Effect of Thermomechanical Stimulation on Pain During IANB Injections

Abstract

Objective

There are very few studies on the use of a thermomechanical device for reducing injection pain in pediatric dentistry, especially for inferior alveolar nerve blocks (IANBs). The purpose of this study was to assess the efficacy of a thermomechanical device (Buzzy, Pain Care Labs) for reducing pain associated with an IANB for pediatric dental patients.

Methods

A total of 30 children, 5 to 8 years of age undergoing bilateral mandibular dental treatment requiring IANBs, were included in this randomized crossover study. The test group received an IANB with the use of the thermomechanical device and the control group received the IANB without the device. The groups were randomized, and the IANB was readministered after a 1-week washout interval. Subjective evaluation of pain was done utilizing the Wong-Baker Faces Pain Rating Scale, and objective evaluation of pain was assessed using the Faces, Leg, Activity, Consolability, Cry (FLACC) scale.

Results

Significant reductions in pain for the objective and subjective measures were noted in the thermomechanical device group (P ≤ .00016). No differences in pain ratings were noted in groups based on treatment sequence.

Conclusions

Less pain was observed when the thermomechanical device (Buzzy) was used during IANB injections vs without the device.

A crucial aspect of pediatric dentistry is the challenge of managing pain and anxiety during dental visits for children.¹ Local anesthetic administration is an essential tool in ensuring successful and comfortable dental procedures. However, the fear of injections and negative experiences can create a barrier to effective pain management and overall dental care.^2,3 Various methods have been investigated to identify the most effective approaches for minimizing pain associated with local anesthesia.⁴

Vibrating devices have generated significant interest in the field of anesthesia for their potential in reducing pain during local anesthetic injections.⁵ These devices operate on the principles of the gate control theory.^6,7 Notable examples such as VibraJect (A. Titan) and DentalVibe (BING Innovations, LLC) have been developed to aid in pain management associated with local anesthetic injections. Despite their promising benefits, it’s important to acknowledge that these vibrating devices do have certain limitations. The use of DentalVibe reduces the tactile sensation of intraoral tissue landmarks, and in cases where the patient’s anterior border of the mandibular ramus is not palpable easily due to either an abundance of tissue coverage or anatomical variations, optimal tip positioning could present a challenge.⁸ The vibratory stimuli of the injection itself with the VibraJect could potentially introduce disruptions to the injection procedure. Furthermore, the visualization of VibraJect in conjunction with a needle might evoke apprehension among children. The comprehensive systematic review by Faghihian et al concluded that DentalVibe did not have a positive impact on alleviating dental injection pain.⁹

Another novel technique used for pain management is precooling of the injection site, which helps in relieving pain and profoundly affects pain management.⁹ Contemporary research highlights the effective utilization of cold therapy combined with vibration to mitigate pain. A novel thermomechanical device (Buzzy, Pain Care Labs), resembling a bee in its design, incorporates the core elements of vibration, cooling, and distraction. Comprised of a central vibrating unit and 2 detachable ice wings, this device is positioned near the local anesthetic injection site and is kept active throughout the injection process.¹⁰ Notably, it has been successfully employed in pediatric settings to manage pain during procedures such as venipuncture¹¹ and immunization,¹² yielding encouraging and promising outcomes. However, according to systematic reviews by Faghihian et al⁹ and Tirupathi et al,¹³ the data is sparse on its application in dentistry.

Only one other study has evaluated the efficacy of the Buzzy system for inferior alveolar nerve blocks (IANBs) in children. However, the previous study did not utilize a split-mouth design, which this study does, adding significant value to our research. Therefore, the primary objective of this study was to determine the effectiveness of the Buzzy thermomechanical device vs conventional topical anesthesia for reducing pain from an IANB in children 5 to 8 years of age.

METHODS

This randomized crossover clinical trial was carried out from January 2022 to January 2023 in the Department of Pediatrics and Preventive Dentistry of Ranjeet Deshmukh Dental College and Research Center after obtaining approval from the Institutional Ethics Committee (IEC; IEC/VSPMDCRC/20/2020). Signed informed consent from the parents along with the child’s consent were obtained.

