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20
Alternatives toConventional Techniques
In this chapter, we review four types of technique that can
be used instead of the traditional methods discussed so far,
although, as we will see, some of these methods yield
poorer results. Nevertheless, they do have a series of advantages. The methods we review are the following:
● Jet injection.
● Electronic dental anesthesia.
● Computer- controlled injection systems.
● Intranasal maxillary local anesthesia (Kovanaze®).
Jet Injection
This alternative injection technique is based on injecting
the local anesthetic solution without a needle. The solution
is propelled at speed in a fine, high- pressure jet in such a
way that it crosses the oral mucosa to reach the subcutaneous tissue painlessly; this is why it is also known as highpressure jet injection.
This technique arose from a workplace accident. Fuel oil
under pressure accidentally penetrated the fingers of a
diesel mechanic. The oil passed deep under the skin,
leading to the loss of fingers owing to its toxic effect.
However, the liquid did not hurt when it penetrated the
skin (Figge and Scherer1947; Stephens and Kramer1964).
Marshall Lockhart is said to have patented the first highspeed jet injection machine in 1936 (Warren et al. 1955;
Bennett etal.1971). However, it was first used in cadavers
by Figge and Scherer (1947). In the same year, it was
applied in clinical practice for the injection of procaine
with epinephrine into the skin (Hingson and Hughes1947).
In 1958, Margetis used it for the first time to administer
local dental anesthetic (Margetis etal.1958). The device in
all these cases was the Hypospray (Stephens and
Kramer1964; Schmidt1966), which was first introduced in
1947 (Kutscher and Zegarelli 1965). Hypospray was followed by many other commercial devices (Annex 33), of
which the most widely used today are Syrijet® and Injex®.
Distribution ofthe Solution
Distribution of the solution has been studied in cadavers
(Figge and Scherer 1947; Kramer 1962; Whitehead and
Young1968), rats (Bennett etal.1971; Ikehara etal.1972;
ElGeneidy et al.1974), and dogs (Bell etal.1971). Once
discharged, the local anesthetic solution crosses the
mucosa and tends to spread through the connective tissue
laterally in parallel to the mucosa (Kramer1962; Stephens
and Kramer 1964; Bennett et al. 1971) and manages to
cover 10–40
mm in 90% of cases (Whitehead and
Young1968). The amplitude also depends on the area of
discharge (Garellek1967), in such a way that it can reach
mm in the buccal, 10 mm in the palate, and only 5 mm in
15
the mandibular sulcus.
The entry wound is round or slightly irregular, with a
diameter similar to that of the needle as it enters tissue
(Stephens and Kramer1964). The solution enters the area
of least resistance and therefore penetrates better in looser
connective tissue (Bell et al. 1971; Bennett et al. 1971;
ElGeneidy etal.1974). However, it does not penetrate or
does so slightly in barrier structures such as bone, periosteum, nerve stem, vessels, salivary glands, and muscle
(Stephens and Kramer1964; Kutscher and Zegarelli1965;
Bennett etal.1971; Epstein1971; ElGeneidy etal. 1974).
When it penetrates the muscles, it does so across fascial
planes but not within the muscle structure (Bennett
etal.1971).
Deep penetration depends on the following: (i) the discharge area – penetration is 5
mm in the buccal and
10–15 in the mandibular sulcus (Garellek1967; Bennett
etal.1971 oral); and (ii) the quantity injected– penetration
is 5 mm with 0.05 ml and 15 mm with 0.2 ml (Bennett
etal.1971).
Microlesions may remain after discharge (Stephens and
Kramer 1964) with subcutaneous edema, separation of
collagen fibers (Ikehara et al. 1972), and inflammatory
reaction (ElGeneidy etal.1974), which differ little from the
microlesions caused by a needle. Furthermore, while the
Local Anesthesia in Dentistry: A Locoregional Approach, First Edition. Jesús Calatayud and Mana Saraghi.
