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implants2_2010 Platform switching This design feature can be created in an im- plant body or achieved by the clinician using a compatible abutment of a narrower diameter than the implant platform. It can be acquired even with the healing abutment in case of non- submerged approach. The purpose of platform switching is to create a horizontal component for the total linear distance between micro-gap and bone crest required for biologic width50 and eventuallytoshiftthestressconcentrationaway from the cervical bone-implant interface.51 Generally, the horizontal component created by platform switching is around 0.5 mm (Fig. 6), sufficient to result in significantly less radiolog- ical detectable crestal bone loss in humans.51, 52 Not only does this concept reduce the risk of peri-implantitis in the future but also has the benefit in the aesthetic zone of providing better soft tissue support.53 Implant-tooth or inter-implant distance For single tooth dental implants, a minimum horizontal distance of 1.5 mm must be left be- tween the implant and the two approximating toothrootsurfacesinordertoavoidcrestalbone loss after biologic width accommodation. When two implants are placed side by side, the crestal bone loss that occurs between them hasamorecomplicatedaetiology.Firstandfore- most, inter-implant crestal bone loss will be af- fected by the horizontal distance between the two implants which should be minimum 3 mm (Fig. 7). It will also be influenced by the level of micro-gap, biologic width, and whether plat- formswitchingwasusedornot.Acleartendency for increased inter-implant vertical bone loss occursasthedistancebetweentwoimplantsde- creases below 3 mm.54, 55 Histological data from animal experiments using 2—piece, moderately rough surface, sub- merged implants, showed that vertical inter- implant bone loss decreased from 1.98 mm for a 2 mm inter-implant distance to 0.23 mm for 5 mm inter-implant distance.56 _Conclusion Significant differences in marginal bone loss have been identified between implants with platform switching and implants without plat- form switching only in the first year after load- ing. It may be concluded that the platform switching concept represents a bone preserving technique. Preservation of crestal bone around dental implants cannot be attributed to a single param- eter. That is the result of a number of important factors, especially in the challenging aesthetic zone. It is important to understand the mechanism that permits the implant-abutment connection to maintain a seal against the bacterial ingress before and after loading due to absence of mi- cromovements. An appropriate understanding of the impor- tance of biologic width and the use of platform switching concept in the routine treatment is of real support in maintaining a more stable mar- ginal bone level around implants. This stable marginal bone as a support of the soft tissue is determinant for the long-term aes- thetic stability. Furtherneutralclinicalstudiesarerequiredto demonstrate the importance of micro-gap, bio- logic width and platform-switching in crestal bone preservation around dental implants. For the support I thank: Dr. Mazen Tamimi, Private Practice, Amman, Jordan, Dr. Rainer Valentin, Private practice, Cologne, Germany, Dr. R. & M. Vollmer, Private practices, Wissen, Germany Editorial note: The literature list can be re- quested from the author. Dr Virgil Koszegi Stoianov Msc Office:Str.Paciurea No.5 300036Timisoara,Romania Tel.:+40 356433733 Mobile:+40 723573443 E-mail:virgil.koszegi@medicis.ro _contact implants