. The Dental cosmos. sive effect of these softtissues and the displacing influence oftheir contact which will give the bestresult. It is well known that in a tem-porary denture in which these portionsextending under the lip are omitted, wecan depend very little on adhesion. () Further, in mouths with little or noalveolar ridge, part of the difficulty inretaining a plate is due to the easy in-gress of air around these margins of theplate. In the mouth with well-definedalveolar ridge, a plate, with no special provision to secure good adhesion saveperfect fit upon the tissues, cannot bedeta
. The Dental cosmos. sive effect of these softtissues and the displacing influence oftheir contact which will give the bestresult. It is well known that in a tem-porary denture in which these portionsextending under the lip are omitted, wecan depend very little on adhesion. () Further, in mouths with little or noalveolar ridge, part of the difficulty inretaining a plate is due to the easy in-gress of air around these margins of theplate. In the mouth with well-definedalveolar ridge, a plate, with no special provision to secure good adhesion saveperfect fit upon the tissues, cannot bedetached by pulling downward on thefront teeth as long as the lips and cheeksare applied to its outer surface, but bydepressing it at the rear, air is admitted,and the plate is readily removed. The vulnerable point for the admis-sion of air is therefore the posteriormargin. To overcome this natural con-dition, it has been proposed that thecontact of this margin be accentuated,that it be arranged to press into the Fig. Cast of upper jaw with almost no alveolarridge. (Am. Text-bk. Pr. Dent.) tissue and displace it slightly. The phi-losophy of this measure is that the elas-ticity of the tissue will cause it to followthe plate margin when the latter isdepressed by the yielding of the tissuesunderlying the front of the plate to pres-sure in the region. The consistence andresistance to pressure of the tissues over-lying the bone vary, and there is alwayssome movement of the plate under pres-sure in consequence of the elasticity ofthe mucous membrane. In some mouths,when the bone has been resorbed exten-sively, there is much soft tissue coveringthe alveolar ridge, and in consequencemuch movement of the plate is the posterior plate margin restsupon the soft tissue, this accentuationof its contact is very desirable. It is TURNER. FULL UPPER PLATE RETENTION. 923 only in the median line along which thehard ridge courses that there is everany difficulty in carrying out this m
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