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implants2_2010 _Discussion There is an association between bone and soft tissue preservation around implants with direct influence on aesthetics. Some authors have proposed different meth- ods to maintain supporting bone: improved im- plant micro-geometry and implant surface treatment, improved implant abutment connec- tion (elimination of bacterial reservoir, absence of movements under bending forces) as well as theuseofwideimplantswithsmallersizedabut- ments (platform switching concept). An alternative in preserving marginal bone levels around implants is the platform switching concept that refers to the use of a smaller diam- eterabutmentonalargerdiameterimplantplat- form. This connection shifts the perimeter of the implant—abutment junction (IAJ) inward to- wards the central implant axis. Lazzara and Porter demonstrated that the in- ward movement of IAJ also shifts the inflamma- tory cell infiltrate inward and away from the bone implant interface, creating a horizontal bi- ologic width that will limit bone resorption around the coronal aspect of the implant. From a biomechanical perspective, stress in the bone is concentrated around the crestal re- gion because of the difference in modulus of elasticity between bone and implant, as demon- strated in photo - elastic and finite element analysis studies.14 Peak bone stresses occurring in marginal bone have been hypothesized to cause bone mi- cro-fracture and may be responsible, at least partially for peri-implant bone loss with saucer- ization patterns after prosthetic loading. The issue of whether platform switching may affect stress patterns by minimizing peak bone stresses in the marginal bone has not been demonstrated yet. The original criteria established for assessing implant success and survival6 identified mar- ginal bone levels as an important indicator for measuring the response of the peri-implant tis- sues to functional loading. More recent studies have considered the ef- fect of stresses established in bone by the direct influence of non passive prosthetic work to be a causative factor in marginal bone loss.7, 8 Another more recent explanation of marginal bone loss is the theory of establishing the bio- logic width directly related to the position of the implant-abutment microgap and its associated microbial flora.9, 10 The concept of “platform switching” in implant dentistry A literature review—Part II Author_ Dr Virgil Koszegi Stoianov, Romania