linners y bases 2011

8/11/2019 Linners y Bases 2011

1/12

Australian Dental Journal2011; 56:(1 Suppl): 1122

doi: 10.1111/j.1834-7819.2010.01292.x

Liners and bases in general dentistry

R Weiner*

*Private practice, Millis, Massachusetts, USA.

ABSTRACT

One of the most controversial areas of restorative dentistry is the subject of liners and bases. Currently, there is no singleprotocol, with respect to the use of liners and bases, for clinicians to follow. This article is an in-depth literature review thatdiscusses the use of liners and bases and the types of materials that are available to the restorative dentist. The new emergingconcept of minimally invasive dentistry will require new restorative techniques. These changes will require the clinician toreevaluate their use of liners and bases. Other clinical considerations and findings from recent research are discussed.

Keywords:Liners, bases, infected dentine, affected dentine, minimally invasive dentistry, review.

Abbreviations and acronyms:BPA = bisphenol-A; CaOH = calcium hydroxide; CHX = chlorhexidine gluconate; GIC = glass-ionomercement; LED = light-emitting diode; ZOE = zinc oxide eugenol; ZOP = zinc oxyphosphate; ZPC = zinc polycarboxylate.

INTRODUCTION

Restorative dentists have many decisions to make intheir general practice, one of which is which material touse for any given procedure. To make matters more

difficult for the clinician is the vast number of availablechoices. Published papers and lectures which concludethat different materials are ideal add to this confusion.Dental manufacturers do not make the decision makingany easier, as they constantly introduce new andimproved versions of existing products.

The subject of liners and bases is not immune to thisconfusion. In 1991, Christensen wrote that the use ofbases and liners is confusing: the state-of-the-art usevaries enormously; many different procedures aresuccessful; and unanimity of opinion is not likely tobe achieved soon.1 Surveys of North American dentalschools both five and 15 years later came to the sameconclusion.2,3 In order to lessen this confusion, Cox andSuzuki suggested that clinicians re-evaluate the linersand bases they use.4 Should clinicians decide to make achange, they should do as Asa recommends, and do soto obtain a better outcome, as opposed to making achange for its own sake.5 He goes on to say that theselection process necessitates that dentists confer withcolleagues and review current literature.

Another aspect of the confusion surrounding linersand bases involves the terminology used, and this can beseen in current dental materials textbooks. In thetextbook, Restorative Dental Materials, the authors

define a cavity liner as a suspension of calciumhydroxide in an organic liquid. Upon evaporation ofthe solvent, the remaining film on the tooth is the liner.6

Contrast this to Ferracane, who defines a liner as amaterial that is applied as a thin layer to seal the dentine

floor and walls of the cavity from the influx of bacteriaand irritants from restorative procedures.7 Additionalconfusion with nomenclature is seen in Phillips Scienceof Dental Materials which defines a liner as a thin layer ofcement used for the protection of the pulp.8

This same perplexity is seen with bases. Anusavicedefines a base as a layer of insulating, sometimesmedicated, cement placed in the deep portion of thecavity preparation to protect the pulp from thermal andchemical injury.8 This is similar to Ferracane but headds that bases are placed in thick layers and must bestrong enough to support a restorative material duringits placement and function.7 Additionally, it shouldprovide thermal and electrical protection (from gal-vanic activity). Craig and Powers separate bases intotwo categories. The first is for low-strength bases ofcalcium hydroxide (CaOH) and zinc oxide eugenol(ZOE) cements which are referred to as liners.6 Thesecond category covers high strength bases, which hasthe same description as Ferracane.7

Two types of materials, polycarboxylates and glass-ionomers, are commonly referred to as cements. Thiscan also lead to nomenclature confusion. Craig andPowers note that cements have two primary purposes:as a restorative filling material used either alone or with

2011 Australian Dental Association 11

Australian Dental JournalThe official journal of the Australian Dental Association


2/12

other materials (essentially a base) and to retainrestorations or appliances in a fixed position in themouth.6 However, Ferracane wrote that the mostobvious use for a cement is for permanently retainingcastings to tooth structure.7 To alleviate the confusion,the present author does not use the word cement when

discussing these materials as a liner or as a base, butwill use instead the words material or product. Thisis because under this subject we are not concerned withretaining indirect restorations or appliances.

The range of materials used for liners and bases isillustrated in Fig 1. Many of these materials belong tothe family of so-called water-based cements, and theirbasic relationship and time of introduction are shownin Fig 2. The silicate cements are now little used.

This paper will discuss liners and bases, review whatthey are, why we use these materials, the physicalproperties needed, the types of the materials available,

touch upon the concept of sealing in caries and discussclinical considerations with respect to their use.

Rationale for use

What is the purpose of these products? It has beengenerally accepted that the materials that were used torestore teeth posed a danger to the tooth and allowedfor the occurrence of postoperative sensitivity. If thiswere true, then a barrier or protective layer needed tobe placed on the tooth before the final restoration. Thisbuffer would, in part, act to reduce or even eliminatepostoperative sensitivity.

Over time we have come to learn that it is not therestorative material that causes problems, but bacteriaand the by-products of bacteria. These bacteria, presentin the oral cavity, enter the tooth at the margin of therestoration through capillary action of oral fluids. Thisis referred to as microleakage.6 Others have defined

microleakage as the marginal permeability of bacterial,chemical, and molecular invasion at the interfacebetween the teeth and restorative material.9

The margin of the restoration is affected by thedifference in thermal expansion between the restorativematerial and the tooth, polymerization shrinkage,effects of finishing and polishing, orientation of enamelprisms, application methods and cavity configuration.This influx of bacteria can cause problems includingpostoperative sensitivity, marginal discolouration, sec-ondary caries, pulpal inflammation, pulpal necrosis,periodontal disease and the possible eventual need for

endodontic therapy.10

Other theories on the cause of postoperative sensi-tivity have been presented and published. Brannstro mhas suggested that postoperative sensitivity is actuallycaused by the movement of fluid in the space or gapbetween the tooth and the restoration,11 resulting in achange in osmotic pressure. This theory is referred to asthe hydrodynamic theory. Bra nnstro m goes on toexplain that dentinal fluid moves in a coronal oroutward direction from the pulp (which is underpressure), and any opening in the dentine allows thefluid out of the tubule. These openings also allow

Lining

materials

Zinc oxide- Zinc Zinc poly- Glass-R i C l i

eugenol

(1890s)

phosphate

(1890s)

carboxylate

(1960s)ionomer(1970s)

esin(1960s)

Varnish alcium

hydroxide

Base

materials)

Fig 1. Materials which can be used as liners and bases, with approximate date of introduction.

Zinc phosphateZinc oxide Phosphoric

acid

SilicateZinc

polycarboxylate

Glass-ionomerPolyacrylic

acidFluoro-

silicate glass

Fig 2. Relationship of water-based cements.