Inclusion criteria for this study were children aged 5 to 8 years who demonstrated positive or definitely positive behavior according to Frankl’s behavior rating scale¹⁴ during visit 1 for oral prophylaxis/topical fluoride application and who required dental treatment bilaterally in the mandible with an IANB. All participants were not previously exposed to local anesthesia for dentistry. Exclusion criteria consisted of neurobehavioral disorders, chronic illnesses, previous surgeries or hospitalizations, allergies to local anesthetics, infections at the injection site, and previous exposure to local anesthetic injections for dentistry.

The process of randomization employed computer software (GraphPad Software, Dotmatics Version 7) to allocate treatment sequences. Each child was assigned a unique identification code by the software, which was then provided to the children in sealed and numbered envelopes to maintain confidentiality. Investigator 1 performed the enrollment, randomization, and sealing of envelopes for the interventions. Investigator 2, a single operator and second-year postgraduate resident specializing in pediatric dentistry, conducted all local anesthetic injection procedures and dental treatment.

Study participants were equally divided into 2 treatment sequences. For sequence 1, the IANB procedure was conducted without a thermomechanical device in visit 2, followed by a repeat of the IANB procedure with the thermomechanical device on the contralateral side at visit 3. Sequence 2 utilized the reverse of sequence 1. The control group consisted of the IANB procedure being performed without the thermomechanical device while the test group included administration of the IANB with concurrent use of the thermomechanical device.

Clinical Procedure

During visit 1, each potential participant underwent noninvasive dental treatment (e.g., dental prophylaxis or fluoride application) to familiarize the child with the dental environment. Their behavior was evaluated via Frankl’s behavioral rating scale, and the Wong-Baker FACES Pain Rating Scale (WBFPRS)¹⁵ was explained to each child.

During the visits 2 and 3, each study participant received the planned dental care following the standard protocol, which involved IANB administration with or without the thermomechanical device as determined by random allocation. A 1-week washout period was used between visits 2 and 3.

Local Anesthesia: Control Group

After the drying of the mucosal surface using sterile gauze, a 5% lidocaine topical anesthetic ointment (Lignospan-O, Septodont Healthcare India Pvt. Ltd.) was applied at the IANB injection site using a cotton-tip applicator. The ointment was kept in contact with the mucosa for 1 to 2 minutes. The IANB was then administered following the established conventional technique as outlined in the Handbook of Local Anesthesia and utilized 1.7 mL of 2% lidocaine with 1:200,000 epinephrine (Cignoken ADR 2%, Indoco Remedies ltd.) drawn from a multidose vial.¹⁶ The maximum recommended dose of 2% lidocaine with 1:200,000 epinephrine was determined according to the child’s weight, ensuring that it did not surpass the maximum recommended limit of 4.4 mg/kg. The injections were administered at an approximate rate of 1.5 mL/min,³ with an average administration time of nearly 2 minutes. An additional 0.5 mL of the 1.7 mL was utilized for the lingual nerve block.^16–18

Local Anesthesia: Test Group

The thermomechanical device with frozen wings (Buzzy, Pain Care Labs) was introduced to the child by the tell–show–do technique. Subsequently, the device was switched on and positioned extraorally on the ramus for a duration of 2 minutes by an assistant uninvolved with any part of the study evaluations. With the device in place, application of the topical anesthetic and administration of the IANB were performed as in the control group.

Video recording was done during both visits 2 and 3, capturing the period from the child sitting in the dental chair until completion of the local anesthetic injection. The recording was captured using a mobile video recorder, ensuring complete visualization of the child.

Pain experienced upon injection was self-assessed subjectively using the WBFPR scale and objectively utilizing the Faces, Legs, Activity, Cry, Consolability (FLACC) scale based on video recordings by Investigator 2 who was not the part of the clinical procedure. The WBFPR scale is composed of 6 facial expressions, each representing a distinct level of pain intensity along a continuum. These expressions are associated with numerical values ranging from 0 to 10, facilitating a quantifiable depiction of pain severity. The FLACC pain assessment tool encompasses 5 categories of pain-related behaviors: (1) facial expressions; (2) leg movements; (3) overall activity; (4) crying; and (5) ease of consolability. Each of these categories is assigned a score ranging from 0 to 2, resulting in a cumulative score ranging from 0 to 10.

