Early and intermediate time response of the dental pulp to an acid etch technique in vivo

Purpose: To present the ultrastructural features of the pulpal responses, following the application of All-Bond 2 to acid-conditioned, deep, unexposed coronal dentin and exposed pulps in human teeth. Materials and Methods: Cylindrical Class V cavities were prepared in human premolars. In the non-exposure group an attempt was made to prepare the floor of the cavity to ± 0.5 mm from the pulp. In the exposure group, the pulps were intentionally exposed. After hemostasis, the preparation was etched with 10% phosphoric acid. The teeth were restored with All-Bond 2. Histological evaluation was done at 0-7, 28-35, and >90 days. Results: A typical connective tissue response to injury was observed in the majority of the specimens. Irreversible injury to the odontoblasts closest to the site of cavity preparations resulted in the death of these cells. This was followed by an early neutrophilic response, a subsequent macrophage response and a fibroblastic response that led to the deposition of either reparative dentin or calcific bridge formation by odontoblast-like cells. However, another notable feature was the consistent observation of resin particulates within the dentin-pulp complex. These resin particulates could have been indirectly introduced into the pulp through the pertubation of the junctional complexes or the death of the odontoblasts. They may also enter the pulp directly through a pulpal exposure. In some specimens, the presence of these resin particulates appeared to have triggered a foreign body response, characterized by the presence of a mononuclear inflammatory infiltrate as well as the appearance of multinuclear giant cells. The persistence of unresolved chronic inflammation was associated with the lack of calcific bridge formation in these specimens.