I generally wait until pick up to tell the parent what happened and also write it in the child's daily report.

It totally sucks to have a child hurt on your watch. It bothers me whenever it happens and I agonize over it but I have to tell myself that it is also a normal part of being a kid. Parents understand.

I usually don't call the parents at work because I think the parent will feel guilty all day, imagine it worse than it is.

However...BusyECE made a good point that these parents may want a dental appt so they may like the heads up just in case they need to book.