Managing Failures Due to Pathway Wear: Part II

This is a continuation of the discussion about the patient from Part I that was referred to the office in need of new restorations. As a reminder, at the time her veneers had only been in place for three months, during that time she had fractured five out of the six restorations.

I used her original models to fabricate a custom incisal guide table to create an analog of her movement pattern. As I moved the initial model into protrusion, the pin of the articulator rode up the guide table until it reached end-to-end position. When I replaced the model with the ceramic veneers on the articulator and went through the same movements, the pin remained in contact with the guide table in protrusion when the lower anteriors were contacting the natural tooth structure on the palatal of the upper anteriors, but as soon as the lower incisal edges started to run up on the ceramic, the pin lifted itself off the guide table. This difference is what was fracturing the restorations.

To determine if the VDO should be increased of the lower incisal edges moved apically, we need to evaluate the lower occlusal plane. Since her lower occlusal plane has a step from the anteriors to the posterior, it was decided that her lower incisal edge position needed to be altered either by ortho intrusion or by shortening the edges with a bur. Both options were discussed with the patient, who chose to forgo orthodontic treatment.

The first step in treating her was to esthetically wax the maxillary incisors (incisal edges and facial surfaces) leaving the pathway un-waxed. To determine how much to shorten the lower incisors, bring the models into the end-to-end position and shorten the lower anteriors until the pin regains contact with the guide table. In this patient, the lower incisors were shortened ~1.5mm. Once completed, the centric contact was waxed back and the guide table was used to determine the pathway.

After finishing the wax-up, I took the information back to the mouth and created full coverage restorations on her six anterior teeth and placed the provisionals. I then shortened the lower anteriors to match what was done on the diagnostic models.

After four months of trial therapy, the only thing that changed in the temporaries was the color had darkened slightly – there were no fractures, the provisional never became loose or uncemented. I proceeded in taking my final impressions and made a new guide table off of the provisional model for the definitive restorations which were porcelain jacket crowns made out of feldspathic ceramic. The restorations have now been in the mouth 12 years with no problems to report.