Dear 100 Hour Board,
I was buying a new toothbrush a few days ago and noticed that all the toothbrushes have numbered head sizes. There are size 30's for little kids and 50's and 60's for normal adults, and 80's for people like me that have gaping, cavernous maws. How are these sizes determined?
- Big Mouth
I believe it is determined by bristle size.
- Crest Kid
The numbering system is actually not systematic. It's just a representation of bristle stiffness and head size. Apparently Oral-B started the trend, and other toothbrush manufacturers just picked it up. It just happens to appear systematic so that store owners can group similar types of toothbrushes together.