Form Follows Function: Testing the Occlusion Before You Start, Part 1

By Dr. Rhys Spoor, DDS, FAGD

Attractive teeth stay attractive over the years because the form of the dentition fits into the functional envelope of the muscles of mastication and the temporomandibular joints. This includes both functional and parafunctional movements. When you observe a wear pattern in a patient, what you are looking at is a history of the forces of attrition (Figures 1 and 2). When we want to restore a smile to youthful beauty, unless you change the functional environment that caused that wear pattern, it will be recreated. This case illustrates a very common wear pattern where the mesio-incisal of the mandibular cuspids have worn the disto-incisal of the maxillary laterals (Figures 3 and 4). These Class III mandibular cuspids will certainly be a factor in potentially chipping the disto-incisal edges or debonding newly placed maxillary lateral restorations because most of the time the new smile includes teeth that are slightly straighter, slightly longer, and usually lighter. If the vertical dimension is conservatively opened, restorations can be designed that require fairly minimal reduction of natural tooth structure. This leaves maximal strength for the supporting tooth and enamel surfaces for the most secure bonding (Figure 5).

In this case the proposed occlusal position was determined by using a combination of low-frequency TENS (trans-cutaneous neuro stimulation), electromyography, and jaw tracking. There are a variety of ways to get this preliminary position but the this technique for this case made for rapid advancement through the testing phase. A bite registration was taken and diagnostic models mounted to that occlusal position. A minimal diagnostic wax-up was done to level the occlusal plane and maximize intercuspation of the new centric occlusion. Cuspid guiding surfaces were also waxed in.

Stints were made over the diagnostic wax-ups and each was filled with B-1 Zenith Luxatemp. To reinforce the maxillary and mandibular anterior areas, a 2mm wide band of Kerr Connect fiber was bonded to the teeth before placement of the Luxatemp fixed orthotic (Figures 6 and 7). The stint (#6-#11) was placed intra-orally and the Luxatemp allowed to cure for two and a half minutes and then removed. The cured Luxatemp was finished intra-orally with diamond burs and polishing cups before being tinted and glazed (Figures 8, 9, and 10). Even though this was a temporary restoration to test function, by finishing the form to a very refined level the patient had the opportunity to begin evaluating and accepting the aesthetics (Figure 11).

The lower arch was then completed (Figure 12) in the same manner. The included teeth were #18-#21, #23-#26, and #28-#31 (Figures 13, 14, and 15). Again the goal was to get maximal intercuspation at the new occlusal position but not all of the tooth surfaces had to be included. This supported the philosophy of minimal dentistry to get to the best result.

Under the influence of TENS, the occlusion was lightly adjusted and a follow-up appointment about a week later further balanced and refined the occlusion. The great advantage of this approach was the ability to determine an acceptable and tested occlusal scheme before proceeding into the final restorative phase.

(Stay tuned for Part 2 in the next issue of Catalyst which will continue to the final restorations.)

Click here to see the original article.

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