Verhandlungen des XInternationalen medicinischen congresses, Berlin, 1890 . it is defective. 6. The gums not affected. V. Anterior protrusion due to extraction of posterior teeth. When all the teeth of the upper and lower maxilla posterior tothe bicuspids are lost, in many cases a straggling arrangement andflaring out of the upper teeth occurs, while some or all of the bicus-pids migrate backward. This condition has usually been ascribed tothe pressure of tartar, which by no means is always present. I wishto point out the changes in occlusion that follow the loss of theposterior tee
Verhandlungen des XInternationalen medicinischen congresses, Berlin, 1890 . it is defective. 6. The gums not affected. V. Anterior protrusion due to extraction of posterior teeth. When all the teeth of the upper and lower maxilla posterior tothe bicuspids are lost, in many cases a straggling arrangement andflaring out of the upper teeth occurs, while some or all of the bicus-pids migrate backward. This condition has usually been ascribed tothe pressure of tartar, which by no means is always present. I wishto point out the changes in occlusion that follow the loss of theposterior teeth and to show the results that must follow from changeof function and shape of the teeth. It is generally known that where the posterior teeth are lostfor some time without the introduction of an artificial denture, thelower jaw gradually approaches the upper near the angle. This isdue to several causes. When the posterior teeth were in position theforce of mastication was distributed over the entire extent of thearches, keeping them nearly parallel to each other; now the force is. Fig. 5. spent on the anterior column alone which is forced to perform thedouble function of cutting and grinding. The grinding, or rathercrushing, of food now done by the incisors introduces a new form ofantero-posterior motion exerted by the cutting edges of the lower in-cisors against the basilar ridge of the upper, extending pressure backwhich forces the incisors forward. This tendency is increased by theform and action of the bicuspids. The two wedgelike cusps of theircrowns direct the force of mastication not only downward, but forwardand backward, forcing these cusps between the crowns of their anta-gonists which can not resist their action when not fortified by the X. intern, med. Congr. zu Berlin 1890. Abtheil. XIV. g 114 Abtheilung XIV: Zahnheilkunde. crowns of adjoining molars. The bicuspids are also forced intothe jaw. T\Then the first molars are lost, the force of the second lowermolar b
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