| Dental implants have won people applause with their characteristic advantages, but there still are many things to do.FEA is a convenient and practical method to investigate biomechanics of dental implants. The dependability and authenticity of results depend on the veracity of the FEA model. Three-dimensional (3D) finite element models of the natural mandible bone with cylindrical implants was constructed by a 3D software Pro/Engineering2001 and a finite element analysis (FEA) software ANSYS8.0, based on computed tomography (CT) scan data of a woman. Through comparing the Von Mises stresses distribution of real model to symmetrical model, a conclusion could be made that the two models were significantly different from each other in the stress distributions and real model more effectively showed the biomechanical characterization of dental implants.To obtain biomechanical matching, it is very important to choose anappropriate shape of dental implant according to the bone density. Based on the real model, the Von Mises stresses inside different bone around implants were calculated to investigate the influence of different shapes of implants. The results showed that the neck could cause high stress concentration and it was the weak part of the implant. Oblique loads could cause higher stress concentration in bone than vertical load and should be reduced. For the same load and bone density conditions, cylindrical implant with lowest peak stress is most favorable to cutting down the cervical bone loss; for screw implant, advantages of thread broaden implant utilize. On the other hand, higher local stress taken place at the protrude apex of thread and lower local stress at the concaved apex of thread are dangerous for longer-term utility of implant; the stepped implant is favorable to promote bone growth in lower region around fixture if the higher local stress there within an appropriate range. For the same implant the mandible bone with high density is beneficial to stress distribution. According to the results of FEA, the dense of the mandible bone and shape of implant were very important to the success of implantation. The optimized designed implant should be cylinder. But, in fact, it is necessary to consider all kinds of factors when choosing an implant in clinic.Many studies documented that the method of implantation was of decisive importance for the mucosal attachment that formed. 3 beagle dogs were included in this study. Three non-submerged implants and three submerged implants were installed in each mandibular quadrant after extracting teeth. The animals were sacrificed and perfused with a fixative after 20, 40 and 60 days, respectively. The mandibles were removed and each implant region was dissected and embedded in PMMA. Sections were stained in toluidine blue and basic fuchsin and subjected to histological examination. The findings from the analysis demonstrated that the method of implantation did not influence the quality of the attachment that occurred between the periimplant mucosa and the implant. Everyone case allowed the formation of a mucosal attachment that includes one epithelial and one connective tissue portion. Osseointegration can be obtained in all implant-bone interfaces.It used to be thought that the smooth abutment portion of the implant was necessary for successful biological sealing. With the same animal experiments, three types of transmucosal segment were investigated: "HA coating segment", and two "Collage-HA coating segment". From the clinical index and Light micrographs, a conclusion can be made that the rough surface in the transmucosal portion of the implant still achieves biological sealing. On the other hand, the common boundary between new bone and connection tissue for "collage-HA coating segment" is lower than that of two others. It was suggested that HA can form soft tissue attachment to implants though the surface of HA coating is rough. Another, collage will promote bone up-growth and it is possible to form "bone-fiber-bone" between implant and soft tissue.
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