**1. Introduction**

332 Contemporary Approach to Dental Caries

Pulido MT, Wefel JS, Hernandez MM, Denehy GE, Guzman-Armstrong S, Chalmers JM,

Reynolds EC. Anticariogenic complexes of amorphous calcium phosphate stabilized by

Reynolds EC, Black CL, Cai F, et al. Advances in enamel remineralization: anticariogenic casein phosphopeptide-amorphous calcium phosphate. J Clin Dent 1999;10:86–8 Reynolds EC, Cai F, Shen P, Walker GD. Retention in plaque and remineralization of enamel

Richter AE, Arruda AO, Peters MC and Sohn W. Incidence of caries lesions for patients

Rose RK. Binding characteristics of Streptococcus mutans for calcium and casein

Rosen S, Min DB, Harper DS, Harper WJ, Beck EX, Beck FM. Effect of cheese, with and

Rosenbloom RG, Tinanoff N. Salivary Streptococcus mutans levels in patients before, during and after orthodontic treatment. Am J Orthod Dentofacial Orthop 1991;100:35-7. Rousseau C, Vaidya S, Creanor SL, Hall AF, Girkin JM, Whitters CJ, et al. The effect of

Skrtic D, Hailer AW, Antonucci JM, Takagi S, Eanes ED. Quantitative assessment of the

Soliman MM, Bishara SE, Wefel J, Heilman J, Warren JJ. Fluoride release rate from an orthodontic sealant and its clinical implications. Angle Orthod. 2006;76:282-8 Stecksén-Blicks C, Renfors G, Oscarson ND, Bergstrand F, Twetman S. Caries-preventive

Sudjalim TR, Woods MG, Manton DJ, Reynolds EC. Prevention of demineralization around orthodontic brackets *in-vitro*. Am J Orthod Dentofacial Orthop 2007;131:705. Todd MA, Stanley RN, Kanellis MJ, Donly KJ, Wefel JS: Effect of a fluoride varnish on

van der Linden RP, Dermaut LR: White spot formation under orthodontic bands cemented with glass ionomer with or without Fluor Protector. Eur J Orthod 1998;20: 219–24. van der Veen MH, de Josselin de Jong E Application of quantitative light-induced fluorescence for assessing early caries lesions. Monogr Oral Sci. 2000;17:144-62. Vivaldi-Rodrigues G, Demito CF, Bowman SJ, Ramos AL. The effectiveness of a fluoride

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Qian F. The inhibitory effect of MI paste, fluoride and a combination of both on the progression of artificial caries-like lesions in enamel. Oper Dent. 2008;33:550-5. Reynolds EC, del Rio A. Effect of Casein and whey-protein solutions on caries experience

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effectiveness of a fluoride varnish: A randomized controlled trial in adolescents

demineralization adjacent to orthodontic brackets. Am J Orthod Dentofacial Orthop

varnish in preventing the development of white spot lesions. World J Orthod

Caries is a dynamic process in which mineral is removed during times of high acid production by bacterial plaque (demineralization) and replaced during periods of neutral pH (remineralization). Remineralization is the process by which mineral is deposited into tooth structure from salivary calcium and phosphate during periods of neutral pH. The remineralization process is facilitated by fluoride and can arrest carious demineralization by the formation of a hard outer surface [16].

Dentinal caries is similar to enamel caries, except that dentin demineralization begins at a higher pH (6.4 compared to 5.5) and proceeds about twice as rapidly since dentin has only half the mineral content. Low fluoride levels are insufficient to initiate dentin remineralization but are adequate to facilitate enamel remineralization. In enamel, at fluoride levels around 3 parts per million (ppm), the balance of mineral uptake and loss is shifted from net demineralization to net remineralization. Because dentin composes most root structure and because root surface caries lesions require significantly greater amounts of fluoride than enamel caries lesions to promote remineralization, restorative materials that release fluoride are often recommended for root surfaces [1]. Root caries appears as a softening and/or cavitation in the root surface with no initial involvement of the adjacent enamel. These lesions generally begin at or slightly occlusal to the free gingival margin but can extend into the gingival sulcus and/or undermine the coronal enamel as the caries progresses. Lesions also begin at the margins of restorations that have their cervical interfaces on root structure [19].

