Comments, especially on this site, are intended to
- Request clarification from the author;
- Leave constructive criticism that guides the author in improving the post;
- Add relevant but minor or transient information to a post (e.g. a link to a related question, or an alert to the author that the question has been updated).
Your comment (a snarky (sorry) prediction of what would happen to the OP's tooth) was none of those, and was, in my opinion, an attempt to answer the question (incorporating measures the OP's asked about to help restore his tooth) without bothering with a reference:
Just as an aside, with nothing protecting that hole in your tooth, I predict you will soon lose the tooth (and possibly more) from the decay that is guaranteed to happen to a tooth with an unprotected hole in it. I predict this will happen regardless of your diet, vitamins, acidity of your mouth, or much of anything else you can do other than filling that hole or removing the tooth. – Carey Gregory
Comments aren't supposed to answer the questions, however tangential the comment may be.
Users can, however, learn by reading the "Please avoid answering in comments" comment that the general expectation on this site is to answer a question with references or not at all.
This has been discussed not only by the mods on the site, but in meta as well on more than one occasion:
You answered that latter question, stating your opinion which relied rather heavily on the comment possibly being the only answer the OP gets.
Clearly, this was not the case here. The OP has an answer with references. As such, your comment does not contribute anything the OP was asking about.
If you want to revisit the discussion of comments as answers, you can re-pose that question, but my opinion (based on what we have in meta already) is that the community favors not answering in comments, which is supported by the CMs. Before you do that, though, I would recommend that you revisit the SE position on comments (When shouldn't I comment?) and remember they are, on all sites, evanescent and subject to deletion by the mods.