Here is the official statement from McIlroy:
"I sincerely apologize the The Honda Classic and PGA Tour for my sudden withdrawal. I have been suffering with a sore wisdom tooth, which is due to come out in the near future. It began bothering me again last night, so I relieved it with Advil. It was very painful again this morning, and I was simply unable to concentrate. It was really bothering me and had begun to affect my playing partners. I came here with every intention of defending my Honda Classic title. Even though the results haven't revealed it, I really felt like I was rounding a corner. This is one of my favorite tournaments of the year and I regret having to make the decision to withdraw, but it was one I had to make."