Smart Materials in Dentistry

Australian Dental Journal 2011; 56:(1 Suppl): 3–10

doi: 10.1111/j.1834-7819.2010.01291.x

Smart materials in dentistry

JF McCabe,* Z Yan,* OT Al Naimi,* G Mahmoud,* SL Rolland*

*School of Dental Sciences, Newcastle University, United Kingdom.

ABSTRACT

Most dental materials are designed to have a relatively ‘neutral’ existence in the mouth. It is considered that if they are‘passive’ and do not react with the oral environment they will be more stable and have a greater durability. At the same time,it is hoped that our materials will be well accepted and will cause neither harm nor injury. This is an entirely negativeapproach to material tolerance and biocompatibility and hides the possibility that some positive gains can be achieved byusing materials which behave in a more dynamic fashion in the environment in which they are placed.An example of materials which have potential for ‘dynamic’ behaviour exists with structures which are partly water-basedor have phases or zones with significant water content and for which the water within the material can react to changes inthe ambient conditions. Such materials may even be said to have the potential for ‘smart’ behaviour, i.e. they can react tochanges in the environment to bring about advantageous changes in properties, either within the material itself or in thematerial-tooth complex. The controlled movement of water or aqueous media through the material may cause changes indimensions, may be the carrier for various dissolved species, and may influence the potential for the formation of biofilms atthe surface. Some of these issues may be closely interrelated.Clearly, materials which do not have the capacity for water transport or storage do not have the potential for this sort ofbehaviour.Some materials which are normally resistant to the healthy oral environment can undergo controlled degradation at low pHin order to release ions which may prove beneficial or protective. It is doubtful whether such behaviour should be classifiedas ‘smart’ because the material cannot readily return to its original condition when the stimulus is removed.Other materials, such as certain alloys, having no means of transporting water through their structure, can display smartbehaviour by undergoing predictable changes in structure in response to applied mechanical or thermal stimuli. It has beendifficult to harness such behaviour to the benefit of patients but progress in this area is slowly being made.

Keywords: Smart materials, fluoride release, fluoride recharging, glass-ionomers, biofilms.

Abbreviations and acronyms: GIC = glass-ionomer cement; HEMA = hydroxyethylmethacrylate; PAA = polyacrylicacid; PAN =polyacrylonitrile; PVA = polyvinylalcohol; QLF = quantitative light-induced fluorescence; RMGIC = resin modified glass-ionomer cement;SMA = shape memory alloys.

INTRODUCTION

Traditionally, materials designed for long-term use inthe body or more specifically in the mouth are thoughtto survive longer if they are ‘passive’ and have nointeraction with their environment. Materials such asamalgams, composites and cements are often judged ontheir ability to survive without interacting with the oralenvironment. Perhaps the first inclination that an‘active’ rather than ‘passive’ material could be attrac-tive was the realization of the benefit of fluoride releasefrom materials.

The nature of smart materials

By definition and general agreement, smart materials arematerials that have properties which may be altered in acontrolled fashion by stimuli, such as stress, tempera-

ture, moisture, pH, electric or magnetic fields. A keyfeature of smart behaviour includes an ability to return tothe original state after the stimulus has been removed.1

Existing smart materials include piezoelectric materi-als which produce a voltage when stress is applied or viceversa.2 Structures made from these products can be madeto change shape or dimensions when a voltage is applied.Likewise, a change in shape can be used to generate avoltage which can be used for the purpose of monitoring.

Thermo-responsive materials, such as shape memoryalloys3 or shape memory polymers4 adopt differentshapes at different temperatures due to remarkable andcontrolled changes in structure. Magnetic shape mem-ory alloys can change their shape in response to achange in magnetic field.

pH-sensitive polymers are materials which swell ⁄collapse when the pH of the surrounding media changes.5

Other materials change colour in response to changes in

ª 2011 Australian Dental Association 3

Australian Dental JournalThe official journal of the Australian Dental Association

pH, light or applied voltage. One common example ofthis sort of technology is the light-sensitive sunglasseswhich darken when exposed to bright sunlight.

