How effective is a crown for treating a cavity?

That depends: That depends on the size of the cavity. Crowns are a very effective way to treat large cavities where a lot of the tooth is missing because they cover over and protect the remaining natural tooth structure. Small to medium sized cavities do not require crowns.

Crowns: Cavities can be small, medium or extensive and cause corresponding destruction and weakness to teeth. Most small to large cavities are repaired with composite tooth colored bonded fillings. Crowns are the most comprehensive and best way to protect teeth from further breakage or decay. All ceramic crowns can also be the most aesthetic restoration. An excellent alternative. Best not to get cavities