12 2011 Australian Dental Association

R Weiner


3/12

bacteria and other substrates to enter the tooth wherethey can move along the tubule into the pulp.

Campset al.concluded that bacteria within the toothstructure are the main factor influencing the pulpalreaction.12 Confirming the need for a buffer layer,Yoshimaet al. showed that sealing the dentinal tubules

completely renders the dentine insensitive, thereforeeliminating postoperative sensitivity.13 In contrast, onepaper concluded that there is an increase in microleak-age with the use of a liner andor base.14

Contact of dissimilar metals, desiccation of the cavitypreparation and thermal conductivity are further pos-sible causes of postoperative sensitivity. Therefore,having a material between the restoration and thedentine will prevent this.

With respect to microleakage, the placement of aliner andor a base is reactive response. Prevention orusing preventive techniques when placing a restoration

is an active measure. It has been suggested thatscrubbing the cavity preparation with 4% chlorhexi-dine gluconate (CHX) (Tubulicid Red; Global DentalProducts, North Bellmore, NY, USA) and sodiumhypochlorite will kill any remaining bacteria andremove any debris found on the dentine surface.15

As a protease inhibitor, CHX has been shown byCarrilho et al. to stabilize the resin-dentine bond. Theyshowed that bond strength was significantly reduced onuntreated teeth compared to CHX-treated teeth after14 months in the mouth.16 As a cavity disinfectant,CHX did not interfere with the microtensile bondstrength of glass-ionomer or resin composite.17

Other methods to reduce or eliminate microleakageinclude isolation with rubber dam and having themargins both as sealed and as smooth as possible. Arough margin increases the difficulty of keeping it clean,thus allowing the accumulation of plaque.

When using a liner andor a base, it is important tomake sure that it will not be harmful to either the toothor the patient, i.e. it must be biocompatible. Biocom-patibility has been defined as a materials ability toelicit an appropriate biological response when incontact with the body.6 Anusavice writes that theinterface between the material and the body is, in fact,

dynamic and not static.8

The interaction between thetwo will determine how the body will react to theforeign material and how the material will resistdegradation by the body. Possible reactions can beclassified as toxic, inflammatory, allergic or mutagenic.

The current view is that the pulp has the ability to laydown more dentine (reparative or tertiary dentine)when irritated by caries, cavity preparation or as aresult of the interaction between the tooth and therestorative material. There are materials that promotereparative dentine formation and others that can causepulpal damage. Hebling et al. write (when discussingadhesive systems) that the response of the pulpal-

dentine complex depends on the remaining dentinethickness.18

Currently, one substance that is being researched forbiocompatibility is bisphenol-A (BPA), a material thatis used to manufacture some plastics and may be foundin dental sealants, dentine-enamel bonding agents and

resin composites. BPA may affect the reproduction anddevelopment by mimicking the effects of female hor-mones. The position of the American Dental Associa-tion (November 2008) is that based on currentresearch. The Association agrees with the authoritativeUnited States government agencies that the low level ofBPA exposure that may result from dental restorativematerials poses no known threat to general health.19

Some liners and bases merely occupy space in thecavity preparation, while others adhere to the toothstructure. Adhesion is defined as the force of attractionbetween the molecules or atoms on two different

surfaces as they are brought in to contact.7

Withrespect to resin composite materials, the basic mecha-nism is the same for all adhesive systems: an acid is usedto demineralize both the dentine and enamel, followedby the placement of the resin-based material onto thetooth, thus sealing the cavity preparation and reducingmicroleakage. The microporosities formed by thedemineralization aid in this sealing and also in retentionof the material to the tooth.20

Failure of adhesion can occur by the formation ofcracks between the tooth and the material. Because thetooth is subjected to stress, these cracks can grow,allow moisture and bacteria to penetrate and thus resultin secondary caries, stained margins and loss ofretention of the material from the tooth. Dentists canreduce the chance of a bond failure by confirming thatthe tooth structure is clean, the material properlycontacts or adapts to the tooth, and that the material isfully set or cured prior to the placement of the nextmaterial. In the case of a liner, this would be before thebase or the final restoration.

Some of the liners and bases in use can releasefluoride ions. In glass-ionomers, fluoride can be foundin quantities of about 5 ppm. In the laboratory, it iswell known that fluoride has anticariogenic properties

and also inhibits secondary caries formation.8

Fluorideinhibits bacterial metabolism by the formation ofhydrofluoric acid, which enters the bacteria and inhibitsenzyme activity, thus reducing the rate of acid produc-tion.21 However, the clinical benefit of fluoride-releasing materials is still unclear.22,23

Unfortunately, the supply of fluoride does not lastforever. If the material is exposed at the margin(external lining or open sandwich technique), thefluoride can be replenished. This can be accomplishedvia the use of fluoride-containing toothpastes, topicalgels and mouthrinses, the most effective being topicalgels.24,25 Clinicians should be aware that there is no





4/12

general consensus on how much fluoride is released norhow much is needed to inhibit caries formation.

Liners and bases can be grouped into varnishes,calcium hydroxide (CaOH), zinc oxide eugenol (ZOE),zinc phosphate (ZOP), zinc polycarboxylate (ZPC),glass-ionomer (GI) and resin (Figs 1 and 2).

Varnish

A varnish consists of one or more resins (from naturalgum, synthetic resins or rosin) in an organic solvent(acetone, chloroform or ether). Varnishes are appliedin a thin layer to the cavity preparation and onevaporation of the solvent, the remaining solute is theliner which seals the tubules. Therefore, varnishescan be considered a liner. They also fit the definitionof a liner in that they seal the dentine, but arecontraindicated when a resin composite is going to be

placed.8

A cavity varnish provides a protective barrier againstirritants (from restorative materials) and from the oralfluids penetrating into the dentine. Varnishes alsoprotect the tooth from the newly placed amalgam. Afresh amalgam shrinks on setting, allowing microleak-age to occur, and a varnish will seal the cavity-amalgaminterface until the amalgam starts to corrode. Varnishalso keeps the corrosive by-products from leaching intothe enamel and staining the tooth.6

Even when varnishes are applied in multiple layers, itis possible that microscopic openings may form in thevarnish and this might allow bacteria to penetrate intothe dentine. Royceet al. have concluded that varnishesare not as effective as other materials at reducingmicroleakage.26 This contradicts a 1998 study whichconcludes that, at least in the short term, varnishes areas effective as adhesive liners.27 Cavity varnishes do notpossess any mechanical strength and they have minimalfilm thickness, which is not adequate for thermalprotection, thus making them unsuitable for use as acavity base.