Polymer gels offer a potential for smart behaviour.1,6

Theyconsistofcross-linkedpolymernetworkswhichmaybe inflated with a solvent such as water. The labile natureof the solvent enables a rapid and reversible swelling orshrinkage in response to a small change in their environ-ment (e.g. temperature). The most common gel formingpolymers are polyvinylalcohol (PVA), polyacrylicacid(PAA) and polyacrylonitrile (PAN). Microsized gel fibresmay contract in milliseconds, while thick polymer layersmay require much longer to react. It has been suggestedthat these gels canpotentiallydeliver a stress equivalent tothat of a human muscle of about equivalent size.

Smart materials by chance or design

The future use of smart materials will involve a degreeof ‘smart behaviour’ by design. However, smart behav-iour was first noted in some materials by chance and thesignificance of the special nature may not be recognizedas being of any practical use until some time later. Thiswas certainly the case for thermo-responsive materials,either shape memory alloys or shape memory polymers.Shape memory alloys3 based upon NiTi alloys havebeen used in orthodontics for many years and theirremarkable properties have been commented uponwithout any insight into how the properties could beharnessed for a practical purpose. Likewise thepotential thermo-responsive smart behaviour of someglass-ionomer cements was first suggested by Davidson7

and was then demonstrated as a result of attempting tomeasure the coefficient of thermal expansion.8–11

Heating or cooling of these materials may result inminimal dimensional change as the expected expan-sions (heating) or contractions (cooling) appear to beoffset by a compensating reaction related to themovement of water in or out of the structure.

Smart alloys – the first smart dental materials

The term ‘smart material’ or ‘smart behaviour’ in thediscipline which is now loosely defined as ‘dentalmaterials science’, was probably first used in connectionwith nickel-titanium alloys, or shape memory alloys(SMAs), which are used as orthodontic wires. Frustrat-ingly, although these materials were found to havefascinating characteristics in relation to the way theirstructure ⁄ properties changed in response to strain andtemperature, it has never been clearly expounded howtheir characteristics could be used beneficially duringpatient treatment. The smart behaviour is essentiallyrelated to the ability of the alloy to initially undergostrain in response to stress in the normal way, but at thepoint identified as the yield stress there is a further

increase in strain which in ‘normal’ alloys would beidentified as irreversible yielding.12,13 In the SMAalloys, however, this ‘yielding’ is related to a reversiblechange in the crystal structure. The reverse process istemperature dependent and this lies at the heart of thedifficulty in harnessing the characteristic for clinicalbenefit as the temperatures required can be very high.However, this knowledge has been used in the manu-facture of wires of similar cross-section but markedlydifferent stiffness. The phase changes involved inthe crystal transitions involve a small exothermic ⁄endothermic response which can be used to monitor ormeasure the extent of the change. However, the amountof energy involved is very small and very sensitiverecording equipment is required (e.g. temperaturemodulated differential scanning calorimetry).14 Inorder to fully utilize the super-elastic or shape memorycharacteristics, it would be essential to enable the phasetransitions to occur in a controlled fashion at or nearmouth temperature, and this is now claimed to bepossible by some manufacturers. Wires exhibitingshape-memory behaviour at mouth temperature nor-mally contain copper and ⁄ or chromium in addition tonickel and titanium.

The role of water

Many types of smart behaviour are related to the abilityof a gel structure to absorb or release solvent rapidly inresponse to a stimulus such as temperature. In the oralenvironment, the key solvent is water and the structuresmay be gels or salts which contain water which may bebound either strongly or loosely and therefore may beabsorbed or released at different rates. Some types ofsmart behaviour may also be defined by any species,such as fluoride ions dissolved in the water and whichare capable of undergoing reversible interactions withthe gel, salt or oral structures. Depending upon thenature of the water and how strongly it is bound, theobserved changes may be dependent upon the dimen-sions of the structures.11

