Broken Orthodontic Retainer

[Cloverjo]

I had my teeth straightened with the railroad tracks at a fairly advanced age of late 30s. The treatment finished about 8 or 9 years ago, but I've been using retainers every few days since then. I've woken up this morning and found I've broken the upper retainer somehow in my sleep. Do I need to get a new one or are my teeth set now after all this time?

I mention my age because I know teeth are more likely to move back to their original position if you're older.

I know I should just phone the orthodontist, but wondered if anyone has any experience of this.