This section is from the book "Dental Medicine. A Manual Of Dental Materia Medica And Therapeutics", by Ferdinand J. S. Gorgas. Also available from Amazon: Dental Medicine.
Astringents are medicinal agents which produce contraction of the tissues, having a corrugating power, either directly exerted on a part, or extended by sympathetic action, and thus removing morbid affections arising from a state of relaxation, such as inflammation of superficial parts, hemorrhage and excessive discharges from mucous membranes. This class of remedies is important in dental practice, owing to their great efficacy as an-tiphlogistics. Astringents are divided into vegetable and mineral, the former owing their peculiar property of astringency to the presence of tannic acid, while the latter possess a more decided astringency, and exert a sedative action on the vascular system. In the treatment of affections of the mucous membrane, such as stomatitis, the object is to arrest the inflammatory action, which is accomplished by the power of the astringent remedies employed locally to increase the tonicity of the tissue, and to diminish the calibre of the vessels supplying the part with blood, thus diminishing the quantity required for the production of the morbid action. Besides diminishing the current of the blood to the inflamed part, astringents also exert an influence on the pores or ducts through which the discharge is poured out, by diminishing their calibre. Astringents also exert an influence on morbidly relaxed tissues, when such a condition results as the sequelae of disease, especially in lymphatic temperaments, where flabbiness of the soft tissues is characteristic.
Care, however, is necessary in the use of astringents, for when long or immoderately used they may act as direct irritants, inducing inflammation followed by ulceration and sloughing. They are contraindicated for the arrest of evacuations that are designated by nature to relieve a plethoric state of the system, unless such evacuations exist to an alarming extent. This class of remedies can be readily detected by the taste, as they convey a sense of roughness to the palate which cannot be mistaken, and which is more marked in some substances than in others. Such agents as tannic acid, gallic acid, nutgall, matico, kino, catechu, 6 rhatany, white oak bark, creasote, salicylic acid, are examples of the vegetable astringents; while the preparations of iron and lead, alum, sulphuric and nitric acids are examples of the mineral astringents. (See Styptics.)