topical anesthetics, how effective are they

ISSN 0975-8437 INTERNATIONAL JOURNAL OF DENTAL CLINICS 2011:3(2):11-13

©INTERNATIONAL JOURNAL OF DENTAL CLINICS VOLUME 3 ISSUE 2 APRIL - JUNE 2011 11

Topical Anesthetics: How Effective Are They

Preeti Dhawan, Gulshan Dhawan

Abstract

Background: Almost every dental procedure requires the use of needle insertion for the

administration of local anaesthetic agent. Aims: To compare the efficacy of various topical anaesthetic

agents with Eutectic Mixture of Local anesthetics (EMLA). Material and Methods: The sample population

consists of 120 children between the age group of 5-15 years were randomly divided into four groups, each

group comprising of 30 children. Four topical anesthetics i.e. EMLA 5%, Lignocaine 2%, Benzocaine 20%

and Placebo (Vaseline) were applied for five minutes before needle insertion. The effectiveness of the

topical anaesthetic agent was recorded by using Visual Analogue Scale (VAS), Lickerts’ scale and the

sound eye and motor scale (SEM). Results: When EMLA (Group I) was compared with other groups in

relation to Visual Analogue Scale, a highly significant difference in pain reduction (P<0.000001) was

found. No significant difference was found between Lignocaine (Group II) and Benzocaine (Group III).

Conclusion: EMLA showed a highly significant reduction in pain as compared to 2% Lignocaine and 20%

Benzocaine.

Key Words: Topical anesthetics; Eutectic mixture of local anesthetics; Visual Analogue Scale

Received on: 13/11/2010 Accepted on: 13/01/2010

Introduction

Pediatric dentistry frequently requires

Local anesthetics by Regional block or local

infiltration, which requires needle insertion. The

objective fears of the child during administration

of local anaesthesia range from the sight of the

needle to the pain associated with needle

insertion. Topical anesthetics are thought to

function by blocking signal transmission in the

terminal fibers of sensory nerves. Thus, their

effects are thought to be limited to the control of

painful stimulation occurring in or just beneath

the mucosa.(1) The main objective of this study

was to compare the efficacy of various topical

anaesthetic agents with Eutectic Mixture of

Local anesthetics (EMLA) during needle

insertion in pediatric dental patients.

Materials & Methods

The sample population consists of 120

children between the age group of 5-15 years

who reported to the outpatient department of

Pedodontics and Preventive Dentistry, who

required the use of local anaesthesia for the

various dental procedures. Those children who

were having no other illness other than for which

they have reported and have no history of any

allergy to local anesthetics were selected for the

study. The children were randomly assigned into

four groups; consist of 30 children in each group.

Group I included children who were applied

EMLA, Group II was the Lignocaine group,

Group III was Benzocaine group, Group IV was

the placebo group. After proper isolation, one of

the four topical anesthetics was applied for five

minutes before needle insertion. The

effectiveness of the topical anaesthetic agent was

recorded by using Visual Analogue Scale (VAS),

Lickerts’ scale and the sound eye and motor

scale (SEM). Statistical analysis was done using

SPSS v.10. The significance was calculated

using students T test.

Results

The sample population consists of 120

children between the age group of 5-15 years.

The table 1 shows the pain and anxiety score

with Visual analogue scale. EMLA (Group I)

shows, a highly significant difference in pain

reduction (P<0.000001) as compared to other

three groups. No significant difference was

found between Lignocaine (Group II) and

Benzocaine (Group III).

Group 't' value 'p' value Significance

I-II 8.224 p < 0.000001 Highly significant

I – III 6.108 p < 0.000001 Highly significant

I – IV 12.157 p < 0.000001 Highly significant

II – III 2.444 0.01759 Non-Significant

II – IV 5.796 p < 0.000001 Highly significant

III – IV 7.709 p < 0.000001 Highly significant

Table 1: analysis of variance for pain and anxiety with different topical anesthetics with respect to visual analogue

scale

The difference between various groups

with respect to VAS was found to be highly

significant between Groups-I and IV (p <

0.000001) and non-significant between Groups-

II and III (p value is 0.01759). When comparison

of means of pain score for different topical

anesthetics was made with respect to Lickerts’

scale, EMLA (Group I) showed a highly

significant p value (P<0.000001). The result was

ORIGINAL RESEARCH ARTICLE



significant when Lignocaine (Group II) was

compared to Benzocaine (Group III) but no

significant difference was found between

Lignocaine (Group II) and Placebo (Group IV)

table 2.

