You do not need to be a dental assistant to apply and enter dental school. The grand majority of students are fresh out of undergrad with practically zero actual hands on dental experience. Plus so many students lie about the number of hours of shadowing they completed, so that section is more just something to tick off on a box.
It would be better if dental schools rewarded people who have worked in the field, be it dental assistants, hygienists, dental lab technicians, foreign dental graduates, but it's really a numbers game. Do you have the specific GPA and DAT score that school is looking for. If you don't meet these basic requirements, your application is not even looked at and goes no further. After that it's really what personal statements, and LORs stand out the most to whoever is reading your app, because most students have the same dental resume e.g did service work in x country, were president of cub y, shadowed so and so, and admissions officers know students are full of ****, and exaggerate their resume. GPA, DAT, LORs are things that are not tampered with by students, although some professors ask their students to write their own LOR and they will sign it, but that's a different story.