When a tooth becomes livid, Galen deduces from this that the tooth is the seat of a morbid process equivalent to inflammation. Besides, he says, we cannot be surprised that the teeth may be subject to a phlogistic process, when we consider that these, like the soft parts, assimilate nourishment. The teeth, by effect of mastication, are continually worn down, but nutrition repairs the losses, and they, therefore, preserve the same size. But when a tooth from want of its antagonist is consumed but little or not at all by mastication, we see that it grows gradually longer, for the very reason that under such conditions the increase due to nutrition is not counteracted by a corresponding waste. The nutritive process of the teeth may, according to Galen, be altered either by excess or by defect; from which arise morbid conditions, quite different the one from the other. An excess of nutrition produces a phlogistic process analogous to that of the soft parts; a defect of nutrition makes the teeth thin, arid, and weak. The first of these pathological states is met with especially in young men and must be fought against with the ordinary antiphlogistic means, designed to eliminate the excess of humors (evacuant, resolvent, revulsive, and astringent remedies). As to defect of nutrition, this is met with most frequently in old people. It has the effect not only of making the teeth thin, but also of enlarging the alveoli, from which there results a looseness of the teeth more or less noticeable. Against this morbid condition we do not possess, says Galen, any direct remedy; however, it can be combated, up to a certain point, by strengthening the gums with astringent medicaments, so that they may close tightly around the teeth and thus make them firm. Dental caries is produced, according to Galen, by the internal action of acrid and corroding humors, that is, it is produced in the same manner as those cutaneous ulcers which appear without any influence of external causes. The cure must consist in acting upon such vicious humors by means of local or general medicaments according to circumstances and also in strengthening the substance itself of the teeth by the use of astringents and tonic remedies.[182] After these preliminary remarks, Galen gives a minute description of the numerous remedies which, from his own experience and from that of other great doctors, were to be considered useful for the cure of the various affections of the teeth and gums. Against gingivitis and the pains deriving from it, the best remedy, according to Galen, consists in keeping in the mouth the oil of the lentisk moderately warm; noting, however, that such a remedy is the more efficacious the more recently it has been prepared.