Methods: Pulp exposure (PX) was performed on the first maxillary molar of 35 rats. Specimens were collected at 1, 3, 7, 14, 21 and 28 days after PX. Teeth were processed for H&E staining and immunohistochemical staining for OX-42, a marker of microgia activation, in the Vc.
Results: We observed that there was a progressive and persistent inflammation in the tooth. At 21 to 28 days after PX, the inflammation extended out into periodontal ligament. Simultaneously, significant microglia activation was observed which starting at 2 weeks and peaking at 4 weeks.
Conclusion: The alteration of microglia in the Vc paralleled injury extent and degree of inflammation. These data suggest that chronic tooth pulp inflammation activates microglia of brainstem. Such microglia changes may contribute to further investigations into the central mechanisms of pain that can be associated with pulpal inflammation.