Management of Shrinkage Stresses in Direct Restorative Light-Cured Composites: A Review

Management of Shrinkage Stresses in Direct RestorativeLight-Cured Composites: A ReviewSHIV P. MANTRI, MDS*, SNEHA S. MANTRI, MDS†

ABSTRACT

In spite of many advances in the field of dental resin composites, polymerization shrinkage continues to be a majorproblem. Shrinkage creates stresses within the material and its interface leading to marginal failure, staining, secondarycaries, restoration displacement, tooth fracture, and postoperative sensitivity.The aim of this review is to explain thefactors affecting shrinkage stresses, their consequences, and clinical strategies for their management.

CLINICAL SIGNIFICANCE

Polymerization shrinkage stress in dental composites is recognized as a significant material limitation that substantiallycomplicates the placement of restorations. Shrinkage creates stresses within the material and its interface leading tomarginal failure, staining, secondary caries, restoration displacement, tooth fracture, and postoperative sensitivity.Thisreview explains the factors affecting shrinkage stresses, their consequences, and clinical strategies for their management.

(J Esthet Restor Dent 25:305–316, 2013)

INTRODUCTION

Resin composites are widely used materials because oftheir bondability and aesthetic properties. They arefinding increased application in modern preventive andrestorative dentistry. A fundamental problem with thecurrent dental resin composites based ondimethacrylates is dimensional shrinkage, an inherentmanifestation in materials polymerizing through a freeradical mechanism. Typical resin composites applied inrestorative dentistry exhibit volumetric shrinkage valuesfrom less than 1% up to 6%, depending on theformulation and curing conditions.1,2

This problem with dental restorative resins on adhesionis attributable to volume shrinkage arisen from an

internal stress developed during polymerization. Theinternal contraction stress can damage the marginalseal of the bonded restorations. This may result ininterfacial gap formation and produce postoperativesensitivity, marginal staining, or recurrent caries.Sometimes, cusp displacement may result in patienthypersensitivity or fracture and crack formation atsurrounding walls.

The polymerization shrinkage stress is dependent onmultiple factors. The material composition,polymerization reaction, degree of conversion (DC),boundary conditions, amount of material, and theresultant properties all play essential role in stressdevelopment and/or transmission to toothstructures.

*Professor, Conservative and Endodontics, Hitkarini Dental College & Hospital, Jabalpur, Madhya Pradesh, India†Professor and Prosthodontics, Hitkarini Dental College & Hospital, Jabalpur, Madhya Pradesh, India

Reprint requests: Dr Sneha S. Mantri, Gulmohar Duplex, 8, Ivory tower, Besides Dainik Bhaskar, South Civil Lines, Jabalpur.482001 M.P., India.Tel.: 9424685622;

Fax: 91-761-2600366; email: [email protected]

REVIEW ARTICLE

© 2013 Wiley Periodicals, Inc. DOI 10.1111/jerd.12047 Journal of Esthetic and Restorative Dentistry Vol 25 • No 5 • 305–313 • 2013 305

mailto:[email protected]

THE COMPOSITION OF THERESIN COMPOSITE

The magnitude of stress is dependent on the material’svolumetric shrinkage strain and its elastic modulus. Thechemical composition of the resin matrix plays animportant role over the magnitude, kinetics ofshrinkage strain, and the elastic modulus development.A resin matrix formulated with monomers of highmolecular weight (Mw) will result in lower shrinkagevalues than those formulated with monomers of lowMw. Thus, monomer functionalities, molecularstructure, molecular mass, and size have majorinfluences upon the amount of shrinkage and alsomonomer viscosity.3,4

Examples of monomers used in dental compositesinclude Bis-GMA, TEGDMA, UDMA, BisEMA.Bis-GMA has been widely used. It has high molecularweight (512 g/mol) and very high viscosity(500,000–800,000 mPa·s). Therefore, diluent monomershave to be used, or other ones have to substitute it, tomake the resin more fluid. TEGDMA (mol. wt.286 g/mol and viscosity 100 mPa·s) is an efficientdiluents monomer. UDMA (mol. wt. 470 g/mol,viscosity 5000–10,000 mPa·s) can be used alone withTEGDMA or associated with Bis-GMA and/or someother monomers. There is wide range of othermonomers that have been used and tested.

