Dentinal caries

There is no clarity yet on a possible causative bacterial species for dentin caries. An increase in the proportion of Gram-positive bacteria has been noted. Especially lactobacilli have been isolated from the most advanced parts of dentin lesions (Edwardsson, 1987). 

In root surface caries, the root is affected after it has become exposed by gingival recession. The cement is damaged first with sequential destruction of laminated cementum layers. When the caries reaches the dentin, the lesion becomes wedge-shaped (Nyvad and Fejerskov, 1990 Schiipbach et ah, 1989). The histochemical changes of root surface caries correspond with those of dentin caries (Frank, 1990). Mineralized surface layers have been reported for both dentin and root surface caries (Mellberg, 1986). 

Dentin caries is inversely correlated with oral hygiene (Axelsson et ah, 1994 0gaard et ah, 1994) and fluoride intake (Frencken et ah, 1991). It can be expected that an improved oral status will decrease the incidence of dentin caries, but will increase root surface caries because the elderly are more dentate. A higher number of teeth retained, however, is associated with fewer root surface caries (Vehkalahti and Paunio, 1994). 

Edwardsson S (1987) Bacteriology of dentin caries. In Dentine and dentine reactions in the oral cavity (eds. Thylstrup A, Leach SA and Qvist V), pp. 95-102. IRL Press, Oxford UK. 

In the present investigation we sought to clarify the purported relation between dentin caries and matrix protein modifications such as the Maillard reaction and cross-linking. 

In the course of dentin caries, both demineralization and reactions with the organic matrix take place. Matrix reactions include proteolysis and covalent modifications. From the introduction (Chapter 2) and the review on discoloration in caries (Chapter 3), it becomes clear that there are still few reports on the effect of matrix modifications on dentin caries. In Chapters 2, 4, and 5, the investigations were aimed at filling the information gap concerning the effect of reactions of dentin matrix on caries. To this end, degradation and modification of dentin were studied in demineralized specimens in vitro. In addition, specimens placed in dentures in situ and caries lesions in extracted teeth were analysed for modifications. 

Kleter GA, Damen JJM and Ten Cate JM (1995) Purification of cross-linking amino acids for their analysis in carious dentine. Caries Res 29, 309. 

Eugenol has been used since the nineteenth century as a flavoring agent in a variety of foods and pharmaceutical products. It has found use as a mild rubefacient in dentifrices, and as an obtundent for hypersensitive dentine, caries, or exposed pulp. Additional uses are in dental cement preparations, analgesics and anesthetics, and temporary dental filling when mixed with zinc oxide. The substance is also used in the perfumery or flavor industries, and also as insect attractant [1, 3, 4]. 

Sadler JP, Hall AF, Creanor SL, Strang R, Foye RH An in situ model to study erosion in enamel and dentine. Caries Res 1997 31 318. 

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. 

L. Zheng, J.R Hilton, S. Habelitz, S.J. Marshall, G.W. Marshall, Dentin caries activity status related to hardness and elasticity, Eur. J. Oral Sci. Ill (2003) 243-252. 

J.M. ten Cate, Remineralization of deep enamel dentine caries lesions, Aust. Dent. J. 53 (2008) 281-285. 

M. Maltz, E. de Oliviera, V. FontaneUa, G. Carminatti, Deep caries lesions after incomplete dentine caries removal 40-month foUow-up smdy, Caries Res. 41 (2007) 493-496. 

Although Actinomyces has been linked with root surface caries (Edwardsson, 1987), contradictory reports on the microbiology of root surface caries still appear (Beighton and Lynch, 1995 Schiipbach et ah, 1995 Schiipbach et ah, 1996 Van Route et ah, 1994). A longitudinal study, however, failed to prove a role for Actinomyces (Ellen, 1993). Actually, lactobacilli and mutans streptococci are considered risk factors for root surface caries (Banting, 1991 Ravald and Birkhed, 1992). Generally, Gram-positive species predominate in the initial attacks on cementum and root dentin (Edwardsson, 1987). 

From the studies summarized above, it is clear that the breakdown of the dentin matrix plays an important role in the pathology of dentin- and root surface caries. In addition, the demineralized dentin can be modified by a number of reactions, with consequences for its degradability. The studies described in this thesis were designed to address the role of degradation and modification of the dentin collagen. 

Beighton D and Lynch E (1995) Comparison of selected microflora of plaque and underlying carious dentine associated with primary root caries lesions. Caries Res 29, 154-158. 

Bjorndal L and Thylstrup A (1995) A structural analysis of approximal enamel caries lesions and subjacent dentin reactions. Eur J Oral Sci 103, 25-31. 

Boonstra WD, De Vries J, Ten Bosch JJ, Ogaard B and Arends J (1993) Inhibition of bovine dentin demineralization by a glutardialdehyde pretreatment an in vitro caries study. Scand J Dent Res 101, 72-77. 

Frank RM (1990) Structural events in the caries process in enamel, cementum, and dentin. J Dent Res 69, 559-566. 

Inaba D, Ruben J, Takagi O and Arends J (1996) Effect of sodium hypochlorite treatment on remineralization of human root dentine in vitro. Caries Res 30, 218-224. 

Schiipbach P, Guggenheim B and Lutz F (1989) Human root caries histopathology of initial lesions in cementum and dentin. J Oral Pathol Med 18, 146-156. 

Van Strijp AJP, Van Steenbergen TJM and Ten Cate JM (1997) Bacterial colonization of mineralized and completely demineralized dentine in situ. Caries Res (in press). 

Root caries can occur when tooth roots are exposed to the oral environment, for example after periodontal surgery or gingival recession. Two stages are distinguished microscopically. First, the dentin mineral is dissolved and bacteria penetrate the tubules. Second, the demineralized dentin matrix is degraded, and bacteria infiltrate the intertubular area (Frank et al., 1989 Frank, 1990 Schiipbach et al., 1989). This sequence of events may indicate that the degradation of the dentin matrix occurs after it has become accessible by the removal of mineral. In an in vitro study, Klont and Ten Cate (1991) confirmed that the dentin matrix cannot be degraded unless it is demineralized. 

Peroxidases from saliva, crevicular fluid, bacteria, and fungi may contribute to this reaction in caries lesions. Although deeper layers of the carious microflora are assumed to be anaerobic, the oxygen required for the reaction may reach the deeper parts of the plaque via oxygen channels (Marquis, 1995). Lactobacilli, however, cause browning of dentin in the absence of tyrosinase (Dreizen et ah, 1957). 

Armstrong WG (1964) Modifications of the properties and compositon of the dentin matrix caused by dental caries. Adv Oral Biol 1, 309-332. 

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