© 2024 John Wiley & Sons Ltd. Published 2024 by John Wiley & Sons Ltd.
Companion website: www.wiley.com/go/Calatayud/local
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most concentrated anesthetic solutions (5% vs 2%) increase
the frequency of tissue lesions (Bennett et al. 1971),
they also enhance clinical outcomes (Lambrianidis
etal.1979–1980).
When we compare high- pressure jet injection with conventional injection, we see that a needle makes it possible
to place the anesthetic solution at the required depth and to
administer the required quantity of solution at this level in
such a way that it leaves a deposit (Stephens and
Kramer1964). However, with jet injection, we can see how
it loses strength from the moment it crosses the mucosa
and cannot reach very deep areas. In addition, the solution
penetrates deeper, therefore a smaller quantity of anesthetic is administered (Stephens and Kramer 1964;
Epstein1971). Since it is injected suddenly, it mixes more
with tissues without leaving a deposit from which it can
then spread out (Bell et al.1971). The microlesions produced by both systems are similar (Stephens and
Kramer1964; Ikehara etal.1972; ElGeneidy etal.1974).
Indications
As we have seen, this technique does not ensure deep
anesthesia because the solution does not penetrate deeply
into the tissue or, if it does, it delivers a small quantity of
anesthetic. It can therefore prove useful in the following
situations:
Disadvantages
The technique has various disadvantages owing to the
characteristics of distribution of local anesthetic solution
(see above):
1) Insufficient depth of anesthesia to ensure pulpal anesthe-
sia (Dabarakis et al.2007): Björn used an electric pulp
tester to show that pulpal anesthesia is achieved in 13%
of cases (Lethinen1979). Anesthesia of deeper
also poorer, therefore it yields poorer results insurgical
techniques, extractions (Kutscher and Zegarelli 1965;
Saravia and Bush 1991; Boj 1992; Arapostathis
et al. 2010), endodontics, pulpotomy (Epstein 1971;
Boj 1992), crown cutting and bridges in vital teeth
(Kutscher and Zegarelli1965), obturations in permanent
teeth (Epstein 1971; Saravia and Bush1991; Boj 1992)
and primary teeth– although there may be some success
in the latter (Saravia and Bush 1991; Boj 1992; Grau
et al. 1997; Miegimolle et al. 2005; Arapostathis
et al. 2010) – and mandibular block (Stephens and
Kramer1964; Bennett and Monheim1971; Boj1992).
2) Cost, since many of the devices used are very expensive.
tissues is
Advantages
The advantages to this technique can be summarized as
follows:
1) As topical anesthetic it is very useful (Kutscher and
Zegarelli 1965; Garellek 1967; Bennett and
Monheim1971; Epstein 1971; Boj 1992), especially in
the palate (Stephens and Kramer1964) since it can be
injected using the conventional technique after a
minute (Kutscher etal.1964).
2) For supra- and sub- gingival anesthesia during scaling
and root planning procedures, respectively. (Kutscher
and Zegarelli1965; Epstein1971).
3) Placement of rubber dam clamps, especially if subgingi-
val clamp placement is necessary for appropriate isolation of the teeth (Garellek1967; Epstein1971; Boj1992;
Arapostathis etal.2010).
primary teeth (Saravia and Bush1991; Boj1992), lancing
fluctuant abscesses (Garellek1967; Epstein1971), gingivectomy limited to one tooth (Epstein1971), excision of
small lesions such as papillomas and fibromas (Greenfield
and Karpinski1972), removal of bone spurs, etc.
5) Placement and removal of fixed orthodontic devices
that can irritate the gingival (Epstein 1971; Greenfield
and Karpinski1972), such as fixed space maintainers,
bands, orthodontic arches and ligature ties, subgingival
matrix bands, etc.
1) The absence of a needle means could be a very positive
attribute for those patients who fear needles, therefore
it could prove very useful in children and fearful adults
(Stephens1962; Stephens and Kramer1964; Greenfield
and Karpinski1972, Miegimolle etal.2005).
