Relief of palatal injection pain by liposome-encapsulated 2% lignocaine prepared by ultrasonic dental scaler

Injections into the palate are common in dental treatment and are unpleasant for the patient. A liposomal encapsulation technique was developed to improve the efficacy of 2% lignocaine dental injection so that it could be used as a topical anaesthetic. Liposome-encapsulated 2% lignocaine was prepared as needed by sonicating 2% lignocaine hydrochloride dental injection (with 1:100,000 adrenaline) with a lipid mixture using a dental ultrasonic scaler for 1 min. The time to onset and time to take effect were calculated by a pinprick test in the palatal mucosa in 10 normal subjects. In another experiment, the preparation was tested in a further 22 subjects for its pain-relieving effect during a standard palatal injection, and compared with 18% benzocaine/2% tetracaine gel. The results showed that the mean (SD) time to onset and time to take effect of the liposome-encapsulated 2% lignocaine were 39.0 (21.4) and 157.5 (2.3) s, respectively, and the mean (SD) pain score measured on a visual analogue scale (VAS) during injection was 4.1 (2.3) cm. After the application of the gel the corresponding measurement was 4.8 (2.8) cm (p = 0.045). The encapsulation of 2% lignocaine dental injection in liposomes by a dental ultrasonic scaler was effective in improving the efficacy of the anaesthetic for topical application.