Efficacy of Tapered 33-gauge Needle (Nanopass™) for the Penetration Pain

Objectives: It has been thought that the use of thinner needle is effective to overcome injection pain during dental local anesthesia. However there were few studies reported about the quantitative analysis of correlation between the diameter of dental needle and the pain by needle penetrations. Nanopasss™ (TERUMO^®, Tokyo, Japan) is a needle for subcutaneous insulin injection, its property has a 33– gauge needle (ø0.20 mm) with tapering structure to relieve injection pain. We examined about the level of pain produced by 31- (ø0.28mm), 33– (ø0.26mm) gauge dental needle and this tapered 33- gauge needle penetrations. Methods: Approval for this study was obtained from the ethics committee of Nagasaki University. 28 healthy volunteers (23 men, 5 women) aged 23 – 29 years participated. Each of the 28 subjects received needle penetrations to four areas of oral mucosa: inter-dental papilla (U1) and gingivobuccal fold (U2) of upper anterior teeth, inter-dental papilla (M1) and gingivobuccal fold (M2) of mandibular molar region with three kinds of needles. After each penetration, the subject assessed the level of discomfort using a 100-mm VAS with end points “No pain” and “unbearable pain”. Results: The mean of VAS scores was [U1; 55.4, U2; 53.3, M1; 45.8, M2; 37.8] in the penetrations of 31 G ， [U1; 50.5, U2; 48.0, M1; 36.2, M2; 30.8] in 33 G， [U1; 55.1, U2; 48.5, M1; 36.9, M2; 28.6] in Nanopass™ (33G). There were no differences in reported VAS for needle penetrations to same area between 31-, 33- gauge dental needles and Nanopass™. Whereas the significant difference in VAS was reported between U1 and M2 to the penetration by the use of same gauge needle. Conclusion: This results indicates that tapering structure may contribute for pain perception during needle penetration.