The Effect of Acupressure at the LI4 Point on Injection Pain of Local Anesthesia: A Randomized Clinical Trial

INTRODUCTION

The injection of local anesthesia remains one of the most painful and stressful steps in dentistry for children. Pain control during dental procedures is a crucial aspect of behavior guidance in pediatric dentistry. If children experience pain during treatment, there is an increased likelihood of developing a negative attitude toward future sessions.^1,2 Previous studies have found that dental injections provoke the most significant negative responses in children; these responses tend to become more pronounced after four or five consecutive injections. ² Therefore, it is essential to minimize pain and discomfort at each appointment.

Several methods have been introduced to reduce dental injection pain in children, which can be divided into two categories:

Pharmacologic methods: These include topical anesthesia, intranasal sprays, and special injection devices.

Acupressure is a subsection of complementary and alternative medicine that originated in ancient China. It shares the same principles as acupuncture. Both practices are based on the activation of acupoints along meridians to balance the flow of energy, known as Qi, in the body. ⁷ Achieving the De-qi is crucial for the success of acupressure or acupuncture treatment and their clinical efficacy. When acupoints are properly activated, patients will experience De-qi. De-qi is a sensation felt during treatments, often described as a dull ache, heaviness, or tingling at the acupoint site, or an electric shock-like sensation through the body.^8,9 Ease of learning, cost-effectiveness, and being needle-free are some of the advantages of acupressure compared to acupuncture. ¹⁰ Acupressure is a needle-free, hand-mediated, and noninvasive method that promotes healing and enhances the patient’s well-being.

The primary focus of acupressure studies is pain control,^11,12 with the LI4 acupoint being one of the most frequently utilized points in this area of research.^13–17 A significant portion of these studies focuses on reducing pain associated with injection or needle entry.^{15,16,18–21} One of the initial studies on reducing pain from local anesthetic injections in pediatric dentistry concluded that acupuncture at the LI4 reduces pain and autonomic distress. ¹⁷ However, few studies have explored the effect of acupressure on injection pain in pediatric dentistry. Therefore, the aim of this study was to investigate the effect of acupressure on dental injection pain in children.

METHODS

Interventions

Acupressure was performed by a single trained individual (qualified by a professor from Beijing University of Chinese Medicine). First, the LI4 (He Gu) point was located on the dorsal surface of the hand, between the first and second metacarpal bones, slightly closer to the second metacarpal (Fig. 1). Our acupressure protocol combined continuous and intermittent methods. First, the acupoint was pressed with the thumb for 2 s, repeated 10 times. Then, continuous pressure was applied for 10 s, with the latter cycle performed at the end. The same process was repeated for the opposing hand. The amount of pressure applied to reach De-qi was adjusted according to each patients’ body size. After acupressure, one postgraduate candidate in pediatric dentistry administered the local anesthesia injection. For all the patients, lidocaine 2% with 1:80,000 epinephrine (EXIR pharmaceutical Co., Iran) was injected with a 27-gauge short needle (Feizteb Co., Iran).

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FIG. 1.

LI4 acupressure point.

In the sham acupressure session, the same acupoint (LI4) was identified, and the same protocol was applied on both hands—2 s of pressure repeated 10 times, followed by 10 s of continuous pressure, with the latter cycle performed at the end. The only difference was the application of light touch on the acupoint without inducing De-qi. Due to the similarity between the two sessions and the patients’ unfamiliarity with acupressure, they were unable to distinguish between real and sham acupressure.

RESULTS

Figure 2 illustrates the study plan based on crossover flow diagram. Statistical analyses were performed on 24 participants (11 boys, 13 girls) with a mean age of 7.16 ± 1.34 years. All follow-up losses were due to the parents’ reluctance to complete the dental treatment. Table 1 shows descriptive data for each scale and each intervention separately. According to the treatment plan, 14 participants received a supraperiosteal injection, while 10 participants received an inferior alveolar nerve block. No participants sustained any harm as a consequence of this study.

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FIG. 2.

Flow diagram of cross-over design.

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Table 1.

Descriptive Data of Pain Scores

Intervention	Mean ± standard deviation	Minimum	Maximum
Acupressure
FLACC	2.67 ± 2.59	0	9
FPS-R	3.17 ± 3.38	0	10
Sham
FLACC	3.54 ± 2.26	0	7
FPS-R	2.92 ± 3.12	0	10

FLACC, Faces, Legs, Activity, Cry, Consolability scale; Faces Pain Scale-Revised.

Based on the Mann–Whitney test, there was no significant difference between the total results of the first and second sessions. Consequently, neither the time effect nor the carry-over effect was significant (p = 0.33).

