A new study found that as people age, the lower jaw, in particular, shrinks up to 1-2 millimeters. This bone size reduction is enough to cause minor crowding in the lower teeth. So if you’re in your 40’s or older and you see your teeth crowding a little bit, where they weren’t before, you can blame the natural aging process. Scientists aren’t sure why the jaw gets smaller as we age.
These results were seen in a new study done in Sweden. Thirty dental students participated to have their jaws measured in their 20's and again in 30's and 40's. Both the length and width of their lower jaws reduced in size, by an average of 2 millimeters. Even this minimal change in bone structure caused a higher incidence of lower jaw teeth crowding.