Caries, in man and animals, is a consequence of internal and external injuries, and is a gauge of abnormalities of metabolism, terminated or current. The cause of caries is a medico-dental problem of great importance. At the beginning and during the course of caries, hereditary disposition plays a demonstrable part. Caries itself is not hereditary, but capacity of germplasm to react definitely to various influences is inheritable. This reaction of individual persons is different according to their hereditary dispositions. Since the dentition is exposed to many external influences, injuries to it often occur during intrauterine life and after birth, especially in infancy and childhood. A chief factor predisposing to caries is impaired nourishment of pregnant mother and child, especially from lack of vitamins and minerals. Perhaps the hereditary capacity of the organism to acquire materials essential for the growth and functions of the tissues, or to change certain precursors of them, is of the highest importance. Certainly no single injury is decisive in the causation of caries; a complex of interacting influences is operative, among them climate, lodging (microclimate), clothing, overexertion of nerves— numerous factors in our refined and unnatural ways of life.
Capacity of a tooth to resist caries (” resistance “) seems to be due especially to the existence or cooperation of the submicroscopic construction of the hard tissues ; the immuno-biological quality of the individual or his humors ; and the hormonal glands (pluriglandular system), which are impaired and discoOrdinated by the degree of civilization of the individual (domestication of the animal). Effects of bacteria and the course of caries depend on numerous conditions which are only partly known. Bacteria do not cause caries, but are only usufructuaries of an existing situation. The physico-chemical reactions of enamel and dentin depend upon the submicroscopic construction of these tissues—the structure of the organic materials (fibrils) and their inorganic intermixtures (crystals of hydroxylapatite)— as shown by x-ray diagrams by Laue and Debye-Scherrer ; permeability to soft x-rays ; reaction to dilute acids, alkalies, salts and other materials (especially medicaments) ; and hardness of the surface and of ground sections. The degrees of hardness of teeth—different in the human races and animals—cor‑respond to their momentary resistance to caries and to the influence of acids. Hardness varies during the life of the individual—paradentosis, avitaminosis, pregnancy, abuse of medicaments, etc. Resistance to caries weakens when hardness decreases. Growing incisors of rodents show, in polarized light, that nutritional and hormonal injuries greatly influence the submicroscopic construction of the hard tissues.
References: Kampf d. Karies (Zahniirz. Mitteil.), 1938; D. Med. Woch., 1938; Klima und Zivilisation in ihrer Auswirkung auf KOrper und Zahne, 1934 (Verl.Anstalt,Berlin).