Many dentists abandon some of the concepts taught in dental school because they seem "academic." Even worse, the steps or techniques were seen as just another hoop to jump through on their way to graduation. Diagnostic casts or study models often fall into this category.

I'm still a firm believer in having a diagnostic cast before any tooth is prepared for an occlusal coverage restoration. Even if you don't mount the model on an articulator or quickly mount it in maximum intercuspation, there are many benefits that will make your work easier and more predictable.

Whether or not the tooth is broken, like tooth #4 and #14 in the above image, there is hopefully a good reason that you are doing the restoration. Most of the time, it's not because you want to replicate the tooth.

If it's broken you are probably interested in avoiding the same fate for your new restoration. If it's cracked, has thermal sensitivity, pain upon biting, or has significant wear, you might be interested in making some changes to improve the prognosis of the tooth that will live below your restoration. You may also need to change the material you'll use to cover it as well. It's always nice to visualize the end before you begin.

By spending just a few minutes re-contouring and/or waxing the changes that might prevent the new restoration from suffering the same fate as the tooth that you are about to prepare, you have created a template for your provisional restoration.

Now you have an opportunity to fabricate a stent for the provisional restoration and the ability to "test drive" the plastic version of the proposed restoration.

This allows you to test your hypothesis of what you hoped to achieve. If the reason you were preparing the tooth was excessive wear, a broken or fractured tooth, or traumatic occlusion, you can make sure the provisional doesn't crack or come loose. If it was sensitivity, you can see if it goes away.

Certainly there is rationale to support the benefit of diagnostic casts mounted on a semi-adjustable articulator with an accurate FSCP bite record. However, a quick alginate impression and model of the arch that will contain the new home of your occlusal coverage restoration can go a long way to bring a level of predictability and ease of treatment that you won't regret.