Orange juice has as much sugar as coca cola by the way.It doesn’t. Some people drink too much of it, some people have poor oral hygiene etc.
It’s nonsense to say that everyone or ‘people’ have manky teeth from it without quantifying that statement.
What does pure mean. Do you mean orange juice - there is not many forms of it. It is either the juice of an orange ‘100%‘ or a diluted form. The liquid from of the fruit is more acidic and damages the teeth enamel very quickly. The sugar content is irrelevant and because fruit is NO more surgery than before has NOT increased in sugar. It’s all about the acid….