Effectiveness of precooling with ethyl chloride versus honey in alleviating intra-oral injection pain in adult patients: A randomized controlled trial

Abstract

Objective:

The objective of the study was to assess and compare the effectiveness of precooling with ethyl chloride versus honey in alleviating the pain of dental injection.

Methods:

About 90 patients were recruited for this randomized controlled trial. In each of the following three groups, 30 patients were allocated: Group 1, precooling with ethyl chloride; Group 2, honey; and Group 3, control. The pain score of patients in each group was measured after injecting the dental local anesthesia using a visual analog scale. Paired t-test and multiple linear regression tests were used for statistical analysis. A p value of ⩽0.05 was considered to be as significant.

Results:

The mean pain scores of participants residing in different groups were as follows: Group 1: 2.83 ± 1.46, Group 2: 4.33 ± 1.62, and Group 3: 7.80. After administrating ethyl chloride, the majority of the 18 (60%) patients reported to suffer from “mild pain.” Furthermore, in patients who were given honey in Group 2, most of the 21 (70%) patients reported suffering from “moderate pain.” In Group 3 (control) where no anesthetic modality was used, the majority of the 25 (83.33%) patients experienced “severe pain.” A significant difference was noted among the pain scores of three groups (p = 0.001).

Conclusion:

The administration of local anesthetic is part of almost all dental procedures. Precooling with ethyl chloride resulted in a greater reduction in pain scores than honey upon administration of local anesthesia injection.

Introduction

Local anesthesia is one of the most important parts of almost dental procedures that are often responsible for triggering anxiety and fear among patients.¹ Patients who are particularly fearful of injections tend to avoid visiting dental practice unless there is an emergency.² Commonly in dental practice, the fear of needles is encountered among patients with the levels of fear varying among pediatric and adult patients. Topical anesthetics such as lidocaine and benzocaine are one of the most commonly used agents before the injection of dental local anesthesia to patients to alleviate the pain of the injection.³ Moreover, at times, patients themselves often request dental practitioners for the use of topical anesthesia.⁴

Fear of dental injection is not just limited to dentistry, but it is also countered in other experiences of the patients such as venipuncture, vaccinations, or any medical procedure that requires the administration of injections.⁵ When such fears of the patients remain unaddressed, avoidance behavior toward dental procedures then takes place. Since the importance of local anesthesia in dentistry is of vital importance, dentists use various techniques that help in alleviating the fear of dental injection among patients. Behavior modifications and pharmacological therapy are one of the most frequently used techniques to reduce the fear of dental injections.⁶

Ethyl chloride is an agent that is widely used in dental practice as the standard modality for pulp vitality tests.⁷ In medical practices, procedures such as venipuncture and vaccination use ethyl chloride as anesthetic and antiseptic agent.⁸ However, in dentistry, the use of ethyl chloride is limited mainly for pulp vitality tests. Some studies have evaluated the effects of precooling using ethyl chloride that do report the benefits of its use over topical local anesthetic solutions.⁹

Honey is a natural substance that has been used for many purposes in medicine such as to treat infections due to its antimicrobial, anti-inflammatory, and pain-relieving properties.¹⁰ Moreover, in dentistry, honey has been used in patients who have suffered from dry socket to reduce their pain levels.¹¹ Honey, a sweet flavored solution, has been used in clinical settings in pediatric patients by administrating orally as a modality to reduce the pain of dental injection.¹² Various studies have found that neonates that undergo venipuncture have reportedly benefitted from sweet solutions such as 30% sucrose prior to cutaneous procedures.¹³ Few studies have evaluated the impact of administrating sweet solutions on analgesia that involves dental injections. Sweet-tasting chewing gums have been used to evaluate their effect on the pain of injection with the conclusion of being ineffective.¹⁴

Considering the need to address the fear of dental injection as it is commonly encountered in dental practice, methods that help in addressing this fear should be considered. Few studies have evaluated the effect of honey in alleviating injection pain in pediatric patients, with no study carried out evaluating its effect in adult patients as per the search of the authors. Honey is a natural substance with no possible side effects when it is used for various purposes in health sciences. As pharmaceutical drugs do have various adverse effects associated with them, honey being a natural substance can offer to be an interesting alternative to it. So, the objective of the study was to assess and compare the effectiveness of precooling with ethyl chloride versus honey in alleviating the pain of dental injection.

Methods

Study design and sample size

This randomized controlled trial was carried out between August and September 2022 in the Department of Operative Dentistry. The study was executed as per the Declaration of Helsinki. This research study has been registered in the registry of ClinicalTrials.gov with registration number NCT05568563. For the recruitment of participants in this study, a non-probability convenience sampling technique was used, where patients who filled the eligibility criteria of this study were recruited voluntarily. To calculate the sample size, OpenEpi software (version 3.01) was utilized. The confidence interval was kept at 95% and desired percentile at 50, and the sample size was calculated to be 28 (14 participants in each of the two groups).¹⁵ This was a single blind study, where the participants were blind only. The specimens of honey and ethyl chloride spray were present in identical unmarked bottles without the original labels on them. The principal investigator who was not kept blind was responsible for collection of data and assessing the pain scores of the patients.

