One of the quick small project I did few months back for one of my client’s friend. Only tricky part was to do bristles soft body dynamics against teeth. At first, I tried default “hair and fur” dynamics in 3ds max but it wasn’t giving desired result. So I then used Flex modifier (recoded with Pointcache modifier) for softbody dynamics of bristles and used “hair and fur” to create bristles. I also used morphing after getting desired dynamics and shape of bristles.
I used mentalray to render entire animation using FG. Toothbrush model was provided by client.