Statistical Analysis

Data entries were recorded using Microsoft Office Excel 2010, and subsequent data analyses were performed employing Statistical Product and Service Solution (SPSS) version 22. Descriptive statistics encompassing mean values with corresponding standard deviations (SD) as well as medians accompanied by interquartile ranges (IQR) were utilized to present the data. In the context of statistical inference, parametric variables such as age were subjected to t-tests to facilitate comparisons between the 2 groups. For categorical data analysis involving frequencies and proportions, the Chi-Square test was applied. For variables that exhibited non-normal distribution characteristics, such as pain scores, nonparametric tests were selected for analysis. Particularly, the Mann-Whitney U test was employed to ascertain disparities in pain scores between the experimental and control groups as well as within the treatment sequences.

An a priori power analysis was performed using SPSS version 22. Using a power of 80%, an alpha error of 5%, and an effect size of 53% for pain scores as reported by Hegde et al³, we calculated the total number of participants to be 30 with 60 IANB injections total (30 IANB in each group).

RESULTS

A total of 30 children were screened, recruited, and enrolled for this study. All 30 children participating in the study completed the planned dental treatment without any instances of refusal or dropouts. Looking at the demographics of the 2 treatment sequences, there were no statistically significant differences in mean age or distribution of sex (Table 1).

Table 1.

Study Demographics According to Treatment Sequence

Characteristics	Groups		P value
	Sequence 1 ( n = 15 )	Sequence 2 ( n = 15 )
Age, mean (SD), y	6.63 (0.84)	6.16 (0.78)	.12a
Sex, No. (%)
Male	9 (60%)	8 (53.33%)	.71b
Female	6 (40%)	7 (46.67%)

^a t-test; ^b Chi-square test.

Comparing the pain scores between groups, the WBFPR scores and the FLACC pain scores were both significantly lower in the test group than the control group (P ≤ .0001 and P = .00016, respectively; Table 2).

Table 2.

Comparison of Pain Scores Between Groups

Pain scale	Groups	Median	IQR (Q1-Q3)	P value
WBFPR score	Test group (n = 30)	2	4 (0–4)	.0001c
	Control group (n = 30)	6	4 (4–8)
FLACC score	Test group (n = 30)	2	3 (1–4)	.00016c
	Control group (n = 30)	5	2 (4–6)

^a Mann-Whitney U-test.

When comparing pain scores between sequences 1 and 2, there were no statistically significant differences noted within the test and control groups for WBFPR or FLACC pain scores (Tables 3 and 4).

Table 3.

Comparison of WBFPR Scores Based on Treatment Sequence

Group	Treatment sequence	Median	IQR (Q1-Q3)	P value
Test	Sequence 1 (n = 15)	2	4 (0–4)	.64c
	Sequence 2 (n = 15)	2	4 (0–4)
Control	Sequence 1 (n = 15)	6	4 (4–8)	.17c
	Sequence 2 (n = 15)	4	2 (4–6)

^a Mann-Whitney U-test.

Table 4.

Comparison of FLACC Pain Scores Based on Treatment Sequence

Group	Treatment sequence	Median	IQR (Q1-Q3)	P value
Test group	Sequence 1 (n = 15)	2	3 (1–4)	.85c
	Sequence 2 (n = 15)	2	4 (1–5)
Control group	Sequence 1 (n = 15)	5	2 (4–6)	.9c
	Sequence 2 (n = 15)	5	2 (4–6)

^c Mann-Whitney U-test.

DISCUSSION

Buzzy, the thermomechanical device used in this study, is a U.S. Food and Drug Administration (FDA) registered, bee-shaped, noninvasive, reusable, inexpensive device with a vibrating base and freezable silicone gel-shaped wings (Figure). This device works on the principles of vibration, cooling, and partial distraction to reduce pain.⁶

Figure.

The Buzzy Thermomechanical Device

Buzzy, the thermomechanical device used in this study, vibrates and has wings that can be frozen to provide a cooling effect.

The vibrational aspect of this thermomechanical device operates based on the principles of the Gate Control Theory. This theory elucidates the transmission of pain signals from the peripheral nervous system to the central nervous system, highlighting the presence of a gating mechanism within the dorsal horn of the spinal cord.⁷ Gate control theory posits that the sensation of a noxious stimuli can be blocked by a non-noxious stimuli carried by nerve fibers that reach the brain before the painful input because those nerve fibers are slower.

Cooling aids in pain management by reducing the conduction speed of signal.⁹ Topical application of ice decreases the activation threshold of tissue nociceptors and the conduction velocity of pain nerve signals, which results in a local anesthetic effect called cold-induced neuropraxia. It also decreases tissue blood flow by causing vasoconstriction which reduces tissue metabolism, oxygen utilization, and inflammation.

