Caries into dentine

Once demineralisation has progressed through the enamel into dentine a variety of bacteria can become permanent inhabitants of the cavitation and they will be able to progress into the dentine itself. Demineralisation will still be driven by dietary substrate. The bacteria will produce acid to dissolve the hydroxy-apatite as well as cause proteolysis of the collagen framework of the dentine. There will a region of demineralisation in advance of the bacterial invasion and the surface layers of demineralised dentine will become totally denatured. There may be some pioneer bacteria in, or even beyond, the area of demineralisation, but these are not clinically relevant. Both the texture and the colour of dentine will change as the lesion advances. The texture (hardness) change is due to proteolysis and demineralisation. The colour will darken due to bacterial byproducts or stain from foods and beverages. In chronic lesions the colour change will be more pronounced and the floor of the cavity will be firmer in texture.