Caries demineralization

Pathology. Tooth plaque produces acids during the fermentation of dietary carbohydrates, causing the underlying tooth mineral to solubilize (demineralization). Upon restoration of a neutral plaque pH, mineral can reprecipitate (remineralization). When this equilibrium is lost, net demineralization occurs, causing dental caries. 

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. 

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. 

Mellberg JR (1986) Demineralization and remineralization of root surface caries. Gerodontology 5, 25-31. 

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. 

So far, the most convincing evidence for fhe discoloration of caries lesions has been provided for fhe Maillard reaction. Since few investigations have attempted to identify Maillard producfs sfraighfforwardly in carious material, further research in this field should be underfaken. In addition, the influence of discolored demineralized matrix, resistant to degradation, on the accessibility of fhe underlying sound tissue for acids and infiltrating bacteria should be established. 

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. 

Chapter 4 describes the in vitro reaction of glucose wifh demineralized dentin. Preliminary tests revealed that use of disfilled insfead of deionized water accelerated browning, consistent with the effect of frace metals on the Maillard reaction. The yellow discolored slices were more resistant than controls to pepsin-mediated breakdown, but not to trypsin-mediated breakdown. It would be worthwhile to investigate proteolysis of denfin collagen covalently bound by the Maillard reaction to proteins, which penetrate into a caries lesion. 

In conclusion, evidence has been gathered for a role of the Maillard reaction in caries. This reaction can cause inhibition of matrix degradation, which in turn inhibits lesion demineralization. Further research is needed to elucidate the pathways and the importance of this reaction in in vivo caries pathology. 

J. Hicks, F. Garcia-Godoy, C. Flaitz, Biological factors in dental caries enamel stmcture and the caries process in the dynamic process of demineralization and remineralization, J. Clin. Pediatr. Dent, part 1 28 (2003) 47-52 part 2 28 2004 119-124 part 3 28 2004 303-314. 

Z. Toth, Z. Gintner, J. Banoczy, P.C. Phillips, The effect of fluoridated milk on human dental enamel in an in vitro demineralization model. Caries Res. 31 (1997) 212-215. 

G.E.H.M. Dijkman, J. de Vries, A. Lodding, J. Arends, Long-term fluoride release of visible light-activated composites in vitro A correlation with in situ demineralization data, Caries Res. 27 (1993) 117-123. 

Caries involves the actual demineralization and destruction of tooth structure. 

To examine the clinical utility of our method, we have conducted various preliminary studies in which we have shown using artificial caries models of demineralization and remineralization that the P959 depolarization ratio of PRS measurements enables us to not only follow the progression and ex-tent/severity of early caries development, but also to monitor the repair process involving fluoride treatment [49, 50]. In addition, other initial studies have... 

The pathogenesis of dental caries may involve three distinct processes (1) adherence of the bacteria to the tooth, (2) formation of glycocalyx due to synthesis of a sticky glucan by the action of the bacterial enzyme glucosyl transferase on sucrose, and (3) accumulation of biobUm (plaque), within which there is continuing acid production by constituent bacteria (including streptococci and lactobacflli) able to metabolize carbohydrates at low pH values. This acid demineralizes an enamel. 

Complexes of Ca, CPP and phosphate have also been shown to reduce caries in a dose-dependent fashion, by increasing the level of calcium phosphate in the plaque, thus influencing the demineralization/remineraliza-tion process (Reynolds et al., 1995), and to significantly reduce the adherence of Streptococci to tooth enamel (Schuepbach et al., 1996). 

Nieuw Amerongen AV, Oderkerk CH, Driessen AA Role of mucins from human whole saliva in the protection of tooth enamel against demineralization in vitro. Caries Res 1987 21 297-309. 

Page DJ A study of the effect of fluoride delivered from solution and dentifrices on enamel demineralization. Caries Res 1991 25 251-255. 

Kirkham J, Robinson C, Strong M, Shore RC Effects of frequency and duration of acid exposure on demineralization/remineralization behaviour of human enamel in vitro. Caries Res 1994 28 9-13. 

Ruben J, Arends J, Christoffersen J The effect of window width on the demineralization of human dentine and enamel. Caries Res 1999 33 214-219. 

White spot lesions are the earliest macroscopic evidence of enamel caries [37], The lesions are caused by acids formed by bacterial fermentation of dietary sugars. This leads to a fall in plaque pH and dissolution of the mineral component of the tooth enamel. Under normal conditions, the demineralization process is balanced by remineralization due to diffusion of ions (Ca, P and hydroxyl) from saliva into the enamel when plaque pH returns to neutrality. However, if demineralization extent exceeds that of remineralization, then an incipient lesion is formed. 

White spot lesions vary from person to person, from tooth to tooth and from surface to surface, as well as with age of the lesion. Their nonstandard nature makes analysis of the lesion incredibly difficult. In order to increase the level of control over experiments with lesions, a standard method of producing in vitro lesions has been used in this study. Many of the features of white spot lesions can be mimicked by in vitro lesions, though no method completely replicates the development of the natural lesion. The lesions produced are usually referred to as caries-like lesions indicating that they are not a natural white spot lesion, but an artificially produced lesion for experimental analysis. These artificial lesions provide invaluable information about the formation, the processes of demineralization and remineralization, and the composition of the lesion at different stages, in addition to being the basis for the understanding of possible treatments of the lesion. 

---