Taking a dog specifically to deter bears is a bad idea, unless the dog is trained for that purpose.

I take my dog whenever and wherever I am backpacking or camping, but he is a service dog, and there is nothing a park ranger can say or do about it. I also take him when I go bow hunting, unless I am going for bear or mountain lion.

My dog lets me know if there are bears or other dangerous animals around, but he would not go out to investigate unless I told him to do so. I would not do that in any case, however. I also know that if something were to attack us and I wasn't able to draw my weapon and tend to the problem, the dog is able to outrun any bear.