Particulate inorganic fillers are the stiff component inthe resin composite. Several types, shapes, sizes, volumefractions and distributions of filler particles are used incommercial products. New options for reinforcingfillers generally have focused on nano-sized materialsand hybrid organic–inorganic fillers. Organicallymodified ceramics were developed and have been usedin commercial products.

The polymer matrix/filler ratio has a dominant effectupon strain and stress developed, and high values ofshrinkage, combined with an increasing elastic modulus,produce increased stress within the composite structureand the bonding region.5 Filler surface area and theamount of the polymerizable coupling agent cancontribute significantly to the shrinkage stress as well.

The most commonly used coupling agent isγ-methacryloxypropyl trimethoxysilane. Thepolymerization process allows the methacrylategroups in the coupling agent to copolymerizewith the resin monomers enhancing the interfacialadhesion.

The photoinitiator type and the photoinitiator/resinratio directly affect the rate of polymerization and DC,so these two factors would also affect the rate and finalmagnitude of stress developed. Camphorquinone(CQ)/tertiary amine system has been recognized as avaluable visible light initiator since its invention in1971. On the initiation mechanism, CQ (wavelength ofmaximum absorbance [λmax]: 468 nm) undergoes aso-called hydrogen abstraction type of photoinitiationmechanism in which CQ (a sensitizer) absorbs light toform a photoexcitation complex (CQ*-amine exciplex)with a tertiary amine (a hydrogen-donating agent) andsubsequently generates amine-derived free radicals.Although CQ/tertiary amine system offers manyadvantages, the tertiary amine (π acceptor) can reactwith an acidic group, i.e., phosphoric acid, phosphonicacid, or carboxylic acid group (π donor) in adhesivemonomers to form charge transfer complexes6,7 orundesirable quaternary ammonium salt.8 It wasreported that the formation of quaternary ammoniumsalt resulted in increased time delay before lightactivation of the resin composite, hence ultimatelyresulting in degraded bond strength to dentin.31 AllCQ/tertiary amine systems are not acid sensitive. It ishighly dependent on the pKb of the amine. The mostcommonly used binary CQ-amine photoinitiator/co-initiator system exhibits limitations for its use indentin adhesive formulations. A certain level of phaseseparation has been suggested to exist due to thepresence of water.9 Consequently, limited conversionfrom monomers into a rigid polymer network occurswhen hydrophobic molecules are surrounded by ahydrophilic matrix. Some ionic derivatives ofthioxanthone dyes are water miscible and represent analternative for the polymerization of dental adhesives.In addition, iodonium salts are efficient water-solubleco-initiator system that improve the polymerizationrate of dental monomers when CQ is used, even in thepresence of a solvent.10,11 CQ can react with one or

MANAGEMENT OF SHRINKAGE STRESSES IN LIGHT CURE COMPOSITE RESIN Mantri

DOI 10.1111/jerd.12047 © 2013 Wiley Periodicals, Inc.Vol 25 • No 5 • 305–313 • 2013 Journal of Esthetic and Restorative Dentistry306

more co-initiators to from free radicals in some cases,e.g., CQ + electron donor + electron acceptor such as adiaryl iodonium salt.

Unlike CQ/amine photoinitiator system, acylphosphineoxide and bisacylphosphine oxide do not requiretertiary amines. These photoinitiators undergo anα-cleavage type of photoinitiation mechanism (Norrishtype I system).

THE POLYMERIZATION PROCESS

Generally, the curing reaction in composite restorativematerials involves visible-light-initiatedphotopolymerization of dimethacrylate monomers toform a highly cross-linked polymer. Thisphotopolymerization reaction consists of threesteps—initiation, propagation, and termination—andcomplexities arise in polymerization kinetics, networkevolution, and the material property development12–15

With respect to the polymerization kinetics, both thepropagation and termination reactions are diffusioncontrolled. Even at low conversion, the terminationreaction, i.e., the coming together of two radicals thatreact to terminate each other, is diffusion controlledand slowed by the network.16 Subsequently, the radicalconcentration increases and the observedpolymerization rate also increases, a phenomenonreferred to as “autoacceleration.” This process isimportant for dental composites since it results in rapidcuring on clinically acceptable time scales.

