Painless palatal local anesthetic injection: A low-cost, effective technique

Abstract

Sir, We read with interest the recently published original article by Gazal et al.[1] The authors observe that palatal injections are much more painful than buccal infiltrations. An existing method of overcoming discomfort is to anesthetize the keratinized, tightly-bound palatal mucosal epithelium with a topical anesthetic preparatory to the injection. While options ranging from 2% lignocaine gel, 5% ointment, to 10%–15% topical anesthetic sprays are available for topical use, the operator's limited ability to simultaneously reduce the rate of injection while maneuvering the needle has been cited as a cause for patient discomfort during palatal injections.[2 3 4] The use of computer-controlled injection devices to slow the rate of flow of local anesthetic solution into the tissues is effective in reducing pain on injection. The pump driven extremely slow rate of flow allows for a very comfortable injection experience. Cost of equipment would be a limiting factor in developing economies, especially in modestly equipped outreach centers and satellite clinics. Hence, an alternative is suggested to provide patients at these centers with a less painful injection experience. Conventionally, a disposable syringe with a volume of 2–2.5 mL is often used for injection following aspiration. We tried an insulin syringe instead. The narrow diameter of the insulin syringe implies a marked increase in piston travel to inject the same 1 mL of solution. This is since the volume of a cylinder (πr2 h) is proportional to the square of radius (r) and its height (h). Hence, to maintain volume constant, a small decrease in radius of a syringe must be compensated for by a large increase in its length. A law of hydraulics states that hydraulic piston travel speed (which is constant for the given operator pushing with his/her thumb) equals the ratio of flow rate to piston area. Since the insulin syringe has a narrow diameter and therefore a smaller piston cross-sectional area, flow rate of the local anesthetic solution also reduces for piston travel speed that is quite constant for a particular clinician. We used a narrow, commonly available 1 mL disposable insulin syringe for palatal injections and received favorable feedback from patients about the choice. Although the needle is a narrower gauge, positive aspiration can be demonstrated. Further, the narrow piston diameter reduces the amount of force needed to inject. This allows for more precise control by the operator with the obvious advantage of permitting extremely slow rates of initial injection.[5] This idea has also found favor with clinicians who find that the insulin injection for anterior palatal injections requires less manual effort. While not claiming that this technique is a substitute for a computer-controlled electronic injection device, our method permits almost painless injections, costs very little, is quick to set up, and is appreciated by patients who had palatal injections previously administered with a conventional larger syringe. We recommend this low-cost improvised injection technique in palatal injections to provide the benefit of painless injections at clinics not equipped with computer-controlled injection devices. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.