Defining a Unit of Measurement

I am trying to get an equation to spit out an answer in the form of Teeth/Inch.

How do I define Teeth as a Unit?

I went through HELP in MathCad...but it tells me to type...

teeth := 'a way of defining it'

i didn't see any units in quantity or just a # of items.

any help would be appreciated !

Thanks !

Jeremy