The Clinical Efficacy of EMLA as a Topical Anesthetic Agent Instead of Palatal Injection During Maxillary Dental Extractions: A Randomized Controlled Trial

Abstract

Background

Even after the invention of the modern injection techniques, palatal injection still remains a painful experience for patients, and this pain is attributed to the presence of rich nerve complement and displacement of tightly adherent palatal mucosa during anesthesia.

Aim

To check the clinical efficacy of EMLA as a topical anesthetic agent instead of palatal injection during maxillary dental extractions.

Methodology

The trial includes a total of 102 participants, in whom maxillary molar extractions were indicated, were randomly divided into the experimental group (eutectic mixture of local anesthesia (EMLA) topical application was used along with buccal injection) and control group (palatal injection along with buccal injection). Pain perception during extraction was recorded using the visual analog scale (VAS).

Results

Mean VAS score for ‘injection’ in control group patients was 5.2 ± 2.08 in contrast to no pain in experimental group. In experimental group, mean VAS score on ‘probing’ was 0.92 ± 1.50. VAS score on ‘extraction’ in EMLA group was little higher though the difference was not statistically significant. The overall experience using Liekert’s scale was higher in experimental group (4.0 ± 0.76) as compared to (3.3 ± 0.82) in control group leading to higher overall satisfaction among patients who underwent extraction in the experimental group.

Conclusion

EMLA application produced a satisfactory level of anesthesia in the palatal tissue when compared with the palatal injection.

Introduction

Dental extractions are the most common among oral surgical procedure done under local anesthesia [1]. The uprising popularity of implants made a paradigm shift from saving grossly decayed teeth by root canal to their removal [2]. Past literature had reported that with few specific concentrations and use of different local anesthetic agent’s, only buccal injection can suffice for extraction procedure and palatal injection can be avoided [3–5]. However, the need for palatal anesthesia cannot be completely eliminated in all cases and patients. A prudent anesthetic agent that abolishes the pain of palatal injection is the need of the hour.

Topical anesthetics aid as an adjunct to local infiltrations in minor oral surgical procedures [6]. Topical anesthetics are thought to function by blocking signal transmission in the terminal fibers of sensory nerves [7]. Most of the times the topical anesthetic drugs’ role is to reduce or relieve the painful stimulus caused by needle injection [7]. In the era of bypassing the palatal injections for extraction of maxillary teeth extractions, an efficient topical anesthesia is required. However, due to thick keratinized tissues and difficulty in retaining the agent in palatal region, most commonly used topical anesthetics have failed to produce desired results [8]. The most commonly used topical anesthesia worldwide is 20% benzocaine but it still lacks the desired potency [9]. Thus, the search of an effective topical anesthesia for one of the most painful sites like palate has been on for decades.

In the quest of improving the efficiency of topical anesthetic action on the palatal mucosa, eutectic mixture of local anesthesia was indicated to use in the oral cavity [7]. The past literature had also shown significant reduction in the pain during probing, rubber dam placement, hand and ultrasonic scaling and palatine nerve blocks using EMLA in the oral cavity [9–13]. Though EMLA has proved as an efficient topical anesthetic agent, good quality randomized controlled trials have not been reported in the literature yet. Thus, considering this knowledge gap, a randomized controlled trial was planned to evaluate the efficiency of EMLA in replacing the palatal injections during maxillary extractions. The primary objective of the study was to check the clinical efficacy of EMLA as a topical anesthetic agent instead of palatal injection during maxillary dental extractions.

Methodology

The present randomized controlled trial was approved by Institutional Ethics Committee, and the present trial was also registered in Clinical Trial Registry of India (CTRI/2019/01/017140). A total of one hundred and two participants, in whom extraction of maxillary teeth was required, were included in the present trial. Individuals with uncontrolled chronic systemic diseases or individuals with known allergy to agents used were excluded from the study. The participants were screened and selected from the outpatient department in a medical college and hospital of national importance.

After being informed verbally about the study, written informed consent was taken from all the participants. The participants were randomly divided into experimental group where participants received EMLA application on palatal tissues with 2% lignocaine hydrochloride injection with 1:80,000 adrenaline on buccal/labial side and control group where the participants received palatal 2% lignocaine hydrochloride injection with 1:80,000 adrenaline along with the same on buccal/labial side. In the experimental group, EMLA application was done 10 min before labial/buccal injection after thoroughly drying the palatal mucosa. Pain on palatal probing was assessed using VAS before giving labial/buccal injection. Pain of palatal injection in control group was recorded using visual analog scale (VAS) immediately after injection. All measurements were recorded by author SK who was blinded to the treatment given. In all the patients, the teeth extraction was carried out 10 min after the use of local anesthetic agent.

Subjective and objective signs of local anesthesia were assessed on palatal tissues before the start of extraction. If pain on probing was intolerable by patient, supplemental palatal injection was given. Also, the patients were asked to indicate the extent of pain during extraction using VAS. Overall experience during extraction was also evaluated with a 5-point Likert’s scale of extremely satisfied, very satisfied, neutral, slightly satisfied, not at all satisfied in both the groups. Any side effects noted during or after the procedure were also documented. The experimental group was considered successful if no additional palatal injection required during procedure and no adverse reactions-local or systemic were reported.

