Restoratives and crown placement are included in the branch of dentistry called prosthodontics.  In veterinary medicine we commonly perform restorations with the same composites used by human dentists.  The composite replaces missing tooth structure.  A more durable restoration is a cast metal crown which can be made from mixtures of nonprecious metals called alloys or even titanium.  Metal crown placement allows forces on the tooth to be distributed over the entre surface to prevent fractures of tooth structure.  Teeth with crowns are not invincible, they may add protection, but can still break with great force.  It is important to eliminate sources of potential tooth trauma such as anything they chew on that you cannot bend or indent with your thumbnail.