In contrast to termination, the propagation reactioninvolves the reaction of a polymeric radical and arelatively mobile methacrylate moiety. This reaction’snature is such that it does not become diffusioncontrolled until significantly higher conversions,generally associated with the polymer becoming glassy,a process referred to as “vitrification.” As the polymervitrifies, the propagation reaction slows and thepolymerization ceases, i.e., autodeceleration occurs.This process is particularly important in dentalcomposites, where autodeceleration results in residual,unreacted methacrylates that remain in the compositerestoration.

In addition to complex polymerization kinetics, thepolymer structure also evolves with numerouscomplexities. There are two critical, macroscopicdemarcations that occur during polymerization. Thefirst of these is the gel point conversion and representsthe point at which an incipient gel is formed. In thechain-growth polymerization of dimethacrylates, thisconversion is generally less than 5% to 10% and iscritical for controlling the shrinkage stress.12 Thesecond macroscale demarcation is the vitrificationpoint, which represents the conversion at which thepolymer becomes glassy, accompanied by a dramaticmodulus increase.

Direct placement restorations require thatpolymerization process be conducted at near ambienttemperature, so photopolymerization is the preferredcuring mode. Visible light activation over the range of400 to 500 nm primarily based on the CQ/amine as thephotoinitiator/co-initiator system remains theconvention in dentistry. Blue light (400–550 nm)activates CQ and converts it to an excited triplet state.The excited CQ then reacts with a co-initiator to formfree radicals, starting the polymerization process(activation and initiation stages).17 When this reactiveradical reacts with a monomer molecule, an activecenter is created and propagates the process. Thepropagation reaction involves the polymer chain growthby rapid sequential addition of monomer to the activecenters via covalent bonds until the maximum DC ofC = C double-bonds into C–C bonds is achieved.

Before the polymerization process, Van der Wall forcesact and keep the monomers grouped.

At this moment, the distance among the monomers isapproximately 4 A°. During the polymerization process,these forces are substituted by covalent bonds, withdistances of approximately 1.5 A°. Consequently,volumetric shrinkage occurs.4,5

DEGREE OF CONVERSION

DC is defined as the degree (%) of conversion ofpolymerizable monomers to polymers. It is a very



important parameter used to measure polymerizationperformance. It is influenced by multiple factors:resin viscosity, the photopolymerization activity ofphotoinitiators and photosensitive resin monomers,and the wavelength, time, and intensity of irradiationlamps.

BOUNDARY CONDITIONS AND THEAMOUNT OF MATERIAL

In 1987, Feilzer et al.18 published a study showingthat the expected magnitude of stress might beestimated through the ratio of the bonded to theunbonded areas, also known as the “configurationfactor,” or simply “C-factor.” The higher amounts ofbonded area result in higher stress level. On theopposite, a higher ratio of unbonded to bonded wallswould be responsible for lower values of stressbecause shrinkage would freely occur at theunbonded surface areas. Although it is evidentthat the C-factor has important role in stressdevelopment, it has been suggested that theC-factor approach in isolation may overestimate theeffect of the degree of constriction.19 In dental fillingprocedures, the cavity configuration varies accordingto the extent of caries removal, the amount ofremaining healthy tissue, the tooth region and thetooth location (anterior, posterior), and type.Consequently, the level of stress might vary accordingto the clinical situation.

MATERIAL PROPERTIES

There are three inherent properties of the resincomposites that are crucial over the magnitude ofstress: the volumetric shrinkage, the material’sstiffness (elastic modulus), and the degree ofconversion from double carbon bonds into simplecarbon bonds.

The complexity of polymerization shrinkagestress relies on the fact that these threecomponents are interrelated and it is hard to identifythe relative contribution of each individual

factor; although some recent studies tried to isolatethose.20,21

ADHESIVE MONOMERS

An outstanding characteristic of adhesive monomers(adhesion-promoting monomers) is their ability tochemically interact with the tooth surface. On themolecular structure of adhesive monomers, it typicallycontains carboxylic acid group or its anhydride group,phosphoric acid group, or phosphonic acid group.Sulfur-containing adhesive monomers were developedfor the purpose of adhesion to precious metals andtheir alloys.

