Intensity of Pulpal Response

The response of pulp should be systematically established. There is a need to record not only the location but also the severity of pulpal responses. The pulpal reactions are categorized into following histopathological characteristics:

1) Cellular Displacement: It is characterized by movement of odontoblasts and leukocytes into the dentinal tubules. This occurs in the first few days and can persist well over 30 days. It provides excellent evidence of the acuteness of initial response.

2) Infiltration of Inflammatory Cells in the Superficial and Deeper Tissues: The infiltration of inflammatory cells into odontoblastic layer, zone of Weil and cell rich zone is arbitrarily graded from zero to three degrees merely on the basis of the number of displaced cells. When the response represents only one or two displaced cells, a graded value of one-half is given.

3) Predominantly Inflammatory Cells: The predominating inflammatory cells (polymorphonucleated leukocyte, lymphocyte, eosinophil, monocyte and plasma cells) are usually recorded as the intensity of the cellular inflammatory response is increased.

4) Special Histopathologic Characteristics: There are a number of histopathological characteristics that can be classified as given below:

a) Abscess Formation: Occasionally, in a healthy pulp, there may occur certain abscess like conditions (dense accumulations of leukocytes between the odontoblastic layer and the predentin), which usually resolve; however, any technique that produces such conditions should be modified or eliminated. These characteristics are not necessarily localized.

b) Foci of Necrosis: The dentinal burns and the lesions induced by toxic restorative materials or chemicals, lead to loss of cellular details, collapse of vascular channels and a paucity of inflammatory cells. Subsequently, these lesions are heavily infiltrated by inflammatory cells and might either resolve with granulation tissue replacement or undergo abscess formation.

c) Lesions of Delayed Healing: Such lesions usually present dense infiltrations of chronic inflammatory cells and may develop abscess formation.

d) Regeneration of Odontoblasts: With the resolution of a lesion, most or all the inflammatory cells may disappear and leave behind an atrophic or degenerate odontoblastic layer, even exhibiting foci completely lacking in primary odontoblasts. In some instances, only regenerated odontoblasts are found and a distinction needs to be made between these two types of layers.

Degenerated odontoblastic layer, exhibiting foci completely lacking in primary odontoblasts

e) Reparative (tertiary) dentin formation: The incidence of reparative dentin formation depends upon the initial irritation caused by cutting the tooth structure and placing the restorative material. With high-speed techniques used these days, a very low incidence of reparative dentin formation results, leaving many primary dentinal tubules patent for the subsequent seepage of toxic products into the pulp.

Reparative dentin seldom occurs in human pulp tissue sooner than 30 days. Many a times, the lesions persist along with inflammatory response and the differentiation of new odontoblasts is difficult.