Comparative study of different syringes in positive aspiration during inferior alveolar nerve block

The purpose of this study was to evaluate the detection of intravascular injection or hematic aspiration in relation to (a) the particular combination of syringe system and needle (there being 3 different syringe systems [2 self-aspirating and 1 non-self-aspirating] and 3 different needles); (b) the anesthetic technique used (direct or indirect) to induce inferior alveolar nerve block; (c) patient sex; and (d) the operator performing the block.

Two operators performed 246 inferior alveolar nerve blocks (on 90 male and 156 female patients) using 3 syringe systems (1 non-self-aspirating (Uniject K) and 2 self-aspirating (Aspiject and Inibsaject)) and 3 types of needle in terms of length and gauge combination (30G/25 mm, 27G/25 mm, and 27G/35 mm) for conventional and surgical extractions of lower third molars. Three aspirations were made at each of 3 different times in each block. Hematic aspiration was accepted only if a blood jet rose forcefully along the cartridge on aspiration. In each block, the age and sex of the patient was recorded, along with the latency or time elapsed from introduction of the anesthetic solution to onset of the anesthetic effect, the depth of the needle at contact with the mandibular ramus, and the operator performing the block.

Significant differences (P <.05) were observed with respect to hematic aspiration and the syringe system used, the Uniject K system yielding higher percentage hematic aspirations (5.69%) than either of the self-aspirating systems, Inibsaject (2.03%) and Aspiject (1. 21%). However, no significant differences (P >.05) were observed with respect to number of aspirations, needle length, needle gauge, anesthetic technique performed, patient's sex, or operator performing the inferior alveolar nerve block. The incidence of hematic aspirations was 8.9%. The mean latency time was 39.03 seconds, and the mean needle depth at contact with the mandibular ramus was 20.72 mm.

The Uniject K non-self-aspirating syringe system was associated with a higher number of hematic aspirations than the self-aspirating systems (Inibsaject and Aspiject). However, the detection of hematic aspirations was not dependent on length or gauge of the needles used, anesthetic technique performed (direct or indirect), patient's sex, or operator who performed the block.