Communicating Predictable Incisal Edge Position

My newly hired dental assistant, Danielle, was looking at some stone models of a recently completed anterior restorative case. While holding both the model of the provisionals and of the final restorations, she commented on how similar the models looked.

“It’s difficult to tell them apart,” she stated.

My response to her was, “It is intentional to create that appearance. Communicating the precise incisal edge position to the dental technician is critical for restoration success and patient satisfaction. Predictable results require specific guidelines and laboratory collaboration.”

This was one of those “learning moments” for Danielle that I could not pass up. Let me share some highlights from that conversation with you.

The role of the incisal edge

Anterior esthetic restorative dentistry is a very challenging procedure. There are so many components and factors that contribute to the success of the final restoration. The list of technical considerations for success is very long. Many seemingly small but important factors are crucial for success and predictability. Additionally, there is the subjective aspects from the patient that require attention and inclusion for restorative acceptance.

But one of the most critical factors for correct appearance and function is the proper positioning of the incisal edge. We know from Frank Spear the important role that the incisal edge plays in Facially Generated Treatment Planning: “Begin with the ideal maxillary incisal edge position, then develop the rest of the treatment plan from there.” If the entire treatment plan revolves around the incisal edge, then it is crucial that, from design through restoration, the edge position is developed and maintained.

Four steps to creating and communicating ideal incisal edge position

“Danielle, let me outline for you the sequencing of these steps so that you may follow the logic that is incorporated.”

Step 1 - The Diagnostic Wax-up

Following the FGTP system of treatment planning, the ideal incisal edge position will be determined. Based upon the pre-treatment photographs of the patient, the approximated length, shape and position of the proposed anterior restoration will be determined. This proposal must now be incorporated into a physical representation. A “blueprint” if you will. The diagnostic wax-up is that “blueprint.” It is possible to create the “vision” of the restoration in wax or composite by shaping contours and incorporating function from face bow mounted study models. The wax-up is the “preliminary drawing” of incisal edge position that will look and function correctly for the patient. These mounted models allow for developing the incisal guidance and the extent of jaw movement into the wax-up.

“Dr. Bonk, that wax -up looks amazing! The new tooth shapes look much improved from the pictures and models of the patients existing teeth. Do you think the patient will like them?”

“I am glad you asked me that question, Danielle. That is precisely the same question that I would like the patient ask. The challenge is, ‘Will that design look appropriate for the patient?’ Step 2 in the sequence of creating a predictable incisal edge position is the creation of an intra-oral mock-up.”

Step 2 - The Intra-oral Mock-up

Creation of the diagnostic wax-up provides correction to the existing tooth deficiencies with which the patient presented. The mock-up is designed to engage the patient into the process of restoration. It helps them “see in their own face” how the restorative changes will appear. This is a powerful tool and can elicit significant emotional response from the patient.

The mock-up (sometimes referred to as a trial smile) is fabricated from an index (silicone or vacuum) of the wax up. This index is filled with a self-setting provisional material and positioned accurately over the patient's teeth. Once cured, the index and any “excess flash” is removed. The resultant mock-up remains adhered to the teeth by locking into the interproximal embrasures.

Now the patient may “see for their own eyes” how the planned changes will improve the ultimate appearance of the teeth. Photographs of the mock-up can be taken and shared with the patient. The mock-up will create emotional desire from the patient to move forward with the restorative treatment proposal.

“From the photos of the mock-up, I can see how the patient would want to move forward with treatment. Will the provisionals look like the mock up?”

“Danielle, the mock-up will become the guide for the actual tooth preparation. Additionally, the provisionals will be fabricated from the same index used for the mock-up.”

Step 3 - Provisonalization

On the day of tooth preparation, the mock-up will once again be applied to the teeth. This mock-up will provide guidance as to preparation depth. The ideal tooth reduction required for the planned restorative materials will be achieved through this technique.

The provisionals are fabricated over the prepared teeth using the same index used for the mock-up. Once the final shaping and contouring of the provisionals is complete, they may be adhered to the tooth preparations. Before the patient is released, a shade is evaluated and the functional jaw movements are established and checked for smoothness. The provisionals are polished and an impression of the provisionals is obtained. The face bow and the bite records are also obtained. Photographs of the newly restored teeth are taken to forward to the dental laboratory. The most critical step is to obtain a study model of the new provisionals. This study model will be utilized as a key reference tool for building the final restorations.

“This seems like many steps. Doesn’t the dental lab know what front teeth look like and can’t they just build them from the impression?”

“Yes, Danielle, there are a lot of steps. And yes, the dental lab does know what teeth look like. But, to achieve predicable results, we must provide guidance to the lab technician to place the incisal edges exactly where they need to be, specific to this patient.”

Step 4 - Final Restorations

Once the patient information is gathered and the models are mounted, it is time to forward the case to the dental lab. To achieve predictable results that mimic the “dry run” of the provisionals, an incisal edge guide must be fabricated to provide the information needed for the lab to correctly place the incisal edges of the final restorations. This index is created by using putty material pressed against the mounted provisional models. The articulated models are positioned in centric occlusion. The putty material is mixed and positioned around the lower model. This putty extends from the lingual on one side of the lower arch around the facial tooth surfaces to the opposite lingual aspect. The putty, while still soft, is “pushed” or molded against the upper buccal and facial surfaces. The critical aspect is that the putty must engage the incisal edges of the upper teeth. Once the putty is cured, the excess material may be removed. The incisal embrasures must be included in the index.

The final restorations may now be fabricated to “fit” into this index of the provisional. The anterior tooth overjet and overlap of the provisionals is definitively replicated in the final restorative, because of using this tool. Once the incisal edge position is established, the functional movements can then be checked and adjusted on the articulated models. Using this technique eliminates guess work and un-predictability of incisal edge positioning of new restorations.

The importance of team buy-in

This four-step process in replicating the incisal edges of restorations is not difficult. Our dental assistants can be easily trained to fabricate the putty incisal edge indices. This is part of the job description for my laboratory assistant, Julie.  She not only fabricates the incisal edge index before the cases are sent to the lab, but, in fact, she checks the final restorations upon their return to verify that the final incisal edges fit into the index before the case is evaluated by me. If the placement is inadequate, she will return the case to the dental laboratory for correction. This process is part of our “laboratory checklist” to assure quality control and efficiency. Predictability and longevity of restoration comes from proper planning, exquisite provisionalization and specific dental laboratory communication. 

“Dr. Bonk, it is amazing how similar the wax-up, provisional and the final models look. Now I understand how you could achieve such great results for that patient. Thanks for taking the time to explain this to me.”

“I am happy to explain this for you, Danielle. The more you know and understand how we are predictable in our office, the more you will grow as an assistant and the better you can serve as an ambassador for our practice when you are talking with patients. A beautiful smile is all about the position of the incisal edges of the teeth!”

Jeff Bonk, D.D.S., P.C., Spear Faculty and Contributing Author - http://jeffreybonkdds.com

(Click this link for more dentistry articles by Dr. Jeff Bonk.)