2) When this technique can be used, patients prefer it to
conventional techniques in 75% of cases (Table20.1).
3) Injection is not painful in 85% of cases (Table20.1).
4) The risk of transmission of blood- borne pathogens to
the provider or dental assistant is reduced because there
are no sharps or infectious waste.
Equipment
Annex 33 discusses the main devices used in dentistry. The
main ones are Syrijet® (designed exclusively for dentistry)
and Injex®, which is the smallest. We comment on both
devices below.
Syrijet®
This device was introduced in 1971 (Annex 33) and is still
in use (Figure20.1). It can be purchased online. As it is
specially designed for dentistry, it has no anesthetic solution deposit, but uses 1.8- ml dental cartridges. The nozzle
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Table20.1 Percentage of patients who do not feel pain, prefer the , and have hematoma at the
injection site in various clinical trials.
Study data Variables analyzed
Reference Device Patients No pain Preference Hematoma
Hingson and Hughes (1947) Hypospray Children/adults 94% — —
Margetis etal. (1958) Hypospray Children/adults 100% — 72%
Kutscher etal. (1964) Hypospray Children/adults 100% —
Kutscher and Zegarelli (1965) Hypospray Children/adults — — 42%
Schmidt (1966) Hypospray Children 95% 81% 10%
Whitehead and Young (1968) Panjet Children/adults 84% 78% 81%
Bennett and Monheim (1971) Syrijet® Children/adults —
Lambrianidis etal. (1979–1980) Panjet Children/adults 98% 98% 10%
Saravia and Bush (1991) Syrijet® Children/adults —
Grau etal. (1997) Syrijet® Children 76% — 33%
Grau etal. (1997) Syrijet® Adults 96% —
Dabarakis etal. (2007) Injex® Adults —
Arapostathis etal. (2010) Injex® Children 30% —
Average 86% 73% 35%
Rounded average 85% 75% 35%
90% 1.5%
73% —
18% 15%
—
24%
61%
Figure20.1 Syrijet®: high- speed jet injection system.
pressure is 2000 pounds per square inch (psi), which is
lower than that of other devices designed to cross the skin
(Stephens and Kramer1964). In this case, it is applied to
the oral mucosa with little or no damage. The solution can
be administered gradually in doses of 0.05
mum of 0.05
ml to a maximum of 0.2 ml (Annex 33).
ml, from a mini-
The head of the device is contra- angled to facilitate access
to the different areas of the oral cavity. The nozzle of the jet
has a rubber ring that can be adapted to the mucosa so that
when the device is discharged, the rubber ring reduces the
sensation of pressure (Epstein1971). The ring is replaceable
and can be sterilized. The problem with this device is its size
(245 mm long) and weight (550 g) (Annex 33).
Injex®
Injex® first appeared in 1999 and has the advantage that
it is small (only 75 g) (Annex 33) (Figure20.2). It comes
with a fixed ampoule reservoir (0.3 ml), but also has a
transporter and adapter that makes it possible to load the
reservoir with anesthetic solution in 1.8- ml dental cartridges. The discharge is set at 0.15 ml, and the solution
Figure20.2 Injex®: high- speed jet injection system.
cannot be dosed. It is used only for anterior teeth (maxillary and mandibular) in the buccal area (Arapostathis
et al. 2010) since it cannot be adapted to the posterior
part of the mouth. Given that the device is used for injection of insulin into the skin, it has a nozzle pressure of
3000 psi (Annex 33).
Technique
● Preparation of the device for high- pressure jet injection.
○ Syrijet®. A 1.8- ml dental cartridge is loaded. The
dose is selected and the spring is activated to
discharge.
○ Injex®. The ampoule is loaded with the transporter and
the spring is activated to inject with the “reset- box.”
● Anesthetic solution. Any dental anesthetic solution can
be used; the most common is the standard lidocaine with
epinephrine. Epinephrine- free solutions yield poorer
results (Dabarakis et al. 2007); those with a higher
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although they also lead to greater irritation of tissue
(Lambrianidis etal.1979–1980).
