Over time a tooth can lose its strength, its structure, or its natural appearance. In our practice, although we usually restore a tooth using the most conservative means possible, such as a bonded composite resin filling, we sometimes need to completely rebuild a tooth. This is when a crown is typically used. A crown is a type of high strength cover over a tooth, usually intended to extend the life of a tooth that is significantly compromised, but sometimes it is used solely for achieving esthetic changes.
Examples of situations when a crown is recommended include when the tooth contains more filling than tooth structure and is not holding up well over time, or when a tooth is missing a large portion due to fracture. This could be due either to trauma or to cracks that gradually grow and weaken the tooth, eventually leading to breakage or splitting. We see this occurring very frequently in teeth that were filled earlier with mercury amalgam or “silver” fillings. All dentists have been trained in this traditional technique for many years, and it is now widely recognized by more progressive and holistic dentists as weakening the teeth and actually contributing to their fracture and breakage over time.
Crowns are also used when teeth are heavily worn from grinding or when strong discoloration is present. Today we are increasingly likely to recommend more conservative options for some of these problems, such as bonded veneers. These have the advantage of maintaining more of the natural tooth structure than crowns, which keeps the tooth stronger overall.
There are several types of crowns in use today, and the technology is constantly developing. The demand for natural appearing crowns for both back and front teeth has driven the development of porcelain or ceramic crowns, and these have been getting stronger, more esthetic, and more biocompatible. We now have an all ceramic zirconium crown that is strong enough not to require the traditional cast metal core that so often causes the dark gumline seen on teeth with older crowns. It is also esthetic enough to look natural without needing the surface layer of porcelain used in older style crowns that is so prone to chipping and breaking. Potential metal allergies and reactions are also avoided with use of the more biologically neutral ceramic. In our practice today, most crowns we place contain no metal at all.
The process of making a crown often begins with rebuilding the core of the tooth, usually with a type of bonded filling material, followed by a precise shaping of the entire tooth and core so that a solid crown can slip right over it and actually cover the entire tooth up to the gumline. We then take a mold of this shaped tooth and send it to a dental laboratory that makes the crown. We make a natural appearing temporary crown that is worn until the second appointment, when it is removed and the permanent crown is fitted and permanently bonded over the tooth.
So to a dentist who believes the least dentistry necessary is the best approach for your health, a crown is often the means of last resort in restoring a tooth. The good news is that the technology of today’s crowns is better than ever, and offers us an excellent combination of natural appearance, strength, and biocompatibility.