In the previous article in this series I showed an example of masking a discolored crown prep by bonding an opaque masking agent and opacious composite over the prep allowing the use of a more translucent final restoration. In this article I'll discuss a central with an existing cast post and core.

Case 6: Discolored endodontically treated central incisor, with existing metal ceramic crown, cast post and core

This patient presented unhappy with the appearance of her old metal ceramic crown on the left central (Fig. 1). The crown is 20 years old and has a cast metal post and core that is quite large and extends to within 4mm of the apex. After removing the old crown and seeing the metal core I consulted with an endodontist about removing the post-core. If it was possible I would have replaced it with a tooth colored post-core, which would have allowed the use of a more translucent final restoration as the rest of the prep color is not bad, and would have improved with the tooth colored post (Fig.2).

Fig. 1Fig. 2

Ultimately the endodontist did not recommend removing the post-core, and the patient, who didn't want to take the risk, agreed. This meant having to mask the metal core. As discussed in previous articles this can be done using an opaque composite and translucent final restoration, or leaving the core alone and using a final restoration with an opaque core.

I chose to use an opaque cored final restoration, as I have never found it easy to prep the metal core and bond opaque composite to it. The question is what opaque cored crown? The answer will be very technician dependent, but the choices are generally Lithium Disilicate, Zirconia, Alumina, or Metal Ceramic.

In many respects this prep is similar to a metal implant abutment, as the crown has to completely mask the metal. The one material that can for sure do that is the Metal Ceramic crown, and it can do it with a coping only .2 or .3mm thick, compared to .5 or .6mm for the other materials. This leaves a few tenths of extra room for veneering ceramic to achieve a thickness of .8 to 1mm.

Fig. 3

The real key for metal ceramics is to have adequate prep reduction. Have a technician who will thin the facial metal down to .2mm and apply a thin layer of opaque. It's then important to use a subgingival margin even if you use a ceramic margin as was done here. If all of those issues are managed, and the patient doesn't have an extremely thin periodontium it is possible to get an esthetic result (Fig. 3).

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Commenter's Profile Image Roger Briggs
May 12th, 2014
Nice result for one of the 'tuffies' we have to deal with regularly.