Assuming a standard deviation of 2 in both the groups and with effect size of 0.83 and clinical meaningful mean difference of 1.66 in VAS score in two treatment groups, with 90 percent power and alpha error of 5%, the sample size was estimated to be 31 per treatment group. A total of 62 participants were needed for the study. The participants were randomized using computer generated simple randomization sequence to experimental and control groups. Randomization sequence concealment was maintained using opaque, sealed envelope concealment. Random allocation sequence was generated, and patient allotment and assignment were done by one of the co-author (SS). The patient and the operator cannot be blinded because of differences in the treatment procedures between control and experimental groups. However, outcome assessor (SK) was blinded to the treatment implemented to the participants.

Statistical Analysis

Descriptive statistics were done for age and sex of the included participants, and mean and categorical data were testing using Student t test and Fischer’s exact test, respectively. The differences in the mean VAS scores between the experimental and control group were tested using the Student t test. All statistical analysis was done using the SPSS software version 21. P value of less than 0.05 was considered as statistically significant.

Results

A total of one hundred and fifty-two participants were screened, and a total of one hundred and two participants were included in the present trial (Fig. 1). As it was a single time point study, all the participants included were analyzed and no follow-up examination was indicated. The patient recruitment was done during the time period from January 2019 to July 2019, and the recruitment was stopped once the required sample size was achieved.

Fig. 1.

CONSORT flow diagram for inclusion of participants

The demographic data of the included participants were presented in Table 1. Mean VAS score during palatal injection in control group patients was 5.2 ± 2.08 in contrast to no pain was observed in experimental group, where EMLA was applied topically. In control group, no pain was observed during palatal probing after palatal injection. In experimental group, however, mean VAS score on probing was 0.92 ± 1.50. One patient in the experimental group had significant pain on palatal probing and was given the conventional anesthetic (as in control group). VAS score on extraction in control group was 0.75 ± 1.05. However, it was little higher (1.0 ± 1.39) in experimental group though the difference was not statistically significant. The overall experience using Likert’s scale was higher in EMLA group (4.0 ± 0.76) as compared to (3.3 ± 0.82) in control group, leading to higher overall satisfaction among patients who underwent extraction under EMLA (Table 2). This may be because of the fact that there was no injection as EMLA had been applied locally; hence, no pain as compared to injection of local anesthetic and pain during extraction was similar among two treatment groups. No side effects or allergic reactions were reported in the treatment groups.

Table 1.

Baseline characteristics in two treatment groups

Parameters	EMLA (n = 51)	Control (n = 51)	P value† (2-sided)
Sex
Male n (%)	23 (45.1)	27 (52.9)	0.530
Female n (%)	28 (54.9)	24 (47.1)
Age (years)
Mean ± SD	37.3 ± 15.20	39.3 ± 16.81	0.276

EMLA eutectic mixture of local anesthetics

^†Difference in mean data and categorical data between the two groups was analyzed using student’s t test and Fischer’s exact test, respectively

Table 2.

Difference in VAS score between two treatment groups

Parameters VAS scores	EMLA (n = 51) mean ± SD	Control (n = 51) mean ± SD	P value† (2-sided)
Injection (mean ± SD)	–	5.2 ± 2.08
Probing (mean ± SD)	0.92 ± 1.50	0 ± 0.00	< 0.001
Extraction (mean ± SD)	1.0 ± 1.39	0.75 ± 1.05	0.298
Overall experience	4.0 ± 0.76	3.3 ± 0.82	< 0.001

EMLA eutectic mixture of local anesthetics

^†Mean VAS scores between the two groups were analyzed using student’s t test; VAS score is 0 to 10

Discussion

Relevance

Even after the invention of the modern injection techniques, palatal injection still remains a painful experience for patients, and this pain is attributed to the presence of rich nerve complement and displacement of tightly adherent palatal mucosa during infiltration. A number of techniques may be used to reduce the discomfort of intraoral injections, including transcutaneous electronic nerve stimulation (TENS), topical anesthetic application, topical cooling of the palate, computerized injection systems, pressure administration, and eutectic mixture of local anesthetics (EMLA) [14]. The efficacy of conventional topical anesthetic agents is also questionable in keratinized tissue like palate because of only superficial effect due to limited penetration potential. Topical anesthetics used commonly do not have promising results and vary considerably in terms of duration and site of application. EMLA lignocaine and prilocaine bases are said to have melting points of 69 degree centigrade and 37 degree centigrade, respectively. However, in eutectic form, the melting point of mixture is lowered to 17 degree centigrade. This new physical property allows the anesthetic agents to form oil at mouth temperature (37 degree centigrade) and thus facilitates increased absorption of local anesthetic agents [15]. Hence, the aim of this present study was to demonstrate if topical EMLA application can eliminate the need of palatal injection in maxillary tooth removal.

