My Doctor Cut the Back Part of my Invisalign, Is that Normal?

Due to distortion in the impression material we sometimes have to alter the invisalign trays to fit around back molars.  Most of the time the back teeth are not moving during the invisalign treatments so it ususally doesn't matter when the back of the trays is cut.  However the dentist neeeds to monitor those teeth closely
 

Sometimes the Invisalign trays/ ALIGNERS have to be altered to fit properly or comfortably. The most common reason is distortion of the impression or incomplete impression which many times is communicated to the doctor during the planning phase of treatment or the CLIN CHECK. Removing or trimming the posterior molar part of the aligner to facilitate fitting or comfort may not affect the success of treatment, however close monitoring of the progress of treatment is necessary to detect any problems with unintended movement of teeth such as hyper-eruption of a posterior molar that is not at least partly covered by the aligner. Your doctor will most likely be aware of any discrepencies during treatment and make the necessary adjustments if needed. Don't hesitate to ask for explanations of the treatment progress at any stage, and realize that at the end of treatment all should be done to provide a reasonable satisfactory result.

Most of the time the back teeth are not moving too much during Inivisalign treatment so it usually doesn't matter if the end of the aligner is cut off.  What probably happened is that the initial impression was distorted in this area which means that none of the rest of the aligners will fit any better.  You just have to be careful because sometimes thing can go wrong if the entier arch is not covered and this needs to be monitored closly