6. anestesia.pdf

ANESTHESIA/TMJ DYSFUNCTION/FACIAL PAIN
Inferior Alveolar Nerve Block Using the
Anterior Technique to Anesthetize
Buccal Nerve and Improve Anesthesia
Success Rates for Third Molar
Extraction: A Randomized Controlled
Trial and Magnetic Resonance Imaging
Evaluation
Shota Tsukimoto, DDS,* Yoshihiro Takasugi, DDS, PhD,y Risa Aoki, DDS,z
Motoshi Kimura, DDS, PhD,x and Tatsuo Konishi, MPhil (Health Sci)jj
Purpose: The lack of anesthesia to the buccal nerve and an insufficient volume of anesthetic have been
reported to be responsible for failed inferior alveolar nerve blocks (IANBs) using the Halsted approach
(conventional IANB). We aimed to determine the extent of anesthesia in the buccal nerve innervation
area and evaluate the anesthetic efficacy of injecting a larger volume of anesthetic during IANB using
the anterior approach (anterior technique) in the clinical setting and with magnetic resonance imaging
(MRI) analysis.
Patients and Methods: The prospective randomized controlled trial included patients scheduled for
removal of a mandibular third molar. The primary predictor variables were the approach for IANB (anterior
technique vs conventional IANB) and anesthetic dose (1.8 vs 2.7 mL). The primary outcome variables were
the extent of anesthesia and the anesthesia success rate, defined as completion without additional anes-
thesia. The secondary outcome variable was the anesthetic drug distribution related to the pterygoman-
dibular space measured on T2-weighted MRI scans. Statistical independence of the anesthesia success
rate among the primary predictor variables was tested with statistical significance set at P #.05.
Results: A total of 108 patients and 10 volunteers were enrolled in the clinical and MRI studies, respec-
tively. Anesthesia of the buccal nerve was evident in patients receiving the anterior technique with 2.7 mL
of anesthetic. The success rate of the anterior technique with 2.7 mL of anesthetic (96%) was greater than
that with 1.8 mL of anesthetic (67%; P = .0113), and increasing the dose had no effect on the efficacy of
conventional IANB (78% vs 81%; P = 1.000). The MRI study showed that the anesthetic was distributed
over the anterior surface of the temporalis tendon and in the pterygomandibular space after the anterior
technique.
*Research Associate, Department of Anesthesiology, Kindai
University Faculty of Medicine, Osaka, Japan.
yAssistant Professor, Department of Anesthesiology, Kindai
zResearch Associate, Department of Anesthesiology, Kindai
xAssistant Professor, Department of Oral Surgery, Osaka Medical
College, Osaka, Japan.
jjRadiological Technologist, Department of Radiology, Kindai
University Hospital, Osaka, Japan.
Conflict of Interest Disclosures: None of the authors have any
relevant financial relationship(s) with a commercial interest.
Address correspondence and reprint requests to Dr Takasugi:
Department of Anesthesiology, Kindai University Faculty of Medi-
cine, 377-2 Ohno-higashi, Osaka-sayama, Osaka 589-8511, Japan;
e-mail: dzc01654@nifty.com
Received January 23 2019
Accepted April 17 2019
Ó 2019 American Association of Oral and Maxillofacial Surgeons
0278-2391/19/30452-5
https://doi.org/10.1016/j.joms.2019.04.021
1

Conclusions: Anesthesia of the buccal nerve using the anterior technique with 2.7 mL of anesthetic so-
lution might contribute to increasing the success rate of anesthesia for removal of mandibular third molars.
Ó 2019 American Association of Oral and Maxillofacial Surgeons
J Oral Maxillofac Surg -:1-13, 2019
The inferior alveolar nerve block (IANB) is the most
common nerve block technique used to reduce pain
due to various surgical interventions involving the
mandible. The conventional approach for IANB (con-
ventional IANB) is the Halsted approach, which in-
volves inserting the tip of the needle near the
mandibular foramen to anesthetize the posterior
branches of the mandibular nerve, including the
lingual and inferior alveolar nerves. Conventional
IANB rarely blocks the buccal nerve.1-5
Hence, if the
lower posterior molars are to be extracted, additional
anesthesia of the relevant buccal gingiva, which is
innervated by the buccal nerve, will be required, in
addition to conventional IANB.
The anterior approach for IANB (anterior tech-
nique) involves injection of local anesthetic solution
into the pterygomandibular space anterior to the
mandibular foramen.6
Okamoto et al,7
found, on
computed tomography (CT) images, that the mixture
containing lidocaine and contrast medium was distrib-
uted, not only in the pterygomandibular space, but
also over the anterior surface of the temporalis tendon.
To the best of our knowledge, the anesthetic effects of
the anterior technique on the buccal gingiva or the
cheek mucosa have not yet been reported. However,
we assumed that the anterior technique would pro-
vide anesthesia in the area of innervation of the buccal
nerve and in the areas of the inferior alveolar and
lingual nerves.
The reported success rates of conventional IANB
and the anterior technique for tooth extraction have
been comparable at 55 to 95%3,8-14
and 75%,6
respec-
tively. Alternative pathways for sensory nerves to the
teeth have been considered as a cause of the failure
of complete anesthesia of the mandibular teeth after
IANB.15,16
The buccal nerve gives off branches that
pass through a small retromolar foramen to supply
the molar teeth.15,17,18
Several reports have indicated
that the volume of anesthetic solution will also
influence the degree of anesthesia.10,19,20
Thus, the
anterior technique, which involves injection of a
larger volume of anesthetic solution, might improve
the success rate of IANB.
