Aspiration in intra-ligamental anaesthesia of lower first molar teeth: a pilot study.

This pilot prospective, randomised, crossover study of positive aspiration frequency in intra-ligamental anaesthesia (ILA) was conducted with the following aims: (1) to determine the frequency of positive aspiration of blood after the administration of ILA at lower first molars, and (2) to evaluate the depth of the pulpal anaesthesia of lower first molars after positive or negative aspiration of blood, using electro-testing. Intra-ligamental anaesthesia with 4% articaine with epinephrine was administered to the lower first molars of 36 dental student participants. Pulpal analgesia of these 36 molars (17 left and 19 right) was obtained after 114 intra-ligamental insertions, with 3.2 insertions on average, with the help of a computer syringe. The depth of pulpal analgesia after each insertion administration was assessed with electro-testing. A total of 114 intra-ligamental needle insertions were administered, of which 44 led to pulpal analgesia. After up to five administrations of ILA, all 36 molars achieved pulpal analgesia. In 34 of 36 (94.4%) subjects, ILA was accompanied by a positive aspiration test (AT). In the other two cases, successful but slow onset pulpal analgesia was obtained after five intra-ligamental needle insertions but with negative ATs. For the first time, the aspiration of blood after the administration of ILA has been studied. The frequency of positive aspiration of blood and successful pulpal analgesia was 94%. There was a very strong association between positive aspiration of blood after ILA and good pulpal analgesia. When there was negative aspiration of blood after the administration of an ILA, in rare cases pulpal analgesia developed after a delay of 3-5 minutes.