Experiment Study Of Using Non-submerged HBIC Implants In Animal

Objective: To study the immediate implants placed into fresh extraction sockets. Before implant, a problem of bony defects usually appears, which will influence the early stability of the implants. Currently the main method to solve this problem is filling defects with bone powder and guided bone tissue regeneration. In this study, root-shaped implants with the same diameter as extraction sockets used in animal experiment, the bone healing process of immediate implantation was observed, and the feasibility of immediate implantation was tested, in order to investigate the better and mature technique of immediate implantation.Methods: 1.Material treatments: Pure Titanium implants were manufactured into screw—shaped cones, screw space was 1.5mm.They were classfied into four types. Ⅰ type: they were length of 10mm, top diameter of 5mm, bottom diameter of 2.5mm, number 9; Ⅱ type: they were length of 12mm, top diameter of 5.5mm, bottom diameter of 3 mm, number 9; Ⅲ type: they were length of 10mm, top diameter of 4.5 mm, bottom diameter of 2 mm, number 18; Ⅳ type: they were length of 12 mm, top diameter of 5mm, bottom diameter of 2.5mm, number 18. 2.Bio-oss: there were 1.0 gram. 3. Animalexperiments: Nine rural adult mongrel dogs were used in this study, from 2 to 4 years, without regard to sex, weighing between 15kg to 25kg. Self-contrast was adopted . Mandibular third and fourth premolars were extracted bilaterally on all animals. Each premolar had two roots which were medial root and distal root .The implants with the same diameter as extraction sockets were placed into right mandibular third, fourth premolar distal extraction sockets and left mandibular third , fourth premolar medial extraction sockets( I , II ,111, IV type implants were placed respectively); The implants with the smaller diameter than extraction sockets were placed into left mandibular third and fourth premolar distal extraction sockets(III,IV type implants were placed respectively). The spaces around the defects were filled with Bio-oss. So they were divided into simple implant placed group (Sim group) and implant plus Bio-oss placed group (Bio group). 3. Specimen preparation: The dogs were killed randomly at 1st month, 2nd months, 3rd months after surgery, the bone segments that contained the implants about lcm3 were removed from the animals. The tissue samples were fixed with 10% Foumaldehyde soaked for one week and 8% formic acid was used to dissolve the calcium. After rinsed with water, the tissue samples were embedded in paraffin. The sections were stained with HE for histological examination and bone histomorphometric parameters were measured to quantify the change of new bone around Titanium implants and to observethe changes of implant-bone interface.Results: 1.General observation: All experimental animals were no postoperative inflammation and no sudden death. One implant was mobile at 1st month in Bio group; Two implants lost respectively at 2nd, 3rd months in Bio group (successful rate was 83.33%); One implant lost at 3rd months in Sim group (successful rate was 97.22%). Other implants were immobile. 2. X-ray check: Radiograph of immediate implant at 1st month after surgery. Sim group: Beside neck, a gap between the implant and the surrounding socket walls had almost disappeared; Bio group: Bio-oss were absorbed, and substituted by the low density of new bone. The low dense imagine could be seen. Radiograph of immediate implant at 2nd months after surgery. Sim group: The implant cervical gap diminished. The density of bone around implant increased; Bio group: The new bone around implants were on increase. The low dense imagine had almost disappeared. Radiograph of immediate implant at 3rd months after surgery. There were no difference in Sim group and Bio group: The gap around implant neck was futher diminished, the density of new bone increased compared with that at 2nd months. Osseointegration image appeared between implant and alveolar bone. 3. The results observed by light microscopy showed as follows: At 1st month after surgery, Sim group: No inflammatory reaction was present at bone-implant interface. The combined bone lamella was thinner and little, and also poor in continuation. A little crestalbone appeared at bone-implant interface and much fibrous connective tissue grew into hollow screw; Bio group: Bio-oss at peri-implant bony defects were absorbed. There were much fibrous connective tissue at bone-implant interface than that in Sim group, which grew into hollow screw. Defects was substituted by woven bone around the underneath implants. A little crest bone appeared at bone-implant interface. At 2nd months after surgery, Sim group: Beside the implant neck was covered with soft tissue, the most rest of implants were directly contacted with new bone. New bone at bone-implant interface formed actively, and grew into hollow screw. The bone density increased. In some areas, osseointegrtion between crest bone and implant could be seen; Bio group: The fibrous connective tissue at bone-implant interface were diminished than that at 1st month. A little soft tissue around implant could be seen. The bone defects were gradually covered by new bone. Woven bone were gradually substituted by crest bone around the underneath implant, which were contacted with implant. At 3rd months after surgery, there were no difference in Sim group and Bio group: Beside the implant neck was covered with a little soft tissue, new bone grew into hollow screw. There were no fibrous tissue between bone and implant. New bone formed much, and bone marrow were a little. New bones were futher mature. Bone-implant interface was firmly osseoingrated. 4. The results of bone histomorphometry were as follow: At 1st month after surgery, contact length fraction (CLF%), bone ingrowth fraction...