Comparison of Transcutaneous Electrical Nerve Stimulation and Cold-vibration Distraction on Pain Perception during Local Anesthesia in Children: A Randomized Controlled Trial

Abstract

Aim

Minimizing discomfort during administration of local anesthetics is crucial in pediatric dentistry to enhance cooperation and help create a pleasant experience for young patients. Both pharmacological and non-pharmacological strategies are used to reduce injection-related pain. This study aimed to assess and compare the effectiveness of transcutaneous electrical nerve stimulation (TENS) and cold–vibration distraction technique on pain perception during administration of local anesthesia in children.

Materials and methods

Ninety cooperative children aged 5–10 years who required local anesthesia for dental treatment were randomly assigned to three groups: group I (TENS), group II (cold-vibration distraction), and group III (conventional syringe). Pain scores were obtained pre and post-administration of local anesthesia using the Wong–Baker faces and FLACC behavioral pain scales. The collected data were evaluated through descriptive and inferential statistical methods.

Results

All three groups demonstrated an increase in pain scores after local anesthetic administration; however, the increase in scores was significantly lower in group I and group II compared with the conventional syringe group (group III). Among the interventions, group II achieved the highest acceptance from the children and appeared to be the most effective at interrupting pain transmission. No statistically significant difference was found between the outcomes of groups I and II.

Conclusion

Both TENS and the cold-vibration distraction technique were effective in lowering perceived pain associated with local anesthetic injections in pediatric dental patients.

Clinical significance

Integrating TENS or cold-vibration distraction device into pediatric dental care can improve patient comfort, enhance cooperation, and contribute to more positive dental experiences for children.

The study is registered with the Clinical Trial Registry of India (CTRI/2024/08/072603).

Introduction

Managing pain continues to be one of the most prevalent and major challenges faced in dentistry. Although pain frequently drives patients to seek dental care, fear of injections may deter them from undergoing dental treatment. Therefore, effective pain management is essential to reduce patient anxiety, improve compliance, and prevent the avoidance of necessary dental care. Typically, pain control in dentistry relies on blocking nerve impulses by administering local anesthetics near the affected nerves. By preventing depolarization of the nerve fibers, these agents inhibit the transmission of painful stimuli beyond the injection site.¹ Ironically, the injection itself can cause pain, thus undermining the objective of pain relief. Therefore, achieving pain-free delivery of local anesthesia is vital in pediatric patients to enhance child's cooperation and promote a positive dental experience.

Emerging evidence supports the use of non-pharmacological strategies including transcutaneous electrical nerve stimulation (TENS), cryotherapy, and vibration to reduce procedural discomfort. TENS, also known as electronic dental anesthesia, has become a recognized technique of pain control in dentistry. This non-invasive approach employs the delivery of low-voltage electrical currents to the skin through electrodes. This effect is interpreted through the gate control theory of pain, which proposes that non-noxious stimuli can hinder the transmission of pain signals to the central nervous system. Thus, when TENS is applied near the injection site, it has been shown to diminish pain associated with needle insertion. Furthermore, cryotherapy provides an alternative approach for pain control during local anesthesia by temporary nerve blockade and reduced discomfort through mechanisms such as cold-induced neuropraxia, vasoconstriction, and decreased nerve conduction velocity.² Similarly, vibratory stimulation using devices such as DentalVibe and Vibraject operates on the gate control theory, using vibrations to activate inhibitory mechanisms and reduce pain perception during needle insertion.³ Buzzy® (Pain care labs, Atlanta, Georgia), a small, handheld device combining vibration and cold, was developed by Dr Amy Baxter, a pediatrician. Its compact and colorful design is intentionally crafted to appeal to children, resembling a friendly, nonthreatening insect. It was used in this study to assess the effect of cold–vibration distraction on pain perception.

