I wear invisalign retainers at night after my invisalign treatment. should i change my toothbrush every month/more frequently since i wear these?

Not necessarily...: Every four to six months should be fine, sooner only if you feel that the toothbrush has worn out due excessive wear and tear.

Toothbrush Changes: Whether or not you wear aligners at night as a retainer should not have an effect on how often you change a toothbrush. Toothbrushes need to be changed about once per month unless you're using a rotary powered brush. I love Sonicare and the new Oral B products as well. And Zila's pro Dentec brushes. :)

When it wears out: The ends of the bristles are the part that does the cleaning. When a brush gets old, the bridles sag and the ends no longer scrub the teeth and gums. When this happens, replace the brush. Keep your aligners clean, wear them regularly and they'll do the job they were meant to do.

Every 3 months: You should change your toothbrush every 3 months. Keep your teeth, gums, tongue and retainer clean with an oral health routine.

No: Change toothbrush every 3 months, at the change in seasons. Put retainers in a bowl, cover with room temperature water, drop in a denture cleaner tablet (Polident, Efferdent) every morning and leave them there 'till ready to put in at night.