Inclusion and exclusion criteria

The inclusion criteria were as follows: Adult patients above 18 years of age, without any systemic disease, and no mental health disorders. The exclusion criteria were as follows: patients below 18 years of age and participants who refused to take part in this study were excluded. For voluntary participation, informed verbal and written consent was taken before the commencement of the study. The nature and purpose of this study were informed to the participants recruited and made aware that information of the participants will be kept anonymous throughout the time period of the study.

Grouping of participants and data collection

On the first appointment of the patients, the lottery method was used for the three groups of this study to ensure the random allocation of patients to one of the three groups. The participants in this study, after their recruitment, were on the basis of randomization placed in one of the three groups as follows: Group 1, precooling with ethyl chloride; Group 2, honey; and Group 3, control. The principal investigator (H.A) carried out the procedure of this clinical trial. Upon isolation of the field of work, one of the two allocated techniques of anesthesia was used on the patient. For all the patients, the infiltration injection was injected in the buccal sulcus slowly over a period of 1 min. For participants that belonged to Group 1, a pea-sized cotton ball was used which was sprayed with ethyl chloride (Ethyl chloride spray 100 ml, PWL Russel, New Zealand ©) (precooling) and placed on the site of injection for 30 s prior to administration of the dental injection.

For participants who belonged to Group 2, honey (Al Shifa 100% Natural Pure Premium Honey, A Shifa, Saudi Arabia ©) was used where the participants were instructed to consume 5 ml honey prior to dental injection was administered. The participants were instructed to hold the honey in their mouths for 1 min and then spit it out. After that, the dental injection was administered to the patient slowly over a period of 1 min. The dental injection was administered using a short 27-gauge needle (Septodont-Septoject Needle, France ©) consisting of 1:80,000 lidocaine solution with epinephrine by the principal investigator (H.A). The demographic data, method of pain reduction, and pain scores of each patient were recorded in a questionnaire.

Measurement of pain scores

The pain scores of the patients in all three groups were measured using the visual analog scale. In this numeric pain scale, the scale is arranged from 0 denoting “no pain” and 10 denoting “severe.”¹⁶ The following categories of the pain scale are 0: no pain, 1–3: mild pain, 4–6: moderate pain, and 7–10: severe pain, as described in Figure 1.

Figure 1.

Visual analog scale for measuring pain scores.

Statistical analysis

For data analysis, we used Statistical Package for Social Sciences (SPSS, version 25, IBM Corp.; Armonk, NY, USA). For demographic characteristics, mean and standard deviation (SD) values were calculated. Paired t-test was used to assess the difference in mean scores among the groups. For the assessment of the effect of age and gender on the pain scores of the participants, multiple linear regression analysis was used. For statistical significance, p ⩽ 0.05 was considered to be as significant.

Results

A total of 90 patients were recruited in this randomized controlled trial, as presented in Figure 2 CONSORT flow diagram.

Figure 2.

CONSORT flow diagram.

Regarding age, the mean values of age in each group are presented in Table 1. For gender, the dissemination of males and females in each group is as follows: Group 1, 16 and 14; Group 2, 16 and 14; and Group 3, 15 and 15.

Table 1.

Sociodemographic characteristics of the patients (n = 90).

Groups	Variables	Mean and standard deviation
Precooling	Age	28.6 ± 5.1
Honey	Age	26.76 ± 7.29
Control	Age	29.60 ± 6.48

The mean ± standard deviation (SD) pain scores of the patients residing in each group were as follows: Group 1: 2.83 ± 1.46, Group 2: 4.33 ± 1.62, and Group 3: 7.80 ± 1.56. After administrating ethyl chloride as a precooling agent to alleviate dental injection pain, the majority of the 18 (60%) patients reported suffering from “mild pain,” followed by 10 (33.33) patients suffering from “moderate pain,” and 2 (6.67%), however, reported “no pain.” Furthermore, in patients who were given honey in Group 2, most of the 21 (70%) patients reported suffering from “moderate pain,” followed by 7 (23.33%) who experienced “mild pain,” and 2 (6.67%) patients with “severe pain.” In Group 3 (control) where no anesthetic modality was used, the majority of the 25 (83.33%) patients experienced “severe pain,” with 5 (16.67%) patients reporting “moderate pain,” as illustrated in Figure 3.

Figure 3.

Distribution of pain scores among different groups.

Paired t-test was used to assess the difference in pain scores in the three groups. Upon comparison, a statistically significant relationship was noted between Groups 1 and 2 (p = 0.001). Likewise, a statistically significant relationship was noted among Groups 1 and 3 (p = 0.001) and Groups 2 and 3 (p = 0.001), illustrated in Table 2.

Table 2.

Assessment of pain scores among different groups (n = 90).

