Can I sue a toothpaste company if I got gingivitis while using their product regularly?

You would have to prove that the tooth paste caused or contributed to the gum disease, which would require experts and cost a large amount of money. ?Unless your attorney could find several other people with the same situation so as to make a class for a class action suit, the costs involved might exceed any damages awarded. Ask your dentist what they think the relationship between the disease and the tooth paste is, but i doubt very much they will blame the tooth paste.