Dynamics of Periodontal Wound Healing Following GTR Therapy

Objective: To describe the periodontal tissues formed in dehiscence-type defects following GTR therapy. Method: 10 adult Macaca fascicularis monkeys were used. Chronically inflamed buccal dehiscence-type defects were created at the maxillary 2nd premolars and 2nd molars. After three months, GTR surgery was performed followed by biweekly plaque control. The animals were sacrificed at 6 weeks, 6 months and 2 years after surgery. Tissue blocks containing experimental teeth were harvested, fixed in 10% buffered formalin, demineralised in trifluoroacetic acid and embedded in paraffin. Bucco-lingual sections of 5 ìm were cut parallel to the long axis of the roots. From each root 3 sections, 50 ìm apart, representing the mid-portion of the defect were selected for microscopy analysis. Results: At 6 weeks the newly formed periodontal tissues were immature. A 10-20 µm thin layer of acellular extrinsic fibre cementum had formed along the instrumented root surface. Supracrestal as well as PDL fibres with about 10 fibres per 100µm of new cementum were embedded in the new cementum. At 6 months, the defect contained new cementum, periodontal ligament and supporting bone. While the width of the supracrestal cementum was comparable to that at 6weks, the width of the subcrestal cementum had increased to 40 -60µm by the apposition of cellular extrinsic/intrinsic fibre cementum. The density of extrinsic fibres in the subcrestal cementum had increased to15 per 100µm. At 2 years the supracrestal cementum was as thin as at 6 weeks, whereas the width of the subcrestal cementum amounted to about 80µm. The density of extrinsic fibres was about 28 fibres per 100µm of new cementum. The healing characteristics at 2 years resembled the structure of pristine periodontium. Conclusion: Periodontal healing following GTR therapy of recession type defects will result in a restitutio ad integrum, i.e.healing by regeneration.