Positioning Maxillary Central Incisal Edges: Finalizing Incisal Edge Position

In the first sections of this series I discussed the role of positioning the incisal edges of maxillary central incisors using visual cues as well as phonetics. In this article I discuss a critical step prior to any lab fabricated anterior restorations: finalizing the incisal edge position. The last thing I want to be doing is deciding after restorations have been seated that I need to alter them. If lengthening is necessary, it is an almost certain redo if they are porcelain; however, if significant shortening is necessary it is possible to destroy the esthetics of the restoration as well as risk creating micro-fractures within the ceramic.

There are several tools that can aid in getting close to the final incisal edge position, such as the use of a direct composite mock-up. I believe the ideal refinement can only occur after the patient has experienced the new tooth position after living with it at least one to two weeks on a 24-hour basis. This is especially true whenever we are contemplating significant changes in incisal edge position, two or more millimeters, which is not at all uncommon in wear cases.

If the desired change in incisal edge position is additive, in the incisal or facial direction, and the teeth don't have existing ceramic restorations, direct composite mock-ups can work very well. In these instances, just etch and bond them so they stay during the trial period. The same is true for using composite mock-ups made from a diagnostic wax-up rather than directly, etch and bond prior to creating the mock-up. In many cases there are old ceramic restorations to deal with, or the desire is to shorten the incisal edge position or move it more to the lingual. In these cases prepping and placing a provisional restoration is generally the most effective way to establish the ideal position.

The patient in figure 1 has crowns on his maxillary incisors and multiple posterior teeth are crowned as well. His desire is to show more maxillary anterior teeth because he notices his posteriors seem longer (reverse smile line). He also thinks he shows too much of the mandibular anterior teeth. My assessment is that the incisal edge position may need to be .5 to 1mm longer at most, but that won't correct his reverse smile line. I believe the real problem is the maxillary posteriors are too long. Figure 2 shows his tooth display at rest, which at age 63 isn't too far from what you would expect, confirming that the existing position probably isn't bad.

Figure 3 shows the drawing I sent to the laboratory to use in performing the diagnostic wax-up. It demonstrates lengthening the centrals 1mm and shortening the posteriors, which will also be restored. I am convinced this is the longest I would possibly consider making the incisal edges, I'll have the wax-up performed at this length; the provisional can easily be shortened if they are too long. Transferring from the drawing to a model is easy since all the lab has to do is measure the width of a central on the photo and the same central on the model. Doing this provides a magnification ratio that can be used to measure the desired changes.

Figure 4 shows the full smile after the maxillary provisional was placed. The centrals are approximately 1mm longer than his old crowns. The posteriors were also shortened to correct the smile line. At this point he now shows about 1.5mm of the centrals at rest. At the appointment the provisional restorations were placed, I made a final impression, bite records and an impression of these provisional restorations. Ideally I would then wait one to two weeks and call the patient. If the patient is happy with everything I use the model of the current provisional restorations as the go-by for the lab for the correct incisal edge position. If they were unhappy I would bring them in, make changes and then a new alginate to create the correct go-by model for the lab.

This patient was scheduled to return to also prepare the lower anterior teeth so I got to evaluate the maxillary provisional myself. It became apparent immediately when I saw him that the maxillary provisional was too long and he agreed. It wasn't a functional or phonetic issue, just an esthetic one. The trick now is to know how much to shorten. I don't want to simply start shortening and discover I have gone too far so I visually shorten by blacking out the incisal edges with a Sharpie marker.

Figure 5 show the black marker painted on the incisal edges of the centrals, laterals and left canine. The difference in his smile was significant even though it is probably only .7mm of a difference in tooth length. It is easy to now just remove the black marker knowing it is the correct amount.

Following shortening the provisional restorations, a new alginate impression is made and the new go-by model sent to the lab to use in the creation of the final restorations. Figure 6 shows the final restorations. They are only a few tenths of a millimeter longer then his old crowns but look much different because the maxillary posteriors were significantly shortened, as were the mandibular anterior teeth.