Between 't' value 'p' value Significance

Lic

ker

t's

I – II 14.441 p < 0.000001 Highly significant



II – III 7.420 p < 0.000001 Highly significant

II – IV 1.621 p < 0.1 Non-significant


Table2 intergroup comparison of mean values for Lickert's

The difference between various groups

with respect to Lickert's scale was found to be

highly significant (p < 0.000001) between all the

groups except between Gr-II and Gr-IV where p

value was 0.1 and the results were statistically

non-significant. Table 3 showed the comparison

of means of pain for EMLA (Group I),

Lignocaine (Group II), Benzocaine (Group III)

and Placebo(Group IV) with respect to SEM

Scale. There was a highly significant reduction

in pain of EMLA (p<0.000001) with Lignocaine,

Benzocaine and Placebo. The difference

between various groups with respect to SEM

scale was found to be highly significant.

Between 't' value 'p' value Significance

SE

M

I – II 15.654 p < 0.000001 Highly significant



II – III 7.562 p < 0.000001 Highly significant

II – IV 8.381 p < 0.000001 Highly significant


Table 3 intergroup comparison of the mean values for SEM

Discussion

In general, common topical anesthetics

like Lignocaine and Benzocaine are effective

only on surface tissue (2-3mm) and tissues deep

to the area of application are poorly

anaesthetized.(2) E R Vickers and A. P Moorthy

suggested that Lignocaine and Prilocaine bases

have melting points of 69oC and 37

oC

respectively. However when these agents are

combined in eutectic form, the melting point of

mixture is lowered to 17oC. This new physical

property allows the anaesthetic agents to form oil

at mouth temperature (37oC) and thus facilitates

increased absorption of local anaesthetic agents.

Hence, the present study was undertaken to

comparatively evaluate the effectiveness of

Eutectic Mixture of Local anesthetics (EMLA)

cream with the commonly available other topical

anesthetics in reducing the pain associated with

intra-oral needle insertion.(3)

In the present study, the evaluation of

pain was done using the following three scales,

Visual Analogue Scale, Lickerts’ scale and

Sound, Eye, Motor Scale. According to these

three scales, highly significant reduction in pain

scores was found (P<0.000001) when EMLA

was compared with Lignocaine, Benzocaine and

Placebo. Topical anesthetics such as Lignocaine

and Benzocaine have the same mechanism of

action. These local anesthetic agents when

applied to the mucous membrane pass through

the epidermis and anaesthetize the superficial

nerve-endings. Thus, their effects are thought to

be limited to the control of painful stimulation

occurring in or just beneath the mucosa.1 These

topical surface anesthetics are effective only on

surface tissue (2-3mm) and tissues deep to the

area of application are poorly anaesthetized.

Lignocaine is the most commonly used

topical anaesthetic agent and according to

Malamed, it is today, the gold standard against

which all other topical anesthetics are compared.

However, it is not favorable, as regards to its

bio-adhesion, analgesic potential and taste

characteristics.(3) In our study, 20% Benzocaine

was found to be better than 2% Lignocaine with

highly significant difference (p<0.000001)

probably because Benzocaine can remain on the

region of application for a longer time and also

mucopain (20% Benzocaine) has a better

acceptable taste than 2% Lignocaine jelly. The

wide difference in the pain scores of EMLA with

other topical anesthetics may be due to different

mechanism of action of EMLA with Lignocaine

and Benzocaine. (4) EMLA was introduced to be

used on skin mainly to reduce pain of venous

cannulation and to provide surface anaesthesia

for the harvesting of skin grafts.