The purpose of the present study was to confirm
anesthesia of the buccal nerve and assess enhance-
ment of the anesthetic effect resulting from increasing
the dose of anesthetic solution injected using the ante-
rior technique. We hypothesized that extension of
anesthesia to the innervation area of the buccal nerve
and increasing the dose of anesthetic solution injected
would increase the anesthesia success rate of the ante-
rior technique. The specific aims of the present study
were to 1) verify the extent of anesthesia in the area of
innervation of the buccal nerve after the anterior tech-
nique with different doses of the anesthetic solution;
2) estimate the increase in the anesthesia success
rate of the anterior technique with a larger dose of
anesthetic solution during removal of third molars;
and 3) evaluate the distribution of the anesthetic solu-
tion using magnetic resonance imaging (MRI) in the
pterygomandibular space and anterior surface of the
temporalis tendon after IANB using the ante-
rior technique.
Patients and Methods
STUDY DESIGN AND SAMPLE
To address the research purpose, we designed and
implemented a prospective, randomized, blinded clin-
ical trial. The medical ethics committee of Kindai Uni-
versity Faculty of Medicine approved both the clinical
and the MRI studies (approval no. 28-270, 30-005),
which was registered with the University Hospital
Medical Information Network (nos. UMIN000027380
and UMIN000033780) on May 18, 2017, and August
16, 2018, respectively. The clinical study was per-
formed at the Outpatient Department of Oral and
Maxillofacial Surgery of Kindai University Hospital, Ha-
nano Dental Clinic, and Terabe Dental Clinic. The MRI
study was performed at the Department of Radiology,
Kindai University Hospital.
The study population for the clinical trial included
adult patients, aged 18 years or older, who had been
scheduled for surgical extraction of a mandibular third
molar under local anesthesia with or without sedation,
from June 17, 2017 to August 2, 2018. The exclusion
criteria were a history of hypersensitivity to lidocaine,
paresthesia in the area of innervation of the mandib-
ular nerve, active infection or abscess in the oral and
maxillofacial region, bleeding diathesis, use of antico-
agulant or antiplatelet medications, and other medical
history that might have affected the clinical trial (eg,
uncontrolled hypertension or diabetes mellitus, heart
failure, hyperthyroidism, psychiatric disorders). For
the MRI study, volunteers who had independently
applied for study recruitment in response to a notice
on the university website or an advertisement in the
institution were enrolled, and the study was conduct-
ed from August 30, 2018 to December 20, 2018. All
participants provided written informed consent
2 IANB TO ANESTHETIZE BUCCAL NERVE

before enrolling in the studies, according to the Decla-
ration of Helsinki (General Assembly, October 2008).
STUDY VARIABLES AND OUTCOMES
The primary predictor variables were the approach
for IANB (anterior technique vs conventional IANB)
and the dose of anesthetic solution injected (1.8 mL
vs 2.7 mL). The secondary predictors were gender,
age, level of impaction of the mandibular third molar,
and duration of surgery. The primary outcome variable
of interest was the anesthesia success rate for removal
of third molars. The secondary outcome variables
were the extent of tactile sensory loss in the buccal
nerve innervation area after IANB, onset to lower lip
numbness after IANB, duration of surgery, and interval
between injection and the end of extraction. The study
variables, definitions, and measurements have been
described in the next section.
DATA COLLECTION METHODS
Anesthesia Procedures
The IANB procedure for the anterior technique was
performed using the method described by Takasugi
et al6
and that for the conventional IANB was per-
formed using the method described by Malamed.8
In
brief, for both IANB procedures, the needle insertion
point was the mucosa on the medial side of the
mandibular ramus, lateral to the pterygomandibular
raphe, at the height of the coronoid notch on the ante-
rior border of the ramus (ie, 10 mm above the
occlusal plane of the mandibular molar teeth). For con-
ventional IANB, the syringe barrel was positioned par-
allel to the occlusal plane over the contralateral
mandibular first premolar, and the needle was inserted
to a depth of 20 mm, in accordance with the reported
mean distance between the coronoid notch of the
anterior border of the ramus and the mandibular fora-
men.21
After ensuring the absence of aspiration of
blood, 1.8 or 2.7 mL of anesthetic solution was in-
jected. For the anterior technique, the syringe barrel
was placed over the contralateral mandibular first
molar, and the needle was inserted to a depth
of 10 mm.
The anesthetic solution used was 2% lidocaine con-
taining 1:80,000 adrenaline. In the clinical study, for
the anterior technique, a dental cartridge syringe and
a 31-gauge, 12-mm disposable needle were used for
both doses (1.8 mL and 2.7 mL). Two injections
were used for the dose of 2.7 mL (1.8 and 0.9 mL).
For conventional IANB, a dental cartridge syringe
and 30-gauge 21-mm disposable needle were used
for the 1.8-mL anesthetic dose, and a 3.0-mL dispos-
able syringe and 30-gauge 21-mm disposable needle
was used for the 2.7-mL dose, because needle insertion
twice for the conventional IANB procedure was
considered to increase the possibility of neurovascular
injury. In the MRI study, a 3.0-mL disposable syringe
and 30-gauge 21-mm or 31-gauge 12-mm disposable
needles were used for the injection dose of 2.7 mL.
In the clinical study, because successful IANB will
result in lower lip numbness, patients without lower
lip numbness within 20 minutes after IANB were
excluded from the present study, and further IANB
or infiltration anesthesia was chosen by the attending
surgeon for tooth extraction.
Determination of Tactile Sensory Loss in Buccal
Nerve Innervation Area
After the IANB, tactile sensory loss in the buccal
nerve innervation area was evaluated using tactile
stimulation with a sharp, specially-manufactured
probe. The application force was 200 mN, because
the normal cutaneous pressure pain perception
threshold has been reported to be 200 mN.22
The
probe consisted of a 12-mm nylon monofilament cali-
brated with a buckling load of 200 mN measured by
a digital force gauge (DS2-200N; Imada Co, Ltd, Aichi,
Japan) and a plastic handle (Fig 1).
The area of tactile sensory loss after IANB was inves-
tigated from the distal retromolar area to the midline of
the lower buccal gingiva and the cheek mucosa corre-
sponding to the positions of the respective teeth. The
tactile sensory loss area and position of the mental fo-
ramen with reference to the orthopantomograph were
mapped on a diagram of the teeth (Fig 2).