Background

EMLA cream, a 1:1 mixture of 2.5% prilocaine and 2.5% lidocaine, was first used as a cutaneous topical anesthetic in dermatology in the 1980’s. Holst and Evers were the first to attempt the administration of EMLA cream within the oral cavity [16]. Their results showed high efficacy in the attached gingiva. Since this study, multiple studies have documented the application of EMLA cream on mucosal surfaces. In addition, several reports have noted that the use of EMLA cream reduced pain during probing, hand scaling, ultrasonic scaling, rubber dam clamp placement, and palatine nerve block. However, none of the studies have been done to evaluate EMLA for palatal soft and bone anesthesia. Nayak and Sudha suggested that the low viscosity of EMLA cream renders it difficult to handle, which in turn makes it difficult to administer locally as a topical anesthetic at the site of the needle injection [17]. To overcome this setback, Svensson and Peterson used an Orahesive bandage, which improved the pain relief effects of the topical anesthetic [18]. In our study too, we found that application of EMLA was found to be difficult in posterior areas where with swallowing or tongue contact, the agent could wash off. We found that drying the mucosa before application, asking the patient to open the mouth wide, application of suction to evacuate salivary pooling helped with adhesiveness.

The advantages of EMLA over conventional topical anesthetics on the oral mucous membrane are due to a deeper depth of penetration, i.e., about 5 mm as compared to only 2–3 mm of other topical agents. It is able to diffuse effectively through the keratinized tissue, i.e., gingival mucosa and hard palate, whereas other topical anesthetics can act only on the non-keratinized tissue. EMLA is said to have bony effects as it may penetrate the buccal cortical plate more effectively to block A-delta and the un-myelinated C-fiber nociceptive fibers [19]. It has been reported that complications with EMLA cream are usually mild and rare. But it can sometimes lead to regional pallor, flare, edema, an early burning sensation, and rare itching. In addition, it may also induce allergic and anaphylactic reactions, including hives, vascular edema, bronchospasms, and shock. Few cases of methemoglobinemia in children are also reported [20]. No adverse effects were observed with any of the agents during in the course of the present study.

In maxillary injections with local anesthetic like articaine, even buccal or labial injections are said to diffuse through bone and soft tissue till palatal region and are effective without any supplemental palatal block [21, 22]. However, these data related to 2% lignocaine hydrochloride with adrenaline are sparse. Conventionally, with lignocaine injection supplemental injection on palatal side is required. Still, to negate this possibility in our study, labial/buccal injections were given only after assessing efficacy of EMLA with palatal probing in experimental group. Among topical anesthetic agents, EMLA has been found to produce desired result that minimizes the needle prick pain. In a randomized split mouth double blind study on 40 patient’s, anesthetic efficacy of 4% articaine was compared with 2% lignocaine in labial/buccal only injections for periodontal therapy. The success rate for palatal anesthesia was 90% for articaine and 20% for lignocaine [22]. Hence, 2% lignocaine alone is not able to provide adequate anesthesia of both soft and hard tissues on palate with a single buccal injection. Thus, EMLA in our case has definitely proved its efficacy by eliminating the palatal injection completely.

Through our study, we aimed to evaluate whether or not palatal injection can be completely eliminated. The results have displayed that though some pain on probing is present in the experimental EMLA group as compared to no pain on probing in the conventional control group (which is the usual standard of care), the difference was statistically significant but not clinically significant as the procedure could be completed without pain. But this could be attributed as one of the limitations of the study as all are subjective measurements taken from the patient intra or immediate postoperatively where the patient’s anxiety, stress also has a role. May be buccal/labial nerve block after checking of palatal probing eliminates that minimal pain too.

Overall pain reported during extraction is higher in the experimental EMLA group as compared to the control palatal injection group though the difference is not statistically significant. This could be explained with the reason that extractions require expansion of palatal bone too. Some pain reported may be due to the lack of complete anesthesia of the palatal bone with EMLA. But the total extraction procedure pain was in the same range as the control group. The results suggest that palatal injections can be replaced with EMLA even with use of 2% lignocaine hydrochloride. The overall satisfaction level assessed depicted statistically significant higher satisfaction levels in EMLA group as compared to control group. This may be because of the fact that there was no injection as EMLA had been applied locally; hence, no pain as compared to injection of local anesthetic and pain during extraction was similar among two treatment groups. As every effort was taken to reduce the bias and inclusion and exclusion criteria of the trial were very specific, the results of the present trial can be generalized to all population groups.

Conclusion

It can be stated that EMLA application produced a satisfactory level of anesthesia in the palatal tissue as assessed by the minimal pain reported during probing. EMLA when coupled with the regular most commonly used anesthetic agent 2% lignocaine can eliminate the need for palatal injection even in cases like extraction where both soft tissue and hard tissue effects are desired. Elimination of painful palatal injection raises the overall satisfaction grading of patients toward the extraction procedure.

Declarations

Conflict of interest

The authors declare that they have no conflict of interest.