The influence of axial and non-axial occlusal loads on the bone remodelling phenomena around oral implants in an animal experiment is simulated in a finite element analysis. The axial and non-axial loading conditions were introduced by inserting a bilaterally supported fixed partial prosthesis and a cantilever fixed partial prosthesis on two IMZ implants in the mandible of beagle dogs. Earlier quantitative and qualitative histological analyses revealed a statistically significant different remodelling response between both loading conditions. Two-dimensional and three-dimensional models are built to analyse and compare von Mises equivalent stress, maximum principal stress, maximum principal strain and strain energy density distributions, first around a free-standing implant and subsequently around the implants of the two prosthesis designs under the respective resultant in vivo loads. Strong correlations between the calculated stress distributions in the surrounding bone tissue and the remodelling phenomena in the comparative animal model are observed. It is concluded that the highest bone remodelling events coincide with the regions of highest equivalent stress and that the major remodelling differences between axial and non-axial loading are largely determined by the horizontal stress component of the engendered stresses.
The aim of this study was to clinically and radiographically evaluate peri-implant bone level changes after rehabilitation of a fully edentulous maxilla by placement of six implants in either fresh extraction sites or healed edentulous ridges up till 18 months after implant placement. Twenty patients with a terminal dentition in the maxillae (11 men, 9 women) received a total of 120 OsseoSpeed® implants; 118 implants could be loaded immediately of which 59 were placed in extraction sockets and 59 were placed in healed sites. Within 24 h after surgery, all patients received a chairside-assembled, fibrereinforced temporary fixed prosthetic reconstruction in occlusion. Six months post-surgery, final screw-retained CoCr (15) or Ti (5) computer numerical control-milled and acrylic-veneered frameworks were placed directly at implant level without interposing abutments. Intraoral radiographs were taken 6 and 18 months after implant placement. Implant survival rate was 100%. Mean marginal bone level was located on average −0.35 mm below the reference point (standard deviation 0.29, range −1.20 to +0.02 mm) 18 months after loading. Whether implants were placed in healed bone sites or fresh extraction sockets did not significantly affect the bone level changes. Furthermore, the use of either CoCr or Ti at the implant level did not significantly affect marginal bone loss. Within the limits of this prospective clinical trial, results seem to indicate that immediate placement and occlusal loading of five to six implants in the edentulous maxilla can be carried out successfully. Whether or not those implants are placed in fresh extraction sockets does not seem to alter the outcome. The present data show a successful 1-year outcome of a treatment protocol involving tooth extraction immediately combined with implant placement and loading.
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