Smart thermal behaviour

The vast majority of materials responds to a temper-ature change in a predictable manner. This involves adimensional change characterized by the coefficient ofthermal expansion or expansivity. One problem withdental filling materials is their tendency to expand andcontract to a greater extent than the natural tooth tissuewhen subjected to hot or cold stimuli. When samples ofrestorative materials were heated in order to determinetheir values of coefficient of thermal expansion, aninteresting observation was made. For compositematerials, expansion and contraction occurred in theexpected way and a coefficient could readily be

4 ª 2011 Australian Dental Association

JF McCabe et al.

determined, and whether testing was done dry or wetmade little or no difference.8 For glass-ionomers, littleor no change in dimension was observed when heatingand cooling between 20 �C and 50 �C in wet conditions(Fig 1).9,10 In dry conditions, the materials showed amarked contraction when heated above 50 �C. Theexplanation for this behaviour is that the expectedexpansion on heating is compensated by fluid flow tothe surface of the material to cause a balancing of thedimensional changes. On cooling, the process wasreversed. In dry conditions, the rapid loss of water onheating results in the observed contraction. Thisbehaviour is akin to that of human dentine (Fig 2)where very little dimensional change is observed onheating in wet conditions and a marked contraction isnoted in dry conditions.11 Both results can be explainedby flow of fluids in the dentinal tubules. Hence, theglass-ionomer materials can be said to be mimicking thebehaviour of human dentine through a type of smartbehaviour.

The role of porosity

The smart behaviour of glass-ionomers and relatedmaterials is closely linked to their water content and the

way in which this can react to changes in theenvironment. Clearly, there are different ways in whichwater can be retained in and transported through thecement structure. One important feature which mayprovide a location for the formation of reservoirswithin the material is porosity. The number and size ofpores within a cement can be controlled by the methodof mixing and is conveniently measured using micro-CTscanning.15 Figure 3 shows typical scans of a glass-ionomer cement mixed mechanically in capsules orhandmixed. The volume of bubbles can readily becalculated and is shown in Table 1.

The results given in Table 1 indicate that both themethod of mixing and the viscosity of the cement havean effect on porosity. In the low viscosity material,handmixing reduces the porosity significantly comparedto mechanical mixing, either by shaking or rotation.For the viscous material the levels of porosity are lowand not significantly affected by mixing. These differ-ences in porosity are reflected in differences in waterabsorption (Table 2).11,16 Hence, this aspect of the

Fig 1. Dimensional change plotted against temperature for threeglass-ionomers (KC, KM, F) and one resin modified glass-ionomer

(FLC).

Fig 2. Dimensional change of human dentine when heated under wetor dry conditions.

Fig 3. Micro-CT scans of a glass-ionomer cement (Ketac-Cem) mixedmechanically by shaking (CapMix) or rotating (RotoMix). L, M andH refer to low, medium and high examples of porosity within each

group.

Table 1. The volume of bubbles in a low viscosityglass-ionomer (Ketac-Cem) and a high viscosity glass-ionomer (Ketac-Molar) using different methods ofmixing

Material

Mixing method

CapMix RotoMix Hand

Ketac-CemAplicap 2.8 (1.6) 1.8 (1.8) –Maxicap 2.7 (2.6) 2.1 (2.1) 0.2 (0.2)Hand – – 0.1 (0.1)

Ketac-MolarAplicap 0.2 (0.2) 0.1 (0.1) –Hand – – 0.1 (0.1)



smart behaviour of dental cements can be controlled bythe operator.

Expansion and radial pressure

Smart materials which combine a special interactivecharacteristic with an acceptable durability or longevityare likely to combine some salt or gel characteristicwith a resin component imparting some stability. Themanufacturing of such materials presents a problem ofcompatibility. Traditionally, such problems are solvedby also incorporating species with both hydrophilic andhydrophobic groups which have the function of bridg-ing or coupling the two distinctly different ingredients.The most commonly used of these compounds ishydroxyethylmethacrylate (HEMA). However, thelarge and rapid water absorption of polymers contain-ing HEMA can cause problems; not only does theabsorption result in swelling but a considerable radialpressure can also be linked to the process.17,18 Profilesof cavities containing a blend of GIC and resin phaseswith HEMA constrained within a cavity show the‘growth’ of the material out of the cavity and this iscombined with a considerable radial pressure measuredas around 26 MPa compared with <3 MPa caused bythe water absorption of a typical resin matrix compos-ite.19

