Effectiveness of Pre-cooling the Injection Site, Laser Biostimulation, and Topical Local Anesthetic Gel in Reduction of Local Anesthesia Injection Pain in Children

INTRODUCTION

Local anesthetic (LA) injections are usually the most scary and anxiety-provoking stimuli in pediatric dental practice.¹ The fear of pain caused during injection of anesthetic agents is definitely a hurdle for delivering appropriate dental care.² Proper local anesthesia is essential for the successful treatment of children which alleviates the anxiety and pain during various treatment procedures.³

To lessen the pain during administration of the LA injection, several pharmacological and non-pharmacological methods such as the utilization of topical anesthetics, slowing down the rate of infiltration, distracting the children, vibrating the tissue around the injection site during injection, heat and cold application before the injection have been tested. Application of flavored topical anesthetic gel is most commonly practiced in pediatric dentistry.⁴

The application of ice is a common practice to reduce signs of inflammation. This technique is being used as first aid in the management of sprain injuries, fractures of bones, and bruises of soft tissues.⁵ Cooling with ice causes vasoconstriction, reduces the tissue metabolism, slows down the inpouring of inflammatory mediators, and activates inhibitory pain pathways which in turn suppresses the pain perception.⁶

Low-level lasers are being used in pain management in dentistry. They have been used for reducing pain during intradermal and intramuscular injections.⁷ Biostimulation with low-level lasers provides analgesia. It stimulates the production of beta-endorphins which are considered as body’s natural pain killers. It decreases the activity of c-fibers and inhibits the conduction of nerve fibers, thereby alters the pain threshold.⁸

The available literature on the use of ice and low-level laser for reducing injection pain in pediatric dental practice is sparse. Hence, the present clinical trial was carried out to test the effectiveness of laser biostimulation (LBS), ice, and LA gel in reducing pain during administration of LA injection in children.

MATERIALS AND METHODS

A 3-arm, crossover randomized controlled trial was carried out in 30 children aged 9–12 years attending the outpatient Department of Paediatric Dentistry. The non-probability proportional quota sampling technique was followed. Ethical clearance was received from the institutional ethical committee (VDC/IEC/2016/30), and the trial was enrolled in Clinical Trials Registry—India (CTRI/2018/05/014298).

Children with cooperative behavior, without any confounding medical history, and who required the extraction of primary maxillary posterior teeth were included. The procedural details were explained to all the children according to their cognitive levels and also to their parents. Written informed consent was taken from the parents or guardians of all the children participating in the study.

RESULTS

It was observed that a score of 0 with a subjective scale suggesting no hurt is expressed by 16 children in the ice group, 14 children in the LA gel group, and only 7 children in the LBS group (Table 1). Similarly, score 1 with an objective scale suggesting comfort is recorded with 28 children in the ice group, 23 children in the LA gel group, and only 12 children in the LBS group (Table 2).

On intergroup comparisons, the difference in the subjective and objective pain scores between LA gel and ice groups is found to be statistically not significant. Whereas, the difference in pain scores is found to be statistically significant between LBS and LA gel groups. Similarly, when scores in the LBS group were compared with the ice group, the differences are found to be statistically significant (Tables 1 and 2).

DISCUSSION

Intraoral local anesthesia is frequently used in children to reduce pain during various dental procedures.³ Paradoxically, administration of LA injection itself produces pain and anxiety which may cause subsequent unfavorable behavior. Application of topical anesthetic gel at the site of injection is the most practiced technique to reduce the pain associated with the LA injection.³

In the present study, strawberry-flavored 20% benzocaine gel was used as a control with a piece of evidence to consider it as the most effective topical anesthetic agent used in pediatric dentistry.⁴ Fewer allergic reactions are being reported on prolonged repeated use of 20% benzocaine proving its safety in children.¹¹

Cooling the injured tissues to suppress/reduce inflammatory signs was in practice since the olden days. Local application of ice packs for pain relief is being done for treating sprain and burn injuries, bruises, insect bites, and musculoskeletal pain. We considered the application of ice for reducing injection pain as one of the test groups based on the understanding of its effectiveness in reducing pain, ease of making the desired shape, and low cost.⁵

The application of lasers for many soft and hard tissue procedures is commonly done in dental practice. It is learned to be less invasive with the least discomfort for the patients.^12,13 Laser biostimulation is considered as other test group to reduce injection pain based on the premise that low-level lasers are effective in producing analgesia.⁷

Measurement of pain is a challenging task, especially while working with children because of their limited experiences and vocabulary, lower cognition, and underdeveloped capacity of expressions.¹⁴ Self-report of pain in children is not reliable since it is influenced by developmental, situational issues, and anxiety. Hence, observational and/or physiologic measures should be considered in conjunction with self-report measures.¹⁵

Subjective measurement is generally considered a gold standard while assessing pain.¹⁶ We employed Wong-Baker FACES Pain Rating Scale for subjective evaluation since this can be used in all age groups, easy to use, and repeatable with fewer errors.¹⁶ SEM scale was used for objective measurement of pain as it consider eyes, movements of the body, and verbal expressions.

Findings of this study have shown that lower pain scores were recorded in the pre-cooling with ice group and found to be equally effective as LA gel. Topical cold application triggers myelinated A-fibers, activates inhibitory pain pathways, which in turn suppresses the pain perception.⁶ The observations by Mohiuddin et al. have shown that pre-cooling before infiltration anesthesia reduced the pain perception in pediatric patients when compared to topical anesthetic gel.¹

Laser biostimulation was found to be less effective compared to LA gel and pre-cooling with ice in reducing the injection pain. Similar observations were reported by Ghaderi et al., who found that there was no reduction in pain perception with concurrent application of laser and topical anesthetics on the buccal mucosa before the administration of LA injection.¹⁷ Contrarily, Sattayut when evaluated the effectiveness of low-intensity laser therapy (LILT), topical anesthesia, pressure, and light touch for pain reduction during palatal injection, found no significant differences in pain scores among the different techniques used.¹⁸ Variations in choice of laser parameters such as the wavelength of the laser unit, the power delivered, mode of application, i.e., either contact or non-contact, time of exposure, type of exposed tissue, and physiological condition of the exposed tissue can affect the outcome.¹³

Pain management during LA injection is a critical step in gaining initial trust and during the subsequent treatment visits. The observations of the current study suggest that pre-cooling the injection site with ice can be considered as an effective non-pharmacological technique to reduce injection pain.

CONCLUSION

Pre-cooling the injection site with ice is equally effective as topical anesthetic gel in alleviating the injection pain during maxillary posterior buccal infiltration in children and it can be considered as a cost-effective, non-pharmacological method for reducing LA injection pain in children. Laser biostimulation therapy was found to be less effective compared to the other two techniques.

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