A system of dental surgery / by Sir John Tomes.

  • John Tomes
Date:
1887
Catalogue details

Licence: Public Domain Mark

Credit: A system of dental surgery / by Sir John Tomes. Source: Wellcome Collection.

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    than at its more external boundaiy ; but no sooner does the crown leave the socket, than the relative dimensions reverse themselves. The base contracts, bv the develop- ment of new bone, to the dimensions of the root. The level of the socket is not, however, at present clianged. If the comparison of the two subjects be continued, it will be seen that altliough the length of the ascending rami has considerably increased in the older jaw, yet that the angle formed by the two portions remains pretty much the same. Forty Months.—If we now pass to maxillse from a subject forty months old, it will be seen that the whole of the tem- pOTary teeth have taken their normal position in the jaws, and appear complete ; but if the roots arc examined, the inaccuracy of this conclusion will be discovered. The incisors are the only teeth in which the fangs arc completely foimed. The canines arc destitute of about one-third, the tir.st tempo- rary molars of a fifth, and the second temporary molars of at least one-half, of their normal length. At this period a change takes place in the form of the jaw, and it may be regarded as the second epoch, at which this bone shows a more rapid rate of development. It was stated that within two months subsequent to birth, tlie angle of the lower maxilla became less obtuse ; and in tracing the same point in jaws of progressive ages, it may be seen that but little further change takes place in respect to the angle until the subject arrives at the third year. But at tliis age a manifest alteration may be observed. If a line be drawn along the alveolar margin, and across the ascending ramus, it will be seen that the angle formed by this line and the latter part is between fifty and sixty degrees; and that the articular and coronoid pi-ocesses rise high above the alveolar lino. It is important to observe how the angle has been diminished, as the recog- nition of this process of change will to a considerable extent elucidate the manner in which the adult form is reduced to that assumed by the jaw in advanced age. At the time of birth, the sockets arc not deeper than the partially
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