Superficial and deep carious lesions

Abstract

Carious lesions start at the dentin surface and are oriented toward deeper regions. Their evolution is rapid or slow. They may be active or arrested, depending on the food intake, the oral mouth hygiene, and nature of the dental plaque. Near the dentinoenamel junction (DEJ), tubules filled with bacteria spread along the enlarged DEJ and start to destroy the mantle dentin. In the coronal part, the carious decay degrades the mantle dentin. In the root, in contrast, the two outer layers (the Hopewell-Smith hyaline and Tomes’ granular layers) are corroded by bacteria diffusing acids and/ or toxic components along the dentin canaliculi. Differences in invasion are due to the number and diameter of dentin tubules, which interfere with the diffusion of the carious lesion (active or arrested lesions). Tubule density and diameter expand from the surface to the middle dentin and reach the maximum diameter near the inner pulp. The wounded odontoblasts and the cells of the so-called Hoehl’s layer beneath the calcio-traumatic line form reactionary dentin. This dentin is similar to the tubular or atubular dentin (similar to orthodentin, but sometimes osteodentin-like formation). Reparative dentine results from the differentiation and secretion of mesenchymal stem cells taking origin among pulp cells (atubular, osteodentin- like structures). Calcospherite (or lamellar pulp stones) structures formed within the pulp are in continuity with the blood vessels, or they may be isolated structures within the dental pulp.