Sealing ability of sectional injection thermoplasticized gutta-percha technique with varying distance between needle tip and apical foramen.

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The purpose of this investigation was to evaluate the influence of the distance of the needle tip from the apical foramen on the apical seal and the length control of the root filling material when thermoplasticized gutta-percha is injected using a sectional injection technique. Ninety-nine human single-rooted mandibular incisors and permanent premolars with straight canals were divided into three equal Groups A, B and C. In Group A the teeth had relatively the wider root canal, in Group C the narrowest, while in Group B root canal size was intermediate. The root canals of all teeth were prepared with a step-back technique. Roots of Group A were instrumented to a Size 70 4 mm short of the working length, while roots of Groups B and C to a Size 70 6 mm and 8 mm short of the working length, respectively. The teeth of all groups were covered with aluminium foil and embedded in acrylic blocks. After the placement of sealer (Roth 811) the root canals of all teeth were obturated with injection-molded thermoplasticized gutta-percha using a three-stage sectional technique. The roots remained in India ink for three days and then cleared by successive immersion in nitric acid, ascending grades of alcohol and finally in xylene. The linear dye penetration and the linear apical underextentionion of the root canal filling were measured by two independent examiners under a stereo microscope. There was no significant difference in the linear dye leakage between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)