Habits such as a reverse swallow, tongue thrust, or sucking the thumb, fingers or the lower lip can apply pressure to teeth. Over time, teeth spread. If these habits aren't corrected before treatment, the teeth may spread even after the braces are removed. Babies who suck their thumbs or pacifiers aren't generally at risk, says Singleton. As long as they break those habits by age 5 or 6, they usually don't cause malocclusion in their permanent teeth.
Baby teeth can greatly affect the look and health of permanent teeth.
If a baby tooth falls out too early or decays, the other teeth may move to fill in the space, blocking permanent teeth from coming in when they are ready. Similarly, if a baby tooth does not fall out soon enough, the bigger tooth behind it may come in crooked. And if a permanent tooth is lost to decay or trauma and is not replaced, the other teeth will drift to fill up the space, sending them out of alignment. The size of teeth can affect their alignment as well. Teeth that are too small can drift, and teeth that are too large will crowd.