Effect of different storage methods on the performance of dental local anaesthetic cartridges

Self-aspirating dental local anaesthetic syringe systems rely on deformation of rubber diaphragms contained in the anaesthetic cartridges to produce the aspirating force. A test has been developed which can examine the performance of these rubber diaphragms under functional conditions. This method could be useful in the production of standards for dental local anaesthetic cartridges. The test has been used to determine the influence of storage conditions on the performance of dental local anaesthetic cartridges. The results show that, with the cartridges investigated, storage at 37 degrees C increased the amount of distortion per unit force of the aspirating diaphragms in comparison with storage at room temperature. However recovery of the diaphragms was unaffected. Storage at the higher temperature decreased the amount of force required to initiate movement of the cartridge rubber bung during injection. Soaking cartridges in alcohol did not affect the distortion of the aspirating diaphragms or the force needed to move the bung during injection, but did increase the degree of recovery of the diaphragm in the bung of self-aspirating cartridges.