You can read part 10 of most common disease before reading part 11.
Protective Reactions of Dentine and Pulp Under Caries
The reactions in dentine are mainly due to odontoblast activity, so that dentine and pulp should be considered as one tissue. These reactions are not specific and may be provoked by other irritants such as attrition, erosion, abrasion and restorative procedures. Reactionary changes in dentine start even before cavity formation in enamel but are more likely to develop significantly under slowly progressing caries.
reactionary changes start to develop early but at best can only slow the advance of dental caries. Even sclerotic dentine is vulnerable to bacterial acid and proteolysis and once bacteria have penetrated the normal dentine they can invade any reactionary dentine to reach the pulp.
A translucent zone. The dentinal tubules are seen in cross section. Those in the centre of the picture have become obliterated by calcification of their contents; only the original outline of the tubules remains visible and the zone appears translucent to transmitted light. On either side are patent tubules filled with stain
Root Surface Caries
When the neck of the tooth becomes exposed by recession of the gingival margin in later life a stagnation area may be formed and the cementum attacked. Cementum is readily decalcified and presents little barrier to infection. The cementum therefore softens beneath the plaque over a wide area, producing a saucer-shaped cavity, and the underlying dentine is soon involved. Cementum is invaded along the direction of Sharpey’s fibres. Infection spreads between the lamellae along the incremental lines, with the result that the dentine becomes split up and progressively destroyed by a combination of demineralization and proteolysis. The further progress of caries in the underlying dentine is essentially similar to that in other parts of the tooth.
Arrested Caries and Remineralization
Precavity (white spot) interstitial caries may become arrested when the adjacent tooth is lost so that the stagnation area is removed. The lesion may become remineralized by minerals from the saliva.
Dentine caries may occasionally be arrested as a result of destruction of so much enamel that a wide area of dentine becomes exposed. If this surface is then subjected to attrition, plaque deposition may be prevented. More frequently, but still uncommonly, dentine is exposed by attrition and remains caries-free for the same reason. It becomes smooth, polished and stained.
A dead tract. The empty tubules below the worn incisal edge have been filled with a stain to which they are permeable from the surface, so that the whole zone appears black. At the proximal end of the tubules the dead tract has been sealed off by impermeable reactionary dentine through which the stain cannot penetrate. The pulp is thus protected from irritants penetrating along the dentinal tubules
Under favourable conditions carious demineralization can be reversed and early lesions can remineralize. Use of fluorides and consumption of a less cariogenic diet may cause a surface lesion in enamel to heal entirely. Even under natural conditions, approximately 50% of interproximal enamel lesions may show no radiographic evidence of progression for 3 years. Similarly, in some patients, secondary caries may not necessarily develop at the margins of restorations overhanging the enamel.
Adult and Childhood Caries
In adults, caries usually progresses slowly and a small cavity may take several months to develop. By contrast, childhood caries, particularly of deciduous teeth, may be so rapid that the pulp becomes exposed long before the tooth is due to be shed.
Pulpitis
Pulpitis follows penetration of dentine by bacteria or their metabolites and represents the breakdown of the protective hard dental tissues and opening of the soft tissues to infection.
Clinical Aspects of Reactions to Caries
The reactive changes described in this article render the dentine immediately under a carious cavity more or less impermeable, unless caries is advancing very rapidly.