A few weeks ago I had the good fortune to find myself speaking to a group of third year dental students. As they were all too polite to stop me, I was waxing on about diagnosis, treatment planning, and other unglamorous things that are an important part of dental school. When one of them asked me how a bridge meets up with the gum, it occurred to me that it's so easy for a dentist to forget that dental jargon slips into our conversations with patients. If a student who has been living and breathing dentistry for the past two years isn't able to visualise a bridge, then I certainly can't expect all of my patients to instantly know what I'm talking about when I tell them they need a 3-unit PFM fixed-movable bridge with a modified ridge lap pontic and metal occlusion. That was a mouthful before the dental treatment has even begun, so let's look at what the differences are between crowns, bridges, and veneers.
Colloquially known as "caps", crowns can be made from ceramic, metal alloy, or a layered combination of both. Crowns are used on weak teeth to prevent breakage, usually because they are more filling than original tooth. There's a lot of factors at play when deciding whether or not a tooth needs a crown, but a general rule of thumb is once there's less than a third of the actual tooth left, a crown will be beneficial. The crown is made in a dental laboratory from a mould taken of the patient's teeth, and then cemented in place to cover the whole tooth. Crowning teeth just to make them look better is not always a good idea. The process involves shaving around 1mm off all the sides, and 1-2mm off the top of the tooth. So, if the tooth has no decay and has never been filled, it's a bit destructive.
Bridges are used when there are one or more missing teeth which need to be replaced. Imagine you have a tooth taken out, which leaves a gap that still has teeth either side. The two teeth next to the gap, (abutments), are shaved down as they would be for a crown, but instead of making individual crowns, the dental laboratory then makes three teeth all joined together. The tooth in the centre is the "fake" one, held in place by the two either side. It's just like a bridge over a river, but instead of a babbling brooke it's spanning across gum. The main disadvantage of a bridge is the trimming which is required on the abutment teeth. It's all well and good if those teeth are heavily filled and could do with a crown anyway, but if they're virgin teeth it's a high biological price to pay to replace one missing tooth.
Veneers are generally done to improve the look of someone's smile. They can be very effective at changing the shade, shape and size of the front teeth. Unlike crowns, they don't wrap the whole way around the tooth. Instead, they fit on the front of the teeth a little bit like a false fingernail. In some cases it's possible to do this without damaging the original tooth underneath, but a lot of the time some shaving back is required to make space for the veneers to fit nicely and look good. Once the tooth has been trimmed, it will need to have some sort of veneer on it for the rest of your life. So, going down the veneers road means having them replaced every 5-15 years, depending on what material is used and how well you look after them.