The Size and Shape of your Teeth

How size and shape of teeth can affect orthodontic treatment

Understanding how the shapes and sizes of your teeth affect your treatment outcome.

When you begin your orthodontic treatment, your teeth are aligned with braces or Invisalign but their sizes and shapes are not changed. Teeth are never as perfectly laid out as they are in photos. Photos are deceptive! The truth is every single one of them are differently sized and shaped. While we are bilateral creatures, the human species is not symmetric. Our left and right sides look and feel different.

Here is an example of an analysis that is done to check for tooth size discrepancies. You can see that each tooth has its own individual width different from its bilateral counterpart.

tooth size chart

Some people ask me why I didn’t tell them about the asymmetry before their treatment had started. A big reason is that often times I cannot detect what is a visible amount of difference until they are straightened as well. When there is a bigger problem like crowding, eyes are drawn to the crowding.

Here’s an example of a patient before starting orthodontic treatment.

Tooth size discrepencies before

What is the first thing you notice? Would you even notice any discrepancies in tooth size and shape?

Here’s the same patient towards the end of treatment.

toothsize example1 after

How about now? As we approach the end of treatment, can you tell that the central incisor in the right is slightly narrower than its counterpart?

Besides the width of the teeth, even front surfaces of the teeth have their own distinct anatomies and differences. There are slopes, ridges, hills, and valleys on the surfaces of some teeth that make them appear crooked. These subtle differences are not noticed when teeth are crooked. Once the more obvious issues like crowding and rotations have been addressed, our eyes can begin to see the more subtle differences.

Here is an example of a prominent ridge and hill on the front of the tooth

toothsize example2

Can you believe that this is the same patient in all three photos? After alignment of the teeth, you can see that the incisor on the left is much thicker with a distinct ridge.

Here is a tooth shape that slopes outward.

Notice the sloping shape of the central incisor on the left. This makes the tooth appear like it is sticking out even when it has been straightened.

The teeth that show the largest variation in shape are the upper lateral incisors. They can be peg shaped, shovel shaped, round instead of flat, have indentations, be extra short or extra small or extra narrow. In rarer circumstances, they can even be larger than the 2 front teeth. These size and shape discrepancies can make them look crooked even when they are well aligned.

In this case, notice that even though all the teeth have been aligned, the right lateral incisor still appears to be set further in than its neighbors. This is due to the small size of the lateral incisor.

From the patient’s view, this small peg shaped tooth appears inset and her front tooth next to it flared even after orthodontic treatment. From the orthodontist’s view, the peg tooth is already centered in the ridge of jawbone. (In this case, you can see in the 3D image, the root of the peg tooth is positioned even more anteriorly than it’s counterpart.) The front tooth looks more prominent when placed next to the smaller tooth. It is simply a problem stemming from tooth shape.

Prior to this patient’s orthodontic treatment, her “peg” shaped lateral incisor was not noticable to her due to its inset position in her crowded dentition.

There are a few takeaways to consider:

  1. It’s hard to tell the shape discrepancies when the teeth are crooked for lay-people and even for dental professionals.
  2. As an orthodontist, we are focused on the issues we can address.
  3. In some cases, we don’t know what amount of discrepancy will matter to you as a patient.Shapes and sizes of teeth affect how you perceive your smile.