no it's not, it's fluoride and some soapy binders like SLS and ceramics or baking soda for whitening/cleaning. I suppose some of the tube might break off and form these microplastics, however I don't know too many people swallowing their toothpaste leftovers. It's a bad idea as you shouldn't ingest that much fluoride, which is much more highly concentrated than fluroide in water. If you're talking about microbeads then those were outlawed in toothpaste/cosmetics/etc in 2016, which went in effect in 2017.
There are toothpastes that contain plastic microbeads [1][2] and an FDA ban (for < 5mm size beads) came in effect only in 2015. Some toothpastes also have polyethele "specks" to provide color [3],
There's more. The gum base of chewing gum is made on the same exact machines as car tires. Once or twice a year the factory will shut down tiremaking, clean the line and do a huge run of gum base. Then they will resume tiremaking.
Source: someone who works at a major candy manufacturer