I had the pleasure of being the teaching assistant to Glenn DuPont this fall as he led the dental treatment planning course in St. Petersburg. I really appreciated his candor in sharing with us some of his "research." Like many of us, Glenn has done "research" on occasion on how not to treat a case. I had the blessing for 16 years of practicing alongside Ron Goldstein and David Garber. As you can imagine, there were incredible opportunities to do comprehensive esthetic dentistry. I learned early in my career and through much "research" of my own that esthetic dentistry cannot be successful without understanding proper function. As a matter of fact, it were these case complications that led me to my first course with The Dawson Academy.
I want to address two particular areas where our desire for ideal esthetics could result in premature failures due to our patient's function.
- The envelope of function, or more specifically restricting the envelope of function
As we learn in most cosmetic courses and from the Vig and Brundo study, it is youthful and desirable to have around 2 to 3 mm of tooth display at rest. However, lengthening the teeth without a good understanding of the patient’s functional matrix can be risky. This alteration can steepen the anterior guidance and restrict the functional envelope.
The most predictable way to lengthen anterior teeth is to do a thorough diagnostic work up with mounted models. If the patient has a significant slide from CR to their maximum intercuspal position then the molars can often be equilibrated and the premolars and anterior teeth can be lengthened to obtain good centric stops and anterior guidance.
It is often possible to lengthen the anterior teeth moderately even without additive equilibration or opening the bite when posterior interferences are removed to prevent driving the mandible forward and the length is added in harmony with the patient’s angle of guidance. These changes can be worked out predictably in the patient’s wax-up and provisional restorations.
Additionally, the envelope of function can be tricky with patients who have had bulimia or severe acid erosion. Often when bulimic patients are restored by treating anterior teeth only without regard to posterior interferences or fremitus, this can result in endodontic issues or severe mobility. These patients will more often require at least one full arch reconstruction to restore the enamel that has been lost due to the erosion.
- Violation of the neutral zone
Many patients and clinicians alike find a wide smile attractive. This along with a noble desire to preserve enamel and save time and discomfort in the dental chair has produced a wide variety of “no prep veneers.” There are undoubtedly candidates for this procedure like patients with a Bolton discrepancy or multiple diastemas and micrognathia, however, it is not ideal for many patients.
It is especially problematic in patients with a small orifice or tight obicularis oris muscles accompanied by palatally inclined maxillary incisors. This is an indication that the patient’s musculature has lingualized their own natural teeth, and will likely do the same thing to over built porcelain veneers. As the patient's muscles push the veneered incisors palatally, they may report heavy contact or “banging” their front teeth, an inability to close their back teeth, or mobility in their front teeth.
It is possible to restore these patients without the maxillary incisors being completely perpendicular to the floor and still give them a beautiful smile that will be comfortable and maintainable for years. Again this feature is best worked out in the provisional restorations with careful evaluation of phonetics and lip competence.
A good working knowledge of occlusion can really help us be truly great esthetic dentists and give our patients beautiful smiles that will operate in harmony with their joints and musculature and last for a lifetime.
Our hope is that many doctors can benefit from our years of “research” and start their functional education early to avoid extended research of their own.
Image Credit: Paul Mison