you don’t own one, consider buying one. This is
particularly essential for hands-on learners. I
bought my first one several years ago when I began
making my own images for CE courses. I bring it
on-site so that participants can see and feel the
anatomy as I talk about the injections. The anatomically correct, 3-D skull is so much more helpful
for feeling anatomy and practicing angulation than
looking at pictures alone. Decent skulls can be
purchased for about $100. Explain to the manufacturer that you need a skull that accurately reflects the important landmarks (lingula, mandibular foramen, internal oblique ridge, mental
foramen, etc). Next, find your head-and-neck
anatomy textbook, and together with the skull
begin to locate important landmarks. Although it
is true that the location of the lingula varies quite
a bit, note how it is positioned relative to the mandibular foramen, and practice placing your thumb/
finger at the coronoid notch and palpating the
internal oblique ridge (see Figures 1, 2).
The target for deposition is the IA nerve after
it exits the foramen ovale but before it enters the
mandibular foramen. Note that the mandibular
foramen is partially covered by the often-elusive
lingula (“little tongue”) (see Figure 3). Deposition
must be within 1 mm of the target for effective
The insertion site is determined by the intersection of two imaginary lines (see Figure 4):
• Height: Imaginary horizontal line from
coronoid notch to pterygomandibular raphe
(PMR) approximately 6–10 mm superior and
parallel to the mandibular occlusal plane.
• Anteroposterior ( front-to-back):
Imaginary vertical line three-quarters of the
distance from the coronoid notch to the
2 Some experts report the vertical line
should be two-thirds of the distance.
REVIEW THE BASIC TECHNIQUE:
Textbooks are very useful, especially for reviewing
the details of anatomical features and technique.
Your local anesthesia textbook can be a guide or
you can buy a more current one, new or used,
online. Used textbooks of the most current editions
that I have purchased online have always been in
excellent condition. I took a look at my original
local anesthesia textbook from 1979 to compare
the technique from that era to what is recommended currently (see Table 1). The biggest changes I identified were:
1. It is no longer recommended to deposit
drops of anesthetic ahead of the needle
along the way to the target.
2. An aspiration test should be performed
in two or three planes, not just one.
3. There is usually no need to provide a
separate injection for the lingual nerve
during withdrawal, as the lingual nerve is
Figure 4: Mandible, left side; insertion site.
Intersection of horizontal green line drawn
from coronoid notch to the pterygomandibular
raphe (PMR) and the vertical yellow line
drawn three-quarters of the distance from the
coronoid notch to the PMR.
Figure 5: Early
bone contact; after
direct barrel more
Figure 6: No bone
direct barrel more
OVERVIEW OF APPROACH TO THE TRADITIONAL IANB
• A 25-gauge, long needle is used to discourage needle deflection and breakage and to facilitate reliable aspiration. The aspiration rate for the IANB is 10%–15%.
• Locate the insertion site as described earlier. After proper preparation of tissue at injection
site (dry, apply topical one to two minutes), redry tissue, and pull the tissue laterally under
the thumb/finger of the nondominant hand to make the tissue taut. Place the barrel of the
syringe over the contralateral premolar area and establish a fulcrum.
• Form a mental image of the target.
• Penetrate mucosa and slowly advance the needle until bone is contacted gently, usually
at a depth of 20–25 mm (two-thirds to three-quarters of the length of a long needle) for an
average skull. There is no need to deposit anesthetic during advancement. Local anesthetic
must not be deposited if bone contact is not made. If bone is not contacted, the needle may
be located within the parotid gland, and deposition can result in complications including
facial nerve paralysis.
- Early contact: For an average skull, if bone is contacted too early (less than half the
length of a long needle), then the needle is located too far laterally on the ramus. Correct by withdrawing needle partially and moving the syringe barrel toward the anterior
teeth on the contralateral side, which will position the needle more medially. Advance
again until appropriate insertion depth and bone contact is made (figure 5).
- No contact: If bone is not contacted at the proper depth of insertion, the needle tip is
located too far posterior on the medial surface, and as described above may be located within the parotid gland. Correct by withdrawing the needle partially and moving the
syringe barrel toward the posterior teeth on the contralateral side. Advance again until
the appropriate insertion depth and bone contact are made (figure 6).
• Carefully withdraw 1 mm or less and aspirate in two or three planes. If aspiration is negative,
slowly deposit 1. 5 mL (approximately three-quarters of a cartridge) over a minimum of 60