One such characteristic is the type of obturation used to seal the chamber and prevent gases escaping through the breech.
12.
Exposure of the obturation material to the oral environment may mean the gutta-percha is contaminated with oral bacteria.
13.
When a cartridge is fired, the internal pressure expands the case to fit the chamber in a process called obturation.
14.
To allow obturation in airguns, pellets use soft alloys in conjunction with a thin, concave base designed to expand more easily.
15.
This required the obturation to be provided by the breech rather than the cartridge case, as is the case in fixed rounds.
16.
A degree of obturation was achieved via a cup on the face of the block being forced into a recessed ring on the chamber face.
17.
The 3D scrubbing effect of the file, combined with the fresh irrigant, result in clean canals, which in turn facilitate better obturation.
18.
Fracturing may be caused by excessive forces placed on the tooth, such as during compaction of gutta-percha during the obturation phase of endodontics.
19.
Finally the de Bange system introduced in 1877 solved the obturation problem with an asbestos pad impregnated with grease which expanded and sealed the breech on firing.
20.
Britain adopted the de Bange breech when it returned to breechloaders in the early 1880s after some initial experiments with the inferior " Armstrong cup " obturation system.
