Experimental Studies Of Guided Bone Regeneration In Alveolar Ridge Augmentation With TiNi-SMA Distractor

The technique of distraction osteogenesis has been successfully used in alveolar ridge augmentation. Xie Min has designed the microdistractor with TiNi-SMA which can elevate the alveolar ridge automatically. But above research has some disadvantages as follows: 1. There exists the imbalance between the tension and stress.2.Because of the inadequacy of the stress, the rebound time of distracor elasticity is too short. 3. The connective tissue interferes with the formation of new bone. 4.The theory of inner distraction lack relative stable period, which reduced a small quantity of fibrous bone 5. The local stability during DO is weak. In our investigation, we selected ADM as guided membrane. The barrier effect of ADM can stop the invasion of peripheral soft tissue. At the same time, the three dimension structure of ADM can induce the osteoblasts and vascular endothelial cell crawl and proliferate so that the bone tissue regenerate accelerately.Part 1: Biomechanical characteristics and the histological structure of ADM Objective: 1. To test the tensile strength and the applicability of ADM in alveolar ridge augmentation with TiNi-SMA distractors. 2. To observe the ultramicrostructure, pore geometry and collagen alignment of ADM through SEM and histological observation. Materials and methods: The ADM was cut into pieces of 4cmx2cm and were tested at 858Mini Bionix II biological materials meachine. Some part of ADM was put into the 10% formalin and the slice was stained with HE. Pieces of ADM was observed throuth SEM. Results: The average tensile strength is (2.81±0.42)×10~4N/mm~2. From SEM we can see that ADM presented regular three diamensions frame structure. Hitological observation showed that there were no structures such as cells, folliculosis, sweat gland. Conclusion: The strength of ADM can endure the tensile during alveolarridge distraction. The three diamensions framework has advantages on the growth of osteoblasts and can make the extracelluar factors permeate into the distraction gap. Part 2: Animal model of alveolar ridge augmentation with TiNi-SMAdistractor and ADMObjective: To set up the animal model of alveolar atrophy of the region of postmolar, to explore the placement way, size and quantity of ADM through a preliminary experiment. Materials and methods: 4 adult male dogs were selected as experimental animal. First, we extracted the 4 premolars and the first molar on both sides of each dogs' mandibular. One month later, the radiographs of bothside of this region were taken to observe the healing condition of extraction socket. Then one of 4 kinds of "S" shape distractors were randomly placed on one side of mandibular of each dog, and the ADM was placed on the buccal side of distraction gap. We measured the height of augmentaed alveolar ridge and taked X graph after distraction and 1 week and 1month after distraction. Results: 1 month after extraction, the mucosa healed up well. 1 week and 1 month after later the height of alveolar ridge were respectively 5.09mm and 5.01mm. with D group distractors. Conclusion: Canine is ideal animal model for alveolar ridge augmentation. D group distractors is ideal which can fulfill the prosthetic need.Part 3: Experimental study of the application of GBR in alveolar ridgeaugmentation with TiNi-SMA distractors I Dynamic study of alveolar ridge augmentation with TiNi-SMAdistractor and ADMObjective: To observe the dynamic changes of alveolar height, bone density and bone strength after alveolar ridge augmentation with TiNi-SMA distractor and ADM. Materials and methods: 12 adult healthy male dogs were selected. After the animal model of alveolar atrophy were set up, on one side of mandible, two "S" shape distractors were placed. The diameter of "S"shape distractor was 1mm, and the rebound temperature was 33℃. The ADM were placed on the distractiongap and were fixed by the feet of distractors.The other side were only placed with distractors, no ADM as control side. 1 week, 1 month and 3 months after distraction, we measured the alveolar height of both sides. 6 dogs' mandibles were harvested after 1 and 3months respectively. We made use of DEXA to scan the distraction gap as well as superior and inferior part of it. We also used mechanical machine to test compression strength and elastic modulus. Results: On the sides of distraction with ADM, the bone density, compressive strength, elastic modulus were high than control sides 3 months after distraction. Conclusion: ADM can accelerate the new bone forming velocity of distraction gap, improve the bone quality, and increase bone density and intensity. It is an ideal membrane of GBR for alveolar ridge agumentation with TiNi-SMA distractor.II Histological study of alveolar ridge bone with TiNi-SMA distractor and ADM.Objective: To analyse the basic structural characteristics of new formed bone trabecula in alveolar ridge augmentation with methods of bone histomorphometry. Materials and methods: The methods are as partI .Augmentaed alveolar ridge both side were harvested. The specimens werestained with HE Masson methods and were analysed by Parfit methods. Results: 1 month after distraction, Bv,Tb.Th,Tb.N of the control side without ADM were lower than that of the experimental side with ADM, but Tb.Sp were higher.3 months after distraction, Bv, Tb.N of the experimental side were higher than that of the control side, but Tb.Sp were lower. Conclusions: ADM can prevent connective tissue invading into distraction gap. The three diamensions structure can make local cytokine assemble into distraction gap and improve the environment of bone forming.