According to an October 2005 survey of NorthAmerican dental schools, only 20% of respondingschools teach the use of varnish in shallow prepara-

tions, versus 3% in deep cavity preparations.3

This isdown from 56% in 1991 for shallow preparations and6% for deep preparations when an amalgam was to beused as the final restorative material.2,3

There are several factors that clinicians need toremember about varnishes. First, due to the readyevaporation of the solvent, the lid should be kept on thebottle when the varnish is not in use. Eventually, dueto evaporation, the liquid will become thick, andmanufacturers have thinners available to restore theappropriate viscosity. Second, there are several types ofvarnish on the market, and care must be taken whenchoosing a product. For example, Fuji Varnish (GC

Corp, Alsip, IL, USA) is used for sealing glass-ionomerrestorations, not as a cavity sealer. Varnishes that areintended to be used as a cavity liner include Copalite(Cooley & Cooley, Houston, TX, USA) and Copaliner(Bosworth, Skokie, IL, USA).

Calcium hydroxide

Calcium hydroxide (CaOH) has two components: abase and a catalyst. The base is composed of calciumtungstate, tribasic calcium phosphate and zinc oxide.The catalyst is composed of calcium hydroxide, zincoxide and zinc stearate. Radiopacity is provided bycalcium tungstate, or in some cases by barium sulphatefillers. Craig and Powers consider calcium hydroxide tobe a low-strength base.6 This is ironic, since theysuggest that calcium hydroxide should not be applied ina thickness greater than 0.5 mm, which would make it

a liner.Calcium hydroxide is considered to be bactericidal

due to its high pH, approximately 12, which is providedby the catalyst. This alkaline property can causecytotoxic effects to both the pulp and any bacteria inthe preparation. Additionally, the acidic by-products ofthe bacteria are counteracted by the high pH.28 Thishigh pH continues even after the material has set due,according to Ferracane, to hydroxyl ions that continueto leach out of the material when it comes in contactwith the dentinal fluid.7

Calcium hydroxide can also irritate the pulp due toits high alkaline nature. This results in the formation ofreparative dentine (a dentine bridge). This new dentineforms because CaOH can stimulate growth factors inthe dentine matrix, and this process may occur morequickly when a resin-based calcium hydroxide formu-lation is used.29 Additionally, Tornecket al. write thatcalcium as well as hydroxyl ions play an important roleon the pulpal healing by modifying the environmentalpH in the zone of inflammation to levels favourable forpulp matrix mineralization.30 There are light-curedresin-based versions of calcium hydroxide and suchformulations are not harmful to the pulp but do notshow any antibacterial characteristics. They have a

demand set and are less soluble than the self-curedproducts. The high solubility of conventional CaOHmaterials requires that clinicians ensure that restorationmargins are sealed.

Operators will find that CaOH is easy to manipulate,hardens rapidly when applied in thin layers, provides arelatively good seal and has positive effects on bothcarious dentine and exposed pulp. Unfortunately, it islow in strength, undergoes plastic deformation and ishighly soluble in water, and resins-based restorativematerials will not bond to conventional CaOH.

Calcium hydroxide products are available in either apaste-paste version or a liquid formulation. Examples


R Weiner


5/12

of calcium hydroxide paste-paste products are Dycal(Caulk Dentsply, Milford, DE, USA) and Life (Kerr,Orange, CA, USA). Liquid versions of CaOH are theresin-based products Hydroxyline (George Taub Prod-ucts, Jersey City, NJ, USA) and Timeline (CaulkDentsply, Milford, DE, USA).

Zinc oxide eugenol

The powder is composed of zinc oxide (70% by weight)with rosin added to reduce the brittleness of the setmaterial. The eugenol is in the liquid portion, derivedfrom oil of cloves (one of the essential oils). Theeugenol is bactericidal on its own, but is more potentwhen combined with zinc oxide.31 The requirementsfor ZOE as a base are given in ISO 3107-2004(Dentistry Zinc oxideeugenol and zinc oxidenon-eugenol cements), under the category of Type 3.

Said to be the least irritating of all dental materials,zinc oxide eugenol (ZOE) has been available for over100 years. Despite having a pH of about 7 and having asedative effect on the pulp, the eugenol can be toxic tothe pulp, especially when present in high concentra-tions.6 It is for this reason that ZOE should not beplaced in direct contact with the pulp.

Eugenol is released from the mixture by hydrolysis.The wet dentine causes enough eugenol to be releasedto form a concentration gradient that kills bacteria, butdoes not damage the pulp. Hume showed that thedentine protects the pulp from chemical irritation andas the remaining dentine thickness increases, so does theprotection.32

Even though ZOE does not bond to the tooth, it doesafford an excellent marginal seal,7 which is better whena lower powder:liquid ratio is used.33 The advantage ofthis seal is the prevention of diet-derived substrate fromreaching the micro-organisms found below the restora-tion. This results in the reduction of both acidproduction and of the formation of secondary caries.Essentially, ZOE inhibits bacterial cell metabolism, theend result being a low incidence of postoperativesensitivity.

Hydrolysis of zinc oxide precedes a reaction between

the resulting zinc hydroxide and eugenol, and thisallows the ZOE mixture to set. The reaction occurs inthe presence of water acting as a catalyst, which is whythe reaction occurs faster when wet than when nomoisture is present.8

The preferred technique for mixing ZOE is addingthe powder to the liquid a little at a time usingvigorous spatulation. The resulting material is notexothermic, but clinicians should be aware of ambientconditions, as a humid environment could cause thereaction to speed up. As the powder:liquid ratio isincreased, the mix becomes drier and less tacky. Theresultant mixture is easier to work with and contains

less free eugenol (as it is combined in the material) toirritate the pulp.

ZOE is not marketed as a cavity liner, but as a base(as well as other uses not relevant to this paper). Someproducts contain polymethylmethacrylate, which isincorporated in order to strengthen the material,

making it more appropriate for use as a cavity base.Considered a low strength base by Craig and Powers,6

ZOE has thermal insulating properties that are similarto dentine.

There are no ZOE products that are marketed for useas a liner. An example of ZOE as a base is IRM(Intermediate Restorative Material; Caulk Dentsply,York, PA, USA), available both in powder-liquid andencapsulated versions.

Zinc phosphate

Of all the materials discussed in this paper, zincphosphate (also known as zinc oxyphosphate, ZOP)has been in use the longest. As with ZOE, it has twocomponents, a powder and a liquid. The powdercontains zinc oxide (90%) and magnesium oxide(10%), and some products may have other chemicalsadded such as tannin fluoride (Shofu Corp, Osaka,

Japan). The liquid is composed of phosphoric acid,aluminum phosphate (which acts as a buffering agent)and water. The water influences the rate of the acid-base reaction, and increasing the amount of waterresults in a reduction in both the compressive andtensile strengths8 and a longer setting time.

