Needle-free Dental Anesthesia: a Pilot Split-mouth Cross-over Randomized Clinical Trial.

Many patients experience pain and anxiety from traditional needle anesthesia and may avoid necessary dental treatments. The needle-free liquid jet injection(NFLJI) could solve these problems. NFLJI delivers drug solutions by creating a micro-thin pressure liquid jet to penetrate the skin and disperse in the soft tissue. It has many advantages like eliminating injection pain, needle phobia and needle disposal. However, anesthesia techniques in dentistry were all developed for needle injection, and they are not very effective for NFLJI. Moreover, clinical trials of dental anesthesia using NFLJI have shown inconsistent efficacy.

In this study, we aim to compare the clinical efficacy between NFLJI and needle dental anesthesia in pilot split-mouth cross-over randomized clinical trials, assess the feasibility to conduct such trial on a larger scale.

Participants will be assigned to one of the following four groups: 1. Infiltration on a maxillary lateral incisor,2. Inferior alveolar nerve block, 3.Mental nerve block, 4. Infraorbital nerve block. Each participant will receive one injection with a needle and another one with NFLJI randomly at the same appointment. A washout period of 1 hour between two procedures for participants' to forget the previous experience. Needle injection will be performed according to clinical standards. NFLJI will be performed according to a guideline developed in our research group. Participants will stay in the clinic until the anesthesia effect disappear and be followed for one week.

The primary outcome is the efficacy and effect of two anesthesia interventions. The secondary outcome is the pain and anxiety visual analogue scale before and during injection, taste preference, and complications. Additionally, patients' overall feelings for two interventions as well as any barriers to conducting such a trial will be recorded.