There are quite a few reasons while your teeth may have shifted. Lets explore those reasons.
1. You had orthodontics at some point.
Teeth have a “memory” due to the ligaments that hold them in the jaw bone. People who have orthodontics are at a higher risk of teeth shifting because your teeth have this memory and want to go back to their previous position. Can you hear your orthodontist’s voice reminding you to wear your retainer? Now you know why.
2. Aging.
Your teeth have a tendency to want to push to the front of the mouth so over time that pressure can lead to crowding of your teeth, especially in the incisors.
3. Sleep position/daytime posture.
Stomach and side sleepers have more of a tendency for this. In addition, sitting in front of a computer all day can result in the lower jaw drooping and in turn can lead to tooth movement.
4. Teeth grinding.
The constant pressure from clenching or grinding on the tooth surfaces can cause the teeth to change position, and thus place stress on the surrounding teeth.
5. Tooth loss.
If you have had a tooth extracted and not had a bridge or implant placed soon after, then your teeth are likely to shift. Teeth want to naturally be touching an adjacent tooth and be in contact with a tooth on the opposite jaw when you bite. If you go a long time without a replacement of the lost tooth, you will likely undergo this.
6. Gum disease.
Gum disease leads to the loss of the bone surrounding the teeth. As you lose this bone, the teeth are not held in as strongly and this leads to more tooth movement for a variety of reasons. In fact, shifting of the teeth is one of the most common signs of gum disease.