The test group (IANB with Buzzy) showed significantly lower WBFPR scores in comparison to the control group (IANB without Buzzy). Our results were consistent with Alanazi⁵ and Bilsin,¹⁹ who also found statistically significant differences in pain scores with the lowest WBFPR scores occurring with use of the thermomechanical device vs the conventional syringe technique in studies with split-mouth designs. The Alanazi study featured bilateral buccal infiltration,⁵ and the Bilsin study featured a local mandibular anesthesia technique,¹⁹ while our study featured the use of IANBs in a split-mouth design. Moreover, our results were also in agreement with Sahithi et al,²⁰ who reported significantly lower pain scores in the thermomechanical device group vs the counterstimulation group. Suohu et al⁶ and Faghihian et al²¹ found lower WBFPR scores in the thermomechanical device groups; however, the differences lacked statistical significance.

The mean FLACC pain scores in the current study were considerably lower in the test group than the control group. These findings are similar to those of Hegde et al,³ Suohu et al,⁶ and Alanazi et al.⁵ A split-mouth study done by Faghihian et al²¹ assessed a thermomechanical device (cold wings with and without vibration) for maxillary infiltration. The lowest FLACC pain scores were obtained in the cold and vibration group compared to the control group who received just cold without vibration, and the authors concluded that vibration with cold was more effective at reducing the children’s fear and discomfort during infiltration. Moreover, in a clinical trial with parallel control (conventional) and intervention groups (conventional with thermomechanical device), Jain et al,²² reported significantly lower FLACC pain scores for maxillary posterior infiltration with a thermomechanical device.

No significant differences were noted in pain scores between the groups due to the 2 different treatment sequences. Faghihian et al²¹ reported that precedence or delay in using the thermomechanical device did not cause a significant change in WBFPRS or FLACC pain scores.

This study exclusively enrolled children who demonstrated cooperative behavior (i.e., “positive” or “definitely positive”) based on Frankl’s Behavior Rating Scale. This careful selection criterion was employed to ensure the accuracy of pain assessments, as uncooperative children might provide biased responses. This study focused on children aged 5 to 8 years, a developmental stage believed to mark the emergence of cognitive development. Children less than 5 years of age were not included due to their limited cognitive development and reliance on parental input.

In our research, we selected the IANB to evaluate and compare injection pain, thereby making our study unique compared to other studies where local infiltration was used. This choice was guided by the findings of Kaufman et al,²³ who identified the IANB as exhibiting higher levels of pain and discomfort as compared to infiltration, intraligamentary injection, and mental nerve block techniques. To ensure consistency and mitigate potential examiner-related differences, a single investigator administered all local anesthetic injections throughout the study.

Subjective measures of pain are often subject to large variations between individuals. Hence a split-mouth design was used to overcome such variations and enable more reliable pain assessment¹⁷

Due to the intricate nature of quantifying pain, pain scores were evaluated subjectively as well as objectively. The WBFPR scale was selected based on its robust construct validity, satisfactory psychometric attributes, and user-friendly and swift application along with cost-effective replicability. A comprehensive systematic review conducted by Tomlinson et al²⁴ acknowledged the extensive psychometric scrutiny undergone by the WBFPR scale and its established utilization in appraising acute and condition-related pain in the pediatric population.

The FLACC was used for objective pain assessment because of its enhanced interrater reliability.²⁵

Limitations of the current study include that our results cannot be generalized to uncooperative children as only cooperative children were included. Also, participant behavior was evaluated only during the initial visit and not during the subsequent visits, and there was lack of controlling for injection speed, which is a major source of injection pain. A potentially confounding factor was the use of a topical anesthetic in the current study, which can influence the pain of injections significantly. However, use of topical anesthesia in both groups would have minimized the effect this confounding factor.

CONCLUSION

This study demonstrated that the use of the thermomechanical device Buzzy during IANB injections led to lower pain scores, objectively and subjectively, compared to IANB injections administered without the device. Further exploration of thermomechanical device usage along with other pain control measures (counterstimulation, distraction cards, etc.) during local anesthetic injections should be evaluated. Furthermore, the effectiveness of this thermomechanical device should be studied in uncooperative children.