Pressures produced in vitro during intraligamentary anaesthesia.

An in vitro investigation measured the pressures produced by an Astra type aspirating syringe (modified Sterling) and a pressure syringe (Ligmaject) during periodontal ligament injections. A pressure transducer (0-6.9 MPa) was adapted to record the pressures generated within both syringes, with the output of the transducer connected to a microcomputer. Thirty-five clinicians (male: female ratio 3:2) were instructed in the technique of the periodontal ligament injection and the pressures that they produced from both syringes were recorded. Measurements of both the peak and time averaged pressures were obtained from computer print-outs of the recordings. Significantly higher pressures (P less than 0.01) were produced with the pressure syringe than with the aspirating syringe. It was also found that male operators produced significantly (P less than 0.1) higher pressure with the aspirating syringe, although there was no significant sex difference (P greater than 0.1) between the pressures recorded with the pressure syringe. Recordings from the pressure syringe revealed that either a multiple high pressure technique or a steady pressure technique was used, the former producing significantly (P less than 0.01) higher pressures.