I know OP wants to apply to American schools, but I need to clarify things about Western University in Canada:
1. If you really want to do dental, your odds are actually better getting into a Canadian school like Western, which takes only 2 of your top years, although you have to average 3.90 in those years to be considered. So start a new degree, and get 4.0's the first 2 and apply during your third year.
Also scoring a 24 (99.9 percentile) is easier said than done.
Still very unlikely, here is why:
One thing I need to mention is that Western will only count one extra year. If you take two, they will average them together, and then take that value and your best year in regular undergrad and average it again.
http://www.schulich.uwo.ca/dentistry/faq#cani_repeat
Example:
Year 1: 2.2
Year 2: 2.3
Year 3: 3.0
Year 4: 3.0
Average= 2.63
Extra year 1= 4.0
Extra year 2: 4.0
Average extra years: 4.0
Average calculated: (3.0+4.0)/2= 3.5 <<<<<<<<3.8 required
I highly doubt you will get 3.8+ even if you get 4.0 in two extra years. So do not bother with Western. Also another thing to consider is that your course load must be full 5.0 credits, otherwise penalties apply. Western uses percentage system as well. So A+= 95%, A= 87% A=82%, B+=78% B= 74.5%, etc.
You need minimum 84.6% to get an interview.
For more info look at the following the link and find the averages by comparing your school with midpoint of scale 3. If you school provides percentages they will use that percentage:
http://www.ouac.on.ca/docs/omsas/c_omsas_b.pdf
Your ECs, recommendation letters and etc do not have any factor whatsoever other than on your interview day if you use them in your answers to the questions:
http://www.schulich.uwo.ca/dentistry/faq#reference_letters
Lastly but not least, even if you get interview at your score is composed of 60% GPA, 15% DAT score, and 25% Interview score. With your GPA, it's impossible to get into western dentistry, unless Seymour Schulich is your uncle.
If you have an extra year left in your undergraduate, you will need 3.8+ with full course load, and then another extra year. Otherwise:
The only thing I can tell you is take another undergraduate degree. Extra years won't cut it. Even graduate programs won't:
http://www.schulich.uwo.ca/dentistry/ddsadmissions#AdmissionsRequirements
Read under competitiveness for that detail.