A study of the implant to abutment connection is of paramount importance as it is the primary determinant of the strength and stability of the implant supported restoration, which in turn determines the restoration's prosthetic stability. Traditionally, the Branemark's external hexagon has been widely used but its significant complications like abutment screw loosening, rotational misfit at implant-abutment interface and microbial penetration have led to modification of the external hexagon and

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... the development of the internal implant-abutment connections. This review describes the various implantabutment connections that have evolved overtime from the traditional external hexagon.