Fissure caries

Several different types of dental caries have been described by clinicians. Specifically these are smooth-surface caries, pit and fissure caries, enamel caries, dentinal caries, secondary caries, early childhood caries and root caries [12], All occur by the same essential mechanism, as described above, and all arise as a consequence of a disturbance to the demineralization-remineralization balance. Attack by organic acids produced by bacteria in the plaque favours demineralization, but the natural remineralization processes of the mouth can reverse this. Certain dietary and hygiene behaviours as well as clinical treatments can enhance this natural remineralization provided they occur early enough in the demineralization part of the process. For example, complexes of casein phosphopeptide with amorphous calcium phosphate have been shown in various studies to be capable of enhancing the remineralization step under certain conditions and in specific groups of individuals [16,17]. These are now available commercially as an anticaries treatment for patients. 

Fig. 9.2 a Confocal image of rhodamine-stained enamel proximal lesions treated with resin infiltrant (Icon DMG). b Fissure caries lesions green) infiltrated with resin red) (color figure online). Reproduced with permission from [137] and [138]... 

Paris, S., Lausch, J., Selje, T, Do rfer, C.E., Meyer-Lueckel, H. Comparison of sealant and infiltrant penetration into pit and fissure caries lesions in vitro. J. Dent. 42,432-438 (2014)... 

Another important use for the glass polyalkenoate cement is in preventive dentistry where it can be used to fill and seal naturally occurring pits and fissures in molar teeth which are sites for the initiation of caries (McLean Wilson, 1974, 1977b Komatsu, 1981 Wilson McLean, 1988). Its adhesive quality and ability to act as a long-term fluoridereleasing gel make it particularly suitable for this purpose. Special formulations for this application have been placed on the market. 

Although chlorhexidine affects virtually all bacteria, gram-positive bacteria are more susceptible than are gram-negative organisms. Furthermore, Streptococcus mutans and Antinomies viscosus seem to be particularly sensitive. S. mutans has been associated with the formation of carious lesions in fissures and on interproximal tooth surfaces and has been identified in large numbers in plaque and saliva samples of subjects with high caries activity. 

Unlike erosion, caries damage is localised to areas where plaque most readily accumulates, i.e. between the teeth, at the gum margins and in fissures and irregularities on the tooth surfaces. 

Currently accepted dentifrices contain sodium mono-fluorophosphate, sodium fluoride, or, less frequently, stannous fluoride, all of which reduce caries by approximately 25% when used daily. In some clinical studies, stannous fluoride dentifrices stained teeth, particularly in pits and fissures. This stain is related to the tin in this compoimd, which adheres to plaque. The significance of this staining and its esthetic problems have resulted in a decreased usage in dentifrices. Stannous fluoride dentifrices are marketed in a plastic container because a reaction of stannous ions at an acid pH occurs when conventional soft metal tubes are used. 

Many remineralisation models mimic the situation found on smooth enamel surfaces in the mouth, i.e. appropriate salivary calcium, phosphate and fluoride concentrations and a clean enamel surface with no plaque analogue. Remineralisation of enamel lesions typically occurs during exposure to experimental solutions at neutral pH, whereas demineralisation occurs during exposure to acidic buffers. However, when good oral hygiene is maintained and with the use of fluoride toothpastes, caries is prevalent not on the smooth surfaces of the teeth but on those sites which are difficult to clean and where plaque tends to accumulate i.e. occlusal fissures and approximal surfaces [36], Here, caries is initiated and progresses not on a clean, smooth surface exposed to saliva, but... 

The ability of tooth mineral itself to buffer pH, and hence restrict the cari-ogenic challenge from plaque acids, has been demonstrated in recent laboratory studies. Zaura et al. [60] showed that the pH at the bottom of in situ plaque, in grooves cut into different materials to simulate tooth fissures, decreased in the order polyacrylate > enamel > dentine after an in vitro glucose treatment, i.e. the inverse of the solubility. In chapter 3, Lynch describes his own in vitro work in which the presence of dentine adjacent to a block of enamel could act as a sacrificial source of Ca and Pi and inhibit enamel dissolution in solutions initially undersaturated with respect to both materials. 