Few of the commercially utilized carboxylic acid-typeadhesive monomers, are NPG-GMA, PMDM, 4-META,4- AETA, 4-MET, 4AET, MAC-10. Phosphorus-containing adhesive monomers utilized in theformulations of commercial dental adhesives, arephenyl-P, 10-MDP, PENTA-P, and 6-MHPA.Phosphonic acid monomers, namely, MωP, EAEPA,and MAEPA were recently developed. In particular, todesign single-bottle self-etching adhesives, they havereceived considerable recent attention because of theirsuperior hydrolytic stability.22,23

CLINICAL PROCEDURES TO REDUCESHRINKAGE STRESS

The concurrent clinical and market trends such asdesire to place of fewer increments, the development oflower shrinkage stress materials to address bulk curing,higher intensity light sources coupled with some claimsof shorter cure time are the result of more recentresearch, and development efforts that have addressedthe issue of polymerization shrinkage.

Many clinical methods have been proposed to reduceshrinkage stress, such as incremental layeringtechniques,24,25 control of curing light irradiance,26,27 andflowable resin liner application.28 However, no methodhas been shown to be totally effective in abating theeffects of polymerization shrinkage.



INCREMENTAL LAYERING TECHNIQUE

Many researchers have suggested the use of“incremental layering techniques” for resin-compositerestoration to reduce the polymerization shrinkagestress and cusp deflection.24,25 The rationale is thatshrinkage may be less detrimental when there are fewerbonded cavity walls involved at each stage of therestoration procedures. Incremental curing mayenhance the degree of cure in thick sections and mayundergo higher degree of cure due to lower lightattenuation. It depends on many factors such as theoptical properties of the material, light source intensity,and exposure time, etc. This yields better mechanicalproperties but higher shrinkage as well; however, theC-factor changes as well.

Nevertheless, the literature is not conclusive concerningthe advantages promoted by the incremental layeringtechnique over the effects of resin-compositepolymerization shrinkage. Despite the controversy overthe advantages of incremental build-up of resincomposites, this technique has been broadlyrecommended in direct resin-composite restorationbecause it is expected to decrease the C-factor, allowinga certain amount of flow to partially dissipate theshrinkage stress.

LIGHT-CURING METHODS

Diverse photoactivation protocols have been advocatedto reduce the polymerization stress.29,30 In theory, stressrelease by viscous flow before the vitrification stagewould be allowed to occur without compromising thefinal polymer properties.31 Therefore, initial lightexposure at lower irradiance values might lead to theformation of a reduced number of polymer growthcenters, reducing the reaction rate and decreasing stressdevelopment due to the increased opportunity for resinflow before the vitrification stage.

There are many types of alternative light-curingmethods. The “soft-start” protocol consists of initiallight exposure with reduced irradiance for a certainperiod of time, followed by full irradiance. Another

protocol is “pulse-delay” method, where the clinicianmay apply the initial exposure with reduced lightirradiance for a very short period of time of a fewseconds and follows a waiting period without irradiance(seconds or even minutes) and fully irradiate later.

The alternative light-curing protocols may notsignificantly affect final properties of the hardenedmaterial, some considerations should be noted: (1) theflowability of a material during an extended presetstage, may have minimal consequences because mostshrinkage stress is developed during and after thevitrification stage.32 Therefore, opportunities forpolymer relaxation would be restricted during the shortperiod of light activation.33 (2) Soft-start irradiationprocedures give somewhat lower DC levels, associatedwith reduced stress.34 (3) A reduced polymerization rateis associated with decreased cross-link density,manifested as a greater solvent-softening and/or lowerfinal elastic modulus.35

STRESS-ABSORBING LAYERS WITH LOWELASTIC MODULUS LINERS

Flowable composites are low-viscosity resin-basedrestorative materials, which differ from conventionalresin composites in their filler load and resin content.These materials are less rigid and could have a modulusof elasticity 20% to 30% lower than conventional hybridcomposites. The use of a flowable resin composite as anintermediate thin layer has been suggested as a mean ofovercoming polymerization shrinkage stress based onthe concept of an “elastic cavity wall” suggested forfilled adhesives.36According to the “elastic cavity wallconcept,” the shrinkage stress generated by asubsequent layer of higher modulus resin compositecan be absorbed by an elastic intermediary layer,thereby reducing the stress at the tooth-restorationinterface manifested clinically as a reduction in cuspaldeflection.37

However, actual implementation of such a“stress-absorbing” material is problematic. Flowableresin composites have shown shrinkage stresscomparable to conventional resin composites,



supporting the hypothesis that the use of flowablematerials does not lead to marked stress reduction andthe risk of debonding at the adhesive interface as aresult of polymerization contraction is similar for bothtype of materials.38

PREHEATING

Recently, preheating resin composites have beenadvocated as a method to increase composite flow,improve marginal adaptation, and monomerconversion. The benefits of preheating composites mayhave an impact on daily restorative procedures as well,with the application of shorter light exposure to provideconversion values similar to those seen in unheatedconditions.39 The reasons for increased conversion arebased on many factors. Increased temperature decreasessystem viscosity and enhances radical mobility,resulting in additional polymerization and higherconversion.