Topically applied EMLA penetrates

through the epidermis to act on sensory nerve

endings in the dermis in order to provide

effective anaesthesia. EMLA blocks the Ad-

fibers which transmit cold and pinprick sensation

and the C-fibers which transmits warmth and



dull pain. EMLA also has a high water content

(which softens the stratum corneum, making it

more permeable) together with high proportion

of the lipophilic, un-ionized (basic) form of

anaesthetic, which makes EMLA membrane

permeable.7 The advantages of EMLA over

conventional topical anesthetics on the oral

mucous membrane may be due to following

reasons, a) It has a deeper depth of penetration

i.e about 5 mm whereas other topical

anesthetics have a penetration depth of only 2-3

mm, b) 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, c) -EMLA

is able to penetrate the buccal cortical plate more

effectively to block Ad and the unmyelinated C-

fiber nociceptive afferents.

EMLA has an effective tissue

penetration. It is composed of oil-in-water

emulsion of Lignocaine and Prilocaine local

anesthetics. Rather than relying on an oil solvent

to dissolve the anesthetics, EMLA cream utilizes

the eutectic mixture of two compounds. Pure

Lignocaine and pure Prilocaine have melting

points above room temperature (67% and 37%

respectively) but a 1:1 mixture of the two has a

melting point of about 17oC and is thus,

normally liquid at room temperature. EMLA

cream is prepared by emulsifying this oily liquid

in water to give a final concentration of 25

mg/gm lignocaine and 25mg/gm prilocaine.

Although the final proportion of anaesthetic in

this cream is only 5%, which reduces the

possibility of toxicity, the oil droplets within the

emulsion are composed of 80% anaesthetic,

which provides a highly effective analgesic

concentration.

There are certain disadvantages

associated with EMLA cream viz it is difficult

for EMLA cream to remain in the region of

application for a long time because of the low

viscosity and it does not have very acceptable

taste.

It is recommended that EMLA impregnated

intraoral patches impermeable to saliva if

available would be a major advantage for its use

intraorally and the bland taste of EMLA should

be modified if its use in pediatric dentistry is to

be perused.

Conclusion

In conclusion, it can be stated that

EMLA showed a highly significant reduction in

pain as compared to 2% Lignocaine and 20%

Benzocaine. EMLA can be of great help in

eliminating the pain of intraoral needle insertion

and its other advantages such as rapid

penetration on the skin and mucosa and plasma

concentrations not reaching the toxic levels

makes it the useful topical anaesthetic and should

be considered as a useful adjunct in the

management and treatment of pediatric patients

under local anaesthesia.

Authors Affiliations: 1. Dr Preeti Dhawan, M.D.S

Department of Pedodontics, Swami Devi Dayal Dental

College, 2. Dr. Gulshan Dhawan, Anesthesiologist,

M.D (Anaesthesia), Chandigarh, India.

References

1. DeNunzio M. Topical anesthetic as an adjunct to

local anesthesia during pulpectomies. Journal of

Endodontics1998;24(3):202-3.

2. Bernardi M, Secco F, Benech A. Anesthetic

efficacy of an eutectic mixture of lidocaine and

prilocaine (EMLA) on the oral mucosa:

prospective double-blind study with a placebo.

Minerva Stomatologica1999;48(1-2):39-43.

3. Vickers E, Punnia Moorthy A. A clinical

evaluation of three topical anaesthetic agents.

Australian Dental Journal1992;37(4):266-70.

4. Tulga F, Mutlu Z. Four types of topical

anaesthetic agents: evaluation of clinical

effectiveness. The Journal of Clinical Pediatric

Dentistry1999;23(3):217-20.

Address for correspondence

Dr Preeti Dhawan, M.D.S (Pedodontics)

Swami Devi Dayal Dental College,

Golpura Distt, Panchkula, India.

Ph:0091. 9896778118

E-mail: [email protected]

Source of Support: Nil, Conflict of Interest: None Declared

topical anesthetics, how effective are they

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