The bottle and package of Sensodyne ProName says:

"WARNINGS
When using this product do not use longer than 4 weeks unless
recommended by a dentist or physician."

Why???? And, why does it say that in the fine print, but the front of
both the box and the tube say:

"DAILY ANTI-CAVITY FLORIDE TOOTHPASTE FOR SENSITIVE TEETH"

And, elsewhere it says:

"USE WHEVER YOU NORMALLY BRUSH"

Is there something about potassium nitrate that it's bad to use for
long periods?

Thanks.

Steve