Size Doesn’t Matter: Needle Gauge and Injection Pain
Howard E. Strassler, DMD
Schmitt MM, Wahl MJ, Wahl JA, et al. General Dentistry. 2007;55(3):216-217.
Many dentists prefer using smaller gauge (27- or 30-gauge) needles for anesthesia injections, believing that needles with a smaller diameter result in less injection pain than wider-diameter needles. For this study, three dentists in a general practice administered 930 injections to 810 adult patients using 25- and 27-gauge needles for mandibular inferior alveolar block injections and 25-, 27-, and 30-gauge needles for maxillary buccal infiltration or palatal injections. Patients who were blinded as to the needle gauge were asked to rate the injection pain on an 11-point scale (0-10). There was no statistically significant difference in perceived injection pain based on needle gauge when analyzed for injection location (mandibular, maxillary posterior, maxillary anterior, and palatal), injection site, patient gender, treating dentist, or overall. These results indicate that when it comes to injection pain and needle gauge, size does not matter.
This article helps dispel a dental urban legend—that smaller gauge needles are more comfortable when administering dental local anesthesia. At the dental school where he teaches, the author routinely sees the recommendation for the use of a 30-gauge needle for the administration of local anesthesia for infiltration injections so that the patient will be more comfortable. Several studies have demonstrated no difference in pain perception based on needle gauge.1-3 This study corroborates their results, but with a larger number of patients. The researchers used a topical anesthetic administered to the injection site so that there was clinical relevance and to standardize the methodology. Injections were administered and the patients who were blinded to the needle gauge were asked to rate the pain of the injection on an 11-point scale. The clinicians administering the injection were not blinded to the needle gauge because the needle diameter can be perceived by the dentist by appearance and stiffness.
While the selection of needle diameter has often been decided based on patient comfort, this study and others have demonstrated that when topical anesthetic is used, patients cannot perceive a difference. More importantly, the decision to use a specific diameter and length of needle should be based on risk factors to the patient. The goal is to achieve local anesthesia with minimum risks to the patient both safely and effectively. It has been reported that smaller-gauge needles are more likely to break during use and deflect, causing inaccurate injections.4 Also, aspiration with a narrower-gauged needle requires additional pres-sure, leading to an increase in the chance that the harpoon in the anesthetic cartridge stopper becomes dislodged during aspiration. The authors refer to the old adage “size does not matter” as true when it comes to dental needles. Larger-diameter needles have no significant difference in perception by patients as it relates to pain during injection. It is important that a slower injection also be used to increase patient comfort during the administration of local anesthetic agents. Other advantages of large-gauge needles include less chance of needle breakage or deflection and less pressure needed for aspiration.
References1. Hamburg HL. Preliminary study of patient reaction to needle gauge. NY State Dent J. 1972;38:425-428.
2. Farsakian LR, Weine FS. The significance of needle gauge in dental injections. Compend Contin Dent Educ. 1991;12:262-268.
3. Fuller NP, Menke RA, Meyers WJ. Perception of pain to three different intraoral penetrations of needles. J Am Dent Assoc. 1979;99: 822-844.
4. Malamed SF. The needle. In: The Handbook of Local Anesthesia, 4th ed. St Louis: Mosby; 1997:85-90.
Howard E. Strassler, DMD
Professor and Director of Operative Dentistry
Department of Endodontics, Prosthodontics and Operative Dentistry
University of Maryland Dental School, Baltimore, Maryland