COLLAGEN ADHESION REVISITED

Histologic studies of periodontal reconstructive therapies have repeat edly shown a zone of nondescript connective tissue adaptation or colla gen adhesion to the roof surface between the apical extension of the j unctional epithelium and the coronal extension of identifiable regener ated cementum. To clarify the nature of this zone, supra-alveolar peri odontal defects were created bilaterally in the mandibular premolar re gion in three beagle dogs, and exposed roots were instrumented to remo ve the cementum. Flaps were then coronally advanced and sutured. Histo logic analysis after 12 weeks of healing showed instrumented roof dent in not associated with junctional epithelium, new cementum, roof resor ption, or ankylosis in 27 of 60 roof surfaces. In 10 of these specimen s subsequently examined by transmission electron microscopy, collagen fibrils were generally oriented parallel to and in close proximity to the root. A mechanism of collagen attachment was, in fact functioning at sites of collagen adhesion; these areas may validly be included in the histologic attachment level reported in studies of periodontal rec onstructive therapy.