The WSRT showed that acupressure reduced injection pain compared to sham acupressure as assessed by the FLACC scale, although this reduction was not statistically significant (p = 0.14). According to FPS-R, children reported higher pain levels after acupressure, but the difference was not statistically significant (p = 0.72).

Based on the sensitivity analysis, the p-values at the extreme points were 0.108 and 0.092 for FLACC and 0.103 and 0.082 for FPS-R.

DISCUSSION

The aim of this study was to investigate the effect of acupressure at the LI4 point on the pain from local anesthesia injections in children.

The results indicated that acupressure did not significantly reduce injection pain. Although few studies have investigated the effects of acupuncture or acupressure during dental injections, those have generally demonstrated significant pain reduction. The effectiveness of acupressure, in terms of both type and level of response, in comparison to acupuncture, remains unclear. ²² Therefore, caution should be exercised when extrapolating the findings from acupuncture studies to acupressure.^19,21 In one study, parents stimulated the needles by massage throughout the dental procedure. ¹⁷ This could have distracted children, preventing a proper assessment of the true effects of acupuncture. In this study, we did not perform acupressure during the injection to eliminate any distraction-related effects. Another reason for the difference in our results compared to others is the lack of a uniform protocol regarding acupoint selection, pressure application, and duration of acupressure, as highlighted in Lin’s systematic review. ²³

Contrary to our study, where the injection was administered immediately after acupressure, another study performed the dental injection 15 min after completing acupressure and reported significant pain reduction. ²⁴ One reason for the difference in results between our study and Gurharikar’s is that we did not allow for the 15–20 min needed for endogenous peptide release and its associated effects. This process is an effective mechanism through which acupressure exerts its effects.^22,25 Moreover, the LI4 is located far from the painful area, which may have prevented immediate pain relief through acupressure. ²⁶ Despite this assumption, some studies have reported that acupressure effectively reduced injection pain even when acupoints were distant from the injection area and there was no waiting period for endogenous peptides release.^13,14,26 To examine this hypothesis, further experiments using high-quality study designs are necessary.

In our study, the use of sham acupressure as the comparison group stood out as a key strength, as it played a crucial role in enhancing blinding and ensuring the reliability of our findings. Based on the FPS-R results, pain reports were lower in the sham acupressure group compared with the acupressure group, but this difference was not statistically significant. Other studies have reported that acupressure significantly reduces pain compared to sham acupressure, while also noting a pain-relieving effect of sham acupressure when compared to a control group.^15,19 However, unlike these two studies, our research did not include a control group. As a result, pain perception without any intervention was not measured for each child. This lack of baseline measurement could be a reason for the lack of significance in our results, as observed in Bao’s study. ²⁷ Cloquhoun and Novella believe that acupuncture may have only a placebo effect or that its impact is too small and transient to be clinically significant. ²⁸ The need for further research to determine whether acupressure has a placebo effect is evident.

Another key strength of this study lies in its crossover design, which allows for the individual comparison of confounding factors that influence children’s pain perception, such as age, gender, temperament, cognitive abilities, previous experiences, and parental anxiety.^29–32 One factor that still remains as a confounder is children’s anxiety during each session. Anxiety and pain influence each other mutually: anxiety can lower pain perception thresholds, while increased pain perception can raise anxiety levels. ³³ Furthermore, it appears that anxious patients experience pain for a longer duration. ³⁴ Many studies have reported that acupressure can significantly reduce anxiety level.^22,35–38 Future studies are recommended to use a combination of acupoints related to both pain and anxiety to gain better insight into pain perception.

This study was not without limitations. First, we didn’t have a control group without intervention, which necessitated performing three similar injections on each participant. This design required a longer sampling period, which was impractical within the environment of an educational center due to fixed academic schedules and the restricted availability of participants. Second, the number of individuals who received sham acupressure in the first session was not equal to those who received actual acupressure, which may have affected the validity of our results. Third, a key limitation was participant dropout, mainly due to financial constraints. As our study used a crossover design, only participants who completed both phases could be included in the analysis. Nevertheless, these dropouts did not affect the final conclusion, as the sensitivity analysis remained consistent with the primary results. However, they may still introduce selection bias and limit generalizability. Fourth, although potential performance bias was reduced through measures such as recruiting a single operator and implementing a triple-blind design, the different sensory perception among participants due to the nature of the interventions remained inevitable.

Future research should consider strategies, such as participant compensation, to minimize dropout and address missing data more effectively.

CONCLUSION

This study found no significant difference in pain levels between the acupressure and sham acupressure groups. Consequently, acupressure did not demonstrate a reduction in dental injection pain. Furthermore, research in the field of dentistry, exploring various acupoints, is needed to draw conclusive results.