Stages of Pulpal Inflammation

The reaction of the pulp to external stimuli is reflected in two broad processes:

Inflammatory changes and secondary dentin formation. Various authors have graded these changes for evaluating pulpal response. The inflammatory processes have been qualitatively divided into slight, moderate and severe. Slight reaction recognizes the increased number of cells in the cell free zone and in the adjacent pulpal tissue. These cells are similar to fibroblasts and undifferentiated cells. However, few inflammatory cells are also observed. The capillaries blood flow is also increased localized to the affected dentinal tubules. The irregularities in the odontoblastic layer are also observed.

Slight inflammatory reaction.Note the irregularities in the odontoblastic layer

Moderate reaction is characterized by increased number of cells around the injury site. The mononuclear leucocytes and the neutrophils invade the odontoblastpredentin area. Some odontoblastic nuclei can be seen in dentinal tubules. The number of capillaries is increased along with the blood flow. Occasional haemorrhage in odontoblastic or subodontoblastic zone is also observed.

Moderate reaction, Haemorrhage in subodontoblastic zone

Severe reaction is characterized by marked cellular infiltration, including abscess formation. The odontoblastic layer remains unidentified. This layer is either destroyed or greatly disrupted. The predentin is not formed. Numerous blood vessels are found in the tissues surrounding the cellular infiltration.

Severe Reaction. Odontoblastic layer remains unidentified

Since the qualitative approach is subjective, attempts have been made to quantitatively designate pulpal reactions. The technique measures the cytoplasmnucleus ratio of the odontoblasts along the area of pulpal reaction. Statistically, quantitative method is considered more accurate, however, at initial level, the qualitative approach is more appropriate.

Earlier plus sign was used to indicate the degree of infiltration of inflammatory cells in the odontoblastic layer and in the rest of the pulp. The plus sign was also used to indicate the different amounts of secondary dentin formation.

Later, the inflammation and secondary dentin formation was graded as I0-I3 and D–1 – D3 respectively.

• I0 – Absence of inflammation and no disturbance of the odontoblastic layer.
• I1 – Involvement of the odontoblastic layer only, including aspiration of the nuclear debris.
• I2 – Extension of inflammation to the subodontoblastic layer.
• I3 – Involvement of the central pulp.
• D–1 – Absence of secondary dentin formation and destruction of odontoblasts.
• D0 – A normal appearance of odontoblastic layer with a normal width of predentin (20-30 μm).
• D1 – A slight amount of secondary dentin formation (35-60 μm)
• D2 – A moderate amount of secondary dentin formation (60-90 μm)
• D3 – A considerable amount of secondary dentin formation (90 and >90 μm)