If we could look at a tooth straight the bone and if you could look through the tooth itself. 
With pressure from your braces your tooth starts to move.
So again looking through your tooth.
Nature helps the tooth loosen to relieve the pressure, but there is temporary discomfort while this happens. Gradually the bone makes room on the compressed side and new bone grows in to support the stretched side…so the supported tooth becomes comfortable again.
But, we can’t stop there! So on your next appointment the process is repeated. However, once your tooth has loosened from this first movement, each adjustment is easier and little or no discomfort follows. Once your teeth have been placed where we want them, your retainer holds them in their new position allowing the bony support to return to a normal and stable condition.