Both my DDs 14 and 12 play basketball for a club and for their schools, and in particular my younger DD is very serious about it.
They don't wear mouthguards, and I haven't seen other kids who do.
My older DD had braces when she was younger because her front teeth jutted out a little and the orthodontist said that if she got knocked, her teeth would get knocked out given the angle.
She's now in braces again.
At one point my younger DD was in a mouth guard but it was for field hockey.
To me, rec is less intense than club...I'm not saying to not do it, but I think it's good that you are seeing info and advice.