Traditional caries management has consisted of the detection of carious lesions followed by immediate restoration. In other words, caries was managed primarily by restorative dentistry. However, when the dentist takes the bur in hand, an irreversible process begins. Placing a restoration does not guarantee a sound future for the tooth; on the contrary, it may be the start of a restorative cycle in which the restoration will be replaced several times. The decision to initiate invasive treatment should be preceded by a number of questions: Is caries present and if so, how far does it extend? I a restoration required, or could the process be arrested by preventive treatment? Sometimes the decision to restore may be based on questionable diagnostic criteria.

<sup>\*</sup> Corresponding Author

Filling Materials for the Caries 335

dehydration with a varnish or light-cured resin, applied to the surface immediately after placement. Finishing was delayed for 24 hours with the earlier materials; this delay was later shortened, through modification of the material, to 7 minutes. The unmodified glass-

Several mechanisms have been suggested for the anticaries effects of fluoride. These include the formation of fluorapatite, which is more acid resistant than hytdroxyapatite, the enhancement of remineralization, interference of ionic bonding during pellicle and plaque formation, and the inhibition of microbial growth and metabolism. Fluoride relased from restorative materials can inhibit caries through all these mechanisms, although it seems likely that enhancement of remineralization is the most important mechanism in the adult. Although the recurrent caries inhibition effects of fluoride-releasing materials are evident, their clinical effectiveness has been questioned based on the durability of the material. Even in primary teeth, these materials should be used selectively, and the time that the material will be expected to survive (how long the tooth will remain in the oral cavity) should be

For treating carious lesions, especially in the patient with high caries risk, resin-modified glass ionomers and fluoride-releasing resin composites have the greatest potential for success. Resin-modified glass ionomers are recommended as the esthetic restorative materials of choice in the Class 5 situation for patients with high caries risk, especially those with diminished salivary flow, due to their high fluoride release and fluoride recharge

As materials continue to proliferate, it becomes increasingly difficult to choose the appropriate material for a particular clinical situation. Fluoride-releasing materials are no exception, and clinicians need guidelines to select and use these materials. There is modest but growing evidence from clinical trials that fluoride-releasing materials, especially glass ionomers, reduce the occurrence of recurrent caries. There is also evidence of a doseresponse relationship between fluoride release and decreasing caries. While higher fluoridereleasing materials have greater caries protecting effects, these materials are not panaceas. The physical limitations of glass ionomers and compomers and their poor wear resistance contribute markedly to restoration failure. Evidence suggests that resin-modified glassionomer materials may provide an improved combination of physical integrity and caries

The surfaces are important because all restorative dental materials meet and interact with tooth structure at a surface. Also, all dental surfaces interact with intraoral constituents such as saliva and bacteria. Changing a material's surface properties can mitigate the extent of that interaction. The type of interaction between two materials at an interface is defined as the energy of interaction, and this is conveniently measured for a liquid interacting with a solid under a standard set of conditions as the contact angle (θ). The contact angle is the angle a drop of liquid makes with the surface on which it rests (Fig. 1A). This angle is the result of an equilibrium between the surface tensions of the liquidgas interface (ϒLG), solid-gas interface (ϒSG), and solid liquid interface (ϒSL). These relationships can be expressed as an equation, as shown in fig. 1A. If the energy difference of the two materials in contact is large, then they will have a large contact angle. If the energy difference is very small, then the contact angle will be low and the liquid will

ionomer materials are rarely used today [16].

evaluated against its wear effectiveness [52].

capability [16].

inhibition [16].

A different treatment strategy is recommended, based on a proper diagnosis of caries, taking into account the dynamics of the caries process. The activity of caries should be determined, and causative factors should be evaluated. Caries risk should be assessed before treatment is considered, and treatment should include preventive regimens to arrest the caries process by redressing the imbalance between demineralization and remineralization.

The treatment goal in caries management should be to prevent new lesions from forming and to detect lesions sufficiently early in the process so that they can be treated and arrested by nonoperative means. Such management requires skill and is time-consuming and worthy of appropriate payment. If these attempts have failed, high-quality restorative dentistry will be required to restore the integrity of the tooth surface [81].

The first popular fluoride-releasing tooth-colored restorative material was silicate cement. Although this material had no bonding properties and did not survive well in the oral environment, recurrent caries lesions associated with silicate cement restorations were rare. This anticaries effect was eventually associated with fluoride-releasing materials have the goal of inhibiting recurrent caries, especially in patients at high risk for developing new lesions.

Fluoride-releasing materials may be classified into four categories (1. Resin composites, 2. Compomers, 3. Resin-modified glass ionomers, and 4. Conventional glass ionomers based on similarities in physical, mechanical, and setting properties. Fluoride-releasing resin composites are on one end of the continuum and conventional glass ionomers on the other. Compomers appear near the resin composite end, and resin-modified glass ionomers are positioned nearer to the conventional glass ionomers [16].