Extent of Tactile Sensory Loss in Buccal Nerve
Innervation Area After IANB
IANB was performed by dental anesthesiologists
and experienced oral-maxillofacial surgeons, and the
results of IANB were assessed by other clinicians
who were unaware of the IANB procedure performed.
The time course of tactile sensory loss in the buccal
FIGURE 1. Stimulation probe with a nylon monofilament cali-
brated with a buckling load of 200 mN.
Tsukimoto et al. IANB to Anesthetize Buccal Nerve. J Oral Maxillo-
fac Surg 2019.
TSUKIMOTO ET AL 3

nerve innervation area after completion of the IANB
procedures was examined. In total, 108 patients who
had undergone removal of a mandibular third molar
were enrolled. The patients were divided into 2
groups of 54 patients, the anterior and conventional
IANB groups, using a computerized random number
generator. The patients in each group were further
randomly divided into 2 subgroups of 27 patients
each to receive an anesthetic dose of 1.8 or 2.7 mL.
For both IANB procedures, the points of sensory loss
on the lower buccal gingiva and cheek mucosa were
mapped at the point of onset of lower lip numbness
and at the end of extraction. Furthermore, anesthesia
of the buccal gingiva surrounding the molars was
evaluated using dental explorer stimulation or nee-
dle puncture.
Success Rates of IANB With Different Volumes of
Anesthetic Solution
Before removal of the third molars, both the conven-
tional IANB and the anterior technique were followed
by infiltration of 0.9 mL of 2% lidocaine containing
1:80,000 adrenaline around the third molar to reduce
bleeding during tooth extraction and achieve anes-
thesia of the buccal gingiva. When the tooth extraction
had been completed without the need for any addi-
tional infiltration or IANB and the patient had not com-
plained of pain during removal of the tooth using an
elevator or forceps, removal of bone around the tooth,
or cutting the tooth, the IANB was considered success-
ful. The success rates were compared among the
IANB subgroups.
Distribution of Anesthetic Solution After IANB
After IANB, distribution of the anesthetic solution in
the pterygomandibular space and over the anterior sur-
face of the temporalis tendon was evaluated by MRI ex-
amination. An MRI system (Achieva 3.0T; Philips
Japan, Tokyo, Japan) with a 1.5-mm slice thickness
was used in the present study. The cross-sectional im-
ages were reformatted in multiple planes. A web-
based DICOM (Digital Imaging and Communications
in Medicine) viewer (Weasis, version 2.5.3; Atlassian
Pty Ltd, Sydney, NSW, Australia) was used for the subse-
quent measurements. In a preliminary study, the mus-
cles, mandible, and fat-rich structures, including the
pterygomandibular space and submucosal tissue,
could be readily differentiated on T1-weighted images
(T1WIs), and the solution of 2% lidocaine containing
1:80,000 adrenaline could be clearly detected as
brightness (high signal intensity) on T2-weighted im-
ages (T2WIs). The distributions of high signal areas
on 3 consecutive T2WIs at intervals of 5 minutes after
the injection were comparable.
Ten volunteers (6 men and 4 women; median age,
28.5 years) participated in the MRI study. The MRI ex-
amination was performed after confirmation of effec-
tive IANB. Effectiveness was determined by the
FIGURE 2. Diagram for recording the anesthetized points on the lower buccal gingiva and cheek mucosa.
Tsukimoto et al. IANB to Anesthetize Buccal Nerve. J Oral Maxillofac Surg 2019.

appearance of lower lip numbness after injection of
2.7 mL of 2% lidocaine containing 1:80,000 adrenaline
by either of the IANB procedures and evaluation of the
extent of tactile sensory loss in the buccal gingiva and
cheek mucosa. Several days later, the other IANB pro-
cedure was performed on the same side, followed by
the second MRI examination.
With reference to the structures surrounding the
mandibular ramus on the T1WIs, the horizontal and
vertical distributions of the anesthetic solution after
IANB using both approaches in each subject were eval-
uated on the axial, coronal, and sagittal T2WIs.
STATISTICAL ANALYSIS
Sample Size Calculation
The aims of the present study were to verify the
extent of anesthesia of the buccal nerve innervation
area and to compare the success rate of the anterior
technique with a large volume of anesthetic solution
versus that of the anterior technique with 1.8 mL of
anesthetic solution or the conventional IANB tech-
nique for third molar extraction. The present study
lent itself to a noninferiority design.
In the sample size calculation for the present nonin-
feriority trial, based on a previous report23
and the pre-
liminary data from 20 patients, who had undergone
third molar extraction under IANB using the anterior
technique with an injection of 2.7 mL of anesthetic so-
lution, the expected success rate was 65 and 90% for
the control (conventional IANB with 1.8 mL of anes-
thetic solution) and treatment (anterior technique
with 2.7 mL of anesthetic solution) groups, respectively.
The noninferiority margin was set at 10%. Thus, the aim
of our noninferiority trial was to demonstrate that the
anesthetic success rate of IANB using the anterior tech-
nique with 2.7 mL of anesthetic solution would not be
more than 10% worse than that with 1.8 mL of anes-
thetic solution. A sample size of 22 patients per group
was required to achieve more than 80% power with a
1-sided type 1 error of 0.025. Assuming a clinically
reasonable failure rate (ie, no lower lip numbness
within 20 minutes after IANB) of 20%, the required
number of participants included in each group in the
study was 27, allowing for potential withdrawals.
The sample size calculation was performed using
EZR (Saitama Medical Center, Jichi Medical University,
Saitama, Japan), which is a graphical user interface for
R (The R Foundation for Statistical Computing, Vienna,
Austria). More precisely, it is a modified version of R
commander designed to add the statistical functions
frequently used in biostatistics.
