The Schilder’s technique of vertical compaction of warm gutta-percha
latter situation and the tip of the cone is of lesser diameter than the apical foramen, once the friction is overcome in the compaction phase the cone will be pushed beyond the apex and will stop only when its body is entrapped by the apical foramen. It is therefore necessary to determine the site of the “tugback”. This can be done by taking another cone of smaller size (less tapered) and gradually shortening it until it also exhibits tug-back. The lengths of the two cones (the first more tapered, for example a medium or .08 taper), the second thinner, for example a fine-medium or .06 taper) are then compared. If the two lengths are identical but the .08 taper cone has a smaller diameter as compared to the .06 taper cone (! 27.17), this means that the .08 taper cone has a lateral, instead of apical, tug-back. In summary, the gutta-percha cone must be shortened so that its apical diameter is of the same size as the apical foramen. For this purpose, the instrument designed by Maillefer and shown in Fig. 27.13 is very useful. The cone should now be fitted to the working length, should have adequate tug back and should be checked radiographically: then, after being shortened about half a millimeter, it is ready for obturation. If the canal was prepared using NiTi instruments systems like ProTaper Gold®, ProTaper Next®, WaveOne® Gold, TruNatomyTM, TRUShape®, and similar ones, the cone fit is much easier and the clinician will choose the
a
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cone corresponding to the taper prepared in the root canal (see ! 27.6). However, the principles are exactly the same: the cone should have an adequate tug-back, should fit slightly short of the working length, and should then reach the apical foramen during compaction, to assure an adequate apical seal of the root canal system.
Radiographic control of the cone fit When the cone has been shown to descend to the desired depth and to have sufficient tug-back, it is reinserted into the canal and a radiograph is obtained. One should not proceed to obturation if the radiograph does not give precise information regarding the position of the cone. Following the radiographic control of the cone, which has been notched with the cotton pliers at the reference point, it is shortened about half a millimeter, then it is placed on the sponge next to the last apical file of the respective canal (! 27.18) and everything is ready for obturation. It is very important to make the radiographic check before shortening the gutta-percha cone, so as to confirm that the tip of the cone is at the right working length, the radiographic terminus of the canal. Only after the radiographic check the cone is shortened, and later in the postoperative radiograph the cone should be back to the previous depth, to confirm that it moved apically to engage the foramen.
b
! 27.18 After radiographic verification of the cone fit, the cones are removed from the root canals and placed on the sponge, each next to the apical files of the respective canal. a) Cones for an upper right first molar. b) Cones for a lower molar.
