Practical treatise on the diseases of infancy and childhood / by Thomas Hawkes Tanner.

  • Thomas Hawkes Tanner
Date:
1870
Catalogue details

Licence: Public Domain Mark

Credit: Practical treatise on the diseases of infancy and childhood / by Thomas Hawkes Tanner. Source: Wellcome Collection.

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    number of teeth are not uncommon ; and on the contrary supernu- merary teeth have been observed. 2. Eruption of Temporary Teeth.—The germs or rudi- ments of the teeth appear at a very early period of foetal life, for —according to Serres—Nature works at their formation almost immediately after conception ; so that the jaws of the foetus at the third or fourth month contain—although in a very limited space—the rudiments of all the temporary and many of the perma- nent teeth with which the child and the adult are to be supplied. As the embryo grows, so of course the formation of the teeth progresses pari passu; but at birth none as a general rule have appeared above the gums. When the child, however, is about seven months old, the two central temporary incisors of the lower jaw make their appearance through the gum; being followed, in a week or two, by the corresponding teeth of the upper jaw. In a month or six weeks after the eruption of the central incisors we may expect the lateral incisors to make their appearance; those of the upper jaw being evolved first. About the twelfth or fourteenth month the anterior molars of the under jaw are cut, and shortly afterwards those of the upper maxilla. The canines appear between the sixteenth and twentieth ; and between the twentieth and thirtieth the second milk-molars pass through the gum. Thus, according to this statement, the twenty milk-teeth are complete by the thirtieth month. (Tomes.) Thus it will be seen that the temporary, deciduous, or milk-teeth, are twenty in number—four incisors, two canines, and four molars in each jaw : and that usually they are not all cut until the end of the thirtieth month, or even later,—the whole period during which they are being gradually evolved being known as that of the first dentition. There are some variations in the period of dentition which seem to correspond pretty accurately with certain constitutional peculiari- ties—for instance : in the rickety constitution, the process of denti- tion is always delayed, and it may be altogether arrested for some time. It very commonly happens in a rickety child that the first teeth do not make their appearance till the 18th, and sometimes not till the 24th month. On the other hand, in a tubercular child the first teeth are sometimes cut by the fourth or fifth month, and their subsequent evolution proceeds with great rapidity. Again, in the syphilitic child, contrary to what we might have anticipated perhaps, the teeth are generally cut early and without any difficulty. 3. Eruption of Permanent Teeth.—After the completion of the first dentition at the end. of the thirtieth month, there is generally a pause until between the sixth and seventh years; when stronger organs of mastication being required—the second or permanent teeth begin to make their appearance in the elongated and expanded maxillse. At this period, as Mr. Bell remarks, the jaws contain no less than forty-eight teeth: namely, twenty deciduous—the whole of
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