Thanks. The excess salivation and may be due to a fractured tooth, considering that there is a canine tooth missing where you have not noticed it missing before. Other possibilities include toxin exposure, eating a frog, lizard or bug; foreign body stuck in the mouth, stomatitis, ginivitis, dental disease, kidney problems, liver problems, pancreatic problems or a gastrointestinal foreign body obstruction. If he is panting, that is not generally a good sign in cats. My best advice to you would be to rinse his mouth out with some water for a couple minutes. You can use a water hose with a gentle spray, a water faucet sprayer or a cup with some water. Make sure his nose is pointed down for all of these, so you don't drown him. If you can see a foreign body in his mouth anywhere, you may be able to pull it out. If the panting or excessive salivation continues, veterinary attention would be needed as soon as possible. Like I said, panting in cats is not generally a good sign and usually requires immediate veterinary care. Besides rinsing his mouth out, there is not much else you can do for him at home. Please let me know if you have any other questions. Hope this helps.