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Azerbaycan Saytlari

 »  Home  »  Endodontic Articles 4  »  In vivo performance of the new non-instrumentation technology (NIT) for root canal obturation
In vivo performance of the new non-instrumentation technology (NIT) for root canal obturation
Discussion - References.

In this in vivo study hand instrumented root canals were obturated using the non-instrumental filling technology (NIT) and the results compared to conventionally obturated canals. The NIT-obturation technique will be required for the obturation of canals cleaned with the hydrodynamic method (NIT), should the latter become applicable in vivo . This technique would allow debridement and disinfection of the root canals without the use of traditional endodontic instruments. It does not remove dentine from the canal wall, thus allowing the canals to keep their irregular and often tortuous anatomy. Since it is not possible to obturate canals cleaned by the NIT-technique using traditional techniques, a new method of root canal obturation was required. The concept of this new method was to produce a below ambient pressure within the tooth and thus aspirate sealer into the entire root canal system. It was demonstrated in vitro that a reduced (absolute) pressure of 15 hPa was sufficient to produce radiographically dense root canal obturations (Portmann & Lussi 1994, Lussi et al . 1999b). The present study has demonstrated that it was possible to reach negative pressures lower than 10 hPa in vivo under a routine dental practice setting.
Since the obturation is a purely physical process, it can be assumed that the tightness of the seal in vivo would correspond to the results obtained in vitro . The new filling method allows obturation of complex root canal systems, including lateral canals. It was demonstrated that internal resorptions (Lussi et al . 1997a), C-shaped as well as type-II canals, could be filled completely.
The canals obturated with the new technique were filled to 0.14 mm 0.1 mm short of the apical constriction, when no gutta-percha cones were inserted. The insertion of guttapercha cones is advised in order to facilitate re-entry. The slightly short obturation can be explained using Boyle- Mariotte’s law of the behaviour of gases: given a pressure in the root canals of 8 hPa, an ambient pressure of 1000 hPa and an approximate total volume to be filled of 16 mm 3 for hand instrumented and of 8 mm 3 for NITcleaned root canals (Lussi et al . 1995), the volume under consideration (‘rest-volume’) would become 0.13 mm 3 . The value of 0.13 mm 3 explains why the apical part was not completely filled by the NIT-obturation method alone, i.e. without a gutta-percha point. This volume will be smaller when the root canal system is cleansed with the NIT, because no enlargement of the root canal is carried out.
Hand-instrumented canals usually exhibit a smear layer. We have shown that cleaning with the NIT-method creates no smear layer and that dentine tubules may also account for this ‘rest-volume’.
In fact, previous studies have demonstrated that even dentinal tubules and branches could be filled with the new obturation method (Lussi et al . 1997a). This phenomenon may explain the better seal in vitro , even after artificial ageing of the NIT root-filled teeth (Lussi et al . 1999b, Lussi & Imwinkelried 2000). Tightness of the seal of the obturation is important for long-term success of any root canal treatment. This is even more important, with the NIT-method, since potentially infected dentine is not removed and cutting the nutritional supplies for remaining bacteria is important for the success of the treatment.
Two-dimensional radiographic analysis revealed voids in the filling material, especially in their centre. This could be explained by initial curing of the material beginning at the warmer periphery and in the dentinal tubules drawing unset liquid material from the centre to the outer zones, thus creating voids. The NIT/gutta-percha group had fewer voids and were more extended after the obturation process (Lussi et al . 1997a). This observation may be explained by the very tight and bubble-free obturation combined with the vacuum in the root canal system and the piston effect gutta-percha points.
At the outset, it was not known whether or not the application of such powerful vacuum would produce discomfort or even pain to the patients. It was interesting to note that this was not the case. No patient received local anaesthesia for the obturation procedure and none reported any sensation or discomfort.


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