I was looking in Webster's mouth when I noticed he has a chipped tooth & a tooth that looks like it has a spot where the enamel is missisng.  Is this something I need to be concerned about?

As long as  Webster is not botherd by it, I wouldn't worry. Just have your Vet check it out the next time you have Webster in for something else.  Rocky has a broken off canine front tooth which has a brown center and my Vet examined it and said not to do anything at this point and not to worry unless it the tooth turned blue then Rocky will have to have it pulled. His gum line is not inflammed and he has no pain so I will have our Vet check it at each exam. I donot want to go to a dog dental specialist and have Rocky have a root canal which could be an option.