Custom Fitting Gutta Percha cones with Cold Rolling and the Solvent/Impression Technique
The warm Gutta percha technique is based upon intimate three-dimensional adaptation of the filling material (and sealer) to the canal system. Cone fitting is an essential part of the technique. Fitting cones requires understanding the shape of teh prepard canal and where getting as close adaptation as possible so teh least amount of selaer is used in obturation.
Canal preparations must be performed in keeping with the size and shape of the canal and root. With more conservative canal preparation shapes or in very selnder roots. the preparation may not allow us to use the regular “non-standardized – taper matched gutta percha cone”. This problem is more frequent, now that canal shapes have become more conservative with increasingly flexible Ni-Ti files and emphasis on dentin conservation.
In one scnario, the gutta percha teh less tapered preparation may “hang up” in the cone in the more coronal aspects of the canal preparation, giving you a false sense of “tugback”. (Close inspection of tehecone with a surgical operting microscope will often lead to identification of indentations or striations in the coronal aspect of the cone where it is binding.) If you proceed with obturation in this less than optimally fit cone, you may find that once this “hung up area” is freed as it is warmed, the more apical cold section of the cone will suddenly shoot apically as you pack it, resulting in less than optimal apical fit, sealer excess and and likely “long”gutta percha fill past the apex.
To prevent this and better fit the cone, sometimes the gutta percha cones must be “custom cold rolled” between two glass slabs to make them less tapered and better adapted to teh canal shape. Heavy pressure is applied to the top slab as the desired area of the cone is altered in shape and taper to better correspond to the canal shape.
Contrarily, cases with larger apices, internal resorption, apical bifidities or those in which the standard “tugback” of the Gutta percha cone is not possible, another technique may be used.
Chloroform is used in a 2-second dip technique. (Such a technique was described some years ago by Fava et al in the JOE) The cone is dipped in a small vial of solvent such as chlorofom and then fit into the canal. The cone is inserted and removed a few times in order to take an “impression” of the apical portion of the canal. It is important to remove the excess chloroform by rinsing the cone in alcohol and drying it with an air syringe for a full 30 seconds. Excessive chloroform present in the Gutta percha cone can result in shrinkage of the filling material and loss of Gutta percha integrity. Both of these problems can affect apical seal. The Gutta percha now has initimate adaptatation to the canal walls, so caution must be used when applying sealer. Excessive amounts of sealer can be hydraulically extruded during insertion of the point if too much sealer is used. Pack the case with warm vertical compaction technique as usual. Packing of canals with the warm gutta percha technique should always be done gradually, moving the warmed sections serially down the canal like an elevator.