Groups		Mean	Standard deviation	Std. error mean	95% confidence interval of the difference		t	df	p Value
					Lower	Upper
1	Group 1 precooling versus Group 2 honey	−1.50	1.65	0.30	−2.11	−0.88	−4.96	29	0.001
2	Group 1 precooling versus Group 3 control	−4.96	1.93	0.35	−5.69	−4.24	−14.03	29	0.001
3	Group 2 honey versus Group 3 control	−3.46	1.87	0.34	−4.16	−2.76	−10.15	29	0.001

When age (p = 0.069) and gender (p = 0.522) were compared with the pain scores of the participants, a statistically significant relationship was not found, as illustrated in Table 3.

Table 3.

The effect of age and gender on the pain scores of participants (n = 90).

Variables	Unstandardized coefficients		Std. coefficients	t	p Value
	B	Std. error	β
Age	−0.086	0.047	−0.200	−1.844	0.069
Gender	0.360	0.560	0.070	0.642	0.522

Discussion

Almost all routine and complex dental procedures require the injection of local dental anesthetic agents, the most common among which is lidocaine. Many patients are subjected to the fear of dental injections which makes them avoid visits to dental clinics unless an emergency arises. The initial pain of the prick of the dental injection is an uncomfortable feeling for most patients, with tolerance to such pain varying from patient to patient. Uncomfortable experiences generate fear in the long term for the patients. So, optimum measures are to be taken by dental practitioners to alleviate the fear of the pain of dental injections. In this study, the first group was administered ethyl chloride as a precooling agent and the second group was provided with honey, with the aim of both agents to assess the alleviation of pain associated with dental injections.

First, the first group was given ethyl chloride as a precooling agent before injection of the local anesthesia solution. This study reported that most of the participants suffered from mild pain with some patients experiencing moderate pain. Such findings correspond with a study by Chilakamuri et al. who report that the application of ethyl chloride as a precooling agent was found to reduce the pain scores of the patients in comparison to topical anesthetic lidocaine.¹⁷ However, such findings are not always found as in a study where ethyl chloride was used for chronic villus sampling, this agent resulted in increased pain scores of the patients.¹⁸ Such differential findings suggest that the perception and level of pain experienced by the patients are variable. Moreover, when ice is used, one study has reported that it resulted in a decrease in discomfort for the patients.¹⁹

Honey is a natural substance used in dentistry for the prevention of caries, treating gingivitis, and treating receding gingiva.²⁰ In our study, we used a natural sweet-tasting solution such as honey to assess its effect on pain experienced by the patients in administrating dental injections. In this study, patients who were given honey, the majority of the patients suffered from moderate pain with a few cases of mild and severe pain being experienced. Such reduction in pain scores has been reported in a study carried out on pediatric patients.¹² Moreover, one study suggests that adolescents were able to register lower levels of pain due to being able to suppress their pain of discomfort from dental injections.²¹ However, many studies do report that adults appear to tolerate pain at a higher degree as compared to children due to a higher threshold for pain.²² The exact mechanism as to how sweet taste results in a decrease in the level of pain requires further studies but one study reports a greater production of internally derived opioids.²³ A study by Kakeda et al. using 3-T functional magnetic resonance imaging it was found when a sweet drink is kept in the mouth, it led to a positive state, and such state results in a decrease in pain perception.²⁴

Although the use of honey has been known to decrease the injection pain that is associated with dental local anesthesia, the exact mechanism by which this takes place is yet to be discerned. The sugary taste of honey has been shown not to be the reason behind the reduction in pain.¹⁴ One of the purposed methods by which honey leads to a reduction in pain has been by when a sweet substance is administered, this leads to an increase in endogenous opioid production which led to a decrease in the perception of pain.¹² Therefore, this gives the idea that the chemical properties of the honey that are probably responsible for a decrease in pain associated with dental local anesthesia injection.

Besides the use of ethyl chloride and honey, many different analgesic modalities have been used in literature such as topical anesthetics such as lidocaine and clove–papaya-based gel.²⁵ Moreover, this study found that age had no statically considerable relation to the scores of the pain of the participants. In contrast to such findings, the literature suggests that pediatrics and young adults tend to experience higher levels of pain.²⁶ Furthermore, this study found that gender had no relationship with pain scores of the pain. Nevertheless, literature has suggested that females tend to experience pain to a greater degree as compared to males.^27,28

Ethyl chloride and honey, as per the results of our study, can be effectively used as analgesic agents to decrease the pain associated with the prick of dental local anesthetic injections. However, future studies should focus on honey being used as an analgesic and further comparison should be carried out with other analgesic modalities. The strengths of this study are as follows: first, adequate measurement of pain scores was carried out and then a follow-up of the patient’s pain scores was carefully done. However, we encountered some limitations such as first, the sample of patients recruited for this study was small. Lastly, the distribution of gender in each group was unequal which could have affected the results of this study.

Conclusion

Properly addressing the fear of dental injection among patients is of vital importance, especially for patients previously known to suffer from needle phobia. Precooling with ethyl chloride has been proven to be more effective in reducing the pain of prick with dental injection as compared to honey. Therefore, both of these analgesic modalities can be provided to the patients.