Ion release and recharging

The beneficial effect of fluoride release of dentalmaterials has been the subject of much research overmany years. There is some doubt about the efficacy offluoride release in caries prevention since even productswith high initial fluoride release tend to rapidly lose theability to release fluoride in significant amounts. Even inthe case of GICs, the fluoride release rate can becomenegligible within a week.20–22 However, the smartbehaviour of materials containing GIC salt phasesoffers some long-term solutions to this problem. Thereis evidence that the fluoride released from salt phasescan be replaced when the material is bathed in a highconcentration of fluoride as may occur in a toothpasteor mouthrinse.16,17,23,24 In the long term, the fluoridere-released after recharging may be much more impor-tant than the initial ‘burst’ which is sustained only for ashort time.

Figure 4 shows data for one material in whichfluoride release over 24-hour periods into water is seen

to decline sharply over just a few days. As the materialbecomes depleted of its inherent fluoride it is interestingthat the ‘spikes’ of fluoride in the 24-hour period afterrecharging appear to increase slightly with age.17 Thisimplies that the more inherent fluoride lost, the greatercapacity for uptake through recharging. The levels offluoride release maintained can be increased by begin-ning the recharging process as soon as possible aftersetting. Other work has shown that the rates of fluoriderelease and recharging are temperature sensitive.16

Hence, a more rapid recharging could be accomplishedby using warm fluoride containing solutions and thiscan generate a more sustained release at mouthtemperature.

Another area where ‘smart’ fluoride interactions canhave a significant benefit is in the prevention ofdemineralization around orthodontic brackets (Fig 5).Using fluoride releasing cements can help to preventdemineralization. This has been studied using quanti-tative light-induced fluorescence (QLF) (Fig 6).

Results of laboratory studies25 show that the useof fluoride-releasing cements can minimize the

Table 2. Porosity and water absorption of Ketac-Cemglass-ionomer cement

Mixing method Porosity (%) 24 h water absorption (%)

CapMix 2.7 (2.6) 1.32 (0.25)Hand 0.2 (0.2) 0.84 (0.11)

Fig 5. White lesions corresponding to areas of demineralized enamelremaining in the areas surrounding the site where orthodontic brackets

were bonded.

Fig 4. Twenty-four hour fluoride release for a resin matrix systemcontaining some GIC salt matrix zones as a function of time of storagein water. At days 8, 17, 23 and 30 the specimens were subjected to asoak in 250 ppm NaF solution for 1 hour. The two lines are for

different methods of measuring fluoride concentration.


JF McCabe et al.

demineralization, and that this effect is not simplydependent upon the extent of the initial fluoride release.Materials having various levels of fluoride release

appear to be almost equally effective when comparedwith a material having negligible fluoride release, asshown in the QLF images (Fig 7). Another aspect ofsmart behaviour for this type of material involves thedevelopment of materials having mechanical propertiesadequate for the retention of brackets but which enableeasy debonding of brackets at the end of treatment.26

Some resin based materials have a potential to releasefluoride and neutralize acids.27 Other resin basedmaterials have been designed to release calcium,fluoride and hydroxyl ions at low pH28,29 and thesematerials are reported to have the potential to neutral-ize acids and to prevent, or even reverse, demineraliza-tion. However, clinical performance of such reactiveproducts is often reported to be unsatisfactory. Thishighlights the potential problem which exists for manytypes of smart material: their smart behaviour dependsupon a degree of reactivity which may not be compat-ible with longevity. Taking this a stage further, smartcomposite materials have been developed30–35 whichcontain amorphous calcium phosphate particles orwhiskers which at low pH provide a source of calciumand phosphate ions which may act to prevent demin-eralization of tooth structure and reportedly maintainacceptable mechanical properties in the process.

