Feasibility Study On Reconstruction Of Soft Tissue Implant Site With Free Skin Graft Transplanted On The Bone Surface

Maxillary and mandibular defects are common in the oral and maxillofacial surgery, which are caused by postsurgical trauma, inflammation and so on. Reconstruction of jaw and intraoral soft tissue defect through vascularized bone and skin graft is the common way and reconstruction of dentition through dental implant is the last link of masticatory function restoration. For the reconstruction of jaw defect through vascularized bone and skin graft, there is usually removable skin on the surface of the bone. The tissue is too thick and the removability is too large, which result in the poor integration with the gum of the implant and inaccessibility of fine biological seal. This often leads to the peri-implantitis. Ideal implant site of soft tissue requires that the soft tissue of the implant area is no thicker than 4mm, no wider than 6mm and closely integrated with the bone surface. In pursue of ideal implant site of soft tissue with the reconstruction of jaw defect through vascularized bone and skin graft, we employed free skin flap on the bone under tissue to solve the problem. Preliminary exploration on the form of attachment between bone and skin after skin graft of bone surface was carried out and initial understanding of bone remodeling with different time periods after skin graft of bone surface was obtained. Specific contents are as follows:1. Feasibility study of free skin graft on the bone surface buried in the soft tissueObjective: explore the feasibility of free skin graft on the bone surface buried in the soft tissue and the success rate of grafts with different thickness. Methods: transplant free skin graft on the bone surface buried in the soft tissue with different thickness and compare the success rate. General specimen observation, histological observation (HE and MASSON) and transmission electron microscope observation were carried out. Results: split-thickness skin graft has high success rate which is similar to that of skin flap. The thickness, elasticity, pressure resistance and wear resistance all meet the requirements of implant site when reconstructing the implant. Therefore it is a feasible method.2. Observation study of new attachment between bone and skin after completion of free skin graft on the bone surface buried in the soft tissueObjective: study the binding mode of new attachment between bone and skin after completion of free skin graft on the bone surface buried in the soft tissue. Methods: General specimen observation, histological observation (HE and MASSON) and transmission electron microscope observation were carried out on the animal model with successful transplants using full-thickness and split-thickness skin grafts. Results: the skin and the surface of bone cortex had fine concrescence and the skin had little removability. In transmission electron microscope observation the interface of skin and bone showed a close connection and the non-smooth region of bone cortex surface provided larger area for the integration of dermis layer and bone cortex. There were possibly gomphosis between dermis layer and bone surface, which would help enhance the attachment between bone and skin and restrict the removability in horizontal and vertical directions. The collagenous fiber in dermis tissue extended towards the interior of bone cortex. It combined with the fiber within the bone cortex and formed the structure resembling the perforating fiber, which is similar to the connection between bone and periosteum. The fact explained the reason why the skin has little removability and strong connection after the concrescence of skin with bone surface.3. The change of bone cortex after the formation of new attachment between bone and skinObjective: study the change of bone cortex after the formation of new attachment between bone and skin. Methods: cover the bone cortex surface of rabbits with skin flap and then carry out general specimen observation and histological observation after 4, 8 and 12 weeks. Results: after the bone cortex was directly covered with skin, osteoclasis occurred as a result of the osteoclast. As time elapsed, the number of osteoclast declined and osteogenesis began to appear. At the 12th week bone remodeling nearly completed and a dense layer of cells was formed in the dermis layer near the surface of bone cortex, which would possibly replace the role of periosteum.