Finished treatment

Finally (!) after 17 months I have finished my invisalign treatment. Attachments all taken off today.

My question is this. Ive been told ill be waiting around a week for my long term retainers (to wear at night) which means im going to be going for about a week with no retainer.

Is this normal? Anyone had this done before? Im worried by the time i get the retainers my teeth will have moved and itll be an issue

Thanks!