Crown Lengthening Part II: Matrix Options

In a previous article, I discussed the option of the restorative dentist preparing into the soft tissue prior to osseous crown lengthening. By doing this, you are giving the periodontist a built in surgical guide so they know just where they need to move things.

In this article I will discuss two options that help identify how far into the soft tissue the restorative dentist needs to go when doing their preparation and provisionalization.

Utilizing the Matrix

Option one is to mark a preoperative model where you plan to move the tissue to then form a sheet of Copyplast (or something similar) over the model and then trim back to where you want the new gingival margin. Once this is done, the matrix is then placed in the mouth and the restorative dentist simply trims along the edge of the matrix with a 12 blade, thus marking and identifying where the margin need to be placed.

The next step is to prepare the teeth to the newly identified marginal position and, in the process, remove the excess gingiva.  It is important to remember that it is critical that you have excellent repeatable stops for this matrix to rest on – otherwise the matrix will give your inaccurate information.  It is for this reason that when using this method, I like to make the matrix on a preoperative model and use the matrix prior to preparing the teeth and ensures I have plenty of solid, accurate stops.

Option two, which works really well with net additive cases, is to create a Copyplast matrix – but  this time of a stone duplicate of your wax-up (I have my lab make this model typically) then fill this with bisacryl and seat it in the mouth. This will create a direct mock-up in the mouth and you can then prepare into the mock up.  It is important to note that this method is only accurate when dealing with cases in which you will be adding tooth structure in the areas you plan to use the matrix. The reasoning behind this is that any areas that require reduction would result in distortion of the matrix and the bisacryl guide.

If you desire to use this method but have areas that had net reduction in the wax-up, it is critical that you reduce these areas in the mouth prior to seating the matrix in the mouth. Just like with the first option discussed in this article, it is critical for good accuracy to ensure you have plenty of solid stops for the matrix. One downside to this technique is that since the teeth and tissue will be covered in bisacryl you will not have direct visualization of the underlying tissue as you make your cuts.

Another option for this technique is to make a silicone matrix of the wax-up itself rather than a stone model. However, even if using silicone instead of Copyplast, I prefer to use a stone model made by my lab so there is no risk of damaging the wax-up.

John R. Carson, DDS, PC, Spear Visiting Faculty and Contributing Author www.johncarsondds.com