● Preparation of the patient.
○ Show the device to the patient (Lambrianidis et al.
1979–1980; Saravia and Bush 1991; Munshi
etal. 2000a).
○ Inform the patient that during the discharge, he/she
will hear a sound. We can avoid language with a high
emotional content by not using the term “discharge,”
but rather “jet.” Similarly, try to avoid the term “sound,”
but rather euphemisms, such as “pop” or “click.”
○ Advise the patient that he/she should not move during
this stage.
● Dry and clean the area where the jet is to be applied
(Bennett and Monheim1971; Greenfield and Karpinsky
1973; Lambrianidis et al. 1979–1980; Saravia and
Bush1991).
● Apply the device to the mucosa.
○ Hold the device so that it does not move during the
discharge. Remember that the Syrijet® is fairly heavy
(Bennett and Monheim 1971; Greenfield and
Karpinsky1973; Boj1992).
○ Place the mouth of the device against the attached
mucosa and rest it on the bone to avoid tearing during
the discharge (Greenfield and Karpinsky 1973;
Boj 1992) and at a right angle, perpendicular to the
point of discharge (Margetis etal.1958; Kutscher and
Zegarelli 1965; Bennett and Monheim 1971;
Lambrianidis et al. 1979–1980) (Figure 20.3).
Remember that it may be difficult to position the
Syrijet® device correctly in the areas of the tongue and
molars (Arapostathis etal.2010).
● Discharge.
○ Advise the patient to remain still and inform him/her
that the process will only take a second (Stephens and
Kramer 1964; Kutscher and Zegarelli 1965;
Garellek 1967).
○ The noise of the discharge causes the patient to react
with a slight involuntary movement (Kutscher et al.
1964; Whitehead and Young1968; Epstein1971). He/
she may also feel a slight jolt against the gingiva (Grau
etal.1997; Miegimolle etal.2005).
○ This maneuver is painless in 85% of cases (Table20.1).
○ The dose to be injected varies with the site:
■ Palate, 0.1–0.15 ml (Stephens and Kramer 1964;
Epstein1971).
■ Buccal infiltration, 0.15–0.3 ml (Schmidt 1966;
Greenfield and Karpinsky1973; Boj1992).
● After the discharge:
○ A small mucosal lesion with mild hematoma appears at
the site of the discharge. There may sometimes be slight
Jet Injection 363
Figure20.3 Discharge of Syrijet® with the nozzle of the jet
supported against the inserted gingiva. Redrawn from
Andlaw and Rock (1994).
bleeding and mild blanching around the hematoma.
Occasionally, we observe slight elevation of the area.
○ Wait 1–3 minutes (Kutscher etal.1964; Stephens and
Kramer 1964; Garellek1967), sometimes 5
minutes
(Lambrianidis et al. 1979–1980) to the onset of
anesthesia.
○ It is important to remember that the patient barely
notices the soft tissue anesthesia (tingling, dullness, fat
lip, etc.) (Stephens and Kramer1964), although the area
of anesthetized soft tissue can vary depending on the site:
■ Palate, 10 mm (Garellek1967).
■ Buccal area, 10–40 mm (Garellek1967; Whitehead
and Young1968).
● If anesthesia is insufficient, we have two options:
1) Discharge more anesthetic, although more discharges
and a larger quantity of anesthetic do not generally
improve the results (Greenfield and Karpinsky1973;
Boj1992).
2) Inject more anesthetic using the conventional tech-
nique, with the advantage that the superficial- topical
anesthesia prevents the discomfort normally associated with the conventional injection.
Complications ofthis Technique
1) Bleeding and sometimes hematoma at the injection site
in 35% of cases (Table20.1), especially when several discharges are made at the same site (Greenfield and
Karpinski1972,1973).
