Look at it from a pragmatic approach. If you haven't applied to dental school, I would suggest not taking a lot of courses that could tank your gpa. If you have already applied, just pass with a C or better, but this depends on the admission criteria/terms of acceptance (i.e do they want you to pass all your remaining classes, do they want you to maintain the GPA, get your degree, etc...) If they want you to maintain your GPA, just take easy underwater basketweaving classes. That courseload is easier than dental school, but I find that its easier to do well in dental school than in undergrad.
Why did you find it easier to do well in dental school?
I had a similar course load for my last two semesters of UG. I ended up having an exam every week once things picked up, which is how it is at my dental school. It wasn't too difficult, just make sure you manage your time wisely and you will get the grades you want.
You only have one exam a week in dental school? Holy crap, that would be awesome.