Of course he would be anxious at a dentist because no-one should ever get all of their teeth pulled out especially at a young age. It is ludicrious to advice him to go with it.
It is possible for you to save most of your decaying teeth as long as they stay alive. You need a drastic change in diet. I don't know how bad things are but if you are willing to do this it would take about a month for the first noticeable improvements.
USA people are constantly being fed with absolutely terrible processed food, diseased cattle, refined everything, food deprived of minerals, vitamins, nutrients.
You need to supply yourself with meat and edible organs from naturally bread and grass-fed animals, you need wholegrain foods which are not processed or refined in any way, as well as vegetables and fruits and quality fats like milk and cheese which come from the mentioned above healthy animals and also quality fish products. It might not be easy to find all of this but it's definitely worth the try. There's information on the internet about this, there's online shopping too if necessary. I can't post links here but if you're lost then i can PM you more detailed information.
People need to supply their bodies with minerals and vitamins and nutrients in order to maintain great health. You are what you eat. If you are eating fast, highly processed foods frequently then you have been deprived of so many goods which are so vital for teenagers, you are still growing up, your body is still in the process of development and it's in huge need of healthy foods in order to be healthy.
I forgot to state the (hopefully) obvious fact that teeth and your oral health as a whole should be thought of as one living organ, which is supposed to last your entire life in good condition. Oral health and teeth are very dependent on your food intake, just like every other part or organ of your body. The above mentioned foods are especially (but not limited to) good for keeping your teeth healthy or helping them heal and function normally.
P.S. Just noticed that this thread is old, so shameful because i'm probably too late with my advice