File:Principles and practice of operative dentistry (1920) (14595745279).jpg

Identifier: principlespracti1920mars (find matches)
Title: Principles and practice of operative dentistry
Year: 1920 (1920s)
Authors: Marshall, John Sayre, 1846-1922
Subjects: Dentistry, Operative
Publisher: Philadelphia and London, J.B. Lippincott
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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f its creation, but which is to gradually give place to astronger and more enduring counterpart of itself. Pathology, we aretaught to believe, is perverted physiology ; but just where normal func-tion ceases and morbid conditions begin science has not as yet been ableto demonstrate. The accompanying diagram (Fig. 225, page 87), drawnby Professor C. K. Peirce, most admirably illustrates the periods at whichcalcification takes place in the deciduous and the permanent teeth, andalso the decalcification or resorption of the roots of the deciduous teeth. ERUPTION OF THE PERMANENT TEETH. Normal secondary or permanent dentition begins at about the sixth yearby the eruption of the first molars, which take position directly behindthe second deciduous molars, the growth of the jaws having made thispossible by increasing the distance between the second deciduous molarand the ascending ramus in the lower jaw, and between the same tooth andthe tuberosity in the upper jaw. ERUPTION OF THE TEETH. 87
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88 OPERATIVE DENTISTRY. The growth of the jaws, which keeps pace with the eruption of thepermanent teeth, is mainly confined to an elongation of the horizontalramus of the lower jaw between the second deciduous molar and the angle.There is, however, a certain amount of growth taking place at the sym-physis menti, and in the upper jaw at the mediau and intermaxillarysutures, and also in the interstitial substance of the jaws. This statement is corroborated by the fact that as the period of seconddentition approaches, spaces appear between the deciduous teeth whichgradually widen until the primary teeth are exuviated. The widest spacein the lower jaw is between the central incisors, while in the upper jaw itis between the central incisors and between the lateral incisors and cus-pids. Nature thus beautifully provides for the increase in the numberand of the size of the succeeding teeth by arranging the growth of thejaws in harmony withthe space required for a normal arrangement of thein

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