Incisal edge position: and how do the incisal edges of the maxillary incisors fit into the framework of our smiles?
Generally, youthful smiles show more of the maxillary teeth on the upper, and as we age and gravity takes over, we may show more of both the upper and lower teeth or even just the lower teeth.
Later in life, patients with underbites or Class III occlusions tend to show less of their upper teeth as well.
We tend to accept one to two millimetres of pink gingival display above our maxillary incisors as acceptable. But excessive gingival display sometimes can be unaesthetic..
If those maxillary incisors are too low in our smile and we see too much of the pink gingiva we can consider orthodontics or surgery to change the amount of gum showing.
With orthodontics, we tend to try to move the central incisors and the canines on a level horizontal plane, and the laterals may be one millimetre shorter than the canines and the central incisors.
Designing and shaping the contours of the incisal edges of the teeth
Occasionally, if the canines are pointed, we may make them maybe a half millimeter longer than the central incisors, or if the canines are rounded on the incisal edge, we might make the central incisors slightly extruded compared to the canines.
Making the central incisors longer and the canines a little bit shorter helps to follow the curvature of that lower lip line.
We tend to like—when we look from the side view of the face—the incisal edge of the maxillary incisors to touch that wet / dry border of the lip when viewed from the lateral.
We want that maxillary incisor edge position to touch right there on the border of where the lower lip is wet and dry when we say words like 55..
The shapes of the incisal edges
If we’re doing any kind of incisal recontouring, maybe because the incisal edge is worn or chipped, or if we’re designing crowns and veneers and we want to really create the architecture of that incisal ledge…
We need to think a little bit about how the mesial and distal corners of each of the central and lateral incisors can be either a squared corner, slightly rounded or more curved.
Typically, we see the incisal edges be more squared toward the mesial, incisal edge of the central incisor. And as we move towards the distal, we see more curvature towards the distal incisal edge of the lateral incisor.
Setting up a prosthetic design
If we think about those four corners of the mesial, incisal, distal incisal of the central and mesial, incisal, distal incisal of the lateral, we can think about setting that up as square, square, square, square edges.
Canines can be pointed or rounded, but I think it’s most beneficial to leave a curve on the distal incisal edge of the lateral incisors so that the lower canine in a class one occlusion, that lower canine is going to fit between the maxillary canine and the maxillary lateral incisor.
It needs that space for canine guidance and a class one occlusion. When doing a bridge from the canine to the central incisor to replace a lateral incisor, it’s important on that bridge in a class one occlusion to have a curve on the distal incisal edge to have adequate space.
The lateral incisor on that maxillary bridge needs tohave space for that lower canine and lateral movements in that class one occlusion.
Otherwise, you may see that that pointed edge of that distal incisal edge of that lateral incisor become chipped and no one wants to see a porcelain fracture on their bridge.