Molecular and cellular changes occur during tooth aging. Odontoblasts, derived from ectomesenchymal cells of the dental papilla, are implicated in reactionary dentin formation. Direct or indirect pulp treatments are acceptable procedures for reversible pulp inflammation, and sealing leakage-free restorations. In vitro and in vivo experiments leading to reactionary or reparativeodontogenesis demonstrate that pulp cells may differentiate into new odontoblast-like cells implicated in pulp repair. The rationale for the use of calcium hydroxide (CH) and zinc oxideeugenol paste (ZOE) evidences that these treatmentsarereserved to asymptomatic teeth. The ideal dressing material should be bactericidal, harmless to the pulp and surrounding structures, and should not interfere with the physiologic process of root resorption. Due to the deposition of successive new layers of reactionary dentin, the pulp volume is gradually reduced, asymmetrically. The highest reduction occurs in the occlusal roof, followed by the furcation zone. Less reactionary dentin is formed along the lateral walls. In association with the closure of pulp horn exposure, reparative dentin formation results from the transformation of pulp cells into odontoblast-like cells. The use of for mocresol was considerably decreased, whereas better results were obtained with MTA (Mineral Trioxide Aggregate) and/or with other pulp-capping materials. Internal root resorption, a finding seen both after ferric sulphate and for mocresol treatment, was not observed in MTA capped teeth. Due to the narrowing of the pulp in the root, endodontic treatments gain difficulties in the aging patient.