The setting time, according to ISO 9917.1-2007(Dentistry Water-based cements Part 1: Powderliquid acid-base cements), is required to be between 2.5and 8 minutes. Varying the setting time can be accom-plished first, by reducing the powder:liquid ratio, whichwill increase the setting time and also lower the pH);second, by adding the powder to the liquid a little at atime (which will extend the setting time); third, bydelaying mixing the last amount of the powder, as thiswill destroy the matrix and lengthen the setting time;and fourth, by mixing on a cold glass slab, which willcool the exothermic reaction and lengthen the setting

time. The exotherm is derived from the surface of thealkaline powder dissolving in the acid liquid. Thefourth method is the most effective method and allowsmore powder to be included in the final mix, whichimproves the physical properties.8 Operators need toremember that water affects the mix, and therefore theglass slab needs to be dry and thus not cooled below thedew point.7

Unlike ZOE, the pH of ZOP is much lower, startingat around 2. However, 24 hours after the mix iscomplete, the pH is about 5.3,7,26 From a clinical pointof view, this is important since premature dispensing orleaving the cap off the bottle of liquid will allow some





6/12

water to evaporate. This results in a more acidic liquidand a thicker mix. To account for this evaporation, ISO9917.1 requires that there be 20% more liquid in thebottle than is needed to mix with the powder in thepackage.

There are several advantages of ZOP. These

include a long history of clinical success, it is easilymixed and is to an extent strong. Unfortunately, it isbrittle, lacks adhesion, is soluble in the mouth, isthought to be an irritant to the pulp and lacks anyantibacterial properties (except for the copper-basedproducts).

When ZOP was first introduced to dentistry, somecontained copper and these were thought to possessantibacterial characteristics. Unpublished studies(Montana State University Center for Biofilm Engineer-ing) have shown that copper-based ZOP does exhibitsuch antibacterial properties. Zinc phosphate is not

usually thought to be used as liner, however, oneproduct (not yet available in Australia) is advocated asa liner when mixed with copal varnish to achieve a thinmix.34

When ZOP is to be used as a base, it should be mixedto a thick, dry, putty-like consistency. Doing so willresult in a strong, hard base and a short setting time. AZOP base will provide a thermal and chemical barrier,allowing the final restoration to be placed at the samevisit. An additional result of a thick mix will be less freeliquid available to act as an irritant.

Many years ago it was thought that ZOP, due to itsacidic nature, was a cause of postoperative sensitivity,but this has since been shown not be true.35 For thosewho wish to prevent any affect that ZOP has on thetooth, a layer of copal varnish can be placed on thecavity preparation to seal the dentine, prior to the zincphosphate.

Examples of zinc phosphate are marketed by HenrySchein Halas, Dentavision PL and Ivoclar VivadentPL.

Zinc polycarboxylate

A material that is similar to ZOP is zinc polycarboxy-

late (ZPC), also known as zinc polyacrylate. As withZOP, the powder is composed of zinc oxide andmagnesium oxide. The liquid contains a 3540%aqueous solution of polyacrylic acid. Because the liquidis more viscous than that of ZOP, the mix will appearto be thicker (pseudoplastic). The correct consistency isa mix that, when pulled up, will flow back under itsown weight. It resembles ZOP in strength and ZOE inbiocompatibility. The pH of the liquid is about 1.7, andupon mixing, the free acid is quickly neutralized.Available in powder-liquid formulations, ZPC bondsionically to tooth structure via the negatively chargedcarboxyl ions from the liquid and the positively charged

calcium ions from the tooth structure. The bond toenamel is stronger than that to dentine.

Freshly mixed ZPC is not as stiff as ZOP and itsworking time is about half. Unlike ZOP, the liquid ofZPC should not be refrigerated as this will cause it togel. However, the ZPC powder can be refrigerated in

order to extend the working time.As with zinc phosphate, the ZPC liquid must be

protected against water loss from evaporation. Whenmixing ZPC, the powder should be added all at once.When the mixing is complete, a glossy surface will beapparent, indicating that there are enough free carboxylgroups available to bond to the tooth.

Both ZOP and ZPC have close adaptation to thecavity preparation because both are acidic and helpremove the smear layer. Hodash has shown that whenpotassium nitrate is added, ZPC becomes an effectiveliner and does not have an adverse effect on the vitality

of the pulp.37

Zinc polycarboxylate is also similar toZOP when used as a base and mixed to a thick dryconsistency, thus allowing a final restoration to beimmediately placed over it.

Good biocompatibility exists because the polyacrylicmolecules are large and cannot diffuse into the dentine,the pH rises rapidly after mixing and minimal dentinalfluid movement occurs in response to the ZPC.36 In astudy comparing both ZOP and ZPC in deep cavitypreparation, it was shown that there was no significantirritating effect on the pulp.35 It was concluded that anyirritation was due to the bacteria that remained in thepreparation.

In the 2005 survey study by the present author, noneof the responding dental schools claimed to be usingZPC as a liner or base, despite the fact that ZPC hasmany advantages which include its biocompatibility,adhesion to tooth structure, easy manipulation andstrength. The negative aspects of ZPC are the need foraccurate measuring when dispensing, high viscosity,short working time, and the need for a clean cavitysurface to obtain better bonding.34

Hybond Polycarboxylate Cement (Shofu) and Dur-elon (3M ESPE, St Paul, MN, USA) are examples ofpolycarboxylate materials.

Glass-ionomer

Composed of acid soluble calcium or strontium fluoro-aluminosilcate glass and an aqueous solution of poly-acrylic acid, conventional glass-ionomers (GI), whichare governed by ISO 9917.1-2007 (Dentistry Water-based cements Part 1: Powderliquid acid-basecements) have been available for about 40 years. Tomake these products radiopaque, some contain zincoxide or barium glass.8 After mixing powder andliquid, the acid etches the glass which results in a releaseof calcium, aluminium, sodium and fluoride ions into


R Weiner


7/12

solution. This is an acid-base reaction where the waterserves as the medium for the reaction. Set GI has acompressive strength similar to that of ZOP, a tensilestrength higher than ZOP and a modulus of elasticity ofabout half of ZOP.8

Glass-ionomer comes in several different versions or

systems, each of which has advantages and disadvan-tages. These include powder-liquid, paste-paste andencapsulated versions. The powder-liquid products areusually less costly, whereas the paste-paste versionsallow for a more constant ratio of the active compo-nents (acid and base) and are easy to clean up.

An important characteristic of glass-ionomer is itsability to bond to tooth structure, one mechanism beingthat of a hydrogen bond between the carboxyl group ofthe polyacid and the calcium in the tooth structure. Ithas also been shown that there is a micromechanicalpenetration of the GI into the tooth.38 Glass-ionomer

has a coefficient of thermal expansion similar to thetooth, which may help reduce microleakage andtherefore postoperative sensitivity.39

The fluoride released during the acid-base reaction ishigh initially then declines over time. Those cliniciansthat use the cervical lining or open sandwichtechnique (bringing the GI to the margin) will find thatthe released fluoride can be replaced by the methodsdescribed earlier. The fluoride released does not inhibitcaries but rather causes the formation of fluorohydr-oxyapatite in the adjacent tooth structure which makesit more resistant to demineralization.40 Another advan-tage of the cervical lining technique is that the GIexpands slightly when in contact with moisture, andthis may compensate for the polymerization shrinkageof the resin composite41 and may therefore reducemicroleakage.42

Glass-ionomer has more of an antibacterial effectthan does CaOH,43 and Alex writes that the use of aresin-modified GI is the easiest and most predictablemethod to manage microleakage.44 To encourageadhesion of the GI to the tooth, it is necessary tohave a clean surface. This can be accomplished usingpumice, phosphoric acid or polyacrylic acid followedby a water rinse. However, it is important that

clinicians follow the manufacturers instructions forthe particular product they are using. Clinicians shouldalso be aware that once the surface of the mix loses itsglossy appearance, it should not be used, as this is anindication that there is no unreacted polyacid availablefor bonding.

