It's true - it's not a good idea to share your toothbrush. We heard somewhere that millennials once told pollsters they would be more apt to share their toothbrushes with someone than their phones. (ModernDental Network)
Yuck! A toothbrush, for instance, can be home to streptococcus mutants - which are responsible for, among other things, tooth decay! So-bacteria, food particles, viruses, fungi and peridontal disease can all be spread via the shared toothbrush - Just say "no"!