Accurate pain assessment is fundamental in pediatric dentistry, as a child's pain perception significantly shapes their experiences and treatment outcomes. Pain evaluation in children relies primarily on three methods: (1) self-report, (2) behavioral observation, and (3) physiological indicators. These methods tend to show moderate correlation, indicating their assessment of different aspects of pain, such as subjective experience, behavioral distress, and physiological responses.⁴ While physiological markers such as heart rate or blood pressure are frequently used, they are unreliable as they have influence of emotional, social, and health-related factors that produce inconsistent results across individuals. Multiple self-report scales have been developed to make pain assessment accessible for different ages and cognitive abilities. The notion that self-report is the “gold standard” is debated due to potential biases and complexities, as pain is a multidimensional and subjective experience, incorporating sensory, emotional, cognitive, and behavioral components. Reducing it to a single self-reported score oversimplifies this complexity. In addition, the sole use of these pain scales to assess pain perception ignores critical contextual and behavioral indicators and undermines the clinician's judgment.⁵ The same pain score may be interpreted differently by different children. Children's self-reports can also be influenced by cognitive development or fear of consequences, leading to under- or over-reporting of pain. These biases are often unintentional but introduce significant variability and errors. Therefore, relying solely on self-reports may not provide an adequate assessment of pain. An important dimension of pain recognized by Snow et al.⁶ is the behavior. Typically, healthcare professionals observe a patient's behavior to validate or support self-reported pain levels.

Although the individual efficacy of TENS and cold–vibration distraction devices in managing pain in pediatric dentistry is well established, limited research has compared cold–vibration distraction with TENS. Therefore, this study aims to address this gap by evaluating and comparing the effectiveness of these modalities on pain perception during local anesthesia administration.

Materials and Methods

Ethical Clearance

This study was designed as a randomized controlled clinical trial and conducted in the Department of Pediatric and Preventive Dentistry at the Dasmesh Institute of Research and Dental Sciences, Faridkot. Ethical clearance was obtained from the Institutional Review Board. The trial was registered in the Clinical Trial Registry of India (CTRI/2024/08/072603).

Sample Size Calculation

The sample size was calculated using the G*Power Version 3.1.9.6 program developed by Franz Faul at the University of Kiel. Based on the anticipated effect size, a study power of 80%, and a significance level of 5%, a total of 90 children were included, with 30 participants assigned to each of the three groups.

Inclusion Criteria

Children between 5 and 10 years of age, ASA physical status I (good general health), cooperative behavior (Frankl rating 3 or 4), and indication for local anesthesia.

Exclusion Criteria

Medically compromised children or local infection at the injection site, known allergy to anesthetic agents, neurological disorders, or cardiac pacemaker presence, and behavioral/cognitive impairments compromising pain assessment reliability.

Interventions and Pain Assessment

The child was made comfortable in the dental chair, and the procedure was clearly explained to the parent and patient in their preferred language, followed by obtaining written informed consent and assent. Baseline pain assessment was performed using the Wong–Baker Faces Pain Rating Scale (WBFPRS) and the FLACC Behavioral Pain Scale prior to local anesthesia administration. To assess WBFPRS, the child was instructed to select the image corresponding to the discomfort they were experiencing at that time. FLACC was recorded by a trained observer. Patients were then randomly and equally divided into three groups using a computer-generated randomization sequence to ensure unbiased distribution.

Group I (Transcutaneous Electrical Nerve Stimulation Group) (n = 30)

The TENS device (Omron Healthcare, Inc., Japan) was introduced to the child. The working principle of the device, including the vibration and tingling sensations as well as the process of administration of local anesthesia, was explained in simple terms to help the child feel at ease. Electrode pads were placed extraorally over the site where the local anesthetic solution was to be administered. The TENS was turned on, and the intensity was adjusted. After that, local anesthesia was administered (Xicaine, ICPA Health Products Ltd., India) using a 2 mL syringe (Dispovan, 2 mL, 0.55 × 25 mm needle size, Hindustan Healthcare Limited, India) (Fig. 1).

Fig. 1.

Administration of local anesthesia using TENS

Group II (Cold–Vibration Distraction Group) (n = 30)

The device was introduced to the child, and its working as well as the process of local anesthesia administration was explained in simple terms. The device with frozen wings was placed extraorally over the site where the local anesthetic solution was to be administered. After that administration of local anesthesia was done using a 2 mL syringe (Fig. 2).

Fig. 2.

Administration of local anesthesia using cold–vibration distraction

Group III (Conventional Syringe Group) (n = 30)

The process of local anesthesia administration was explained in simple terms to the child. Local anesthesia was then administered using a 2 mL syringe.

After the administration of anesthesia, the child was again asked to select the image from the WBFPRS, and a trained observer recorded the FLACC scores.