Data Collection and Statistical Analyses
We used a custom data collection form in the clinical
study. Panoramic radiographs were used to assess the
level of impaction of the mandibular third molar. The
data were analyzed using Prism software, version 5.0
(GraphPad, San Diego, CA). Data are presented as
the median and interquartile range. The Kruskal-
Wallis test was used to compare the demographic vari-
ables among the groups, and Dunn’s multiple compar-
ison test was used as a post hoc test. In the clinical
evaluations, the anesthetic effects among the measure-
ment points on the lower buccal gingiva and cheek
mucosa, level of impaction of the third molar, and suc-
cess rates for each IANB technique for tooth extraction
were compared and analyzed using the c2
test or the
Fisher exact test. A value of P # .05 was considered
to indicate statistical significance.
Results
EXTENT OF TACTILE SENSORY LOSS IN BUCCAL
NERVE INNERVATION AREA AFTER IANB
In the clinical study, all the patients had experi-
enced lower lip numbness within 20 minutes after
IANB. The patient demographic data and clinical
characteristics are summarized in Tables 1 and 2,
respectively. No statistically significant differences
were found in gender, age, level of impaction of the
mandibular third molar, or duration of surgery among
the groups. The onset of numbness after the anterior
technique with 1.8 mL of anesthetic solution was
later than that with the other IANBs. However, no sta-
tistically significant differences were found in the
onset of numbness between the anterior technique
with 2.7 mL of anesthetic solution and conventional
IANB. The interval between the injection and the
end of extraction with the anterior technique with
Table 1. PATIENT DEMOGRAPHIC DATA
Variable
Dosage (mL)
P Value
Conventional
IANB (n = 27)
Anterior
Technique
(n = 27)
1.8 2.7 1.8 2.7
Gender .9844
Male 11 11 11 8
Female 16 16 16 19
Age (yr) .3912
Median 28 34 28 31
IQR 24-46 26-47 23-43 23-38
Abbreviations: IANB, inferior alveolar nerve block; IQR, in-
terquartile range.
fac Surg 2019.
TSUKIMOTO ET AL 5

2.7 mL anesthetic solution was shorter than the inter-
val with the other IANBs.
When the patients had developed numbness of the
lower lip after IANB, tactile sensory loss had simulta-
neously appeared on the gingival mucosa of the injec-
tion side, extending from the mesial area of the lower
central incisor to the area of the mental foramen of the
lower buccal gingiva. At the onset of lower lip numb-
ness after the anterior technique with 1.8 and 2.7 mL
of anesthetic solution, all the patients had tactile sen-
sory loss in the buccal nerve innervation field. Of the
27 patients in the 1.8-mL group and the 27 patients
in the 2.7-mL group, 15 (56%) and 18 (67%) revealed
tactile sensory loss over the entire lower buccal
gingiva and 18 (67%) and 19 (70%) revealed tactile sen-
sory loss on the cheek mucosa up to near the upper
mucobuccal fold, respectively. None of the patients
complained of needle puncture pain during infiltra-
tion anesthesia at the buccal gingiva. In contrast, after
conventional IANB with 1.8 and 2.7 mL of anesthetic
solution, 4 of 27 (15%) and 9 of 27 (33%) revealed
tactile sensory loss over the entire lower buccal
gingiva and 5 (19%) and 9 (33%) revealed sensory
loss over the entire cheek mucosa, respectively. More-
over, all patients receiving conventional IANB com-
plained of needle puncture pain during subsequent
infiltration anesthesia, except for 2 patients who had
undergone conventional IANB with 2.7 mL of anes-
thetic solution (Fig 3).
At the end of third molar extraction, 30 minutes af-
ter the IANB injection, tactile sensory loss was present
over the entire area of the lower buccal gingiva and the
cheek mucosa in all the patients in all subgroups.
SUCCESS RATES OF IANBs WITH DIFFERENT
ANESTHETIC SOLUTION VOLUMES
The success rates of third molar extraction after
IANB using the anterior technique or conventional
IANB with 1.8 mL or 2.7 mL of anesthetic solution
are shown in Figure 4. None of the patients experi-
enced neurovascular complications during or after
the operation.
Increasing the volume of the anesthetic solution
increased the success rate of the anterior technique,
with a success rate of 67% with a dose of 1.8 mL of
anesthetic solution and 96% with a dose of 2.7 mL of
anesthetic solution (P = .0113). However, increasing
the anesthetic volume with conventional IANB had
no effect on its efficacy (P = 1.000). No statistically sig-
nificant differences were found in the success rates
among the IANBs performed using the anterior
Table 2. CLINICAL CHARACTERISTICS AFTER CONVENTIONAL IANB AND THE ANTERIOR TECHNIQUE
Characteristic
Dosage (mL)
P Value
Conventional IANB Anterior Technique
1.8 (n = 27) 2.7 (n = 27) 1.8 (n = 27) 2.7 (n = 27)
Level of impaction of third
molar
.4836
Normal 6 3 4 7
Impacted 21 24 23 20
Onset of lower lip numbness
(minutes)
.0001
Median 5* 6* 10y
5*
IQR 3-8 3-8 8-12 4-8
Duration of surgery (minutes) .0933
Median 20 23 21 15
IQR 11-27 13-32 13-28 9-22
Interval between injection and
end of extraction
(minutes)
.0420
Median 36 34 36 27*
IQR 26-42 30-46 29-45 21-37
Note: The c2
test was used to compare level of third molar impaction among groups, the Kruskal-Wallis test was used for
comparisons among groups, and Dunn’s multiple comparison test was used as a post hoc test.
Abbreviations: IANB, inferior alveolar nerve block; IQR, interquartile range.
* P .05 vs anterior technique with 1.8 mL of anesthetic solution.
y P .001 vs conventional IANB with 1.8 mL of anesthetic solution.

technique and conventional IANB with the same dose
of anesthetic solution.
DISTRIBUTION OF ANESTHETIC SOLUTION AFTER
IANB
Two of the 10 subjects who participated in the MRI
study, one who had received IANB using conventional
IANB and one who had received IANB using the ante-
rior technique, indicated lower lip and tongue numb-
ness but showed significant amounts of anesthetic
solution in the medial pterygoid muscle on MRI.
