A variation in the sequence of dentition is most commonly associ ated with rickets. Occasionally, the upper incisors appear before the lower; sometimes the upper lateral incisors appear first; very rarely the canines pierce the gums before the molars.
Changes in the Shope of the Teeth as a Symptom of Certain General Diseases.—It is obvious that severe diseased conditions, which advance with a profound disturbance of nutrition, may affect the substance of the teeth, particularly- when the osseous system forms the chief tissue affected. It follows that in the course of rachitis, or as a feature of a post-rachitic process various abnormalities in the shape of the teeth may be observed. Even excepting the fact that the abnor mal growth of the jaw bones causes a crowding of the teeth in rachitic children, the permanent incisors in individuals who suffered from rickets previously, are subject to ridges, grooves, and erosions soon after their eruption. This deficient development of the permanent teeth probably depends on changes produced in the dental germ by the rachitic process during the first years of life.
The so-called rachilic teeth are by no means a reliable sign of a previous rickets, as there are persons whose extremities show a former rachitis and yet possess faultless teeth. Local diseases of the teeth may produce imperfections in persons who IleVET had rickets. These deformities of the teeth then, can be utilized as a corroborative sign of a previous rachitis only when other evidences of this disease are present.
Hutchinson's teeth, to which a special diagnostic value in hereditary syphilis has been attributed by that author (Hutchinson's triad), are similar in their nature, but differ in form and loealization. The deform ity consists in a sentilunar excavation of both upper central incisors. The diagnostic value of this anomaly has been shattered in a great measure by very careful observers for reasons similar to those men tioned above.
It is the special merit of Neumann to have emphasized the rela tionship of circular caries and the circular adherent deposits at the neck of the milk teeth to serophulo-tuberculosis. Circular caries, which
may affect the tooth at any time after its eruption, is located immedi ately at the junction of the tooth and gum, and, therefore, attacks that part of the tooth nearest to the gmn. This caries is preceded by a greenish or brownish discoloration of that part of the tooth, which, bow shaped, follows the line of the gum at first, but soon becomes larger. The onset of the caries is revealed by the loss of the shining surface and in place of this a rough chalky appearance is noticed, which is easily seen when the tooth is dry. Then the enamel crumbles off and when the dentine is exposed, the caries rapidly penetrates the tooth at its neck and leaves a circular groove. It may happen that the healthy distal part of the tooth may be entirely separated from the root by this circular caries.
If the caries attacks a tooth before its eruption is complete and then grows ott, it is clear that the carious ring may not he at the neck but in some place near the middle of the tooth, which indicates the earlier location of the gums. The earlier the caries begins the smaller is the healthy part of the tooth. The distal end which is almos.t separated may break off and leaves a very. pointed stump.
As a rule, the upper central incisors are attacked first, then the lateral and the molars, occasionally also the canines (Meyer), while the lower teeth generally are spared. The green coating of the tooth is not a deposit, but is incorporated in the enamel and can only. be removed with the latter.
The statistical collection of Neumann indicates that scrophulo tuberculous children show this affection chiefly and Meyer (in Heubner's Polyclinic) has corroborated this discovery-.
The process is not. a specific expression of tuberculosis, but rathe.r a consequence of the associated disturbance of nutrition.
The onset of the caries is attributed to an acid fermentation of the mucus in the mouth (Neumann).