Biofilms and smart behaviour

Biofilms formed on the surface of materials in themouth may enhance the smart behaviour of materialscontaining fluoride releasing salt phases.36,37 Recentwork with saliva, using live ⁄ dead staining tech-niques,23,36 has shown that fluoride release from

Fig 6. QLF device used to study demineralization in teeth and thepositive effects of fluoride release and recharging. Taken from

InspektorTM Pro Manual.

Fig 7. Pre and post-demineralization QLF images around orthodontic brackets showing significant demineralization around a non-fluoride releasingcement and minimal demineralization around cements with ‘large’ or moderate fluoride release or recharging capacity.



materials does not prevent biofilm formation orgrowth. Figure 8 shows that the daily fluoride releasein natural saliva is significantly lower than the releaseinto distilled water or artificial saliva. However, whensamples are stored in acidified (pH 4) saliva the rate offluoride release is markedly increased (Fig 9). Moreinteresting are the results which show that when thespecimens are cycled through both acidic and neutralconditions, an increase in fluoride release is seen at day1 and then also at day 2 after placing into acidicconditions.36 This offers some proof that fluoridebecomes concentrated within the biofilm and is madeavailable when the film is disturbed.

The presence of a biofilm on the surface of a materialalters the interaction of the surface with the environ-ment and in the case of a restorative material, thebiofilm may act as a lubricant which prevents abrasivewear (Fig 10).36 The formation of biofilms and the wayin which this changes the interaction of the materialswith the environment represents a clear example ofsmart behaviour for these materials. It seems thatbiofilms can protect surfaces from abrasive forces and

at the same time concentrate fluoride which is liberatedthrough a change in pH or mechanical debridment.

Design of smart materials

Now that the ways in which materials containing apolysalt matrix can exhibit smart behaviour have beendemonstrated, it is appropriate to consider whetherfuture materials can have ‘smartness’ designed intothem. If so, can the smart behaviour be accommodatedwithout compromising the other key requirements,such as clinical function and longevity? Of the currentlyavailable dental materials, the products which mostpositively react with their environment in a mannerwhich could be interpreted as smart are the glass-ionomer cements. However, these products are knownto have limited durability and longevity due to theirbrittleness and solubility.

Materials demonstrating an optimum combination ofsmart interactions and longevity are likely to have somecombination of stable resin matrix combined with acoexistent salt matrix or discrete gel phase. The rapiddevelopments in nanotechnology suggest that suchfeatures can be manufactured into compounds by usingbuilding blocks at a molecular or even atomic level.However, in 1996 Friend38 stated, ‘The development oftrue smart materials at the atomic scale is still some wayoff, although the enabling technologies are underdevelopment. These require novel aspects of nanotech-nology (technologies associated with materials andprocesses at the nanometre scale, (10)9 m) and thenewly developing science of shape chemistry’. Thisstatement still holds true to an extent today. However,our understanding of the potential benefits of smartbehaviour have enabled scientists to appreciate thepotential benefits of ‘active’ as opposed to ‘passive’materials and the development of materials exhibitingsmart behaviour is now recognized to be possibleoutside the realms of nanotechnology with its ratherartificial and restricting boundaries and definitions.Hence, even with existing technologies we are able toconsider building materials with controlled structureand properties.

Within the spectrum of materials which lie in thecontinuous scale between resin matrix composites andsalt matrix glass-ionomers,17,39 we are already able toidentify various materials described as resin modifiedGICs (RMGICs), polyacid-modified resin composites(compomers) or glass-ionomer composites (giomers).These have been shown to exhibit some smart charac-teristics, albeit more through chance than design. Thenext stage is to harvest the current knowledge into thedesign of materials with controlled and designedstructure in which the requirements of longevity andsmart interaction are balanced. For example, whenresin matrix and salt matrix setting reactions are

Fig 8. Fluoride release (24-hour values) from a GIC into differentstorage media. Release into natural saliva is slower than into water or

artificial saliva.

