Okay, time for me for a moment to get up on my soap box and rant a bit about this.
Dental school isn't undergrad, it's a professional school. It's your "job" to act in a professional manner, which includes going to class. Most schools aren't of a large enough class size where your absences go unnoticed and right or wrong, some profs WILL judge you based on that.
Especially in light of the couple of cheating scandles at various dental schools across the country the last few years, "professionalism" is becoming a trait/quality that IS being actively noted during ones education. Outwardly, you may not always (or sometimes at alll) respect your professors, but you SHOULD always respect the profession and that starts by doing your "job" as a student which is attending class if your physically healthy enough to do so.
(climbing down off my soap box now)