Dog gum ulcers exhale a fowl smell and may be caused by a bad denture. Poodles suffer from them very frequently. Important: Because the symptoms described above can be the first signs of another affliction, you should take your dog to the veterinarian. Only he can give a good diagnosis.Dog Tumors & Dog Ulcers: We have on occasions discovered some tumors in the gums. If they are bothersome while eating, they should be surgically removed. It is not a difficult case, although the possibility of it being a malignant tumor has to be discarded.