Horned frogs - Why do some have open mouths const

Hi, I have a horned frog and it is doing very well. However, everytime I go to a pet shop I see so many of them that have mouths that are constantly open/cannot close. I understand that some are because of calcium deficiency and their lower jaw bones become deformed. But some even with normal shaped lower jaws seem to have their mouths a little open all the time and unable to close. Does any one know why this is and how to prevent it?

Thanks.

I don't have an answer for that. It would be really sad to find out it was because of a calcium problem. So easily preventable.

Pet store amphibians often fare poorly, even compared to other herps. From examples I've seen, it's likely they're suffering from mild to severe cases of various diseases, infections, and/or deficiencies. It could be caused by improper nutrition while the frog was growing, or from glass rubbing. If the mouths are actually open and you can see inside, then some of the above scenarios are still possible, but it could also be that the frogs are too hot.

Alright thanks for the replies. Does that mean however that there is no definitive answer or research on this subject as of yet?

I highly doubt there are any research papers on the mouth problems of pet store horned frogs. Not that there shouldn't be one though.