A routine procedure in my office is the restoration of a single posterior tooth with a crown or onlay The tooth is being restored for structural or biologic reasons, and we are accepting the existing occlusion with only minor alterations to the existing tooth form. At the completion of the preparation we need to fabricate a provisional that will seal the prep and hold tooth position occlusally as well as interproximally.
One of the most efficient and effective ways to create a matrix for the provisional is with a triple tray and bite registration silicone. Silicone bite registration material is highly accurate and captures all of the existing tooth anatomy and occlusal form. It is also extremely rigid and undergoes very little distortion so the provisional requires only minor adjustments with a bur. The two complications that can occur with this technique are that the patient does not bite down during the impression into MIP, and that the teeth may be to wet.
If the patient does not bite down into MIP, you will not capture the occlusal contacts and the provisional will require adjustment after the material is set. I have the patient practice, by placing the triple tray in the mouth without any silicone in it and ask the patient to bite on their back teeth. I verify that they have closed down into MIP, and that they did it cleanly without sliding into it, which would distort the material.
I use regular set silicone bite material for this technique to allow me enough working time to load the tray and place it. I only load the side of the triple tray that will be against the arch we are preparing, leaving the other side empty. Silicone bite material will slide off teeth that are wet with saliva, in this technique this will result in pulls in the material, and excess provisional material that has to be trimmed and contoured. As soon as I load the triple tray with bite silicone, I use an air water syringe and very carefully dry all of the teeth prior to placing the triple tray in the mouth. I place the try against the teeth, ask the patient to wait, and allow the 45-60 seconds for the material to come to a full set.
Silicone bite material is rigid enough to trim with a bur, so this technique will also work if you have a small portion of the tooth missing, as you can hollow out the impression with a bur prior to loading it with provisional material. I find this technique more accurate then using silicone putty, heavy body tray material or the plastic button formers. Let me know what you think.
[…] on a bisacryl provisional that gunks up and ruins burs. This same smear layer remains inside the provisional matrix, and can result in reduced accuracy if they are reused. It is also the layer that can bond your […]