In my opinion, there is a big difference. First authorship is reserved for someone who puts in the most effort/ time into the project. This person does most of the work and writing. While doing research as a grad student, it made a huge difference in applying for grants, recognition, post docs, and ultimately, a job. But, that is for my previous work as a PhD student. In my dental school interview, they asked a ton about my research. But I did it for over five years, and it is still not complete. I am actually short selling it due to dental school.
As for dental school, it will depend if the school is more research based. But, based on only two months on a project, that is not long at all. My grant proposal took me three months to write. Some of my data collecting took me a year. And here I am in my first year of dental school, I am still doing data analysis and a final write up.
But none-the- less, any authorship will be good for dental admissions. I would recommend trying to manage your time for that first authorship.
Do you know the process it takes to get something published? It will probably take a minimum of five months to get it approved for publication. First you have to find a publication that fits your paper, then you write it in that format, then your PI as to review it and approve it. Then it is sent to three or four reviewers in the field, (which you must find), And all reviewers must agree on your paper. Most of the time the reviewers will kick it back out for a revision. Once done, you have to get it approved by your PI again and resubmitted. If that suffices them, then it goes to the editor. And they may say to do more revisions. It is not uncommon for the process to take six to nine months to publish. Some even longer if they only publish the journal quarterly. I takes a lot of work and time, so you better get started.
hope this helps.