Undersized Teeth and Orthodontics

In this article I'll discuss a simple yet effective way to make your cases that involve teeth of reduced size and orthodontics much more predictable. Usually the reasons for cases like these are pathologic wear or developmental issues such as peg laterals.

One way that really hurts the predictability of these cases is to ask the orthodontist on your team to suspend the teeth of decreased size. They are floating in space perfectly positioned in the right position for the restoring dentist to then restore the teeth back to the proper size.

At first, this might seem reasonable and maybe even simple; however, what seems simple and reasonable at first is anything but.

Think about it, how reasonable is it to expect to accurately visualize the undersized teeth at full contour, place them in the perfect position and then hold them there in space accurately? If you and your team have tried this you know you made your life a whole lot more complicated.

The key to both simplifying and increasing the predictability of these cases is to make the teeth that are too small the correct size with bonding or provisional crowns prior to the end of orthodontics. While in some cases this can be done before the orthodontics begin, in many cases the bonding or provisional crowns have to be done during orthodontics.

Unless you build the teeth up directly in the mouth, impressions are needed so that a wax-up can be done. In order to get an accurate impression at least some of the orthodontic hardware will have to come off to prevent excessive tearing of the impression material. If the orthodontic hardware will be left off for any significant amount of time it's important to realize and plan for some sort of retention to keep the teeth from shifting while the case is being waxed up. When it comes to the wax-up it's critical that whoever is waxing it knows that the purpose of the wax-up is to only make the teeth the proper dimensions and not align them. It is important to realize that done properly the previously undersized teeth will likely appear more out of alignment after the wax-up.

The next challenge is to transfer the wax-up to the mouth. In my experience the easiest way to do this is with either a putty or Copyplast matrix of the wax-up. More details on transferring a wax-up to the mouth are covered in a previous article, “Adding Incisal Length With Composite”. Once the teeth are built-up to the proper size the orthodontic hardware can then be put back on and the orthodontics finished accurately without any guesswork.

Once the orthodontics is completed you can then convert the bonding or provisional crowns to porcelain as desired or needed. Another benefit to the transitional phase is it allows you to phase the final restorations as you and the patient desire while still giving them an esthetic result immediately upon the completion of the orthodontics.

John R. Carson, DDS, PC, Spear Visiting Faculty. [ www.johnrcarsondds.com ]