Three Shell Provisional Techniques and a Relining Case Study

Would you like to make your shell provisionals (also known as temporaries) faster and easier? Would you like to achieve the durability and finish of a lab-processed provisional in one appointment? There are three basic methods for shell provisional techniques, each with its advantages and disadvantages. The following techniques improve your outcomes in terms of ease, efficiency, and quality of the final product.

Chairside Fabricated Provisionals

First, we have chairside fabricated provisionals using an impression or index of the pre-operative condition or wax-up using bis-acryl or acrylic. The benefit here is a low entry cost, but the time it takes can vary, and it is not as durable as a milled or lab-processed provisional. The quality of the final product will depend on the material used and the user's skill, but it does turn out to be a nice product once you get good at this method.

The second method is chairside fabricated provisionals using in-office milling or printing. This method is typically more durable and can be more esthetic than bis-acryl or acrylic, depending on the materials used. It does have some disadvantages:

• The cost of equipment and materials can be high, and it can take a long time to mill multi-unit provisionals.
• The esthetics can suffer depending on the materials you use.
• The resins used for printing are relatively new, so their “real world” record is still being established.
• Printing can take a long time, depending on the materials and equipment used.

Relining of the Provisional Shell

The final provisional technique, and the focus of this article's case study, is relining of a provisional shell that is made before the patient's restorative appointment. This method does require planning to have the shell made, and it can sometimes be challenging to orient the shell precisely when relining it. Still, the increased durability over bis-acryl and acrylic is significant, the esthetics are excellent, and it can be very efficient and precise.

Summary of the Shell Provisional Techniques

As someone who has used all the above methods other than printing, I will say there are times I would pick one over the others based on the demands of a particular case. I am growing to like relining of shell even more, as I have recently found a way to make positioning the provisional shell much easier and more precise. To my way of thinking, we ought to be planning all our cases (except emergency cases) ahead of time anyway, eliminating the most significant disadvantage of using multi-unit shell provisionals. The key is having your lab create structures that index to unaltered areas in the mouth. In the case of the maxilla, this can be something like a palatal “strap” and on the lower “rests” that sit on the teeth.

Provisional Shell Case Study

The case I am sharing was done digitally, which was particularly useful because the patient had an existing fixed partial denture replacing tooth #8 that was fractured at the 7/8 connector, so taking an intraoral scan posed much less risk of dislodging the bridge than a traditional impression would. Once the scan was taken, it was uploaded, along with the patient's photos, to the laboratory to be digitally designed. Once designed, but before fabrication, my lab and I reviewed the design using Team Viewer to make sure it was what we wanted. The photos below show the technique step-by-step.

Once approved, everything was fabricated and sent back.

This model is not representative of what the preparation will have to be, and as you can see, #8 was not prepared for a pontic as it ideally would have been. I contacted the lab to have them correct this and send me a corrected provisional shell.

The next step is to prepare the teeth to allow the shell to seat fully. Once done, you reline the shell and finish the margins. In this case, I used a bonding agent and my typical composite to reline the shell.

The Final Outcome

There are, of course, other restorative provisional techniques, as I outlined earlier. I have found this method to be one of the most accurate — if not the most accurate — and straightforward and easy to do.

John R. Carson, D.D.S., is a member of Spear Visiting Faculty and a contributor to Spear Digest.