Tensile Strength, Histological and Immunohistochemical Observations of Periodontal Wound Healing in the Dog

This study was designed to study wound strength at the dentine/connective tissue interface and at the bone/connective tissue interface following full thickness flap surgery. Flaps of uniform dimension were outlined in four young adult beagle dogs using a standardised double bladed knife and vertical incisions 10 mm apart, which extended 8 mm apical to the gingival margin. Bone was removed from half the sites (eight sites in each dog), giving 32 flaps replaced on dentine and 32 sites on bone. A tensile force was applied using a microprocessor force gauge at 1, 2, 3, 7, 10, 14, 21, and 28 days. Mean tensile strengths were markedly weaker for the dentine/flap interface. At 7 days the value for flaps to dentine was 1.82 N, in contrast to 5.08 N for flaps replaced on bone. Inflammatory cell counts tended to fall markedly at 3 days for both modalities, but were higher for the dentine/flap modality at all time points. Fibroblast density peaked at 7-14 days but did not vary with type of flap over the time points studied. The amounts of fibrin were greater for the dentine/flap interface at all time points but decreased for both flap types as time progressed. Collagen type V was localised to the basement membrane and blood vessels and tended to show more foci for flaps replaced on dentine. Procollagen levels showed little change over the healing interval for both flap/bone and flap/dentine interfaces. Type III collagen synthesis was at peak levels during the first week. These findings would support efforts to stabilise periodontal flaps at early time points, especially those on dentine.