In our smile design process, we have learned from Dr. Dawson how to develop incisal embrasures. And also from Dr. Dawson and the American Academy of Cosmetic Dentistry, how to develop the apparent contact zone between teeth.
So between two centrals it should be 50%, a central and lateral, 40%, and a lateral and a canine, 30%.
There are times, though, where, depending on the restorative interfaces, say, for example, two implants, we cannot create an apparent contact zone that falls in those parameters. And if we want to keep the incisal embrasures developed, as Dr. Dawson's taught us, we need to have a long contact zone.
The problem with two implants, for example, is in order to prevent a black triangle from forming, you have to set the contact 3.5 millimeters away from the bone, which is a significant difference than, say, from an implant to a pontic, which is 5.5 millimeters, or just between two teeth, which is 5.
The key is, is that patients are more accepting of a long contact, a long connector, a long contact zone, than a black triangle. That being said, it should still be communicated to them that this will occur.
Between, let's say, two implants for two centrals, it's easier to make it look more natural because we can create two more square-like restorations. And it will look more natural to a patient. But between a central and a lateral implant, it is harder to do that.
Again, let your patients know the situation that they will have a long contact zone. And one of the ways to prevent this and make it easier to create a more aesthetic result between, say, a central and lateral, is to have, say, one implant in the central's location, and a cantilever pontic for the lateral. At that point, between an implant and a pontic, it's 5.5 millimeters away from the bone to create the pillar fill and prevent a black triangle, and that would ensure a more natural-looking contact zone.