CHANGES IN MATERIAL FORMULATIONS

Formulations containing one or more of the basemonomers, BisGMA, EBPADMA, UDMA, andTEGDMA, have been utilized commercially fordecades. A vast amount of research has focused ondeveloping systems with alterations and improvementsto the formulations, including the incorporation ofmonomethacrylate diluents, dimethacrylates, andmultimethacrylates.

Multimethacrylates

Modifications of bisphenol-A-based dimethacrylatesystems have included the use of pendant bulky(aromatic) constituents40 as well as pendant alkylurethanes41 to increase molecular weight and therebydecrease volume shrinkage. Derivatives of urethanedimethacrylate have been synthesized to increasemolecular weight, reduce water sorption, and/orincrease mechanical properties by incorporatingaromatic or aliphatic groups. Bile acids were utilized asstarting materials to form multimethacrylate

monomers.42 These materials showed reduced volumeshrinkage and promising mechanical properties;however, they exhibited extremely high viscosities(higher than BisGMA).

Monomethacrylate Diluents

These monomers contain secondary and tertiaryfunctionalities that lead to their unique polymerizationand polymer property behavior. These monomersexhibit rapid polymerizations that rival and oftenexceed those of equivalent di(meth)acrylates, and thepolymers exhibit a high glass transition temperature.Additionally, the mono(meth)acrylates exhibit highconversion, limiting the potential for leachablemonomer. These materials showed great promise whenutilized as diluents, and several monomethacrylateswere evaluated as alternatives to TEGDMA.43,44

Acidic Monomers

Incorporating acidic monomers in relatively small molefractions into methacrylate resins may enable a separateadhesive layer to be eliminated and result in improvedoverall performance. Acidic monomers have beensynthesized from o-hydroxyaryl phosphonates thatexhibited rapid polymerization kinetics.45

Monomers with increased molecular weight such asModified UDM Resin DX511 (895 g/mol), dimer acidmonomer (673–849 g/mol) have been developed forcomposites with reduced shrinkage.46 Urethanemonomer TCD-DI-HEA has been shown to producelower polymerization contraction stress.47

NOVEL POLYMERIZATION MECHANISMS

Presently, composite restoratives suffer from severaldrawbacks associated with the chain growth nature ofthe methacrylate-based free radical polymerizationprocess. It is fundamentally limited in several aspects.The chain-growth polymerization mechanism leads toearly gelation,12 whereas the methacrylate consumptionis linked to a defined volume reduction associated withthe consumption of each methacrylate.48 Improvements



in the methacrylate monomer structure, as notedpreviously, have the potential for addressing many ofthe shortcomings of current composites; however, aneven greater potential lies in completely changing thereaction mechanism, either by changing the activecenter (from radical to cationic), by changing the natureof the network/molecular weight evolution (bychanging to a step growth reaction or by changing to acovalent adaptable network), by changing the nature ofthe reactive chemistry (by going to ring openingspecies), or by changing the physical behavior thatarises during polymerization (by inducing phaseseparation).

Thiol-ene-based resins polymerize by a step growthradical polymerization mechanism. This result inreduced volume shrinkage per double bond and adelayed gel point conversion. The combination ofreduced shrinkage and delayed gelation promotessignificant reductions in shrinkage stress. However, theyexhibit reduced mechanical properties relative todimethacrylate-based systems.49,50 The use of thiol-enesas reactive diluents in ternary formulations results in asynergistic combination of both thiol-enepolymerization kinetics and shrinkage dynamics withdimethacrylate mechanical properties.50 The hybridnature of methacrylate-thiol-ene polymerization resultsin even greater reductions in shrinkage stress withoutcompromising mechanical properties.

