I strongly believe and have found that your performance will outshine any undergraduate preferences. There are the occassional people that get into a dental school with somwhat lower stats and a weaker application because the school values the undergrad. There are also people who will NOT get into a school with an amazing application, and perhaps their college or university just doesn't go over well with that particular adcom.
But, with almost ALL people, you are sending in an application for yourself, and it represents YOU. You need an excellent academic record, experience, proof that dentistry is the one thing you want desperately to do, and show that you're an interesting, engrossing person. We can all try to find factors that may lean an adcom one way or another - family members, certain majors, age, location, undergrad, people who write the LORs, whatever.
But these smaller factors will not make up for a poor record and will not necessarily detract from an excellent one.