Fig 9. Fluoride release into natural saliva in acidified, neutral orcycled (A&N or N&A) conditioned. Note the marked increase in

fluoride release over both the first and second day of placement intoacidic conditions.


JF McCabe et al.

competing during the setting of an RMGIC material, itis possible to conceive of means of controlling theextent to which one or other of the processes dominatesand hence to influence the structure and properties ofthe set material.

ACKNOWLEDGEMENT

The authors are grateful to Professor Seiji Ban, editor ofthe Dental Materials Journal, for permission to repro-duce large parts of this paper which was originallypresented at the International Dental Materials Con-gress, Bangkok in 2003 and published in Dent Mater J2009;28:37–43.

REFERENCES

1. Zrinji M, Szilagyi A, Filipcsei G, Feher J, Szalama J, Moczar G.Smart gel-glass based on the responsive properties of polymergels. Polym Adv Technol 2001;12:505–510.

2. Allameh SM, Akogwu O, Collinson M, Thomas J, Soboyejo WO.Piezoelectric generators for biomedical and dental applications:effect of cyclic loading. J Mater Sci Mater Med 2007;18:39–45.

3. Gil FJ, Planell JA. Shape memory alloys for medical applications.Proc Inst Mech Eng 1998;212:473–488.

4. Lendlein A, Langer R. Biodegradeable, elastic, shape-memorypolymers for potential biomedical applications. Science2002;296:1673–1676.

5. Stayton PS, El-Sayed ME, Murthy N, et al. Smart delivery systemsfor biomolecular therapeutics. Orthod Craniofac Res2005;8:219–225.

6. Prabaharan M, Mano JF. Stimuli responsive hydrogels based onpolysaccharides incorporated with thermo-responsive polymersas novel biomaterials. Macromol Biosci 2006;8:991–1008.

7. Davidson CL. Glass ionomer cements, intelligent materials. BullGroup Int Rech Sci Stomatol Odontol 1998;40:38–42.

8. Sidhu SK, Carrick TE, McCabe JF. Temperature mediated coef-ficient of dimensional change of dental tooth-coloured restorativematerials. Dent Mater 2004;20:435–440.

9. Yan Z, Sidhu SK, Carrick TE, McCabe JF. Response to thermalstimuli of glass ionomer cements. Dent Mater 2007;23:597–600.

10. Yan Z, Sidhu SK, McCabe JF. The influence of microstructure onthermal response of glass ionomers. J Mater Sci Mater Med2007;18:1163–1166.

11. Yan Z. Smart materials in dentistry. Newcastle University, UnitedKingdom, 2006. PhD thesis.

12. Gil FJ, Planell JA. Shape memory alloys for medical applications.Proc Inst Mech Eng H 1998;212:473–488.

13. Gil FJ, Planell JA. Effects of copper addition on the superelasticbehaviour of Ni-Ti shape memory alloys for orthodontic appli-cations. J Biomed Mater Res 1999;48:682–688.

14. Brantley WA, Iijima M, Grentzer TH. Temperature-modulatedDSC provides new insight about nickel-titanium wire transfor-mations. Am J Orthod Dentofacial Orthop 2003;124:387–394.

15. Nomoto R, Komoriyama M, McCabe JF, Hirano S. Effect ofmixing method on the porosity of encapsulated glass ionomercement. Dent Mater 2004;20:972–978.

16. Yan Z, Sidhu SK, Mahmoud GA, Carrick TE, McCabe JF. Effectsof temperature on the fluoride release and recharging ability ofglass ionomers. Oper Dent 2007;32:138–143.

17. McCabe JF. A laboratory evaluation of the water and fluorideequilibrium characteristics of reactmer giomer. InternationalMeeting Proceedings, Shofu Inc., 2001.

18. McCabe JF, Rusby S. Water absorption, dimensional change andradial pressure in resin matrix dental restorative materials. Bi-omaterials 2004;25:4001–4007.

19. Momoi Y, McCabe JF. Hygroscopic expansion of resin basedcomposites during 6 months of water storage. Br Dent J1994;176:91–96.

