I can understand that you might have gotten excited by the word “instinct” on the package. Maybe you became just a little enraged by the plastic’s resistance.
I can also understand that you may have overlooked the “cut here” mark.
However, your dentist and I agree, you should not open things with your teeth, unless you are missing a thumb.
If you are missing a thumb, you can open things in whatever way that works and/or gives you joy.
That’s also the dogs’ point of view on the subject… and hey!! Thanks for feeding them!!