APEX
The instrument in the canal, carried down by the slidePremolar sectioned through its canal, 5:1Inflamed pulp; past the apex on the locatorThe tooth is cut through its long axis so the canal shows on the face. Access opens the pulp chamber; an apex locator reads 0.0 when a #10 file reaches the apical constriction, which sets the working length (22.1 mm from the cavity rim here). Files from 15/.02 to 40/.06 cut the canal to a tapered shape, sodium hypochlorite dissolves the remaining tissue, and a gutta-percha cone with sealer, compacted with heat, seals it from the constriction to the orifice. A core and crown close the tooth, and over the following months bone fills the apical lesion.