When a resin is added to the glass-ionomer, it isreferred to as a resin-reinforced, hybrid or, prefera-bly, a resin-modified glass-ionomer. Dentists will findthat these usually have a longer working time and areless moisture-sensitive.8 However, it must be remem-bered that most resin-modified glass-ionomer restor-atives set by the acid-base reaction as well as the resin

photo- and self-cure polymerization reactions, thusworking time is not unlimited.

Examples of conventional and resin-modified glass-ionomers include those marketed in Australia by 3MESPE, GC Corp, Shofu, SDI Ltd (Bayswater, Australia),Oradec PL, Dentsply PL, Gunz Dental PL, Henry

Schein Halas, Dentavision PL, Voco PL and GoDental PL.

Resin-based materials

The final materials that can be used as either a liner or abase are those that are resin-based. These can becategorized in two different ways: either by fillercontent (unfilled or filled), or by how they are cured(either self-, light- or dual-cured). For the purposes ofthis paper, only those that can be used as a liner or as abase will be discussed, keeping in mind the definitions

used in the Introduction.When resin-based products are used, manufacturers

either include the bonding system in the package orrecommend a separate purchase of one of their own.The bonding systems are usually composed of a primer(wetting agent) andor a bonding agent (unfilled resin).From the perspective of a liner, the material that is firstplaced in the cavity preparation is most important tothe clinician, as it is this material that will act as theliner.

The acidic nature of the primer dissolves the smearlayer and the surface hydroxyapatite, which allows forthe adhesive component of the primer to infiltrate theexposed dentinal collagen. This results in the formationof the so-called hybrid layer and a zone of occludeddentinal tubules, and the solvent (either acetone,alcohol or water) then evaporates. The adhesive (bond)is then placed, which is a low viscosity, hydrophilicmaterial that promotes the bond of the filled resin to thetooth.8 Complete penetration of the primer monomersinto the collagen is essential to create strong adhesionas well as an optimum seal. The occluded tubulesreduce the amount of microleakage.

A comparison study of acetone systems and watersystems was conducted to evaluate the effect on the

hybrid layer. It concluded that the acetone-basedsystems resulted in a thick hybrid layer that includedwell formed resin tags that were well adapted to thetubular wall. In contrast, the water-based systemsproduced a thinner hybrid layer that was less wellsealed, thus allowing more microleakage.45

Bonding systems can be divided into etch-and-rinsesystems and self-etching primer systems (available inone- or two-bottle versions). With respect to micro-leakage, a study published in 2006 concluded that theetch-and-rinse products were associated with lessmicroleakage than self-etching systems.46 The self-etching systems are more acidic because of carboxylic





8/12

acid. Originally developed to be easier for the clinicianto use (due to less steps), self-etching systems wereshown not to produce improved results when comparedto total etch products.47

Clinicians should also be aware that prior toplacement of a bonding material, the tooth needs to

be clean and free from all water, saliva and blood.Contamination can interfere with adhesion and canresult in the dentine tubules being left open, leading topostoperative sensitivity.

The deeper the cavity preparation into dentine, themore dentinal fluid that will be encountered, whichreduces the bond strength. To account for this, Tay andPashley have written that it is best to over-dry thedentine.48 Additionally, blocking or occluding thedentine tubules will reduce dentine permeability andprevent fluid contamination, which will improve bondstrength.49 Dentinal fluid can become trapped within

the bonding agent in the cavity. This fluid willeventually form bubbles that evaporate, making thehybrid layer permeable. The over-drying will helpprevent this. Water or any moisture that is in thebonding agent can: (1) inhibit polymerization of thebonding agent; (2) produce these so-called waterchannels that increase the porosity; and (3) soften theresin. All these will cause the adhesive to weaken overtime and also reduce the bond strength.50

Moisture contamination can also be from thepatients breath, which is an additional reason forusing rubber dam. From an examination of theinfluence of humidity and temperature on bondstrength, it was concluded that bond strength decreasedwhen humidity was increased.51

There are times when the operator will be replacingan existing restoration, and quite likely bond tosclerotic dentine. The tubules in such dentine areoccluded with mineral salts which reduce resin tagformation.52 Additionally, dentine with a hyperminer-alized surface has been shown by some to resist acidetching, which results in lower bond strengths,although others have not confirmed this. Kusunokiand others suggest that sclerotic dentine allows the resinto adapt to the cavity preparation better than with

normal dentine, and conclude that sclerotic dentineshould be preserved and not etched.53

Similar to the materials discussed earlier, self-etchingbonding agents can also have handling disadvantages.The acetone-based materials particularly will evaporatewhen exposed to the air, and therefore they should notbe dispensed until they are to be used.54

From a clinical point of view, placing primers andunfilled resins needs to be done with care. Primers havea very low film thickness compared to unfilled resins,and placement of unfilled resins in the cavity prepara-tion can result in pooling if not done with care. Onfollow-up or recall bitewing radiographs, this may look

like secondary caries. Another reason that thick layersare not ideal is because the coefficient of thermalexpansion does not match that of filled resin.55 Thereare numerous dentine bonding systems on the market,and most are now used as combined enamel anddentine bonding systems. An extensive review of such

systems is to be found elsewhere in this special issue.Resins as liners or bases are not only confined to

primers and bonding agents. Manufacturers also mar-ket filled resins, in the form of flowable composites, forliningbase purposes, even though a primer and bond-ing agent is placed in the cavity preparation first. Withrespect to a liner, conventional composites are notapplicable as they do not meet the definition givenearlier. On the other hand, flowable composite resinsdo.

Flowable composites can reduce microleakage asthey have the ability to adapt to the restoration and flex

with the tooth, which it is claimed allows for a betterseal. However, Christensen stated that these materialsare not intended to be used as a liner, and recom-mended instead the placement of a fluoride-releasingproduct. Some flowable resins do contain fluoride, butthe amount is very low and decreases after the firstthree weeks.56 A clinician who is going to place aflowable composite in the preparation will need toevaluate that product. Special attention should be paidto the radiopacity of the material as the clinician willneed to distinguish it from the surrounding toothstructure on a radiograph; a radiolucent flowable couldbe misdiagnosed as secondary caries. Flowable com-posites are available from most filled resin compositemanufacturers and distributors.

