It won't really make a difference if it is a regular 2 years MS or a SMP, same with thesis vs. non-thesis. What really matters are the numbers at the end of it... your GPA.
To be brutally honest a 2.75 is very low... and even if you did a 1 yr SMP ~ 30 credits and got a 4.0, it would still bring you up to only a 3.0, which is still very low for dental admissions. You also have to consider how they calculate your GPA's. You will have an undergrad GPA and a Masters GPA, then an overall. Even if you have a 4.0 with your SMP, you will still have a 2.75 undergrad GPA, which is not only a red flag, but also might be below some schools cutoffs, which equals automatic rejection.
I think personally you should do a year of upper division informal postbac and then go from there. To be honest, you really need to look deep inside yourself and see if you are even capable of achieving A's in upper division sciences... and not just 2 or 3... you need to take 4-5 a semester. B's will simply not cut it and raise your GPA enough... do you have what it takes?
After the 1 year of postbac, you will have a 3.0, which may be enough. If not you can then do a 1 year SMP, but either way you need to get your undergrad GPA up.
Best of luck!!!