Dental Crowns and Bridges (Prosthodontics)

How do I know if I need a crown?

Crowns are most often used when

A direct filling (amalgam/composite resin) may not be strong enough to repair the tooth with anymore. Usually the case when the cavity has grown too large and the remaining natural tooth structure too little or too weak to withstand normal biting forces.
To protect a structurally compromised tooth from further wear and tear. This could be due to a very large preexisting filling (Point 1) or perhaps a tooth with history of crack and/or fracture that is starting to break down. This buys time to allow your teeth to live to bite another day!
To cover and re-contour otherwise misshapen or discoloured teeth as a form of aesthetic recovery. A crown can help to restore both form and function in these situations. Yes, sometimes you can have your cake and eat it.
After endodontics (root canal treatment) of a tooth (so as to achieve any or all of Points 1, 2 and 3)
To restore an implant. Again, this helps in both form and function. An implant would be missing a biting and smiling surface and not really complete without a Crown.

Crowns not only come in different shapes and sizes but also materials.

Each material of course comes with inherent benefits and drawbacks. As with most things in life, there is no one size fits all. Your dentist will of course be more than happy to explain each material to you and come to a combined decision with you as to which is the best material to suit your needs.

Crown materials can perhaps be broadly and simplistically classified into

Metallic crowns – Gold alloys and other Metal alloys. Traditionally the more lasting stuff with the obvious trade off being appearance and aesthetics. Subjective of course but not everyone may want a shiny metal tooth.
White crowns – Full Ceramic/Porcelain crowns and Zirconia crowns. The more pretty stuff if you will. With advances in materials research, modern ceramics and zirconias are actually no slouch and may surprise you with their strength and longevity as well.
Combination – Porcelain fused to Metal crowns where porcelain is layered over a metal substructure. A halfway house serving up a combination of both advantages and disadvantages of the metallic and white crowns.

Unlike Crowns, Bridges are more a means of tooth replacement rather than tooth protection, somewhat like the case of a Crown in an implant restoration. A Bridge is in essence two or more Crowns at the ends of a gap or row of missing teeth, joined by other false teeth (also known as Pontics). Sort of like an architectural bridge! See the resemblance now?

Bridges vary in design and complexity and can range from a traditional bridge involving two Crowns linked by a span of Pontics as described above, to something like an Acid-Etched Bridge or Maryland Bridge which involves a Pontic and wings to hug the adjacent teeth without any Crowns to hold onto – often used in the case of a single missing tooth.

Materials used for Bridges are very similar to those of Crowns and again your dentist would be in the ideal position to discuss with you what bridge design and material choice would best satisfy your situation.