Statistical Analysis

The data gathered for the present study were tabulated in Microsoft Excel 2007 and analyzed using SPSS statistical software, version 23.0. The descriptive statistics included mean, standard deviation, frequency, and percentages. The intergroup comparison was performed using one-way ANOVA to determine the differences among groups. The ordinal variables were compared using the chi-square test. The level of significance for the present study was fixed at 5%.

Results

Demographic Data

This study included 90 subjects. Males were more predominantly distributed (72.3%) than females (27.7%). The mean age group was 8.3 ± 1.98 years.

Subjective Pain Perception

The WBFPRS features six facial expressions accompanied by word descriptors and numerical values from 0 to 10. Results of the WBFPRS showed that before local anesthesia administration, subjects of all three groups reported pain scores ranging between scores 0 and 2. While after local anesthesia administration, subjects of group I and group II reported pain scores ranging between scores 0 and 6, while subjects of group III reported higher pain scores (Table 1).

Table 1.

Intergroup comparison of WBFPRS scores observed before and after Local Anesthesia administration in Group I, Group II and Group III

Group (n = 30)	Before local anesthesia administration				After local anesthesia administration
	Score 0	Score 2	p-value	Significance	Score 0	Score 2	Score 4	Score 6	Score 8	Score 10	p-value	Significance
Group I	22	8	0.830	Nonsignificant	4	10	14	2	0	0	0.001	Significant
	73.3%	26.7%			13.3%	33.3%	46.7%	6.7%	0%	0%
Group II	24	6			6	12	11	1	0	0
	80.0%	20.0%			20.0%	40.0%	36.7%	3.3%	0%	0%
Group III	23	7			0	0	1	3	13	13
	76.7%	23.3%			0%	0%	3.3%	10.0%	43.3%	43.3%

Group I: transcutaneous electrical nerve stimulation; group II: Cold–vibration distraction; group III: conventional syringe

Objective Pain Perception

The FLACC scale comprises five categories scored from 0 to 2, yielding a total possible score of 0–10. The mean FLACC value after the local anesthesia administration showed that the least pain was observed in group II (1.80 ± 1.60), followed by group I (3.23 ± 1.94) and group III (9.16 ± 1.23) (Table 2).

Table 2.

Intergroup comparison of FLACC scores observed before and after Local Anesthesia administration in Group I, Group II and Group III

		Before local anesthesia administration			After local anesthesia administration
FLACC	Groups (n = 30)	Mean	Standard deviation	p-value	Mean	Standard deviation	p-value
	Group I	0.333	0.606	0.873 (nonsignificant)	3.233	1.994	0.001 (significant)
	Group II	0.266	0.583		1.800	1.606
	Group III	0.266	0.520		9.166	1.234

Group I: Transcutaneous electrical nerve stimulation; group II: cold–vibration distraction; group III: conventional syringe

Discussion

Pain in a child is a multifaceted experience encompassing sensory, emotional, cognitive, and behavioral components. It is influenced by multiple factors, including developmental stage, sociocultural background, and situational context. Additionally, there is considerable variation in how pain is perceived among different individuals, based on intensity, duration, location, and subjective unpleasantness. Unlike adults, young children—especially toddlers and preschoolers—often struggle to accurately describe their pain, making it challenging for clinicians to assess and manage discomfort effectively. Beyond the physical sensation of pain, children may also experience distress, characterized by fear, anxiety, and behavioral agitation in response to dental treatment. This emotional distress can amplify the perception of pain, creating a cycle of fear and avoidance that negatively impacts future dental visits.⁷

In the present study, TENS and cold-vibration distraction were compared with the conventional technique to evaluate their impact on pain perception during the local anesthesia administration. Ninety cooperative children between 5 and 10 years of age who required local anesthesia for dental treatment were randomly and equally divided into three groups: group I (TENS), group II (cold–vibration distraction), and group III (conventional syringe). Children aged 5 to 10 years were included in this study, as children within this age range are generally cooperative in clinical settings and capable of following instructions. However, they may still exhibit considerable fear or anxiety related to dental procedures, making them an appropriate population for evaluating the effectiveness of pain management techniques. Pain assessment was done using WBFPRS, as it is a widely accepted self-report pain scale for children.⁸ Research has shown that most children aged 3 years and older can use this scale effectively and accurately. Numerous studies in pediatric populations have confirmed its validity and reliability. Furthermore, compared to other pain assessment tools, both children and their parents have shown a preference for scales that use facial expressions depicting different emotions.⁹ Healthcare professionals observe a pediatric patient's behavior to validate or support self-reported pain levels. This is especially true when children's self-report seems exaggerated, minimized, or influenced by emotions or the situation. So, the FLACC observational pain scale was chosen in addition to the WBFPRS. All assessments were recorded by a single observer, who served as the gold standard to prevent any interobserver bias.