Fig. 15.1 Severe, untreated dental caries. Dental caries initially affects the occlusal pits and fissures of posterior teeth. In severe caries, the smooth surfaces, especially the interdental surfaces of all teeth may be involved...

Sealants are placed in pits and fissures of molars, either primary or permanent, in order to prevent the development of caries. By sealing a deep fissure in a newly erupted tooth, the space is filled and therefore cannot be occupied by plaque and pellicle [ 146]. This prevents caries in locations that are otherwise difficult to maintain in a clean and plaqne-free condition. 

Since this time, there have been numerous studies to compare the clinical effectiveness of glass-ionomer cements with that of composite resin sealants. These have typically determined the relative retention rates, and they have usually found that glass-ionomer sealants show inferior performance [149]. However, when caries rate in teeth are compared it turns out that glass-ionomers are at least as effective as composite resins [150,151]. It has been suggested that this is due to retention of glass-ionomer cement deep within the fissure and also because of the fluoride release into the enamel prior to the loss of the bulk cement [1]. 

Glass-ionomers have other advantages over composites in this appUcadon, namely that they are hydrophilic and dimensionally stable. Their hydrophilic character enables them to absorb fluid that can be left at the bottom of the fissure without jeopardizing the adhesion to enamel. The dimensional stability is important because it allows the cement to retain its marginal adaption and seal, so that there is no risk of caries developing under the fissure sealing material. Fluoride release is also potentially advantageous. 

J. Avinash, C.M. Marya, S. Dhingra, P. Gupta, S. Katana, Meenu, H.P. Bhatia, Pit and fissure sealants an unused caries prevention tool, J. Oral Health Comm. Dent. 4 (2010) 1-6. 

E.l. Cueto, M.G. Buonocore, Sealing of pits and fissures with an adhesive resin its use in caries prevention, J. Am. Dent. Assoc. 75 (1967) 121-128. 

V. Yengopal, S. Mickenautsch, A.C. Bezerra, S.C. Leal, Caries-preventive effect of glass ionomer and resin-based fissure sealants on permanent teeth a meta-analysis, J. Oral Sci. 51 (2009) 373-382. 

There have been pubhcations on the effectiveness of glass carbomer as a pit-and-fissure sealant. In one [16], the study compared glass carbomer with a resin-based sealant in 48 teeth in 24 patients. After 6 months, both materials showed 100% retention and after 12 months, they both showed 75% retention. This showed that in terms of one important requirement of fissure sealants, namely retention, the glass carbomer performed quite well. However, further work is necessary to establish whether the enhanced bioactivity confers any further or longer term benefits by way of caries inhibition. 

A variety of sealants have been explored or developed (168), with many people having one or more applications of a sealant. Sealants are vital for promotion of adhesion, which significantly reduces caries formation (169-177). Pit and fissure sealants are covered under the American Dental Association (ADA) Acceptance Program. These materials are used to seal high caries-susceptible pits and fissures of the deciduous and permanent molars, and also to seal microspaces between the tooth and restorative materials, enabling these materials to adhere firmly both to prepared cavity walls and to other restoratives. They provide dental pulp protection and protection from secondary caries formation. 

Preventive dental sealants, used to seal the susceptible areas of teeth, are classified into pit and fissime sealants and smooth simface sealants. From a material science perspective, pit and fissure sealants can be further classified iuto resin sealants and GI cements. Preventive dental sealants are usually placed onto molar teeth of young children who are at high risk for caries development. 

Surface Polysaccharides in Cariogenicity. The production of dental caries (tooth decay) is strongly associated with the presence of Streptococcus mutans. Other oral streptococci, e.g. S. sanguis and 5. salivarius, and lactobacilli are also found in the lesions, but are not considered to be primary pathogens, except in caries initiated in dental fissures and pits where food has become impacted and strong adhesive properties are not essential. 

Fissure sealing is a preventive technique carried out on newly erupted teeth. Deep fissures in such teeth may act as sites into which plaque and pellicle may become occluded, and it cannot be removed from these sites by brushing. Left undisturbed, this is likely to result in the development of caries. 

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