Human pulpal modifications after low mechanical injuries : histologic evaluation

Several studies analyzed the biological reactions of exposed human dental pulp, but few histological data on pulp reaction to low intensity mechanical injuries are available. Aim of the present study was to evaluate the morphological variations of human pulp tissue in a young permanent maxillary central incisor three months after a minimal mechanical trauma. Methods. A 30-years-old man presented himself with a traumatic fracture of the incisal margin of the central permanent right maxillary incisor. At clinical evaluation the trauma exposed the dentin without pulpar involvement: the residual distance between the margins of the fracture and the coronal pulp was about 3 mm. Radiologically, an enlargement of the periapical space was observed. The tooth was then reconstructed using a light-cured composite. Three months later, a sensitivity test was performed with a negative result. Moreover, the tooth was not mobile or tender to percussion. Therefore, a pulpectomy of the incisor was decided: the pulp tissue was extracted and immediately immersion fixed in 10% formalin in 0.1M phosphate buffer saline (PBS) (pH 7.4) for 12 hours at room temperature, routinely dehydrated, paraffin embedded, and serial sections were obtained at 5 mm. Sections were stained with haematoxylin-eosin and with Brown-Brenn to identify Gram-positive bacteria. Results. The histologic examination revealed a normally organized pulp tissue with a reduced number of pulp cells and an increased amount of collagen fibers. No inflammatory cells were observed in the specimens. Several irregular calcifications were seen in the coronal and radicular portion of the pulp. Intensive fibrosis surrounded the calcifications of the radicular pulp tissue in the middle and in the apical third of the root canal. No stained bacterial colonies were evidenced in the pulp tissue. Conclusions. Permanent teeth suffering for mechanical trauma display pulpar modifications with irregular calcifications, an intensive fibrosis, free from inflammatory cells and from bacterial colonization. Traumatic lesions could then cause pulpar necrosis in young individuals, although the apparent shock is light. This information could be useful for the clinician to closely monitor the teeth affected by a low intensity trauma.