Resins as a base are usually marketed as core build-up materials, but like flowable composites, a primerand bonding agent are placed first. As a base, the resincan be shaped and contoured, and will act as atemperature buffer. These products are available ineither tooth-coloured or non-tooth-coloured versions.The advantage of a non-tooth-coloured product is thatwhen used under a metallic restoration (direct orindirect), it can be distinguished from the dentine ifthe tooth needs to be retreated. Several core build-up

products are available.

Clinical considerations

Clinical considerations should always be part of thedecision making process when purchasing dental prod-ucts because dental materials cannot be completelyseparated from clinical technique. With respect to linersand bases, important aspects of the clinical techniqueare the cavity preparation and the curing light.

Cavity preparation can be accomplished with highand low speed handpieces, hand instruments, laser andair abrasion. Setien

et al.showed that microleakage did


R Weiner


9/12

not occur for any preparation method where the enamelwas etched prior to placement of the composite,57 andnumerous others support this finding. This indicatesthat a better seal is obtained when acid etching ofenamel has taken place.

Now that liners and bases have been discussed in

detail, it should be noted that according to a 2003presentation, the interactions of the tooth, cavitypreparation and the restorative material on pulp injuryappeared to have minimal influence on the pulp. Theimportant factor was the remaining dentine thicknessbetween the cavity floor and the pulp, not therestorative material itself. By maximizing the remainingdentine, less pulp injury occurred.58

There are numerous manufacturers of liners andbases, and they provide their products in a variety ofdelivery systems. These include powder-liquid, paste-paste, capsules, conventional syringe and automix

syringe. Also, products can be found in self-, light-and dual-cured formulations. Not all products areavailable in every version, so clinicians need todetermine which material and which system is bestfor them. When choosing a product, dentists must alsobe comfortable with the packaging, labelling andinstructions for use. If a dentist is going to purchase anew product, that decision should be founded onscientific information. Additionally, the operator mustunderstand the manufacturers instructions for use, asthere may be procedures that are new to the office.Peutzfeldt and Vigild performed a study on dentinebonding agents, and reported that the extent to whichdentists followed the manufacturers instruction de-pended on the degree that the dentists were satisfiedwith the instructions.59

Since many of the products marketed as a liner or abase are light sensitive, a look at light curing units is inorder. The wavelength of the light sensitive photoini-tiator should be known by the dentist, so that there isan assurance that the curing light being used iscompatible. There are many different types of lightson the dental market: halogen, light-emitting diode(LED), fast halogen plasma arc and laser. No one typeof curing unit is ideal and it is incumbent on the

clinician to determine which light is best for that office.Many dentists use the same material in deep and

shallow preparations, and doing so involves a differ-ence in the distance between the light tip and the floorof the cavity. A greater distance results in a decrease inthe light intensity, and a 1 mm space between the lighttip and the resin could cause a reduction in powerintensity ranging from 8 to 16%. Increasing the curetime may counter this.60 It is also important toremember that darker resins need longer light activa-tion; the clinician should know the depth of cure that isrecommended by the manufacturer for each shade ofmaterial.

Light tips need to be examined on a regular basis tocheck for build-up of deposits on the exit tip, as thisbuild-up can reduce the effectiveness of the light.61

Single-use barriers are available for infection control,and they do result in a loss of light intensity from thecuring tip. However, this loss is minimal and not likely

to affect the cure. Clear plastics kitchen wrap wasshown to have no significant effect.62

A study published in 2007 evaluated curing lights inoffices from two United States metropolitan locations.The authors concluded that: (1) nearly 10% of the unitstested had an output of


10/12

dormant and therefore pose no risk to the dentition.Ricketts et al. suggest that there is insufficient evidenceto know whether it is necessary to re-enter after aperiod of time and excavate further, but studies thathave not re-entered do not report adverse conse-quences. It has also been shown that the presence of

affected dentine did not increase the susceptibility tosecondary caries.70

The concept of affected dentine is relevant to linersand bases as it is this layer which will be in contact withthe liner. A review of the literature shows that thematerials involved in studies with affected dentine havebeen limited to glass-ionomers and resins. The othermaterials, discussed above, have not been studied.Glass-ionomers have the potential to remineralizeaffected dentine to varying extents. However, theextent to which a glass-ionomer can augment normalphysiological remineralization remains to be deter-

mined.71

Palma-Dibb and others have shown thatconventional glass-ionomers had lower mean bondstrengths to caries-affected dentine than did resin-modified glass-ionomers.72

The relationship between resins and affected dentineseems to be dependent on a number of factors. First, themethod of cavity preparation has an influence, as it hasbeen shown that one-step products have a lower bondstrength to inner dentine than do total-etch systems,when a bur was used to prepare the cavity. When alaser was used, there was no significant differencebetween the two adhesives.73 Second, resin infiltrationinto dentinal tubules of caries-affected dentine ishampered by the presence of mineral deposits,74 andthis is especially true with self-etching materials com-pared to total-etch products.75 In an attempt to increaseinfiltration, etching of the dentine is necessary, andincreasing the etching time significantly increases thetensile bond strength to caries-affected dentine. How-ever, this is still less than that to sound dentine.76 Thisis different from a 2004 study, where the authorsconcluded that extra etching of caries-affected dentineresulted in no difference in bond strengths.77 The lowerbond strength may be because caries-affected dentinecontains more water than normal dentine.78 Clinically,

this may not be a problem, since such lesions arenormally surrounded by normal dentine or enamel.Hybrid layers in caries-affected dentine have beenshown to be thicker than in sound dentine, andcaries-affected dentine is also more porous which maybe because it is partially demineralized.79,80 As men-tioned earlier, it is the hybrid layer which is essential tomaximize the strength of the bond of the resin to thetooth and optimize the seal of the cavity preparation.With respect to affected dentine, it has been shown thatcleaning the prepared surface with 2% chlorhexidinedigluconate prior to the placement of the restorationdoes not effect the immediate bond strength. However,

this was not the case after six months.81 Lastly, a recentstudy concluded that during photopolymerization,there was a greater increase in temperature at theresin-dentine interface when bonding to caries-affecteddentine compared to normal dentine.82

CONCLUSIONS

As can be seen from the above review, the materialsscience of liners and bases is a not a finite area of study.It is an evolving situation that requires the clinician tostay abreast of the constantly changing research.

DISCLAIMER

The lists of examples of proprietary products may notbe exhaustive, and do not imply endorsement by theauthor or by the Australian Dental Association Inc.

REFERENCES

1. Christensen GJ. To base or not to base. J Am Dent Assoc1991;122:6161.

2. Weiner R, Kugel G, Weiner L. Teaching the use of liners andbases: a survey of North American dental schools. J Am DentAssoc 1996;127:16401645.

