Is there a Latin idiom for food that is cooked just right (not too much, not too little), similar to the popular Italian phrase "al dente"? I doubt the direct translation denti or ad dentem makes any sense. Perhaps something like apte coctus would work, but I would like to know if there is any attested — or even better, common — phrase for this. Maybe Apicius has something suitable, but I am not familiar with the work.
Pliny NH XV has palati gratia. It's not exactly al dente, of course, but at least it indicates that taste was referred to the palate, rather than the teeth:
oleum ipsum sale vindicatur a pinguitudinis vitio. cortice oleae conciso odorem accipit. medicatio alias ut vino; palati gratia nulla est nec tam numerosa differentia: tribus ut plurimum bonitatibus distat. odor in tenui argutior, et is tamen etiam in optimo brevis.
In the absence of anything better, I think you might justifiably use dentium gratia, though I'd personally prefer your ad dentem. Or you might get a bit nearer with ad morsum.
Apicius regularly gives the word mollis for "cooked until soft", such as in 3.2:
polypodium in tepidam mittes. ubi mollierit, rades, et minutum cum pipere et cumino trito in patinam ferventem mittes et uteris.
Parboil polypody root so as to soften them, cut them into small pieces, season with ground pepper and cumin, arrange in a baking dish, finish on the fire and serve.
Given that, I would actually offer the suggestion of mollis fere or paene mollis, "almost soft," as an appropriate description since, especially since, as brianpck points out, talking about teeth here would be anachronistic and a forced idiom.