Platform switching is one of them.

Materials & Methods
A 3D FE model of a mandibular section of bone with a missing premolar and an implant to receive a crown structure was used in this study. Two implant models were created.
1. Standard implant abutment combination without horizontal mismatch
2. Implant With Platform Switching
Bone block – 24.2 mm in height, 16.3 mm in width and length
Co- Cr was used as a crown framework material of thickness 0.8 mm.
Feldspathic porcelain on occlusal surface of thickness 2mm.

All materials were presumed to be linear elastic, homogenous and isotropic (Table/Fig 5).

The finite element on the X-axis of each design was assumed to be fixed, which defined the boundary condition.

A static occlusal force of 300 N was from the buccal cusp and the distal fossa in the centric occlusion. Sevimay et al 2005.

The implant, superstructure and supporting bone were simulated using FE software (Pro/ Engineer 2000i; Parametric Tech. Corp, Needham, Mass)

The analysis was performed using software ANSYS 10.0. Stress levels were calculated using von Misses stress values. Maximum stress values were noted at the cortical bone for both implants. However, for a standard implant without a platform switch, the value was 785 Mpa and for an implant with platform switching, it was 465.71 Mpa (Table/Fig 6),(Table/Fig 7).

Within the limitations of this study, it can be concluded that: Von Mises stresses reached the highest values at the neck of the implant. Platform switched models exhibited lower values of Von Mises stresses than the standard implant without platform switching. These results are in accordance with previous studies on the same concept. Schrotenboer et al investigated the effect of microthreads and platform switching on crestal bone stress levels, with finite element analysis. They showed that when the abutment diameter decreased from 5.0 to 4.5 mm and then to 4.0 mm, the microthread model showed a reduction of stress at the crestal bone level from 6.3% to 5.4% after vertical loading. Cappiello et al, in their clinical and radiographic prospective study, evaluated the bone loss around two-piece implants that were restored according to the platform-switching protocol. The data collected, showed that vertical bone loss for the test cases varied between 0.6 mm and 1.2 mm (mean: 0.95 +/- 0.32 mm), while for the control cases, bone loss was between 1.3 mm and 2.1 mm (mean: 1.67 +/- 0.37 mm). Hürzeler et al reported preliminary data from a prospective clinical study about the peri-implant bone level around implants with platform-switched abutments, stating that mean bone level change from the baseline to 1-year follow-up was -0.12 mm +/- 0.40 mm for the platform switched group and -0.29 mm +/- 0.34 mm for the control group.

Conclusion
Long term clinical studies are still awaited. However, considering the foregoing biological and biomechanical analysis, the concept of platform switching appears to limit crestal resorption and seems to preserve peri-implant bone levels. A certain amount of bone remodeling one year after final reconstruction occurs, but significant differences concerning the peri-implant bone height when compared with the non-platform-switched abutments, are still evident one year after final restoration. The reduction of the abutment of 0.45 mm on each side (5 mm implant/4.1 mm abutment) seems to be sufficient to avoid peri-implant bone loss.

It is certain that this concept of platform switching holds promise as a simple method to reduce crestal bone loss, physiological prosthetic contours and optimum aesthetics.