The introduction of adhesive restorative materials has allowed dentists to make smaller preparations, which has led to preservation of hard dental tissues and, along with declining disease prevalence, has allowed elimination of G.V. Black's principle of "extension for prevention." Maximum tooth structure is preserved. However, this approach, sometimes described as a "dynamic treatment concept," cannot prevent repeated treatment procedures and the occurrence of iatrogenic damage [3]. Resin composites have better mechanical properties, no inherent adhesive properties, greater thermal expansion coefficients, and better wear resistance compared with other materials in the continuum, but they have the least fluoride release. Glass ionomers have inherent adhesive properties, release comparatively high amounts of fluoride, and have thermal expansion coefficients similar to tooth structure, but their mechanical properties and wear resistance are poor. Resinmodified glass ionomers contain elements of glass ionomers and light-cured resins. These materials have properties similar to glass ionomers and, like glass ionomers, should not be used for restorations in occlusal load-bearing areas. Although compomers are blends of resin composite and glass ionomer, they incorporate more resin than resin modified glass ionomers, and their physical and mechanical properties are more closely related to fluoridereleasing resin composites. Compomers require a bonding system and acid etching of tooth structure to achieve a clinically usable bond. They release more fluoride than resin composites but less than glass ionomers and are more abrasion resistant than conventional or resin-modified glass ionomers.

The early glass-ionomer restorative materials, called glass-ionomer cements, were rough, had less than optimum esthetic qualities, and had to be protected from hydration and

A different treatment strategy is recommended, based on a proper diagnosis of caries, taking into account the dynamics of the caries process. The activity of caries should be determined, and causative factors should be evaluated. Caries risk should be assessed before treatment is considered, and treatment should include preventive regimens to arrest the caries process by redressing the imbalance between demineralization and

The treatment goal in caries management should be to prevent new lesions from forming and to detect lesions sufficiently early in the process so that they can be treated and arrested by nonoperative means. Such management requires skill and is time-consuming and worthy of appropriate payment. If these attempts have failed, high-quality restorative dentistry will

The first popular fluoride-releasing tooth-colored restorative material was silicate cement. Although this material had no bonding properties and did not survive well in the oral environment, recurrent caries lesions associated with silicate cement restorations were rare. This anticaries effect was eventually associated with fluoride-releasing materials have the goal of inhibiting recurrent caries, especially in patients at high risk for developing new lesions.

Fluoride-releasing materials may be classified into four categories (1. Resin composites, 2. Compomers, 3. Resin-modified glass ionomers, and 4. Conventional glass ionomers based on similarities in physical, mechanical, and setting properties. Fluoride-releasing resin composites are on one end of the continuum and conventional glass ionomers on the other. Compomers appear near the resin composite end, and resin-modified glass ionomers are

The introduction of adhesive restorative materials has allowed dentists to make smaller preparations, which has led to preservation of hard dental tissues and, along with declining disease prevalence, has allowed elimination of G.V. Black's principle of "extension for prevention." Maximum tooth structure is preserved. However, this approach, sometimes described as a "dynamic treatment concept," cannot prevent repeated treatment procedures and the occurrence of iatrogenic damage [3]. Resin composites have better mechanical properties, no inherent adhesive properties, greater thermal expansion coefficients, and better wear resistance compared with other materials in the continuum, but they have the least fluoride release. Glass ionomers have inherent adhesive properties, release comparatively high amounts of fluoride, and have thermal expansion coefficients similar to tooth structure, but their mechanical properties and wear resistance are poor. Resinmodified glass ionomers contain elements of glass ionomers and light-cured resins. These materials have properties similar to glass ionomers and, like glass ionomers, should not be used for restorations in occlusal load-bearing areas. Although compomers are blends of resin composite and glass ionomer, they incorporate more resin than resin modified glass ionomers, and their physical and mechanical properties are more closely related to fluoridereleasing resin composites. Compomers require a bonding system and acid etching of tooth structure to achieve a clinically usable bond. They release more fluoride than resin composites but less than glass ionomers and are more abrasion resistant than conventional

The early glass-ionomer restorative materials, called glass-ionomer cements, were rough, had less than optimum esthetic qualities, and had to be protected from hydration and

be required to restore the integrity of the tooth surface [81].

positioned nearer to the conventional glass ionomers [16].

or resin-modified glass ionomers.

remineralization.

dehydration with a varnish or light-cured resin, applied to the surface immediately after placement. Finishing was delayed for 24 hours with the earlier materials; this delay was later shortened, through modification of the material, to 7 minutes. The unmodified glassionomer materials are rarely used today [16].

