True or false: past participles agree in gender and number with indirect object pronouns.

It if false that past participles agree in gender and number with indirect object pronouns.
Agreement only occurs if there is a direct object IN FRONT of the verb. However, if there is an indirect object pronoun, then there is no agreement. Here is an example:
Elle se les est brossées. - you can see there is agreement here because the pronoun is in front of the verb
Elle s'est brossée les dents. - there is no agreement here