One of the most frustrating experiences you can have as a clinician during the maxillary anterior restoration try-in appointment is identifying an occlusal cant problem in the incisal plane. Usually, this also results in a cant to the midline. There is little room for error with these two elements in terms of the esthetic outcome of the case—in fact, there is a maximum allowable error of one degree from a level occlusal plane or midline cant.

Assessing why the error occurred and resolving the problem is essential. The cant may or may not be due to an error made by the technician during restoration fabrication. You want to be able to troubleshoot the reason for the problem to minimize the chance of it occurring again, as there are significant emotional challenges with the clinician and staff, as well as related financial implications. Additional chair time and another appointment may be required.

Determining If There Is an Occlusal Cant Problem

To determine if there is an incisal plane cant, first place the restorations on the master cast that has been mounted on the articulator.

Determine if the occlusal plane is canted or level to horizon. If it is level on the mounted cast but not intraorally, an error was made in the facebow transfer and the restorations were fabricated correctly based on the information provided.

If a cant is visible on the articulator, the technician made an error. The clinician can recognize this before the patient's appointment. At this point, you can modify the restorations by adjusting the incisal edges or return the fabrication to the laboratory for the technician to modify. The evaluation you make here is critical. Is a simple reduction of tooth length of the long teeth needed, or is there a need for ceramic addition to the short teeth? How will these changes affect the edge-to-edge function of the lower teeth?

What to Do for An Occlusal Cant Problem

When you try-in a patient's final restorations, if you do find a cant to the occlusal plane or midline, you can follow these steps to assess or rectify the situation.

1. Evaluate the restorations intraorally.

2. Try in all the restorations individually and confirm the proper marginal integrity.

3. Try-in the restorations two at a time to check and adjust interproximal contacts. A frequent cause of canted restorations or poor marginal integrity is tight interproximal contacts.

4. Evaluate the occlusal plane and midline with the patient standing before you.

5. If the incisal plane is canted, assess if it can be leveled intraorally by adjusting the length of the incisal edges.

 

If there is an occlusal cant problem that needs to be corrected in the laboratory, follow these steps:

1. Temporarily seat the restorations.

2. If the restorations are crowns, seat them with a very small amount of Mock 2 (or Mock Slow if you require more time for this procedure). If they are veneers, you may need to use an extremely small amount of temporary cement to lightly secure the restorations to the tooth.

3. Take a facial photograph of the restorations with the patient standing: lips retracted, correct head posture, teeth slightly apart (1-2 mm), so the maxillary and mandibular occlusal planes can be seen. Align the lens of the camera at the level of the maxillary arch. This photograph must show the occlusal cant problem which needs to be corrected.

4. Take a new facebow with the restorations temporarily secured to the teeth. Be certain to level the facebow with the patient standing. Photograph the facebow transfer.

5. Return all the original information and casts to the laboratory along with the new facebow transfer and photographs. (Fill out a new prescription identifying the corrections needed, including a diagram of the occlusal planes and midline relative to the interpupillary line and horizon.)

 

Using the new facebow transfer, the laboratory mounts the original master cast with the restorations in position. If the new mounting and photographs accurately represent the clinical situation, both the laboratory and the dentist can be confident that the occlusal cant problem has been corrected.

Robert Winter, D.D.S., is a member of Spear Resident Faculty.


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