,Fujishima A, et al. (1997). In vitro inhibition of cariesaround a resin composite restoration containingantibacterial filler. Biomaterials 18:1051-1057.

Tarim B, Hafez AA, Suzuki SH, Suzuki S, Cox CF (1998).Biocompatibility of Optibond and XR-Bond adhesivesystems in nonhuman primate teeth. Int l Periodont RestDent 18:87-99.

Terakado M, Yamazaki M, Tsujimoto Y, Kawashima T,Nagashima K, Ogawa J, et al. (1984). Lipid peroxida-tion as a possible cause of benzoyl peroxide toxicityin rabbit dental pulp-a microsomal lipid peroxidationin vitro. J Dent Res 63:901-905.

Torstenson B, Nordenvall KJ, Brannstrom M (1982).

354 Crit Rev Oral Biol Med1(3):333-355

354 Crit Rev Oral Biol Med 1 1(3):333-355 (2000)

at BIOLOGICAL LABS LIBRARY on December 27, 2013 For personal use only. No other uses without permission.cro.sagepub.comDownloaded from

Page 24: resin obturation

Pulpal reaction and microorganisms under Clearfilcomposite resin in deep cavities with acid etcheddentin. Swe(i Dent 1 6:167-176.

Tronstadt L. Spangberg L (1974). Biologic tests of amethylmethacrylate composite material. Scand I DentRes 82 93-98.

Tronstadt L, Wennberg A (1980). In vitro assessment of thetoxicity of filling materials. Int Endodont 1 13:131-142.

Tschernitschek H, Wolter S, Korner M (1998). Allergy todental materials. Derniatosen/Occup Environm 46:244-248.

Tyas MIl Browne RM (1977). Biological testing of dentalrestorative materials. Oral Rehabil 4:275-290.

Ulukapi H Benderli Y Soyman M (1996). Determinationof fluoride release from light-cured glass-ionomersand a fluoridated composite resin from the viewpointof curing time. 1 Oral Rehabil 23:197-201.

Updegraff DM, Chang RWH, loos RW (1971).Antibacterial activity of dental restorative materials. IDent Res 50 :.82-387.

Vaikuntam 1997). Resin-modified glass ionomerements (RM GICs) implication for use in pediatric

dentistrv. Dent Child 64' 131-134.

Valcke CF, Cleaton-Jones PE, Austin IC, Pain E, VieiraE (1980). The pulpal response to a direct fillingresin without an inorganic filler-Isopast. OralRehabil 7: 1-10.

Waggoner WF Siegal M (1996). Pit and fissure sealantapplication: updating the technique. J Am Dent Assoc127:351-361.

Wennberg A, Mjbr IA, Hennsten-Pettersen A (1983).Biological evaluation of dental restorative materi-als-a comparison of different test methods. BioniedMater Res 17:23-36.

White KC, Cox CF Kanka J1 Dixon DL, Farmer IB SnuggsHM (1994). Pulpal response to adhesive systemsapplied to acid-etched vital dentin: damp versus dryprimer application. Quintessence Int 25:259-268

Wilder AD, Bayne SC, May KN, Leinfelder KF, Taylor DF(1991). Five-year clinical study of a u .v. -polymerizedposterior composite. I Dent 19:214-220.

Yoshii E ( 1997). Cytotoxic effects of acrylates andmethacrylates: relationships of monomer structuresand cytotoxicity. I Bionmed Mater Res 37 5 7-524.

3551131 333 355 2()tiOGrit Rev Oral Biol MedCrit Rev Oral Biol Med113) .333-355 2000)

at BIOLOGICAL LABS LIBRARY on December 27, 2013 For personal use only. No other uses without permission.cro.sagepub.comDownloaded from