Silorane resin reveals lower polymerization shrinkagecompared to the dimethacrylates. These “cyclic”monomers “open” their molecular structures with localvolumetric expansion and this may partly or totallycompensate for volumetric shrinkage from C = C orsimilar polymerization.51,52

Besides change in the resin matrix composition, studieshave demonstrated reduced shrinkage stress throughalterations in filler content. Condon and Ferracane53

suggested that addition of nonbonded 40-nm colloidalsilica might act as stress-relieving sites through plasticdeformation. They also verified that composites withnanofiller particles treated with a nonfunctional silanedeveloped 50% less stress than composites fully treatedwith the functional coupling agent. Efforts to modify

fillers have been aimed at improving the properties ofcomposites by the addition of polymer nanofibers, glassfibers, and titania nanoparticles.54,55 Silsesquioxanenanocomposites, which are essentially anorganic–inorganic hybrid molecule, reduce shrinkage,but also reduce mechanical properties if used in toohigh of a concentration.56 Changes in the photoinitiatorsystems and polymerization inhibitors have also beenreported. Another possible approach is inclusion of acomponent readily allowing plastic deformation duringstress development, such as ultrahigh molecular weightpolyethylene fibers.57

Thus, many factors affect the polymerization efficiency,be they intrinsic; photoinitiator type and concentration,viscosity (co-monomer composition and ratio, fillercontent) and optical properties, or extrinsic; light typeand spectrum, irradiation parameters (radiant energy,time, and irradiance), curing modes, temperature, andlight guide tip positioning.58

CONCLUSION

The success and longevity of the dimethacrylate-baseddental resin composites restoration can becompromised because of their inherent association withdimensional shrinkage. Various clinical procedures havebeen proposed to reduce shrinkage stress, but none ofthe methods has shown to be totally effective in abatingthe effects of polymerization shrinkage. The field ofcomposite dental restoratives continues to propose andachieve significant and exciting advances in resinformulation, filler loading and modification, and curingmethodologies and mechanisms.

DISCLOSURE AND ACKNOWLEDGEMENTS

The authors do not have any financial interest in thecompanies whose materials are included in the article.

REFERENCES

1. Kleverlaan CJ, Feilzer AJ. Polymerization shrinkage andcontraction stress of dental resin composites. Dent Mater2005;21(12):1150–57.



2. Weinmann W, Thalacker C, Guggenberger R. Siloranes indental composites. Dent Mater 2005;21(1):68–74.

3. Charton C, Falk V, Marchal P, et al. Influence of Tg,viscosity and chemical structure of monomers onshrinkage stress in light-cured dimethacrylate-baseddental resins. Dent Mater 2007;23(11):1447–59.

4. Feilzer AJ, Dauvillier BS. Effect of TEGDMA/BisGMAratio on stress development and viscoelastic properties ofexperimental two-paste composites. J Dent Res2003;82(10):824–28.

5. Ferracane JL. Buonocore Lecture. Placing dentalcomposites—a stressful experience. Oper Dent2008;33(3):247–57.

6. Bowen RL, Cobb EN, Rapson JE. Adhesive bonding ofvarious materials to hard tooth tissues: improvement inbond strength to dentin. J Dent Res 1982;61:1070–76.

7. Ikemura K, Endo T. Effect on adhesion of newpolymerization initiator systems comprising 5-monosubstituted barbituric acids, aromatic sulfinateamides and tert-butylperoxymaleic acid in dentaladhesive. J Appl Polym Sci 1999;72:1655–68.

8. Tay FR, King NM, Suh BI, Pashley DH. Effect of delayedactivation of light-curing resin composites on bonding ofall in- one adhesives. J Adhes Dent 2001;3:207–25.

9. Spencer P, Wang Y. Adhesive phase separation at thedentin interface under wet bonding conditions. J BiomedMater Res 2002;62:447–56.

10. Ogliari FA, Ely C, Lima GS, et al. Onium salt reduces theinhibitory polymerization effect from an organic solventin a model dental adhesive resin. J Biomed Mater Res BAppl Biomater 2008;86:113–8.

11. Ely C, Schneider LFJ, Ogliari FA, et al. Polymerizationkinetics and reactivity of alternative initiators systems foruse in light-activated dental resins. Dent Mater2012;28:1199–206.

12. Kloosterboer JG. Network formation by chaincrosslinking photopolymerization and its applications inelectronics. Adv Polym Sci 1988;84:1–61.

