There is not a lot of evidence but what evidence there is suggests that abx don;t work to treat the infection or the pain so I don't do it. If they have something to drain I drain it, otherwise I send them to a dentist with pain control. Pubmed search: ("dental pain" or "dentalgia") AND antibiotics
Let me make a couple comments on the abstracts you linked, but only for the sake of clarification.
Over 1/3 of the patient pool are unaccounted for in the results of this study. In my [empirical and entirely non-evidence-based] opinion, I suspect this group draws disproportionately heavily from the experimental group compared to the placebo. If the full text indicates otherwise, I'll rescind the objection, but as it stands I don't think these results are as compelling as the abstract suggests.
This study is about *preventing* periapical disease, not treating it. It makes no distinction between different states of pulpal & periapical disease, which makes all the difference in the world. I don't give antibiotics unless I have a confident clinical diagnosis of acute periapical disease (as opposed to inflammation/necrosis confined within the tooth).
Again, this study is investigating relationships between antibiotics and pulpal inflammation, not periapical disease.
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Just like anywhere else, the key lies in properly diagnosing the problem before jumping forward to treatment decisions. I don't believe, by any stretch of the imagination, that every toothache warrants antibiotics. Even when they are indicated, they're adjunctive only, to provide symptomatic relief until the tooth can be appropriately treated via endodontics or extraction. In that limited capacity, however, they're invaluable for the temporary relief they can provide.
In short--I do it because it works. Bartleby is right that pen works just fine for your run-of-the-mill oral infections. I usually give 12 vicodin 1q4 along with 21 amoxicillin 500 1q8 (for no better reason than that q4/q8 dosing is easier than q4/q6 with pen VK). It's not evidence-based, and I don't begrudge you your approach to managing dental complaints, but I'm equally comfortable with my own. Sorry if I came on a little strong in my first post to this thread.