At the time of cohesive gel implant FDA approval a couple of years ago, Mentor only initially received approval for one shape in its range of implants. Why? Because they only tested one shape in their trial.
Allergan tested 4 of its twelve shapes and only got those four approved. But Sientra got all approved.
Why is that? Because Sientra is focused on one device and its regulatory consultants know breast implant manufacturing very well.
Allergan and Mentor/J&J farm out their breast implant-related regulatory stuff to other people in their company who do not know breast, and hence they failed. This is but one more example of the problems that occur when big businesses buy small businesses and apply economies of scale.
One shudders to think what will happen to the great pipeline of Allergan implants if Valeant Pharmaceuticals succeeds in their hostile takeover. They have expressly stated that their ONLY responsibility is shareholder value, and that they achieve it by increasing margin and not doing any R&D.