Several mechanisms have been suggested for the anticaries effects of fluoride. These include the formation of fluorapatite, which is more acid resistant than hytdroxyapatite, the enhancement of remineralization, interference of ionic bonding during pellicle and plaque formation, and the inhibition of microbial growth and metabolism. Fluoride relased from restorative materials can inhibit caries through all these mechanisms, although it seems likely that enhancement of remineralization is the most important mechanism in the adult. Although the recurrent caries inhibition effects of fluoride-releasing materials are evident, their clinical effectiveness has been questioned based on the durability of the material. Even in primary teeth, these materials should be used selectively, and the time that the material will be expected to survive (how long the tooth will remain in the oral cavity) should be evaluated against its wear effectiveness [52].

For treating carious lesions, especially in the patient with high caries risk, resin-modified glass ionomers and fluoride-releasing resin composites have the greatest potential for success. Resin-modified glass ionomers are recommended as the esthetic restorative materials of choice in the Class 5 situation for patients with high caries risk, especially those with diminished salivary flow, due to their high fluoride release and fluoride recharge capability [16].

As materials continue to proliferate, it becomes increasingly difficult to choose the appropriate material for a particular clinical situation. Fluoride-releasing materials are no exception, and clinicians need guidelines to select and use these materials. There is modest but growing evidence from clinical trials that fluoride-releasing materials, especially glass ionomers, reduce the occurrence of recurrent caries. There is also evidence of a doseresponse relationship between fluoride release and decreasing caries. While higher fluoridereleasing materials have greater caries protecting effects, these materials are not panaceas. The physical limitations of glass ionomers and compomers and their poor wear resistance contribute markedly to restoration failure. Evidence suggests that resin-modified glassionomer materials may provide an improved combination of physical integrity and caries inhibition [16].

The surfaces are important because all restorative dental materials meet and interact with tooth structure at a surface. Also, all dental surfaces interact with intraoral constituents such as saliva and bacteria. Changing a material's surface properties can mitigate the extent of that interaction. The type of interaction between two materials at an interface is defined as the energy of interaction, and this is conveniently measured for a liquid interacting with a solid under a standard set of conditions as the contact angle (θ). The contact angle is the angle a drop of liquid makes with the surface on which it rests (Fig. 1A). This angle is the result of an equilibrium between the surface tensions of the liquidgas interface (ϒLG), solid-gas interface (ϒSG), and solid liquid interface (ϒSL). These relationships can be expressed as an equation, as shown in fig. 1A. If the energy difference of the two materials in contact is large, then they will have a large contact angle. If the energy difference is very small, then the contact angle will be low and the liquid will

Filling Materials for the Caries 337

This chapter reviews the glass-ionomer cements, compomers, and direct composite restorative materials (also dentin bonding agents) and their composition, classification, and

The original glass-ionomer cements (GICs), which are governed ISO 9917.1-2007 are waterbased materials which set by an acid-base reaction between a polyalkenoic acid and a fluroaluminosilicate glass [86] and have been one of the most widely researched dental materials since their introduction in the 1970s. Since these were brittle materials, attempts were made to enhance the physical properties by the addition of either metal particles (silver or gold), by a fusion process resulting in a 'cermet' (ceramic-metal), or amalgam alloy particles by a simple addition ('admix'). An important characteristic of glass-ionomer is its ability to bond to tooth structure, one mechanism being that of a hydrogen bond between the carboxyl group of the polyacid and the camcium in the tooth structure. It has also been shown that there is a micromechanical penetration of the GI into the tooth. They have a coefficient of thermal expansion similar to the tooth, which may help reduce microleakage and therefore postoperative sensitivity and can be bulk-filled and finished faster than a composite. The newer generations of glass ionomer materials are faster setting and no longer sensitive to hydration or desiccation during setting. One main advantage of glass ionomer materials is their chemical bonding ability to tooth structure, making them more resistant to leaks. Compared with resin system bonding, glass ionomer bonding is more degeneration-resistant and does not breakup, unlike the hydrolytic degradation of the hybrid layer of the resin system. Further modification of water-based ('conventional') GICs took place in the early 1990s by the addition of water-soluble resin, to produce the 'resinmodified' GICs. The purpose of adding resin was to enhance the physical properties and to reduce the sensivity to water balance of the conventional GICs. The first of the 'resinmodified' GICs (RM-GICs) was Virtabond (3M Dental Products, St Paul, Minnesota, USA), now called Vitrebond (3M/Espe Dental). Other names for RM-GIC which have been used include 'resin-ionomers', 'resinomers', 'hybrid ionomers' and 'light-cured glass ionomers'