3. Weiner R. Teaching the use of liners, bases, and cements: a 10-year follow-up survey of North American dental schools. DentToday 2006;25:7479.

4. Cox CF, Suzuki S. Reevaluating pulp protection: calciumhydroxide liners vs. cohesive hybridization. J Am Dent Assoc1994;125:823831.

5. Asa R. Dental materials arent what they used to be. AGD Impact2004;32:1013.

6. Craig RG, Powers JM. Restorative dental materials. 11th edn. StLouis, MO: Mosby, 2002.

7. Ferracane JL. Materials in dentistry: principles and applications.2nd edn. Philadelphia: Lippincott Williams and Wilkins, 2001.

8. Anusavice K. Phillips Science of Dental Materials. 11th edn.Philadelphia: WB Saunders, 2003.

9. Gordan VV, Vargas MA, Cobb DS, Denehy GE. Evaluation ofacidic primers in microleakage of Class V composite restorations.Oper Dent 1998;23:244249.

10. Murray PE, About I, Franquin JC, Remusat M, Smith AJ.Restorative pulpal and repair responses. J Am Dent Assoc2001;132:482491. Erratum in: J Am Dent Assoc2001;132:1095.

11. Bra nnstro m M. Etiology of dentin hypersensitivity. Proc FinnDent Soc 1992;88 Suppl 1:713.

12. Camps J, Dejou J, Remusat M, About I. Factors pulpal responseto cavity restorations. Dent Mater 2000;16:432440.

13. Yoshiyama M, Masada J, Uchida A, Ishida H. Scanning elec-tronic microscopic characterization of sensitive vs. insensitivehuman radicular dentin. J Dent Res 1989;68:14981502.

14. von Fraunhofer JA, Marshall KR, Holman BG. The effect ofbaseliner use on restoration leakage. Gen Dent 2006;54:106109.

15. Strupp W. Critical factors for clinical success with all ceramicrestorations. Crown and Bridge Update 2004;7:2532.

16. Carrilho MR, Geraldell S, Tay F,et al.In vivo preservation of thehybrid layer by chlorhexidine. J Dent Res 2007;86:529533.


R Weiner


11/12

17. Ersin NK, Candan U, Aykut A, Eronat C, Belli S. No adverseeffect to bonding following caries disinfection with chlorhexidine.

J Dent Child (Chic) 2009;76:2027.

18. Hebling J, Giro EM, Costa CA. Human pulp response after anadhesive system application in deep cavities. J Dent 1999;27:557564.

19. American Dental Association. Positions and Statements: Bisphe-

nol A and Dental Materials. URL: http://www.ada.org/prof/resources/positions/statements/bisphenola.asp. Accessed 23 Sep-tember 2009.

20. Latta MA. Six principles of adhesion. Dent Econ 2007;97:52.

21. de Jong HP, van Pelt AW, Busscher HJ, Arends J. The effect oftopical fluoride applications on the surface free energy of humanenamel: an in vitro study. J Dent Res 1984;63:635641.

22. Randall RC, Wilson NHF. Glass-ionomer restoratives: a sys-tematic review of a secondary caries treatment effect. J Dent Res1999;78:628637.

23. Wiegand A, Buchalla W, Attin T. Review on fluoride-releasingrestorative materialsfluoride release and uptake characteristics,antibacterial activity and influence on caries formation. DentMater 2007;23:343362.

24. Ugarte J, Lagravere MO, Revoredo JA, et al. Fluoride agentsuptake effect over two glass ionomer cements and a resin modi-fied glass ionomer cement. J Dent Res 2003;82 (Spec issue):Ab-stract 938.

25. Gao W, Smales RJ. Fluoride releaseuptake of conventional andresin modified glass ionomers and compomers. J Dent2001;29:301306.

26. Royse MC, Ott NW, Mathieu GP. Dentin adhesive superior tocopal varnish in preventing microleakage in primary teeth. Pedi-atric Dent 1996;18:440443.

27. Kennington LB, Davis RD, Murchison DF, Langenderfer WR.Short-term clinical evaluation of post-operative sensitivity withbonded amalgams. Am J Dent 1998;11:177180.

28. Prati C, Fava F, Di Gioia D, Selighini M, Pashley DH. Antibac-terial effectiveness of dentin bonding systems. Dent Mater

1993;9:338343.

29. Smith AJ, Garde C, Cassidy N, et al. Solubilization of dentineextracellular matrix by calcium hydroxide (Abstract). J Dent Res1995;75:829.

30. Torneck CD, Moe H, Howley TP. The effect of calciumhydroxide on porcine pulp fibroblast in vitro. J Endod1983;9:131136.

31. Meeker HG, Najafi MM, Linke HA. Germicidal properties ofdental cavity liners, bases, and cements. Gen Dent 1986;34:474478.

32. Hume WR. Are restorative materials and procedures harmful tothe pulp? A focus on in vitro investigations. Transactions of theAcademy of Dental Materials 1998;12:105119.

33. Anderson RW, Powell BJ, Pashley DH. Microleakage of IRM

used to restore endodontic access preparations. Endod DentTrauma 1990;6:137141.

34. Weiner R. Liners, bases, and cements: an in-depth review. Part 2.Dent Today 2008;27:4854.

35. Brannstrom M, Nyborg N. Pulpal reaction to polycarboxylateand zinc phosphate cements used with inlays in deep cavitypreparations. J Am Dent Assoc 1977;94:308310.

36. OBrien WJ. Dental materials and their selection. 3rd edn. Chi-cago: Quintessence, 2002.

37. Hodash M, Hodash SH, Hodash AJ. Capping carious exposedpulps with potassium nitrate, dimethyl isosorbide, polycarboxy-late cement. Dent Today 2003;22:4651.

38. Lin A, McIntyre NS, Davidson RD. Studies on the adhesion ofglass ionomer cements to dentin. J Dent Res 1992;71:18361841.

39. Leinfelder K. Characteristics of a new glass ionomer material.Inside Dent 2006;1:4244.

40. Mount GJ. Minimal intervention dentistry: rational of cavitydesign. Oper Dent 2003;28:9299.

41. Trushkowsky R. The role of glass ionomers in minimally invasiverestorative dentin. Dent Today 2005;24:7277.

42. Aboushala A, Kugel G, Hurley E. Class II composite restorationsusing glass ionomer liners: microleakage studies. J Clin PediatrDent 1996;21:6772.

43. Eli I, Cooper Y, Ben-Amar A, Weiss E. Antibacterial activity ofthree dental liners. J Prosthodont 1995;4:178182.

44. Alex G. The use of resin modified glass ionomer liners undercomposite resins: should they be used to help control micro-leakage? Inside Dent 2005;1:3033.

45. Georgoire GL, Akon BA, Millas A. Interfacial micromorpholog-ical differences in hybrid layer formation in water and acetonesolvent based dentin bonding systems. J Prosthet Dent2002;87:633641.