20. Shaw A, McCabe JF, Carrick TE. Fluoride release from glassionomers and compomers. J Dent 1998;26:355–360.

Fig 10. Surface profiles of a GIC at baseline and after brushing in acidified saliva (natural or artificial). This illustrates the protective effect of thebiofilm formed in natural saliva.



21. Momoi Y, McCabe JF. Fluoride release from light-activatedglass ionomer restoration cements. Dent Mater 1993;9:151–154.

22. McCabe JF, Carrick TE, Sidhu SK. Determining low levels offluoride released from resin based dental materials. Eur J Oral Sci2002;110:380–384.

23. Al Naimi OT, Itota T, Hobson RS, McCabe JF. Fluoriderelease for restorative materials and its effect on biofilm forma-tion in natural saliva. J Mater Sci Mater Med 2008;19:1243–1248.

24. Itota T, Carrick TE, Yoshiyama M, McCabe JF. Fluoride releaseand recharge in giomer, compomer and resin composite. DentMater 2004;20:789–795.

25. Mahmoud G, Pretty IA, Gordon PH, McCabe JF. Effect offluoride release on enamel de-mineralisation adjacent to ortho-dontic brackets. Proceedings BSDR 2007, Abstract 217.

26. Larmour CJ, McCabe JF, Gordon PH. An ex vivo assessment ofresin-modified glass ionomer bonding systems in relation toceramic bracket debond. J Orthod 2000;27:329–332.

27. Itota T, Al-Naimi OT, Carrick TE, Yoshiyama M, McCabe JF.Fluoride release and neutralizing effect by resin-based materials.Oper Dent 2005;30:522–527.

28. van Dijken JWV. Three-year performance of a calcium-, fluoride-,and hydroxyl-ions- releasing resin composite. Acta Odont Scand2002;60:155–159.

29. Heintze SD. A new material concept for inhibiting the formationof secondary caries. Am J Dent 1999;12:S4–S7.

30. Skritic D, Antonucci JM, Eanes ED. Amorphous calcium phos-phate bioactive composites for mineralized tissue regeneration. JRes Nat Inst Stand Tech 2003;108:167–182.

31. Xu HHK, Weir MD, Sun L. Calcium and phosphate ion releasingcomposite: effect of pH on release and mechanical properties.Dent Mater 2009;25:535–542.

32. Xu HHK, Weir MD, Sun L. Nanocomposites with Ca and PO4release: effects of reinforcement, dicalcium phosphate particle sizeand silanization. Dent Mater 2009;23:1482–1491.

33. Antonucci JM, Fowler BO, Weir MD, Skrtic D, Stansbury JW.Effect of ethyl-a-hydroxymethylacrylate on selected properties ofcopolymers and ACP resin composites. J Mater Sci Mater Med2008;19:3263–3271.

34. Namen FM, Galen J, De Deus G, Cabreira RD, Filho FC. Effectof pH on the wettability and fluoride release of an ion-releasingresin composite. Oper Dent 2008;33:571–578.

35. Xu HHK, Sun L, Weir MD, et al. Nano DCPA-whisker com-posites with high strength and Ca and PO4 release. J Dent Res2006;85:722–727.

36. Al Naimi OT. Surface interaction of biomaterials with biologicalfluids. Newcastle University, United Kingdom, 2005. PhD thesis.

37. Rolland SL, McCabe JF, Robinson C, Walls AWG. In vitro bio-film formation on the surface of resin-based dentine adhesives.Eur J Oral Sci 2006;114:243–249.

38. Friend C. Smart materials: the emerging technology. MaterialsWorld 1996;4:16–18.

39. McCabe JF. Resin-modified glass ionomers. Biomaterials1998;19:521–527.

Address for correspondence:Professor JF McCabe

School of Dental SciencesNewcastle University

NE2 4BWUnited Kingdom

Email: [email protected]


JF McCabe et al.

Smart Materials in Dentistry

Documents

Transcript of Smart Materials in Dentistry