Assessment of anesthetic properties and pain during needleless jet injection anesthesia: a randomized clinical trial

Abstract Pain due to administration of local anesthetics is the primary reason for patients' fear and anxiety, and various methods are used to minimize it. This study aimed to measure the degree of pain during administration of anesthesia and determine the latency time and duration of pulpal anesthesia using two anesthetic methods in the maxilla. Materials and Methods: A randomized, single-blind, split-mouth clinical trial was conducted with 41 volunteers who required class I restorations in the maxillary first molars. Local anesthesia was administered with a needleless jet injection system (experimental group) or with a carpule syringe (control) using a 30-gauge short needle. The method of anesthesia and laterality of the maxilla were randomized. A pulp electric tester measured the latency time and duration of anesthesia in the second molar. Visual analogue scale (VAS) was used to measure the degree of pain during the anesthetic method. Data were tabulated and then analyzed by a statistician. The t-test was used to analyze the differences between the groups for basal electrical stimulation. Duration of anesthesia and degree of pain were compared using the Mann-Whitney test. A 5% significance level was considered. Results: There was no statistical difference in the basal electrical stimulation threshold (mA) and degree of pain between the two methods of anesthesia (p>0.05). Latency time was 2 minutes for all subjects. The duration of pulpal anesthesia showed no statistical difference (minutes) between the two methods (p<0.001), with a longer duration for the traditional method of anesthesia (median of 40 minutes). Conclusions: The two anesthetics methods did not differ concerning the pain experienced during anesthesia. Latency lasted 2 minutes for all subjects; the traditional infiltration anesthesia resulted in a longer anesthetic duration compared with the needleless jet injection.


Introduction
Fear of pain and anxiety in patients is the most notable reason to avoid dental treatment. Injection of local anesthetics is the most painful phase of a treatment 1 procedure and a significant reason for its premature discontinuation 2 .
There is a relation between anxiety and fear of pain and the actual sensation of pain. Stress induced by anxiety and fear reduces a patient's pain threshold 3 .
Moreover, the sensation of pain further results in increased anxiety, and a cycle is established 1,2 .
The efficacy of local anesthetics and the quality standard in needle manufacturing have improved over time. However, the method administrating local anesthetics has practically remained unchanged. Even currently, it is common to use a needle attached to a non-disposable syringe 4 .
Administrating an anesthetic agent with a traditional syringe causes discomfort during the puncture and injection stages 5 . Incorrect handling of the syringe is a determining factor for pain 6 , which is exacerbated due to excessive pressure on the plunger and rapid injection of large volumes of anesthetic solution 7 .
To minimize the painful sensation during local anesthesia, other methods can be adopted, such as applying topical anesthetics prior to injection 8 , using computerized injection systems 9 , manual controlling the injection speed 10 , and using needleless jet injection systems. A needleless system includes a spring coupled to an apparatus that generates sufficient pressure to 11 push the plunger of the ampoule 12 and makes the anesthetic solution pass through a microorifice at high speed. According to the manufacturer's recommendations, it administers effective local anesthesia with lower anesthetic volumes compared with the traditional anesthesia method 13 .
The absence of a needle in a jet injection can result in a more comfortable experience, as this eliminates the puncture and injection phases 13 , which are considered the most painful steps during traditional anesthesia 5 . This difference is important as approximately one in five adults have phobia of dental anesthesia due to fear of injections, which leads to interruption of dental treatment 14 .
Since there are few studies about the efficacy of jet injection systems in dentistry, the aim of this the clinical trial was to measure and compare the degree of pain, latency times, and pulpal anesthesia duration in both the traditional method of infiltration anesthesia and needleless jet injection during the treatment of maxillary molars, in a split-mouth trial.

Subjects and ethical considerations
A randomized, single-blind, split-mouth clinical trial was performed. Experimental design followed the Consolidated Standards of Reporting Trials (CONSORT) guidelines; the experimental flow chart is shown in
According to the t-test, the basal electrical stimulation threshold did not show any statistical difference between its values measured before administration of anesthesia using the two anesthetic methods   The latency time recorded for the two anesthetic methods was 2 minutes for all subjects.
The Mann-Whitney test showed a significant difference in pulpal anesthesia duration (minutes) between the two methods (p<0.001). The median duration of pulpal anesthesia for the needleless jet injection and traditional infiltration anesthesia was 20.0 and 40.0 minutes, respectively (Figure 4).
No volunteers required additional anesthesia at any stage of the restorative procedure.

Discussion
The need for local dental anesthesia should be determined according to the clinical situation and should be administered with minimal pain sensation 21 .
Pain during dental anesthesia has a negative impact on the patient. In this study, for both anesthetic methods, the median values were within the score range considered to indicate low degree of pain. This is contrary to the results of a study that compared pain levels during anesthesia between the WAND electronic system and the Injex needleless jet injection system; the mean pain was higher for the needleless The needleless jet injection eliminates the puncture and needle insertion phases, which may make injection of the anesthetic less painful. However, the pulpal anesthesia duration reported in our study can be considered insufficient for dental procedures such as endodontic treatment and dental extraction.

Conclusions
The two anesthetics methods did not differ concerning pain experienced during the anesthesia.
The anesthetic latency was 2 minutes for all subjects, and the traditional infiltration anesthesia resulted in a longer anesthetic duration when compared with the needleless jet injection.