Bite Registration Materials

While old standbys such as plaster and wax can still be used, vinyl polysiloxane-based materials dominate this category, although one bis-acryl composite has invaded this territory. These materials need to set quickly, be reasonably stiff, and trim cleanly.

TESTS

Wettability

When syringed onto occlusals of teeth, does the material stay put or can patients displace it with their tongues? Most of our CHOICES were not displaced, except for LuxaBite, probably because of its slower set time.

Flexibility

If it flows into an undercut, can it be removed without fracturing? Yes, for most of our CHOICES and, occasionally, some of the other materials. LuxaBite, with its very rigid set, cannot be removed from an undercut, period.

Brittleness

When trimming the excess, can it be done without breaking? Yes, for most of our CHOICES if you use a sharp scalpel. Occasionally, one will fracture, depending on how thick it is. LuxaBite requires a rotary instrument for trimming due to its hardness and brittle nature.

Consistency and Handling

All products scored 5 (least flow) in our flow test. This does not necessarily mean they have identical viscosities, just that none of them could be considered runny.

Adequate Working Time for Full Arch

On a test patient, we took full arch and quadrant bite registrations. For the full arch, it took approximately 15 seconds to dispense the material (which is less time than the working time of any product), while quadrants only required no more than 10 seconds. If the two were visually similar, with the same penetrations due to occlusal contacts, we concluded the material had adequate working time to register a full arch. However, if the quadrant showed more penetrations than the full arch, we concluded that the material was already starting to set and it would not be prudent to use it for full arch registrations. If this was the case and you needed a bilateral bite, you should register one side at a time. With the fast set materials, this would only take another minute or so, which is not much of an inconvenience.

Mouth Removal Time

After dispensing the material intraorally for a quadrant (about 10 seconds), we checked the material in the mouth with an instrument after 15 seconds (from the time the patient occluded into the material) and then every 10 seconds. When the material felt set, we removed the bite. If it still felt rubbery, we allowed it to set an additional 10 seconds and then checked it again.

We then repeated this test by dispensing the materials between glass slides using the temperature/humidity chamber as an intraoral simulator. The time for dispensing and placing it into the temperature/humidity chamber was about 10 seconds (similar to intraoral delivery). The materials were removed from the temperature/humidity chamber and the resulting disks were removed from between the glass slides and tested for relative hardness using a digital durometer reading in Shore A units. The higher the reading, the harder the material.

We used as test periods the time we found the material felt set in the mouth as well as at the recommended time. These readings were also taken after 24 hours on the benchtop (to simulate the hardness when the lab would receive the bite). While we did not correlate the results with clinical accuracy, it is logical to assume that a material, which is more completely polymerized, should be less likely to distort and, therefore, waiting an additional few seconds to assure this set may be prudent. In other words, we have chosen as the safest mouth removal time that which comes closest to the 24 hour hardness.

Hardness

The harder a material is, the less chance there will be an error mounting the models. This is due to the fact that, with hard materials, the model must seat completely into the bite. With flexible materials, you can force the model into the bite, but it is unlikely you will have an accurate mounting. Therefore, hard materials should result in less bite adjustments when seating a definitive restoration. However, harder materials also tend to be more brittle. This means you need to be more careful when trimming the bite with a scalpel.

Product Selection

Many of the products in this group are quite similar, with only slight differences in set times and viscosity. Granted, some are definitely harder and some are more flexible than others. Or you may want a product that sets in the least amount of time. Nevertheless, many of the products in this group could be used interchangeably.

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