Hence, these cases were excluded from the MRI ana-
lyses. All the subjects receiving the anterior technique
(100%) and 3 subjects receiving conventional IANB
(33%) indicated numbness over the lower buccal
gingiva and cheek mucosa, as well as numbness at
the lower lip and tongue, after injection of 2.7 mL of
anesthetic solution.
After the anterior technique, the axial T2WIs of all
the subjects indicated distribution of the anesthetic so-
lution from the anterior surface of the temporalis
tendon to behind the mandibular foramen in the pter-
ygomandibular space. On the sagittal T2WIs, the distri-
bution of the anesthetic solution after both the anterior
technique and the conventional IANB procedure were
almost the same, except for distribution at the anterior
surface of the temporalis tendon with the anterior
technique. The upper level of the distribution of the
anesthetic solution behind the temporalis tendon
was at the lower surface of the lateral pterygoid mus-
cle, and that at the narrow gap between the temporalis
tendon and the anterior portion of the lateral pterygoid
muscle was near the level of the junction between the
FIGURE 3. Incidence of tactile sensory loss on the lower buccal gingiva and cheek mucosa at the onset of lower lip numbness after conven-
tional inferior alveolar nerve block (IANB) and the anterior technique. The teeth numbers 1 through 8 indicate the teeth in order from the central
incisor to the mandibular third molar.
FIGURE 4. Comparison of success rates of third molar extraction
among inferior alveolar nerve block (IANB) methods and anesthetic
volumes using the Fisher exact test.
fac Surg 2019.
TSUKIMOTO ET AL 7

superior and inferior heads of the lateral pterygoid
muscle (Fig 5).
On the coronal T2WIs after both methods, the anes-
thetic solution was distributed in the pterygomandibu-
lar space, where a narrow gap is present between the
mandibular ramus and medial pterygoid muscle in the
lower region, and the mandibular ramus and lateral sur-
face of the lateral pterygoid muscle in the upper re-
gion. The distribution continued up to near the
junction between the superior and inferior heads of
the lateral pterygoid muscle. On the coronal T2WIs
through the mandibular condyle, the anesthetic
solution was distributed as high as 20 mm below
the base of the skull, in the vicinity of the foramen
ovale. At the anterior surface of the temporalis tendon,
the anesthetic solution was vertically distributed from
the level of the occlusal plane to 20 mm above using
the anterior technique, but not with conventional
IANB, without tactile sensory loss at the lower buccal
gingiva and the cheek mucosa (Fig 6).
In the patients with obvious numbness of the buccal
gingiva and cheek mucosa after conventional IANB,
the anesthetic solution extended forward to the ante-
rior surface of the temporalis tendon. The density
FIGURE 5. Typical distribution of anesthetic solutions in the pterygomandibular space after conventional inferior alveolar nerve block (IANB)
and anterior technique with 2.7 mL of anesthetic solution. Numbness of the buccal gingiva and cheek mucosa was indicated after the anterior
technique but not after conventional IANB. T1- and T2-weighted magnetic resonance imaging (MRI) scans were obtained at the same axial and
sagittal plane levels. Arrows indicate presence of the anesthetic solution (high signal). A, Coronal slice showing the anterior surface of the tem-
poralis tendon; and B, sagittal slice showing the temporalis tendon. LPM, lateral pterygoid muscle; MM, masseter muscle; MPM, medial pter-
ygoid muscle; MR, mandibular ramus; PG, parotid gland; T1WI, T1-weighted image; T2WI, T2-weighted image; TM, temporal muscle.

and area of spread of the anesthetic solution was
thinner and narrower than with the anterior technique
(Fig 7).
Discussion
The present study aimed to determine the efficacy
of anesthesia of the buccal nerve and the anesthetic
effect achieved by increasing the dose of anesthetic
solution for IANB. We hypothesized that anesthesia
of the buccal nerve and increasing the dose of the
anesthetic solution administered for IANB using
the anterior technique might increase the anesthesia
success rate for mandibular molar tooth extraction.
Therefore, we evaluated the extent of anesthesia in
the area of innervation of the buccal nerve and
compared the anesthesia success rate between the
anterior technique and conventional IANB in a clin-
ical study. We also evaluated the distribution of anes-
thetic solution in the pterygomandibular space in an
MRI study. In the clinical study, the anterior tech-
nique provided anesthesia, not only in the innerva-
tion area of the inferior alveolar and lingual nerves,
but also in that of the buccal nerve. Furthermore,
faster onset and a greater success rate for third
molar extraction were obtained with 2.7 mL
compared with 1.8 mL of the anesthetic solution.
The MRI study showed that after injection using
the anterior technique, the anesthetic solution was
distributed, not only in the pterygomandibular
space, but also in the adipose tissue over the ante-
rior surface of the temporalis tendon. We also
demonstrated that although some patients who
had received conventional IANB showed tactile
FIGURE 6. Typical distribution of the anesthetic solution on coronal magnetic resonance imaging (MRI) scans after conventional inferior alve-
olar nerve block (IANB) and the anterior technique with 2.7 mL of anesthetic solution. The T1- and T2-weighted images (T1WIs and T2WIs,
respectively) showed the same levels in the coronal plane. A, Coronal MRI scan through the anterior surface of the temporalis tendon; B, coronal
MRI scan through the posterior surface of the temporalis tendon; C, coronal MRI scan through the mandibular notch; and D, coronal MRI scan
through the mandibular condyle. Arrows indicate presence of the anesthetic solution (high signal intensity). LPM, lateral pterygoid muscle; MC,
mandibular condyle; MM, masseter muscle; MPM, medial pterygoid muscle; MR, mandibular ramus; TM, temporal muscle.
TSUKIMOTO ET AL 9

sensory loss at the gingival mucosa, the level of
gingival anesthesia required for needle puncture
was rarely achieved.