The results obtained from the study indicated that pain scores in group III (conventional syringe group) were significantly higher than in both group I (TENS) and group II (cold–vibration distraction). This outcome could be attributed to the pharmacological interventions used in groups I and II. Conversely, the conventional syringe technique lacks any such counter-stimulation, leaving the child more vulnerable to the direct sensation of the needle, which often causes fear and discomfort, especially in pediatric patients. The visual appearance of the syringe, anticipation of pain, and absence of distraction were the likely contributors to the significantly higher pain scores obtained in group III. These results align with Alanazi et al.¹⁰ and Faghihian et al.¹¹ who found that the use of cold and vibration during injections resulted in significantly lower WBFPRS scores compared to conventional injection techniques. Furthermore, Sahithi et al.¹² observed that the use of cold and vibration led to a delayed pain perception following local anesthesia, which was notably more effective than traditional methods. Similarly, Choudhari et al.¹³ reported lower WBFPRS scores for TENS when compared to the conventional injection technique after local anesthesia administration. Although each group experienced an increase in behavioral signs of discomfort, group III showed the most pronounced rise, with significantly higher scores across all five FLACC categories: face, legs, activity, cry, and consolability. This suggested that the children in the conventional syringe group experienced greater behavioral distress compared to those in the intervention groups. Similar results were obtained in a study conducted by Singh et al.,¹⁴ where mean FLACC scores were higher for the conventional group than the cold–vibration group and TENS group. Similarly, in studies conducted by Alanazi et al.¹⁰ and Suohu et al.¹⁵ a notable reduction in FLACC score was observed during the intervention visits where the cold–vibration was used, in comparison to the control visits involving conventional injections. Singh et al.¹⁴ also concluded that TENS and precooling vibration provided superior pain and anxiety control compared to conventional local anesthetic injection methods.

Although the difference in pain scores between group I (TENS) and group II (cold–vibration distraction) was not statistically significant, the cold–vibration distraction device demonstrated the lowest pain scores. This enhanced pain control may be attributed to the synergistic effects of vibration and cooling, which work together to disrupt pain signal transmission. Vibration masks pain signals via sensory nerve stimulation, and cold numbs the skin and reduces the perception of discomfort at the injection site. Additionally, the playful and child-friendly design of the Buzzy® device used for cold–vibration distraction further enhances acceptance among pediatric patients.¹¹

The limitations of this study were that only cooperative children were included; it cannot be generalized to non-cooperative children. Psychological variables and prior dental experiences were not considered. Blinding was impractical for both patients and observers because of the differences in the appearance of the interventions used. Larger and more diverse studies in the future are warranted.

Conclusion

Based on the results of the present study, the following conclusions can be made:

• Transcutaneous electrical nerve stimulation and cold–vibration distraction are both effective, non-invasive methods to minimize pain during local anesthesia administration in pediatric dental patients.

• Additional research is required with larger sample sizes to elucidate these findings.

Clinical Significance

Incorporating alternative pain management techniques such as TENS and cold–vibration distraction into routine pediatric dental practice has the potential to enhance patient comfort, improve cooperation, and promote more positive dental experiences for young patients.

Acknowledgment

None.

Author Contributions

Nishtha Sardana: Conducted the research, data collection, wrote the initial draft of the paper.

Nitika Bajaj and Meenu Bhola: Supervision, manuscript review and final approval.

AI Disclosure

No artificial intelligence (AI)−assisted technologies were used.

Orcid

Nishtha Sardana https://orcid.org/0009-0001-5575-8615

Nitika Bajaj https://orcid.org/0000-0003-2810-7144

Meenu Bhola https://orcid.org/0000-0001-9746-1943

Data Availability

All data generated during this study are included in the manuscript.