I would enroll in the SMP since it will give you a new graduate GPA. SMP courses will mimic courses you will take in dental school (gross anatomy, histology, neuroanatomy, etc) and will better prepare you. If you do well in these courses, it will show dental schools you would be able to handle their course loads. Some schools will look highly on your graduate GPA because of this and will give you more leeway on your undergrad GPA. Plus, since your science GPA is so low now, it will take several classes of A's to pull it up to a decent level if you stick with undergrad courses.
I agree with the above poster, with GPA that low it is best to start fresh. Although the undergrad GPA will stay with you. However, you can prove to the schools that you are capable of mastering material of higher level courses via SMP.