Although it is generally accepted that adverse forces can impair osseointegration, the mechanism of this complication is unknown. In this study, static and dynamic loads were applied on 10 mm long implants (Brånemark System, Nobel Biocare, Sweden) installed bicortically in rabbit tibiae to investigate the bone response. Each of 10 adult New Zealand black rabbits had one statically loaded implant (with a transverse force of 29.4 N applied on a distance of 1.5 mm from the top of the implant, resulting in a bending moment of 4.4 Ncm), one dynamically loaded implant (with a transverse force of 14.7 N applied on a distance of 50 mm from the top of the implant, resulting in a bending moment of 73.5 Ncm, 2.520 cycles in total, applied with a frequency of 1 Hz), and one unloaded control implant. The loading was performed during 14 days. A numerical model was used as a guideline for the applied dynamic load. Histomorphometrical quantifications of the bone to metal contact area and bone density lateral to the implant were performed on undecalcified and toluidine blue stained sections. The histological picture was similar for statically loaded and control implants. Dense cortical lamellar bone was present around the marginal and apical part of the latter implants with no signs of bone loss. Crater-shaped bone defects and Howship's lacunae were explicit signs of bone resorption in the marginal bone area around the dynamically loaded implants. Despite those bone defects, bone islands were present in contact with the implant surface in this marginal area. This resulted in no significantly lower bone-to-implant contact around the dynamically loaded implants in comparison with the statically loaded and the control implants. However, when comparing the amount of bone in the immediate surroundings of the marginal part of the implants, significantly (P < 0.007) less bone volume (density) was present around the dynamically loaded in comparison with the statically loaded and the control implants. This study shows that excessive dynamic loads cause crater-like bone defects lateral to osseointegrated implants.

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The implant-abutment connection design did not significantly influence the biomechanical environment of immediately placed implants. Avoiding implant overloading and ensuring a sufficient initial intraosseous stability are the most relevant parameters for the promotion of a safe biomechanical environment in this protocol.

Since loading is increasingly believed to be a determining factor in the treatment outcome with oral implants, there is a need to expand the knowledge related to the biomechanics of oral implants. The aim of this study is to gain insight in the distribution and magnitude of occlusal forces on oral implants carrying fixed prostheses. This is done by in vivo quantification and qualification of these forces, which implies that not only the magnitude of the load but also its type (axial force or bending moment) will be registered. A total of 13 patients with an implant supported fixed full prosthesis were selected. Occlusal forces on the supporting implants were quantified and qualified during controlled load application of 50 N on several positions along the occlusal surface of the prostheses and during maximal biting in maximal occlusion by use of strain gauged abutments. The test was conducted when the prostheses were supported by all (5 or 6) implants and was repeated when the prostheses were supported by 4 and by 3 implants only. Despite considerable inter-individual variation, clear differences in implant loading between these test conditions were seen. Loading of the extension parts of the prostheses caused a hinging effect which induced considerable compressive forces on the implants closest to the place of load application and lower compressive or tensile forces on other implants. On average, higher forces were observed with a decreasing number of supporting implants. Bending moments were highest when 3 implants only were used.

In knees with chronic medial collateral ligament insufficiency, isometric repair of the superficial medial collateral ligament can be attempted. A medial patellofemoral ligament reconstruction with a double fixation on the medial patellar border is supported. The cranial bundle should be tightened at full extension and the caudal bundle at 30 degrees of knee flexion.

Finite element models were created to study the stress and strain distribution around a solitary Brånemark implant. The influence of a number of clinically relevant parameters was examined: bone-implant interface (fixed bond versus frictionless free contact), bone elastic properties, unicortical versus bicortical implant fixation and the presence of a lamina dura. Bone loading patterns in the vicinity of the implant seem to be very sensitive to these parameters. Hence they should be integrated correctly in numerical models of in vivo behaviour of oral implants. This necessitates the creation of patient-dependent finite element models.

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