Like the previous poster said, and as it has been mentioned to me, it's okay to list future dates of research/volunteering if it's a sure thing that you will have completed what you put, i.e. you've already started usually. It's completely up to you though whether you apply before your research is completed or after. I would say it also depends on your goals in dental school and what schools you're applying to. If you end up with good stats and you apply to schools that aren't specifically looking for heavy research experience, then it might not be that critical--such is the case with me. But, if you plan to go into academic dentistry or research-based dentistry or are applying to research-based schools, it might be (almost surely would be) more advantageous for you to apply AFTER you've completed the research so you can expound on that experience in interviews and more in-depth on your application. There's a lot of variables here though, so it's highly subjective depending on the course you plan to take.