46. Gueders AM, Charpentier JF, Albert AI, Geerts SO. Microleak-age after thermocycling 4 etch and rinse and 3 self-etch adhesiveswith and without a flowable composite lining. Oper Dent2006;31:450455.

47. Soderholm KJ, Guelmann M, Bimstein E. Shear bondstrength of one 4th and two 7th bonding agents when usedby operators with different bonding experience. J Adhes Dent2005;5:5764.

48. Tay FR, Pashley DH. Have dentin adhesives become too hydro-philic? J Can Dent Assoc 2003;69:726731.

49. Sadek FT, Pashley DH, Ferrari M, Tay FR. Tubular occlusionoptimizes bonding of hydrophobic resins to dentin. J Dent Res2007;86:524528.

50. Weiner R. Liners, bases, and cements: an in-depth review. Part 3.Dent Today 2008;27:6570.

51. Miyazaki M, Rikuta A, Tsubota K, Yunoki I, Onose H.Influence of environmental conditions on dentin bond strengthsof recently developed dentin bonding systems. J Oral Sci

2001;43:3540.52. Nakajima M, Sano H, Burrow MF, et al. Tensile bond strength

and SEM evaluation of caries affected dentin using dentin adhe-sives. J Dent Res 1995;74:16791688.

53. Kusunoki M, Itoh K, Hisamitsu H, Wakumoto S. The effi-cacy of dentin adhesive to sclerotic dentine. J Dent 2002;30:9197.

54. Fujita K, Nishiyama N. Degradation of single bottle type selfetching primer effectuated by the primers storage period. Am JDent 2006;19:111114.

55. Overton JD, Gureckis K. Preparation designs for mini-mally invasive dentistry. Contemp Esthet Rest Pract 2007;1126.

56. Christensen GJ. Direct restorative materials. What goes where?J Am Dent Assoc 2003;134:13951397.

57. Setien VJ, Cobb DS, Denehy GE, Vargas MA. Cavity preparationdevices: effect on microleakage of Class V resin-based compositerestorations. Am J Dent 2001;14:157162.

58. Asawang K, Windsor LJ, About I,et al. Cavity preparation andrestoration events and their effects on pulp cellular injury. Pre-sented at 81st General Session of the IADR, 2528 June 2003,Gothenberg, Sweden. Abstract 1404.

59. Peutzfeldt A, Vigild M. A survey of the use of dentin bondingsystems in Denmark. Dent Mater 2001;17:211216.

60. Chang Tl, Sim A, Hammer L, et al. Effect of curing source,distance on composite depth of cure. Presented at IADRAADRCADR 82nd General Session, 1013 March 2004,Honolulu, Hawaii, USA. Abstract 2678.

61. Sarrett DC, ed. LED curing lights. ADA Professional ProductReview. 2006;1:15.





12/12

62. Scott BA, Felix CA, Price RB. Effect of disposable infectioncontrol barriers on light output from dental curing lights. J CanDent Assoc 2004;70:105110.

63. Barghi N, Fischer DE, Pham T. Revisiting the intensity output ofcuring lights in private dental offices. Compend Contin EducDent 2007;28:380384.

64. Cakir D, Sergent R, Burgess J. Polymerization shrinkage: a clin-

ical review. Inside Dent 2007;3:8487.65. Banerjee A, Watson TF, Kidd EA. Dentine caries: take it or leave

it? SADJ 2001;56:186192.

66. Restorative and Endo Data Online. URL: http://www.onlinedentallearning.com/index.php?option=com_content &task=view&id=37. Accessed 3 November 2009. URL: http://www.eclipse.co.uk/moordent/glossa. Accessed 3 November 2009.

67. Kidd EA. How clean must a cavity be before restoration? CariesRes 2004;38:305313.

68. Thompson V, Craig RG, Curro FA, GreenWS, Ship JA. Treatmentof deep cariouslesions by complete excavationor partialremoval:acritical review. J Am Dent Assoc 2008;139:705712.

69. Ricketts DNJ, Kidd EA, Innes N, Clarkson J. Complete orultraconservative removal of decayed tissue in unfilled teeth. AustDent J 2008;52:252253.

70. Borczyk D, Piatowska D, Krzemiski Z. An in vitro study ofaffected dentin as a risk factor for the development of secondarycaries. Caries Res 2006;40:4751.

71. Smales RJ, Ngo HC, Yip KH, Yu C. Clinical effects of glassionomer restorations on residual carious dentin in primarymolars. Am J Dent 2005;18:188193. Erratum in: Am J Dent2005;18:295.

72. Palma-Dibb RG, de Castro CG, Ramos RP, Chimello DT,Chinelatti MA. Bond strength of glass ionomer cements to cariesaffected dentin. J Adhes Dent 2003;5:5762.

73. Sattabanasuk V, Burrow MF, Shimada Y, Tagami J. Resinadhesion to caries affected dentine after different removal meth-ods. Aust Dent J 2006;51:162169.

74. Say EC, Nakajima M, Senawongse P, Soyman M, Ozer F, Tagami

J. Bonding to sound vs. caries affected dentin using photo- anddual-cured adhesives. Oper Dent 2005;30:9098.

75. Strydom C. Self etching adhesives: review of adhesion to toothstructure. Part 1. SADJ 2004;59:415419.

76. Arrais C, Giannini M, Nakajima M, Tagami J. Effects of addi-tional and extended acid etching on bonding to caries-affecteddentine. Eur J Oral Sci 2004;112:458464.

77. Yazici A, Akca T, Ozgunaltay G, Dayangac B. Bond strength of aself-etching adhesive system to caries-affected dentin. Oper Dent

2004;29:176181.78. Ito S, Saito T, Tay FR, Carvalho RM, Yoshiyama M, Pashley DH.

Water content and apparent stiffness of non-caries versus caries-affected human dentin. J Biomed Mater Res B Appl Biomater2005;72:109116.

79. Sakoolnamarka R, Burrow MF, Kubo S, Tyas MJ. Morphologicalstudy of demineralized dentin after caries removal using twodifferent methods. Aust Dent J 2002;47:116122.

80. Yoshiyama M, Tay FR, Doi J, et al. Bonding of self-etch andtotal-etch adhesives to carious dentin. J Dent Res 2002;81:556560.

81. Komori P, Pashley D, Tjaderhane L, et al. Effect of 2% chlorh-exidine digluconate on the bond strength to normal versus caries-affected dentin. Oper Dent 2009;34:157165.

82. Tosun G, Usumez A, Yondem I, Sener Y. Temperature rise undernormal and caries affected primary tooth dentin disks duringpolymerization of adhesives and resin containing dental materi-als. Dent Mater J 2008;27:466470.

Address for correspondence:Dr Randy Weiner10 Pleasant Street

MillisMA 02054

USAEmail: [email protected]


R Weiner

linners y bases 2011

Documents