The Application of Needle-free Device on Dental Anesthesia

Objectives: Many patients experience pain and anxiety from conventional dental anesthesia with needles and thus may avoid necessary dental treatments. These problems could be solved by a needle-free device. It works by creating a micro-thin, high-speed liquid jet to penetrate the skin and disperse in the soft tissue. Needle-free device can provide better local anesthesia treatment with many advantages like eliminating injection pain, needle phobia, and needle disposal. It can also reduce drug volume and increase drug diffusion. All these advantages could benefit both patients and clinicians.
However, anesthesia techniques in dentistry were all developed for needle injection and not effective for needle-free injection. There is a lack of guideline for needle-free dental anesthesia. In this study, a series of in-vitro experiments were designed to understand the mechanism and optimize the dental anesthesia technique for the needle-free device.
Methods: On human tissue mimicking phantom materials, needle-free injection tests were performed to investigate the relationship between penetration depth and settings (pressure/volume/etc.) of the device. Based on the investigation, injections were performed at different anesthesia sites of 14 cadavers. Different techniques were developed and validated by dissections to find the optimal and reproducible techniques.
Results: The result shows that needle-free devices could provide sufficient injection depth of 1-2 cm for both infiltration and nerve block anesthesia in oral cavities. On 14 cadavers, the mental, palatine, infraorbital and mandibular inferior alveolar nerve could be successfully blocked with the newly developed needle-free injection techniques.
Conclusions: This study sets the basis of how to use the needle-free device in the dental clinic in the future, to benefit both patients and clinicians. New optimal infiltration and nerve block anesthesia techniques for the needle-free device are proposed, which could overcome the existing problems. Further clinical studies are needed to confirm the efficacy of new anesthesia techniques.