13. Anseth KS, Newman SM, Bowman CN. Polymeric dentalcomposites:properties and reaction behavior ofmultimethacrylate dental restorations. Adv Polym Sci1995;122:177–217.

14. Lovell LG, Berchtold KA, Elliott JE, et al. Understandingthe kinetics and network formation of dimethacrylatedental resins. Polym Adv Technol 2001a;12:335–45.

15. Bowman CN, Kloxin CJ. Toward an enhancedunderstanding and implementation ofphotopolymerization reactions. AIChE J 2008;54:2775–95.

16. Anseth KS, Wang CM, Bowman CN. Kinetic evidence ofreactiondiffusion during the polymerization ofmulti(meth)acrylate monomers. Macromolecules1994;27:650–5.

17. Loshaek S, Fox TG. Cross-linked polymers. I. Factorsinfluencing the efficiency of cross-linking in copolymersof methyl methacrylate and glycol dimethacrylates. J AmChem Soc 1953;75(14):3544–50.

18. Feilzer AJ, de Gee AJ, Davidson CL. Setting stress incomposite resin in relation to configuration of therestoration. J Dent Res 1987;66(11):1636–39.

19. Miguel A, de la Macorra JC. A predictive formula of thecontraction stress in restorative and luting materialsattending to free and adhered surfaces, volume anddeformation. Dent Mater 2001;17(3):241–46.

20. Gonçalves F, Pfeifer CS, Ferracane JL, Braga RR.Contraction stress determinants in dimethacrylatecomposites. J Dent Res 2008;87(4):367–71.

21. Pfeifer CS, Ferracane JL, Sakaguchi RL, Braga RR. Factorsaffecting photopolymerization stress in dental composites.J Dent Res 2008;87(11):1043–47.

22. Nishiyama N, Suzuki K, Yoshida H, et al. Hydrolyticstability of methacrylamide in acidic aqueous solution.Biomaterials 2004;25:965–9.

23. Moszner N, Salz U, Zimmermann J. Chemical aspects ofself-etching enamel-dentin adhesives: a systematic review.Dent Mater 2005;21:895–910.

24. Lee MR, Cho BH, Son HH, et al. Influence of cavitydimension and restoration methods on the cuspdeflection of premolars in composite restoration. DentMater 2007;23(3):288–95.

25. Park J, Chang J, Ferracane J, Lee IB. How shouldcomposite be layered to reduce shrinkage stress:incremental or bulk filling? Dent Mater2008;24(11):1501–05.

26. Feilzer AJ, Dooren LH, de Gee AJ, Davidson CL.Influence of light intensity on polymerization shrinkageand integrity of restoration-cavity interface. Eur J Oral Sci1995;103(5):322–26.

27. Uno S, Asmussen E. Marginal adaptation of a restorativeresin polymerized at reduced rate. Scandinavian. J DentRes 1991;99(5):440–44.

28. Alomari QD, Reinhardt JW, Boyer DB. Effect of liners oncusp deflection and gap formation in compositerestorations. Oper Dent 2001;26(4):406–11.

29. Silikas N, Eliades G, Watts DC. Light intensity effects onresin-composite degree of conversion and shrinkagestrain. Dent Mater 2000;16(4):292–6.

30. Pfeifer CSC, Braga RR, Ferracane JL. Pulse delay curing:influence of initial irradiance and delay time on shrinkagestress and microhardness of restorative composites. OperDent 2006;31(5):610–15.

31. Cavalcante LM, Masouras K, Watts DC, et al. Effect ofnanofillers’ size on surface properties after toothbrushabrasion. Am J Dent 2009;22(1):60–4.

32. Charton C, Colon P, Pla F. Shrinkage stress in light-curedcomposite resins: influence of material and



photoactivation mode. Dent Mater 2007;23(8):911–20.

33. Lu H, Stansbury JW, Bowman CN. Towards theelucidation of shrinkage stress development andrelaxation in dental composites. Dent Mater2004;20(10):979–86.

34. Lu H, Stansbury JW, Bowman CN. Impact of curingprotocol on conversion and shrinkage stress. J Dent Res2005;84(9):822–26.

35. Feng L, Suh BI. A mechanism on why slowerpolymerization of a dental composite produces lowercontraction stress. J Biomed Mater Res B Appl Biomater2006;78(1):63–9.