The mandibular nerve trunk exiting through the fo-
ramen ovale of the sphenoid bone is located close to
the lateral pterygoid muscle. The buccal nerve
branches from the mandibular nerve immediately
below the foramen ovale proceeds forward between
the lateral pterygoid heads, descends across the ante-
rior margin of the temporalis or through the tendon
of the temporalis muscle, and passes across the
external oblique ridge.24
It then enters the fascial
sleeve in the temporal buccinator band and supplies
sensory fibers to the lower buccal gingiva and lower
buccal sulcus and cheek mucosa and might contribute
to the extraoral cutaneous supply of the cheek.1,2,25,26
It has been widely recognized that conventional IANB
will block the inferior alveolar nerve and lingual nerve
but will only rarely block the buccal nerve. However,
from the findings from a radiologic study, Okamoto
et al7
hypothesized that the anterior technique might
achieve anesthesia of the buccal nerve, as well as the
inferior alveolar and lingual nerves (Fig 8).
In the present clinical study, in contrast to our ex-
pectations, 25 and 60% of the patients undergoing
conventional IANB with a dose of 1.8 and 2.7 mL,
FIGURE 7. Distribution of anesthetic solution on axial magnetic resonance imaging scans of patients with obvious numbness of the buccal
gingiva and cheek mucosa after conventional inferior alveolar nerve block (IANB) and the anterior technique with 2.7 mL of anesthetic solution.
A, Coronal slice showing the anterior surface of the temporalis tendon; and B, sagittal slice showing the temporalis tendon. LPT, lateral pterygoid
muscle; MM, masseter muscle; MPM, medial pterygoid muscle; MR, mandibular ramus; PG, parotid gland; T1WI, T1-weighted image; T2WI,
T2-weighted image; TM, temporal muscle.

respectively, of the anesthetic solution indicated
tactile sensory loss involving the buccal gingiva and
cheek mucosa from the retromolar area to the lower
molars. However, adequate anesthesia for needle
puncture at the buccal gingiva around the third molar
was achieved only rarely. This result of the tactile sen-
sory test indicates the possibility that even with con-
ventional IANB, the anesthetic solution deposited
near the mandibular foramen could occasionally
extend to the buccal nerve.
IANBs performed using the Gow-Gates and Vazirani-
Akinosi methods, in which the needle tip is inserted
closer to the anterolateral condylar neck and medial
surface of the mandibular ramus approximately
halfway between the mandibular foramen and neck
of the mandibular condyle, respectively, have been re-
ported to consistently block the buccal nerve.1,27,28
We have supposed that with the Gow-Gates and
Vazirani-Akinosi methods, the anesthetic solution
might extend upward, posterior to the lateral ptery-
goid muscle and immediately below the foramen
ovale, where the buccal nerve branches from the
mandibular nerve. The volume of the pterygomandib-
ular space has been estimated at 2 cm3
; thus, a 2.2-
mL dose would completely fill the space.29,30
The
MRI study revealed that 2.7 mL of anesthetic
solution, which was deposited in the
pterygomandibular space using conventional IANB
and the anterior technique, resulted in a maximal
upward distribution of the anesthetic solution to the
lower surface of the lateral pterygoid muscle and
backward distribution to the front of the parotid
gland. However, the anesthetic solution did not
extend to the level of the branching of the buccal
nerve from the mandibular nerve.
The buccal nerve proceeds forward between the
lateral pterygoid heads, crosses the narrow fatty gap
into the temporal muscle at its attachment with the co-
ronoid process of the mandible, and descends through
the tendon of the temporalis to the anterior face of the
temporalis. With both IANB techniques, irrespective
of whether tactile sensory loss had been achieved in
the area of the buccal nerve, the T2WIs indicated
that upward spread of the anesthetic solution
extended close to the junction between the superior
and inferior heads of the lateral pterygoid muscle
through the narrow fatty gap. In contrast, in all partic-
ipants who had undergone the anterior technique and
those participants with tactile sensory loss in the
innervation area of the buccal nerve after conventional
IANB, the T2WIs revealed contiguous distribution of
the anesthetic solution from the pterygomandibular
space to the anterior surface of the temporalis tendon,
where the buccal nerve emerges from the temporalis
tendon. Thus, we believe the anesthetic solution could
contact the buccal nerve at the posterior surface of the
FIGURE 8. Diagrammatic representation of the inferior alveolar nerve and related anatomic structures involved in inferior alveolar nerve
blocks. The light blue area indicates the distribution of the anesthetic solution in the pterygomandibular space and over the anterior surface
of the temporalis muscle after local anesthetic injection using conventional inferior alveolar nerve block (IANB) and the anterior technique.
TSUKIMOTO ET AL 11

temporal muscle and might contribute to tactile sen-
sory loss in the innervation area of the buccal nerve.
In the present clinical study, once lower lip numb-
ness had occurred after the anterior technique using
both 1.8 and 2.7 mL of anesthetic solution, tactile sen-
sory loss and anesthesia developed 10 minutes after
injection at the lower buccal gingiva and cheek mu-
cosa corresponding to the molars. Also, after 1.8 and
2.7 mL, 60 and 70% of the patients reported sensory
loss over the entire lower buccal gingiva and cheek
mucosa, respectively. Once infiltration anesthesia
had reached the buccal gingiva, none of the patients
who had received the anterior technique complained
of needle puncture pain. After conventional IANB with
2.7 mL of anesthetic solution, in contrast to previous
reports, 60% of the patients indicated tactile sensory
loss at the area of the buccal nerve. However, only 2
patients revealed anesthesia against needle puncture
around the third molar. The MRI study indicated that
conventional IANB with a volume of anesthetic greater
than the volume of the pterygomandibular space re-
sulted in more widespread distribution of the anes-
thetic solution over the anterior surface of the
temporalis tendon, producing tactile sensory loss in
the area of innervation of the buccal nerve. Thus, an
adequate volume of anesthetic solution at the anterior
surface of the temporalis tendon might be necessary to
produce anesthesia against needle insertion.