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2) Blanching in 90% of cases (Whitehead and Young1968;
Grau etal.1997). This may be tender on palpation and
inflamed (Margetis et al. 1958; Whitehead and
Young1968; Grau etal.1997), especially when various
discharges have been made at the same site (Greenfield
and Karpinsky1973).
3) Laceration (cut in the mucosa) at the discharge site,
especially when the patient moves his/her head as the
discharge is made (Margetis etal.1958; Kramer1962;
Stephens and Kramer1964; Kutscher and Zegarelli1965;
Schmidt1966; Garellek1967).
4) Bitter taste is reported if some of the anesthetic solution
flows into the patient’s mouth. In some series, this
occurs in more than 50% of cases (Arapostathis
etal.2010). To reduce the possibility of this complication, it is best to adapt the nozzle of the device to the
tissues where the discharge is to be made.
5) The patient may become startled owing to the surprise at
the noise of the discharge, especially with Injex®. This
occurs in around one- third of cases (Dabarakis etal.2007).
6) Postoperative pain at the injection site in a small per-
centage of patients (Dabarakis etal.2007). This usually
resolves spontaneously in a few days.
Electronic Anesthesia: Electronic
Dental Anesthesia
Electronic dental anesthesia (EDA) is a totally different
system. We have previously discussed types of local anesthetic injection by various methods; however, EDA is based
on electrical stimulation to generate anesthesia.
Transcutaneous electrical nerve stimulation (TENS) is
used in general medicine. In dentistry, TENS is used to control chronic pain such as trigeminal neuralgia or atypical
facial pain (Yap and Ong1996; Cho etal.1998). EDA is a
variant of TENS that is used in dentistry to achieve anesthesia. It is based on a lower current and higher frequency
(Cho etal.1998).
The first references to the use of electrodes to relieve
dental pain were by James Ferguson in 1770
(Ferguson1770), although in 1858, the College of Dentists
of London advised against the technique because electricity did not have an anesthetic effect and increased pain,
and the few favorable outcomes achieved were the result of
“distraction” (Kane and Taub 1975). However, operative
systems began to be developed after the publication of the
gate control theory in 1965 (see Chapter11) (Melzack and
Wall1965), with the appearance of the first clinical trials in
dentistry (Shane and Kessier 1967; Brooks et al. 1970;
Laster and Pressman 1975). The first practical system
marketed for dental use was UltraCalm, which appeared in
1989. The system was very expensive and required placement of an intraoral electrode in the area of the vestibule to
be treated (Clark etal.1987; Malamed etal.1989). It was
therefore necessary to dry the mucosa well to ensure successful placement (Cho et al.1998). In addition, the electrode blocked the dentist’s vision and hampered the
procedure (Cho etal.1998; Baghdadi1999). The other electrode was placed in the patient’s hand.
In 1993, the company 3M marketed a smaller device for
use in dentistry known as the Dental Electronic Anesthesia
System 8670 (Burke1997; Baghdadi1999). This was much
more affordable and had the huge advantage that it
involved placement of electrodes extraorally on the
patient’s face. The system was introduced in the United
Kingdom in 1997 (Burke1997).
Mechanism ofAction
The mechanism of action of EDA is unknown, although
several factors have been shown to be associated with it
(Munshi etal.2000b):
1) The gate control theory blocks the transmission of
painful messages to the highest levels of the central
nervous system (CNS) (Katch1986; Clark etal. 1987;
Hochman 1988; Silverstone 1989) (see Chapter 11,
instrumental, vibrators).
2) Release of serotonin, a neurotransmitter that is derived
from tryptophan (Clark et al. 1987; Hochman 1988;
Silverstone1989; Cho etal.1998). Adding 2–3 g of tryptophan to the diet, per day, 3
can approve the results (Hochman1988).
3) Release of β- endorphins by the periaqueductal gray
substance of the CNS (Clark etal.1987; Hochman1988;
Silverstone1989; Yap and Ong1996; Cho et al.1998).
Endorphins are endogenous opioids and can produce
analgesia.