36. Braga RR, Hilton TJ, Ferracane JL. Contraction stress offlowable composite materials and their efficacy asstress-relieving layers. JADA 2003;134(6):721–28.

37. Cara RR, Fleming GJP, Palin WM, et al. Cuspal deflectionand microleakage in premolar teeth restored withresin-based composites with and without an intermediaryflowable layer. J Dent 2007;35(6):482–9.

38. Cadenaro M, Marchesi G, Antoniolli F, et al. Flowabilityof composites is no guarantee for contraction stressreduction. Dent Mater 2009;25(5):649–54.

39. Daronch M, Rueggeberg FA, De Goes MF. Monomerconversion of pre-heated composite. J Dent Res2005;84(7):663–67.

40. Ge J, Trujillo M, Stansbury J. Synthesis andphotopolymerization of low shrinkage methacrylatemonomers containing bulky substituent groups. DentMater 2005;21:1163–9.

41. Khatri CA, Stansbury JW, Schultheisz CR, Antonucci JM.Synthesis, characterization and evaluation of urethanederivatives of Bis-GMA. Dent Mater 2003;19:584–8.

42. Gauthier MA, Zhang Z, Zhu XX. New dental compositescontaining multimethacrylate derivatives of bile acids: acomparative study with commercial monomers. ACSAppl Mater Interfaces 2009;1:824–32.

43. Lu H, Stansbury JW, Nie J, et al. Development of highlyreactive mono-(meth)acrylates as reactive diluents fordimethacrylate-based dental resin systems. Biomaterials2005;26:1329–36.

44. Kilambi H, Cramer NB, Schneidewind LH, et al.Evaluation of highly reactive mono-methacrylates asreactive diluents for BisGMA-based dental composites.Dent Mater 2009;25:33–8.

45. Sahin G, Albayrak AZ, Sarayli Z, Avci D. Synthesis andphotopolymerization of new dental monomers fromo-hydroxyaryl phosphonates. J Polym Sci Part A: PolymChem 2006;44:6775–81.

46. Lui H, Trujillo-Lemon M, Ge J, Stansbury JW. Dentalresins based on dimer acid dimetharylates: a route to highconversion with low polymerization shrinkage.Compendium 2010;31(special issue2):1–4.

47. Marchesi G, Breschi L, Antoniolli F, et al. Contractionstress of low-shrinkage composite materials assessedwith different testing systems. Dent Mater 2010;26:947–53.

48. Patel MP, Braden M, Davy KW. Polymerization shrinkageof methacrylate esters. Biomaterials 1987;8:53–6.

49. Lu H, Carioscia JA, Stansbury JW, Bowman CN.Investigations of step-growth thiol-ene polymerizationsfor novel dental restoratives. Dent Mater2005;21:1129–36.

50. Cramer NB, Couch CL, Schreck KM, et al. Investigationof thiol-ene and thiol-ene- methacrylate based resins asdental restorative materials. Dent Mater 2010;26:21–8.

51. Guggenberger R, Weinmann W. Exploring beyondmethacrylates. Am J Dent 2000;13(5):82D–4D.

52. Eick JD, Kotha SP, Chappelow CC, et al. Properties ofsilorane-based dental resins and composites containing astress-reducing monomer. Dent Mater2007;23(8):1011–17.

53. Condon JR, Ferracane JL. Reduction of compositecontraction stress through non-bonded microfillerparticles. Dent Mater 1998;14(4):256–60.

54. Chen M-H. Update on dental nanocomposites. J DentRes 2010;89:549–60.

55. Ferracane JL. Resin composite-state of the art. DentMater 2011;27:29–38.

56. Soh MS, Yap AUL, Sellinger A. Physicomechanicalevaluation of low-shrinkage dental nanocomposites basedon silsesquioxane cores. Eur J Oral Sci 2007;115:230–8.

57. Ferracane JL, Ferracane LL, Braga RR. Effect of admixedhigh-density polyethylene (HDPE) spheres on contractionstress and properties of experimental composites.J Biomed Mater Res B Appl Biomater 2003;66(1):318–23.

58. Leprince JG, Palin WM, Hadis MA, et al. Progress indimethacrylate-based dental composite technology andcuring efficiency. Dent Mater 2013;29(2):139–56.



Management of Shrinkage Stresses in Direct Restorative Light-Cured Composites: A Review

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