To continue with my series of articles discussing pathway wear, I'd like to introduce a patient that was referred to the office in need of new restorations. Although the current veneers have only been in place for three months, during that time she had fractured five out of the six restorations – in fact, she fractured one of them the first night they were placed!
The key is to try and figure out "why" the restorations failed to help prevent the next set of restorations from breaking as well. If you asked this patient what her teeth looked like before the current veneers were placed, she'll tell you she had direct resin veneers in place for 16 years with no problems. Aside from the material change, the main difference between the new restorations and the old restorations is that the new restorations are longer.
The fact that the patient had multiple restorations fracture, indicates an envelope of function problem rather than a problem with adjusting the occlusion. By looking at her pre-treatment model, it was apparent that she had issues with pathway wear and end-to-end wear. The problem with lengthening her anterior teeth was that it prevented her from getting to her old end-to-end position, as there is now ceramic in the way. The result of which was the fracture of the restorations.
Patients that display pathway wear AND end-to-end wear can be some of the most destructive patients we see because we have to address both the pathway and the overbite. My goal for this patient was to provide a guidance pattern that minimized any interfering tooth contacts and matched the patient's envelope of function while decreasing the overbite. To decrease the overbite we have three options: shorten the upper incisors, shorten the lower incisors, or open the VDO. Assuming that the maxillary incisal edges were lengthened to improve the esthetics, we probably don't want to shorten them. This means we are left with either moving the lower incisal edge position apically or opening the VDO.
Typically, you would choose the treatment option that was most appropriate and using an educated "guess" determine how much you needed to open the bite or shorten the lower anteriors. Then you would try it out in the mouth and see if your educated decision was correct by evaluating the "trial therapy." In this specific patient, we had something going for us. We know that the old composite restorations that she had for the last 16 years were working for her, meaning the envelope of function worked for her. Given that the teeth were restored with veneers, the pathway isn't this issue, it was the addition of ~1.5mm length that caused her previous restorations to fail.