If you are planning on doing this in the US, and if you are sure that you want to become a dentist.. I would recommend you going for it and skipping dental hygiene school.
1. You are adding unnecessary years of school in dental hygiene learning concepts that will be repeated in Dental school.
2. You will spend more money than you need to on a degree you will not utilize efficiently. Student loan interest rate is pretty high in the US on average 6.8%
3. If you fear you will not get accepted right away but your application packet looks good, you may want to invest your time maybe doing business degree instead
Hope this helps.