Thank you for the additional information. Blood tests are a great diagnostic tool, but they don't rule out every illness. In most cases the typical blood tests are pretty complete, and since the tests ran before the dental were normal, they served that particular purpose (main organs that are tasked with metabolizing and eliminating the anesthetic drugs form your pets system were functioning properly). There are some conditions that can be sneaky, and basic blood tests and fecal tests can be normal while these illnesses are present. It's also important to keep in mind that approximately 75% of kidney and liver function is lost BEFORE any abnormal values show up on lab tests. This means that an illness can be present in early stages and not necessarily obvious on tests. This is where you come in. You know your pet better than anyone else, even your vet. You live with her and know her habits. If lab tests are normal but you bring her back and tell the vet that she is having worrisome symptoms, it prompts further investigation. Together you and your vet make a team to keep your dog healthy, and your vet really needs your input.
Given the past history of borderline pancreatitis, I think that some further investigation is warranted here. By that I mean that an abdominal ultrasound is probably a good idea, since it is very sensitive, and a good sonographer can tell if the pancreas is inflamed, if the adrenal glands are enlarged, and if the intestines are inflamed. These are all things that you don't typically get to evaluate on x-ray, because it is a 2 dimensional view rather than the 3 dimensional view provided by ultrasound. Please see the following link for more information on ultrasound and x-rays.
Please see the following website for more information on pancreatitis.
The pancreas is also responsible for production of insulin. Sometimes the first signs of diabetes in older dogs is repeated issues with pancreatitis. I don't think your dog is a diabetic, since your vet likely tested her glucose before the dental. I mention it because it is all tied in to the pancreas, and I want to be thorough. As long as I'm mentioning concurrent illnesses, it's also necessary to mention adrenal gland diseases. The adrenal glands are close to the pancreas, and illnesses with these organs can also go hand in hand with pancreatic issues. When the adrenal glands produce too much corticosteroid, you end up with an illness called Cushings disease. Please see the following link for more information on cushings.
When the adrenal glands produce too little corticosteroid, you have an illness called Addison's disease. See the link for more information.
I am not saying that your dog has either of these, but at this point advanced testing will need to be run to rule them out, especially if your dog starts to develop other symptoms in addition to the soft stool. Another condition that can cause the changes in the stool that you are seeing is called inflammatory bowel disease. Is is a little bit like irritable bowel in people. Please see the following website for more information on IBD.
So what you have now is a whole lot of questions, a dog with intermittent soft stool and no other symptoms, normal blood tests, a history of borderline pancreatitis......and no concrete answers. Please keep in mind that the above illnesses are just possibilities given the history and information you provided. Your dog may have nothing more serious than a mild GI upset due to the diet changes, BUT with her history, I would be hesitant to blow that off. I know that it is frustrating because the tests all came back normal. It's important to realize that even though they didn't indicate any obvious disease, normal results also provide value in ruling things out too. Plus the results you have now provide a baseline to compare future blood panels to, which gives you the opportunity to monitor for subtle changes that might otherwise be missed.
I hope you get some answers for your baby soon, and that nothing too serious of complicated is going on (I'm crossing my fingers for the diet change causing some mild upset). Please let me know if I can be of further assistance. Best of luck with your baby.