What are dental crowns?

Dental crown is the name given to the restoration used to return a tooth to it's original form and function. They may be necessary due to :

Multiple previous fillings ( each time a tooth is filled, it has less of it's original structure and strength- eventually there may not be enough tooth to fill any more).

The tooth breaking. This may happen for several reasons. If one is in the habit of chewing on ice, or hard candies, the result may be a broken tooth. When you eat a meal, your teeth come close together , and the food in between the teeth gets ground up, but the teeth don't actually touch. When chewing ice, the teeth become more brittle, and when the ice breaks and the teeth come slamming together, the excessive force can cause the tooth to break. This is true for a tooth that has never had a filling and even more likely for a tooth that has been filled. If the tooth has been filled with an amalgam, which is a combination of silver and mercury, it is more likely to break than if it has been filled with a bonded composite resin. The reason for this is that the mercury in the amalgam is very temperature sensitive- that's why it used to be in thermometers. While it was good in thermometers ( as long as they didn't break- mercury being one of the most toxic materials around) this same temperature sensitivity means that every cup of coffee, or soup or ice cream causes the filling to expand or shrink at a rate 9 times that of the tooth. This expansion/contraction creates micro fractures in the tooth. The cumulative effect of all these fractures may cause the tooth to break, even if you are not chewing anything hard. Kind of like a small chip in a windshield that suddenly turns into a huge crack. If one is grinding or clenching their teeth, either day or night, this too creates excessive stress on the teeth which normally do not touch when eating. If you use your teeth as tools- to open packages, cut thread, strip wire, etc. you are using your teeth in a manner they were not designed to sustain their structure.

In any event, whatever the cause, once a tooth is no longer intact, a crown is used to restore it. Crowns can be made of a gold alloy ( the strongest, but not aesthetic), porcelain bonded to gold ( not as strong but more aesthetic) and all porcelain - the most aesthetic and life like.