In almost all patients and using both IANB ap-
proaches, the entire area of the lower buccal gingiva
and cheek mucosa innervated by the buccal nerve
indicated tactile sensory loss at the completion of
tooth extraction. We presumed that infiltration anes-
thesia around the third molar might block the branch
of the buccal nerve innervating the premolar region,
which was the least affected area.31
Alternative pathways for sensory nerves to the teeth
have been reported to be responsible for the failure of
complete anesthesia to the mandibular teeth after con-
ventional IANB.15,16
The retromolar foramen and
retromolar canal, which are anatomic structures of
the mandible located in the retromolar fossa behind
the third molar tooth, contain neurovascular
structures that provide accessory or additional
innervation to the mandibular molars and buccal
area.32,33
The retromolar foramen will be situated at
a mean distance of 4 to 11 mm from the mandibular
third molar tooth33-35
in 7 to 25% of people.33-38
Reportedly, the additional branches of the buccal
nerve, inferior alveolar nerve, and deep temporal
nerve could enter the retromolar foramen.15-17,32-34
Our MRI study indicated that after injection using
the anterior technique, the anesthetic solution will
be distributed over the anterior surface of the
temporalis tendon up to a height of 20 mm from
the level of the occlusal plane. Thus, blockage of the
buccal nerve proximal to the retromolar foramen
could be involved in the high success rate of the
anterior technique for third molar extraction.
The findings from the present study have indicated
that increasing the volume of the anesthetic solution
injected using the anterior technique will result in a
greater success rate and faster onset of anesthesia for
third molar extraction. Axial MRI studies showed
that when 2.7 mL of the anesthetic solution was in-
jected using the anterior technique, the solution was
distributed from the anterior surface of the temporalis
tendon to the front of the parotid gland. In contrast,
Okamoto et al7
reported a case of backward distribu-
tion to the mandibular foramen on axial CT images af-
ter the anterior technique with an injection of 1.8 mL
of contrast medium-containing anesthetic solution.
We presumed that lack of anesthesia to the mandibular
nerve resulting from an inadequate volume of anes-
thetic solution might have contributed to failed anes-
thesia for third molar extraction using the anterior
technique with 1.8 mL of anesthetic solution.
The results of our study must be considered in light of
some limitations. First, we compared the anesthetic ef-
ficacy of IANBs for third molar extraction using doses of
1.8 and 2.7 mL of anesthetic solution (ie, 1 and 1.5
dental cartridges). Conventional IANB using more
than 2.7 mL of anesthetic solution might result in a
greater success rate compared with conventional
IANB with smaller volumes of injection for third molar
extraction. However, multiple injections with doses
greater than 1.8 mL of anesthetic solution using conven-
tional IANB might increase the risk of complications,
including neural, vascular, and muscle injuries. Second,
we did not examine the anesthetic efficacy of the ante-
rior technique in mandibular molar teeth with symp-
tomatic irreversible pulpitis. Several reports19,20,39
have indicated that increasing the volume of
anesthetic solution for conventional IANB achieved
greater success for molar teeth with irreversible
pulpitis, although not 100% of anesthetic success.
Further exploration is required to clarify this finding.
The anterior technique has been reported to
achieve anesthesia of the inferior alveolar nerve with
a low risk of neurovascular complications.6
The ante-
rior technique using 2.7 mL of anesthetic solution pro-
vided fast onset and a wider area of anesthesia,
including the lower buccal gingiva and cheek mucosa,
and almost complete anesthesia for third molar extrac-
tion. The anterior technique, which requires a lower
volume of anesthetic solution and a smaller number
of injections without needle puncture-related pain,
will, thus, be useful for oral surgery, not only for molar
extraction, but also for soft tissue surgery involving the
mandibular buccal gingiva and cheek mucosa.
In conclusion, IANB using the anterior technique
achieves a wide area of anesthesia involving the

innervation areas of the inferior alveolar, lingual, and
buccal nerves. MRI examinations proved that the in-
jected local anesthetic solution was distributed over
the anterior surface of the temporalis tendon from
the pterygomandibular space, contributing to the
wide extent of anesthesia with the anterior technique.
Acknowledgments
The authors would like to thank the staff of the Department of
Radiology and Department of Oral and Maxillofacial Surgery, Kindai
University Hospital, for supporting our clinical study. The authors
are also extremely grateful to Professor Kazunari Ishii (Department
of Radiology, Kindai University Faculty of Medicine) and Professor
Takamichi Murakami (Department of Radiology, Kobe University
Faculty of Medicine) for guidance with the radiologic study.
