Early tissue reactions after circulatory and skeletal damage to the mandible of the rat.

Skeletal and circulatory damage in the form of a fracture of the mandible, proximal to the entry of the inferior alveolar artery and other perforantes, alone or combined with unilateral or bilateral mucoperiosteal extirpation, was inflicted on growing young rats. A morphological study of the tissue changes in the bone, dental tissues and soft tissues was performed. Cutting of the nutrient vessels together with extirpation of the periosteum was followed after 10 days by extensive infarction of the incisor pulp, the odontoblasts and the apical part of the enamel organ. The bone was damaged centrally in the mandibular corpus and at the lower border of the ramus, and was partly resorbed during the experimental period. The periodontium showed dilated vessels, but was not damaged. The pulps of the three molars showed numerous dilated vessels but were otherwise not damaged. The oral mucosa, bone marrow, peripheral nerve tissue and peripherally situated bone were not altered. In the animals after fracture alone, oedema of the incisor pulp was present, but infarction did not occur with certainty. A similar bone damage as with mucoperiosteal extirpation was present. The incisor with its dentin and enamel-forming cells was most sensitive to circulatory disturbances due to its central location, while the gingivoperiodontal, mucoperiosteal and midline circulatory systems could nourish the peripheral parts of the mandible. The dependence of the different nutrient systems to bone and dental tissues is discussed.