No. Just no. I don't think that adding this to this section will be viewed seriously at all and I certainly see it as a poor excuse.
The way I see it, education adversely affected is for actual circumstances that adversely affected your education and are beyond your control (such as being sick with a verifiable medical disease or something of that nature) and not for things like "long commute."
I think commuting is a normal part of anyone's life. You could have chosen to live closer to the school had you wanted to and paid for the living expenses with loans just like most people do.
I get it. I commuted 1-1.5 hrs to get to my campus because I wanted to save money on living expenses, but I'm not about to argue that that "adversely" affected my situation because:
1) Where one lives is a choice and I could have taken out loans to live closer to school
2)Who doesn't have a commute? People in cities commute and take public transportation. People who don't live in cities drive. Everyone commutes. I know a ton of people who have long commutes to school or work. I actually don't know anyone my age who doesn't have a commute, especially since most of my peers live in huge cities and spend lots of time on public transportation because they don't have $$$$$$ to pony up to live in the expensive areas closer to the city center.
I'm just thinking...how is this going to look to the adcom member who commutes 1.5 hrs to his/her dental school to teach and then comes home to read your application where you say you got lower grades one semester due to commuting? I doubt it'll be taken seriously.
If I was that adcom member, I know I would be thinking, "Well, I have a long commute too and I manage to teach and do x, y, and z. How poor are their time management skills that they are unable to balance a courseload with a commute and their activities? Why didn't this person just move closer to campus mid-semester or take some other action to not spread themselves so thinly if the commute was affecting them that badly? What if this person has a 'long' commute during dental school? They will most likely have to commute while attending dental school. Is this an issue that is bound to come up again while they are commuting to dental school?"
See, that last question right there is a killer. You don't want to put anything on your application that could be construed as a negative point that could come up again.
Take ownership of your decisions and your actions. Don't try to use any excuse in the book you think you might get away with, because I'm sure they've seen it all before and can see through it in a fraction of a second.