adequate running room is necessary to allow the implant-supported crown to exhibit a tooth-shaped contour despite the smaller diameter and circular nature of implant platforms. for example, the mean mesial-distal dimension of a maxillary central incisor at the points at which it contacts the adjacent teeth is 8.6 mm, and the mean mesial-distal dimension of the same tooth at the cementoenamel junction (cej) is 6.4 mm. however, the implant diameter chosen for the maxillary central incisor is usually around 4-5 mm, but the supragingival tooth contours need to mimic those of the natural tooth is esthetic success is intended.