Pulpal response to prolonged dentinal exposure to sodium hypochlorite

Aim The aim of this study was to examine the effect of undiluted NaOCl on v ital pulp tissue when applied to freshly cut dentine. Methodology Class V cavities were prepared to a depth of 2 mm in 20 teeth i n four Beagle dogs. The cavities on one side of each dog were irrigated con tinuously for 5 min with 5.25% NaOCl, whilst the cavities on the opposite s ide in each dog were irrigated with saline for the same length of time. Pri or to filling each cavity with Cavit, they were again rinsed with saline an d gently dried with an air stream. The dogs were sacrificed to allow for in vestigation of pulpal conditions under the cavities after periods of 24 h, 1 week, and 4 weeks. Histological preparations were made and stained with H & E for evaluation of the pulp subjacent to each cavity. The tissues were examined for presence of inflammatory cells and categorized as (i) no infla mmation, (ii) mild, (iii) moderate, and (iv) severe inflammation. Results The six teeth in the 24 h observation group all showed mild inflamm ation, both in the NaOCl and the saline groups. After 1 week and 4 weeks, t he pulps from all the teeth were free of inflammatory cells. Conclusions Under the conditions of this experiment, the use of NaOCl in a freshly cut cavity in an intact tooth of a dog, with exposed dentinal tubul es, does not appear to cause additional pulpal damage to that caused by the physical contact in cutting tooth structure.