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If your crown has a metallic sub-structure (i.e., your crown is a "porcelain-fused-to-metal" crown rather than an all-porcelain crown), the tooth is still sealed, and repair of the crown would only be necessary for cosmetic reasons. If the tooth is not in an area that is conspicuous, you can forego the repair until you are able to have a more formal professional intervention.
However, if the breakage poses a significant cosmetic liability, you may attempt to re-attach the piece using a commercial cyanoacrylate cement
, such as Crazy Glue or Super Glue. You will need to be careful to avoid contact between the cement and your finger to avoid gluing the chip to your finger; use tweezers if possible. Dry the tooth and the porcelain fragment before starting, use a small amount of cement on the fragment, carefully position the fragment on the tooth (use a toothpick
to help maneuver the piece), taking care not to get cement on your lips or other soft tissues, and retract the lip for a minute or two while the cement dries.
Be advised that this will provide no more than a temporary repair; you will need to have your dentist
make you a new crown for a more durable solution.
Hope this helps...