First Day of Invisalign. Unbelievable Pain! When Will It Subside?

What you are feeling is normal, considering it is only the first day.  Different people have different responses to orthodontic tooth movement (whether it is Invisalign or regular braces).  

The pressure that you feel will not be as intense in a few days from now, and is certainly not something to be expected for the whole treatment period.  Usually the worst is the first 2-3 trays of the first aligner.  Then it gets better.  You may also anticipate some pressure/pain for the first day or two of the start of each subsequent aligner. 

Hang in there, and it will get better. 

If you have any questions or concerns, make sure you ask your Orthodontist. 

As the bone adapts to the pressure from the aligners, the pain will ease.  As you switch out subsequent aligners, the bone will already be altered, so pain will be less.  The worst pain is at the beginning.