| Objective:The purpose of this study was to compare the histological impact of two different soft tissue handling methods during implantation:cutting gums implantation and none-cutting gums implantation on the micro-screw bone interface, to detect the incidence of the epithelium implantation to alveolar bone through animal experiment,3-dimensional reconstruction of the micro-screw animal models was set up to check the implants position by CT scans and image processing system.Methods:Six adult hybrid male dogs were randomly numbered1-6.48self-drilling micro-screws,9mm in length,1.6mm in diameter were used. One side of the upper and lower jaws of each dog was selected as the None-cut-gum group,24self-drilling micro-screws were implanted into the alveolar bone of the second and the fourth premolar furcations by none-cutting method. The other side of upper and lower jaws was taken as the gum-cutting group and24self-drilling micro-screws were implanted into the jaws after cutting gums. Each quadrant was implanted with2micro-screws. Both the two groups were loaded immediately with200g constant force by using NiTi-coil springs. After the implantation,3-dimensional images of the micro-screws and the upper and lower jaws were reconstructed by CT scans and image processing. HE staining method was used to observe the difference of the interface of the implant-bone and epithelium incidences with the two different soft tissue handling methods. Statistical analysis was used to compare the Bone to implant contact rates of the two groups.Results:1. Most micro-screws heeled well and kept steady in the whole period of the force application.1micro-screw fell off in the maxilla of the None-cut-gum group during the study period and1showed mobility in the mandibular,1micro-screw showed mobility in the maxilla of the Cut-gum group. The gingival and the mucous membrane around the micro-screws showed slight red and swell, Soft tissues was observed to be hyperplasia under few NITI springs.2. Histological observation:Under the microscope, both the two groups showed different grades of Bone to implant contact rates. The bone-implant interface was surrounded by mass of fibrous connective tissue and the implant was contacted directly with the bone in some areas in the None-cut-gum group. Bone hyperplasia and absorption of pits was observed in some areas in this group. There was little of fibrous connective tissue in the bone-implant interface and the implant was contacted with the bone directly in most areas in the Cut-gum group. Lamellar bone structure and dense bone structure were observed while osteoclasts and inflammatory cells were rare.3. BIC analysis:The cut-gum group(81.4±10.4%)showed more BIC than the None-cut-gum groups(60.1±24.6%),the difference was statically significant.4. Epithelium or epithelium similar tissues were not detected in either group. 5. The CT reconstruction showed that the micro-screws were implanted properly and no micro-screws was observ ed to get in touch with the root of the teeth or the nerves.Conclusions:1. The micro-screws can keep good stability and meet the demands of orthodontic force application when immediately loaded with force of200g with the two different soft tissue handling methods.2. The implantation of the micro-screws without cutting gums in some extent influence the Bone to implant contact rates, while the implantation of the micro-screws with cutting gums can obtain more Bone to implant contact rates than without cutting gums.3. The implanting of micro-screws without cutting gums simplifies the clinical operation procedure, reduces the patient’s fear. The incidence of the implant of the epithelium is extremely small without cutting gums. The none-cut-gum implant method can be used for doctors safely.4. Further study is needed to confirm the long term safety of the implanting without cutting gums.5. The CT reconstruction is a reliable means to detect the implanting conditions of micro-screws objectively and definitely. |
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