After mixing powder and liquid, the acid etches the gllas which reslts in a release of calcium, aluminium, sodium and fluoride ions into solution. This is an acid-base reaction where the water serves as the medium for the reaction. The metal ions react with the carboxyl (COO) groups to form a polyacid salt, which becomes the cement matrix, and the surface of the glass becomes a silica hydrogel. The unreacted cores of the glass particles

Although the clinical set is completed within a few minutes, a continuing 'maturation' phase occurs over subsequent months. This is predominantly due to the slow reaction of the aluminium ions [45] and is the cause of the set material's sensitivity to water balance. The set material needs to be protected from salivary contamination for several hours, otherwise the surface becomes weak and opaque, and from water loss for several months, otherwise

clinical application and performance after removing caries.

**2. Glass-ionomer cements** 

[17, 79, 80, 84].

**2.1 Setting reactions** 

remain as a filler [79, 84].

the material shrinks and cracks and may debond [45, 79].

appear to wet the solid by spreading. Wetting is a qualitative description of the contact angle. Good wetting, or spreading, represents a low contact angle. Partial (poor) wetting describes a contact angle approaching 90 degrees. Non wetting is a contact angle approaching 180 degrees (see fig. 1B).

Fig. 1. Interfacial interactions of materials. A) Interaction quantified as contact angle (see formula). B) Interaction described in terms of good wetting (spreading), partial (poor) wetting, or nonwetting.

It is very important that film formers such as varnishes, liners, cements, and bonding agents have good wetting on tooth preparation surfaces on which these materials may be placed, so that they adapt to the microscopic interstices of the surfaces. However, in other instances, poor wetting may be an advantage. For example, experimental posterior composites have been formulated to have high contact angles to retard water and/or bacterial interactions. In most cases, wetting can be anticipated on the basis of the hydrophilicity (water-loving) or hydrophobicity (water-hating) of materials. Hydrophilic surfaces are not wet well by hydrophobic liquids [7].

Teeth also can be restored using indirect restorations are fabricated outside of the mouth. Most indirect restorations are made on a replica of the prepared tooth in a dental laboratory by a trained technician. Tooth-colored indirect systems include laboratoryprocessed composites or ceramics such as porcelain fired on refractory dies or hot pressed glasses. In addition, at least one chairside computer-aided design/computer-assisted manufacturing (CAD/CAM) system is currently available and is used to fabricate ceramic restorations [73].

appear to wet the solid by spreading. Wetting is a qualitative description of the contact angle. Good wetting, or spreading, represents a low contact angle. Partial (poor) wetting describes a contact angle approaching 90 degrees. Non wetting is a contact angle

Fig. 1. Interfacial interactions of materials. A) Interaction quantified as contact angle (see formula). B) Interaction described in terms of good wetting (spreading), partial (poor)

It is very important that film formers such as varnishes, liners, cements, and bonding agents have good wetting on tooth preparation surfaces on which these materials may be placed, so that they adapt to the microscopic interstices of the surfaces. However, in other instances, poor wetting may be an advantage. For example, experimental posterior composites have been formulated to have high contact angles to retard water and/or bacterial interactions. In most cases, wetting can be anticipated on the basis of the hydrophilicity (water-loving) or hydrophobicity (water-hating) of materials. Hydrophilic surfaces are not wet well by

Teeth also can be restored using indirect restorations are fabricated outside of the mouth. Most indirect restorations are made on a replica of the prepared tooth in a dental laboratory by a trained technician. Tooth-colored indirect systems include laboratoryprocessed composites or ceramics such as porcelain fired on refractory dies or hot pressed glasses. In addition, at least one chairside computer-aided design/computer-assisted manufacturing (CAD/CAM) system is currently available and is used to fabricate ceramic

approaching 180 degrees (see fig. 1B).

wetting, or nonwetting.

hydrophobic liquids [7].

restorations [73].

This chapter reviews the glass-ionomer cements, compomers, and direct composite restorative materials (also dentin bonding agents) and their composition, classification, and clinical application and performance after removing caries.
