Collagen degradation in the gingiva of the mouse incisor

Abstract

In this study we investigated the possible role of the junctional epithelium of the mouse incisor in the degradation of collagen fibers carried during eruption from the periodontal ligament into the gingiva. To eliminate the contribution of fibroblasts to collagen breakdown the periodontal ligament was frozen in the sub‐crestal region by local application of liquid nitrogen. As a result of this treatment the fibroblasts were disrupted and, with ongoing eruption, the ligament was split into two separate sets of collagen fibers, one attached to the incisor and the other to the alveolar bone. The injured connective tissue in the tooth‐related compartment continued to move in the occlusal direction and made contact with the intact gingiva. Following its arrival in the sub‐epithelial region, the collagen fibers were not degraded but carried further towards the incisal edge, a process resulting in a forward shift of the level of connective tissue attachment. The degree to which this occurred was inversely proportional to the number of fibroblasts which had repopulated the connective tissue adjacent to the incisor. The data suggest that degradation of collagen and maintenance of connective tissue attachment in mouse incisor gingiva cannot solely be performed by cells of the junctional epithelium but require primarily the degradative activity of fibroblasts.