Written by Robert J. Harvey, DDS Monday, 30 November 2009 19:00
Figure 1. A severely worn dentition where the vertical is treatment planed to be opened.
|Figure 2. The vertical dimension of occlusion was determined to be opened 2 mm. A leaf gauge is used to open bite 2 mm and a bite is made at the new vertical for the lab to fabricate a preoperative wax-up.|
|Figure 3. The lined and adjusted splint remains seated and the lower jaw is guided into the desired bite position.||Figure 4. The filled splint with bite. Note the blue contact marks left by the articulating paper where the seated splint was adjusted. It took literally 20 seconds to adjust the splint material to provide for a stable bite.|
|Figure 5. The finished crowns at their new vertical, seated. It took between 5 and 10 minutes to adjust the bite into this position.|
What if the VDO needs to be open by 2 mm or more due to excessive wear or breakdown of remaining teeth? This becomes a challenge to correctly and accurately determine the vertical and bite. To overcome this, preoperative impressions should be taken and study models fabricated. A bite registration is taken utilizing a leaf gauge in the anterior representing approximately the new vertical to be established (Figure 2). The models are mounted with this bite and a wax-up of the teeth to be prepared is then done in the dental laboratory on the study models at the new VDO. A sheet of 0.020 temporary splint material (National Keystone Products) is sucked down over a stone refractory model of the wax-up.
After preparation of teeth, the splint will be used to aid in determining the new bite and VDO. The splint is filled with a very firm, fast-set bite material (such as Capture [Glidewell Direct]). It is then seated completely over the prepared teeth (Note: To avoid confusion considering that hard bite material is used to “line” the splint and take the bite, the term “liner” will represent the bite material inside the splint). The patient is instructed to close gently against the splint. The hard liner material is allowed to set completely. The splint with the hard liner material is left in place on the teeth and, after the liner material is completely set, the lower jaw is guided into a centric relation bite against the splint. If there is a slide or uneven bite, adjust the splint and, if necessary, the underlining liner material until the bite is stable.
For tempromandibular disease sensitive patients, where the exact vertical was determined by splint therapy or other neuromuscular means, the splint is adjusted until the desired VDO is reached. This may result where the 0.020 splint material is adjusted away until the lower teeth strike against the underlying hard liner material. In any case, it is best if the splint material remains around the liner, giving the liner material more rigidity. Once stabilized, a bite can be made of the lower teeth against the stabilized splint at the new VDO desired (Figure 3). The dental laboratory technician is instructed to trim away any soft-tissue interference of the liner material inside the splint. This is done so that the liner material is stabilized only on hard tissue (the teeth), and the case may be started at the correctly established VDO and bite (Figures 4 and 5).
The technique, as described above, takes about 3 minutes, is a great stress reliever for the dentist, and the lab tech loves it. It can be utilized wherever there is no occlusal guidance to determine the vertical dimension of occlusion and bite (ie, roundhouse bridge, or lack of posterior support). In most cases this ensures that there will be minimal adjustment of the final restorations while establishing good anterior stops.
Disclosure: Dr. Harvey reports no conflicts of interest.
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