Do you still have time to pad your sGPA with underwaterbasketweaving-science courses? I'd advise doing so to get it up a little bit higher to 3.5+.
I don't think you should explicitly explain it in your application unless they ask for it. In an interview, you need to gauge the interviewer and provide alternative reasons/responses as to why you may have not performed well. Most interviewers will accept your current reason, as a reasonable explanation. Note that I did not use the word excuse, because you do not want to seem like you are making an excuse. Unfortunately, some dental school interviewers/faculty are not as empathic and/or closer to sociopathic, and you may need to fine tune and anticipate a plan B in explaining your circumstances.