4) Placebo effect, because the patient controls the intensity
of the current applied with his/her hand, thus keeping
him/her distracted (Hochman1988; Silverstone1989;
Mellor1993; Modaresi etal.1996).
days before TENS is applied
Indications
● Conventional indications:
1) Topical anesthesia, since this is very useful for reduc-
ing the pain resulting from the needle prick and injection of conventional anesthesia (Croll and Simonsen
1994; Quarnstrom and Libed 1994; Meechan and
Winter 1996; Vongsavan and Vongsavan 1996;
Meechan etal. 1998).
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2) Calculus removal in sensitive teeth and scaling and root
planing (Bishop1986; Clark etal.1987; Hochman 1988;
Pirkner etal.1995; Yap and Ong 1996; Burke1997).
3) Placement of rubber dams, especially if the prongs of
the clamp are placed subgingivally (te-
Duits et al.
1993; Baghdadi1999).
4) Cavities of small or moderate, barely invasive obtura-
tions (Malamed etal.1989; Yap and Ho1996; Cho
etal. 1998). According to Table20.2, the efficacy is
80%, although it is important to take into account that
successful cases include those in which patients
experienced with mild discomfort or pain but were
able to complete treatment without the addition of
conventional local anesthetic by injection. Some
authors report that outcomes are better for primary
teeth than for permanent teeth (Cho etal.1998).
Table20.2 Percentage of patients in whom cavity cutting is successful (mildly aggressive) and who prefer to conventional
systems (results from clinical trials).
Study data Variables analyzed
5) Cementing of fixed prosthesis in vital teeth (Yap and
Ong1996; Burke1997).
● Special indications for this technique:
● Allergy to local anesthetics or their components
because this technique does not involve drugs
(Jedrychowski and Duperon1993; Yap and Ong1996;
Burke1997; Munshi etal.2000b).
● Hemophiliac patients because there is no need for an
injection and, above all, there is no need for truncal
block, with the result that there is no risk of asphyxiating hematomas (Savage1982).
Note: It is noteworthy that EDA is more successful in
children aged 5–12
years; in contrast, the results are not so
good in anxious and/or skeptical patients (Quarnstrom and
Quinn1995).
Reference Device Patients Successful cavities Preference
Bradley etal. (1974) Special air turbine
Savage (1982) HM- 100PSU Adults 92% —
Clark etal. (1987) HFNM Adults 93% —
Donaldson etal. (1989) TENS Adults 33% —
Malamed etal. (1989) EDA Adults 86% —
Esposito etal. (1993) UltraCalm Adults 80% 70%
Jedrychowski and Duperon (1993) UltraCalm Children 83% —
Mellor (1993) UltraCalm Adults 100% 60%
te-
Duits etal. (1993) Spectrum Max- SD Children 78% 78%
Pirkner etal. (1995) DEAS 3M (8670) Adults —
Sasa and Donly (1995) DEAS 3M (8670) Children —
Segura etal. (1995) DEAS 3M (8670) Children — 93%
Jones and Blinkhorn (1996) Cedeta Children 73% 61%
Yap and Ho (1996) DEAS 3M (8670) Adults 93% —
Burke (1997) DEAS 3M (8670) Adults — 41%
Öztas etal. (1997) UCho etal. (1998) DEAS 3M (8670) Children 81% 63%
Baghdadi (1999) DEAS 3M (8670) Children 75% 53%
Munshi etal. (2000b) MES Children 94% —
TENS plus Children 68% 56%
a
Adults 75% —
56%
40%
Average 80% 61%
Rounded average 80% 60%
HFNM, high- frequency neural modulator; MES, Madras Engineering Services; TENS, transcutaneous electrical nerve stimulation; EDA,
electronic dental anesthesia; DEAS, Dental Electronic Anesthesia System.
a
Miniature electrical generator within turbine head.
