
I think it depends on the breed. Hairless Cresteds can have missing and cricked teeth and not be penialized, but if a powderpuff Crested does, then it is a major fault, and can lead to a disqualification.
Dobermans are another breed that missing teeth is looked down upon.
From the size you listed, I am making a guess that you may have a sporting dog? Just a guess mind you, but wouldnt a missing tooth lead to them not being able to do the work they were breed to do. Thats one reason we never showed our springer spaniel. She had the crocked teeth, and in Canada at least, a bad mouth in a sporting dog, is worthless to show. It is one of the highest pointed things in the dog, so out of the 100 possible scored points, there would be no point when competing against otherwise good dentation dogs.
But, I would check out your breed standard for one, then see what it says about mouth. If it is a breed where mouth and dentation is important, you could be wasting your money. If not, then give it a go.
Hope that helps
Crespin