The Concept Of Plataform Switching

Biological Space from an Implant and Aesthetic Perspective

The Concept of “Platform-switching”

Frédéric A. CHICHE

• Consultation Associate UFR Paris VII

• President of the French Society of Aesthetic Dentistry

In the anterior sector, the lack of postoperative bone resorption around the implant collar constitutes a vital factor in stabilizing the papillae and obtaining a harmonious dental neck line in relation to the neighboring teeth.

During the first year of use, stabilization of the crestal bone at the level of the first thread of a screw-retained Brånemark type implant has always been observed and considered normal. While many biomechanical theories have been advanced without really being convincing, better knowledge of biology offers new keys to better understand this phenomenon. In fact, it has been observed that resorption around the collar begins when the implant is exposed, and as long as the latter remains submerged, the crestal bone is stabilized at the level of the collar.

Following loading, or surgical stage 2, bone stabilization beneath the collar seems to depend on several factors, such as, respecting a biological space, the location of an area of inflammatory connective tissue (ICT), and the state of the implant surface.

In 1997, Abrahamsson et al. showed that multiple screwing and unscrewing movements of the healing screw result in apical migration of the epithelial attachment around the implant collar. The authors stress that this epithelial migration results, in turn, in an apical relocation of the bone level, so that a biological space compatible with the health of the peri-implant tissues is restored. The presence of a bacterial infiltration has also been revealed at the abutment/implant interface. This infiltration results in the permanent presence of an area of inflammatory connective tissue (ICT) which continues to contribute to apicalization of the first contact point between the implant and the bone. Finally, the condition of the surface, unlike the parameters mentioned, plays a positive role with regard to the resorption phenomenon. When the implant surface is rough, the bone’s capacity to adhere to the titanium is increased when significant stresses are applied, particularly during immediate loading.

CONCEPT OF “PLATFORM-SWITCHING”

This concept consists of using prosthetic components that are undersized in relation to the diameter of the implant collar in order to limit peri-implant bone resorption. This strategy arose from observation and analysis, as early as 1991, of situations in which bone resorption didn’t occur or occurred minimally around wide 5 mm implants (3i®, Implant Innovations). The crestal bone level remained stable for the entire length of the implant, up to the collar, and this was the case regardless of the loading period. In all cases, undersized prosthetic abutments, 4 mm in diameter, had been used.

The reproducibility of the results leads us to believe that the position of the abutment/implant interface constitutes an essential element in the location and the degree of crestal resorption, and leads us, furthermore, to design the mechanisms governing the biological peri-implant space differently.

In fact, the biological space around implants was defined as the distance (2 to 3 mm) which separates the peri-implant bone from the connection between the implant and the abutment. This distance results from the presence of the ICT when the implant abutment is the same diameter as the implant, i.e. when one part is a continuation of the other.

By using a component that is narrower than the implant collar, the prosthetic connection is displaced towards the center of the implant, and this increases the

distance separating the peripheral bone from the base of the abutment. With regard to the abutment/implant interface, the ICT is located at a more coronal level, at the level of the collar, and no longer migrates apically towards the first thread of the implant. Consequently, resorption is avoided and the crestal bone is stabilized at the level of the implant collar.

CLINICAL APPLICATIONS

“Platform-switching” is particularly indicated in all cases where an optimal aesthetic result is desired. In 2000, Small and Tarnow showed that in 80% of cases, a 1 mm vestibular recession occurred during the first year of loading. This soft tissue recession, which is indicative of an underlying bone loss, represents a major risk in the anterior sector. By applying the concept of “Platform-switching”, using simple means, it is possible to obtain greater stability of the peri-implant tissues, using undersized components for the implant in question. It can easily be applied to 3i® implants. In fact, the 4, 5, and 6 mm implants carry the same external hexagon or, in case of the Certain® line, have the same internal connection. This characteristic shared by the most frequently used implants makes the system more flexible to use. “Platform-switching” can be applied simply by screwing an abutment with a 4 mm diameter onto an implant with a 5 mm diameter without using a specific component. The same procedure can be repeated by providing an implant 6 mm in diameter with an abutment 5 mm in diameter.

This procedure can take place when an implant is loaded upon placement, using the single-stage surgical protocol, in single cases of immediate placement of a temporary prosthesis in sub-occlusion, and finally, in cases of immediate loading for completely edentulous patients. During all phases of the implant treatment, it is important to respect the undersizing of the components, up until the final implant-supported prosthesis is made.

Finally, the state of the titanium surface also constitutes an important parameter in maintaining the bone at the level of the collar. Testori et al. observed in 2001 and 2002 that for rough surface implants (Osseotite®, 3i-Implant Innovations), loaded immediately and placed using trephines used for histological examinations, bone stabilization had occurred at the 3rd thread, i.e. at the interface between the machined section and the rough section of the implants. According to Davies et al., a rough surface simplifies migration of the osteogenic cells towards the surface of the implant through the fibrin network. On the basis of these observations, the Osseotite® implants with a hybrid surface, developed since 1996, are now available in the FS (Full Surface) version that is rough from top to bottom and not just after the 3rd thread, in order to promote the stability of the bone up to the collar of the implant.

CONCLUSION

In