The groove or " Platform Switching"  in the design helps to eliminate bone loss that can occur with other two piece designs. Platform swithing has much peer review iterature to support its use within dental implant systems.

Platform Switching can be summarised:

In many two part systems the Implant abutment interface (IAI) can give rise to an area of local inflamation causing bone resorption. A biological width of 2-3mm is needed above the bone inorder to establish a soft tissue barrier.  It has been found that the bioligical width need not be a vertical dimension but can have a horizontal component, platform switching provides this horizontal distance and so preserves the crestal bone.

Platform switching is present over the entire Combi range, including the smallest 3.25 diameter implant this feature minimises crestal bone loss.