References
1. Aker FD: Blocking the buccal nerve using two methods of infe-
rior alveolar block injection. Clin Anat 14:111, 2001
2. Barker BC, Davies PL: The applied anatomy of the pterygoman-
dibular space. Br J Oral Surg 10:43, 1972
3. Budenz AW, Osterman SR: A review of mandibular anesthesia
nerve block techniques. J Calif Dent Assoc 23:27, 1995
4. Shaw MD, Fierst P: Clinical protection for dental gross anatomy:
A medial approach to the pterygomandibular space. Anat Rec
222:305, 1988
5. Robertson WD: Clinical evaluation of mandibular conduction
anesthesia. Gen Dent 27:49, 1979
6. Takasugi Y, Furuya H, Moriya K, Okamoto Y: Clinical evaluation
of inferior alveolar nerve block by injection into the pterygo-
mandibular space anterior to the mandibular foramen. Anesth
Prog 47:125, 2000
7. Okamoto Y, Takasugi Y, Moriya K, Furuya H: Inferior alveolar nerve
block by injection into the pterygomandibular space anterior to
the mandibular foramen: Radiographic study of local anesthetic
spread in the pterygomandibular space. Anesth Prog 47:130, 2000
8. Malamed SF: 14 Techniques of mandibular anesthesia. Part III:
Techniques of Regional Anesthesia in Dentistry, in Malamed SF
(ed): Handbook of Local Anaesthesia (ed 6). St. Louis, MO,
Mosby, 2012, p 225
9. Donkor P, Wong J, Punnia-Moorthy A: An evaluation of the closed
mouth mandibular block technique. Int J Oral Maxillofac Surg
19:215, 1990
10. Yared GM, Dagher FB: Evaluation of lidocaine in human inferior
alveolar nerve block. J Endod 23:575, 1997
11. Berezowski BM, Lownie JF, Cleaton-Jones PE: A comparison of
two methods of inferior alveolar nerve block. J Dent 16:96, 1988
12. Rood JP: Inferior alveolar nerve blocks—The use of 5 percent
lignocaine. Br Dent J 140:413, 1976
13. Waikakul A, Punwutikorn J: A comparative study of the extra-
intraoral landmark technique and the direct technique for infe-
rior alveolar nerve block. J Oral Maxillofac Surg 49:804, 1991
14. Vreeland DL, Reader A, Beck M, et al: An evaluation of volumes
and concentrations of lidocaine in human inferior alveolar nerve
block. J Endod 15:6, 1989
15. Berkovitz BK: Chapter 31: Oral cavity. Section 4: Head and neck,
in Standring S (ed): Gray’s Anatomy: The Anatomical Basis of
Clinical Practice (ed 41). London, UK, Elsevier, 2016, p 507
16. Rodella LF, Buffoli B, Labanca M, Rezzani R: A review of the
mandibular and maxillary nerve supplies and their clinical rele-
vance. Arch Oral Biol 57:323, 2012
17. Carter RB, Keen EN: The intramandibular course of the inferior
alveolar nerve. J Anat 108:433, 1971
18. Coleman RD, Smith RA: The anatomy of mandibular anesthesia:
Review and analysis. Oral Surg 54:148, 1982
19. Aggarwal V, Singla M, Miglani S, et al: Comparative evaluation of
1.8 mL and 3.6 mL of 2% lidocaine with 1:200,000 epinephrine
for inferior alveolar nerve block in patients with irreversible pul-
pitis: A prospective, randomized single-blind study. J Endod 38:
753, 2012
20. Abazarpoor R, Parirokh M, Nakhaee N, Abbott PV: A comparison
of different volumes of articaine for inferior alveolar nerve block
for molar teeth with symptomatic irreversible pulpitis. J Endod
41:1408, 2015
21. Thangavelu K, Kannan R, Kumar NS, et al: Significance of local-
ization of mandibular foramen in an inferior alveolar nerve
block. J Nat Sci Biol Med 3:156, 2012
22. Chantelau EA, Wienemann T: Pressure pain perception in the
diabetic Charcot foot: Facts and hypotheses. Diabet Foot Ankle
4, 2013
23. Levy TP: An assessment of the Gow-Gates mandibular block for
third molar surgery. J Am Dent Assoc 103:37, 1981
24. Takezawa K, Ghabriel M, Townsend G: The course and distribu-
tion of the buccal nerve: Clinical relevance in dentistry. Aust
Dent J 63:66, 2018
25. Kim HJ, Kwak HH, Hu KS, et al: Topographic anatomy of the
mandibular nerve branches distributed on the two heads of
the lateral pterygoid. Int J Oral Maxillofac Surg 32:408, 2003
26. Hendy CW, Robinson PP: The sensory of distribution of buccal
nerve. Br J Oral Maxillofac Surg 32:384, 1994
27. Yu F, Xiao Y, Liu H, et al: Evaluation of three block anesthesia
methods for pain management during mandibular third molar
extraction: A meta-analysis. Sci Rep 7:40987, 2017
28. Todorovi
c L, Stajci
c Z, Petrovi
c V: Mandibular versus inferior
dental anaesthesia: Clinical assessment of 3 different tech-
niques. Int J Oral Maxillofac Surg 15:733, 1986
29. Murphy TR, Grundy EM: The inferior alveolar neurovascular
bundle at the mandibular foramen. Dent Pract Dent Rec 20:
41, 1969
30. Kohler BR, Castell
on L, Laissle G: Gow-Gates technique: A pilot
study for extraction procedures with clinical evaluation and re-
view. Anesth Prog 55:2, 2008
31. Wongsirichat N, Pairuchvej V, Arunakul S: Area extent anaes-
thesia from buccal nerve block. Int J Oral Maxillofac Surg 40:
601, 2011
32. Kumar Potu B, Jagadeesan S, Bhat KM, Rao Sirasanagandla S: Ret-
romolar foramen and canal: A comprehensive review on its anat-
omy and clinical applications. Morphologie 97:31, 2013
33. Gamieldien MY, Van Schoor A: Retromolar foramen: An anatom-
ical study with clinical considerations. Br J Oral Maxillofac Surg
54:784, 2016
34. Potu BK, Kumar V, Salem AH, Abu-Hijleh M: Occurrence of the
retromolar foramen in dry mandibles of South-Eastern part of In-
dia: A morphological study with review of the literature. Anat
Res Int 296717:2014, 2014
35. Bilecenoglu B, Tuncer N: Clinical and anatomical study of retro-
molar foramen and canal. J Oral Maxillofac Surg 64:1493, 2006
36. Sawyer DR, Kiely ML: Retromolar foramen: A mandibular variant
important to dentistry. Ann Dent 50:16, 1991
37. Lizio G, Pelliccioni GA, Ghigi G, et al: Radiographic assessment
of the mandibular retromolar canal using cone-beam computed
tomography. Acta Odontol Scand 71:650, 2013
38. Alves N, Deana NF: Anatomical and radiographical study of the
retromolar canal and retromolar foramen in macerated mandi-
bles. Int J Clin Exp Med 8:4292, 2015
39. Fowler S, Reader A: Is a volume of 3.6 mL better than 1.8 mL for
inferior alveolar nerve blocks in patients with symptomatic irre-
versible pulpitis? J Endod 39:970, 2013
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