The Dental cosmos . se of the conical shape ofroots. Of course in a dry mouth any tendency to leakage caused bya loosely-binding dam may be, and usually is, overcome by the liga-ture. In the case above described, where there was barely room forthe silk above the border of the cavity, the ligature itself operatedagainst the discovery of the cause of leakage, while it in no way pre-vented the excessive moisture from creeping under it, and immediatelyupon the gold. Another cause of leakage is seen in Fig. 56, which shows the damover two teeth whose crowns are omitted in order that the points ofle
The Dental cosmos . se of the conical shape ofroots. Of course in a dry mouth any tendency to leakage caused bya loosely-binding dam may be, and usually is, overcome by the liga-ture. In the case above described, where there was barely room forthe silk above the border of the cavity, the ligature itself operatedagainst the discovery of the cause of leakage, while it in no way pre-vented the excessive moisture from creeping under it, and immediatelyupon the gold. Another cause of leakage is seen in Fig. 56, which shows the damover two teeth whose crowns are omitted in order that the points ofleakage, a, may be more readily seen. Here the fault has not beenthat the holes were made too large, but insufficient space was left be-tween them, and the stretching necessary to place the dam over twoteeth has produced a space next to each, as pictured. Of course thismay be avoided by proper spacing. In the next diagram, however,Fig. 57, is shown a similar difficulty arising from a different cause. Fig. 56. Fig. Here a section through the teeth near the gum-line discloses a distinctconcavity along the approximal surfaces. The dam stretched oversuch a tooth must follow a straight line from the points 6, &, so that aspace is unavoidably left. The question arises, Can the dam be placedhere so as to avoid leakage ? Moisture cannot be kept out by thedam alone, but, the condition being recognized, a roll of cotton dippedin sandarac varnish should be packed along the leak ; then a ligatureshould be knotted so as to present three or four knots, which shouldbe placed over the cotton and the silk then firmly tied around theneck of the tooth. In a. few moments all leakage ceases. Another occasional source of leakage is where, in placing the damso as to include a molar, the edge is not forced between the teeth atthe posterior border of the molar. The clamp is placed, and all seemswell, but in a wet mouth moisture will inevitably creep in. Indeed,there are many instances where leakage
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