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Disadvantages
This technique has several disadvantages, the most important of which are as follows:
1) Inadequate depth of anesthesia (Harvey and Elliott1995;
Sasa and Donly 1995; Modaresi et al. 1996; Yap and
Ong1996; Burke1997). Consequently, outcomes in oral
surgery and extractions are poor (Bishop 1986; Katch
1986; Clark et al. 1987), as are those of endodontic procedures (Bishop 1986; Clark et al. 1987), cutting of
crowns and bridges in vital teeth (Hochman 1988;
Burke1997), and deep scaling and root planing (Pirkner
etal.1995). Furthermore, the technique is not recommended in procedures where moderate or severe postoperative pain is expected (surgery, endodontics)
(Malamed etal.1989).
2) The cost of the system and devices. While this has
decreased over time, it continues to be high compared
to traditional local anesthetic. In addition, single- use
adhesive electrodes are necessary for each new patient.
3) The time taken to explain the technique to the patient
and to try it, given that the patient’s cooperation is necessary (Modaresi etal.1996; Yap and Ong1996; Burke1997).
Advantages
The advantages of the technique can be summarized as
follows:
1) No needle or injection, with the result that:
○ There are no injections to fear (Jedrychowski and
Duperon1993; Yap and Ong1996; Burke1997). Some
authors recommend this technique in patients with
needle phobia (Hochman1988; Malamed etal.1989;
Burke1997; Munshi etal.2000b), however, efficacy
was not as well established in anxious or skeptical
patients (Quarnstrom and Quinn1995).
○ It can be used in patients with bleeding dyscrasias
because there are no injections. Moreover there is no
need for truncal block and no risk of hematoma
(Savage1982), as seen previously.
2) Patients prefer this technique to conventional tech-
niques in 60% of cases, when it can be used (Table20.2).
3) Since no drugs are involved (local anesthetics, vasocon-
strictors), there are no associated risks (Jedrychowski
and Duperon 1993; Yap and Ong 1996; Burke 1997;
Munshi etal.2000b) such as the following:
● Toxicity induced by accidental intravascular injection
or overdose.
● Allergy to any of the components in the anesthetic
solution. This is one of the indications for this
technique.
4) No long- term postoperative paresthesia (Hochman1988;
Malamed et al. 1989; Silverstone 1989; Jedrychowski
and Duperon 1993; Yap and Ong 1996; Burke 1997;
Munshi et al.2000b) since the effect disappears once
the device is switched off and there is no electric
current:
● There is no risk of self- injury resulting from biting the
lips, tongue, or jugal mucosa or of burning oneself
with hot food.
● The patient can eat and drink after treatment.
● Bite adjustment is easier because the patient’s percep-
tion is not altered by the anesthesia of the soft tissues.
Contraindications
While some contraindications are well established, others
are empirical. However, in case of doubt, we include all
possibilities:
1) Abnormalities of the heart:
● Pacemaker, to prevent electromagnetic interference
(Katch1986; Hochman1988; Donaldson etal.1989;
Malamed et al. 1989; Croll and Simonsen 1994;
Quarnstrom and Libed1994; Yap and Ho 1996; Yap
and Ong1996; Burke1997; Meechan etal.1998).
● Arrhythmias, to prevent alterations to heart rate caused
by electrical depolarization (Donaldson etal.1989).
2) Abnormalities of the CNS and head:
● Cerebrovascular abnormalities such as stroke, tran-
sient ischemic attacks, and aneurysms since EDA can
increase the risks of these occurring (Katch 1986;
Hochman 1988; Donaldson et al. 1989; Malamed
etal.1989; Croll and Simonsen1994; Quarnstrom and
Libed1994; Yap and Ho1996; Yap and Ong1996).
● Epileptic seizures or convulsions, owing to the risk of
triggering them (Katch 1986; Hochman 1988;
Quarnstrom and Libed 1994; Yap and Ho 1996; Yap
and Ong1996; Burke1997; Meechan etal.1998).
● Brain tumors, owing to the risk of worsening them
(Croll and Simonsen1994; Yap and Ho1996).
● Neuralgia of the head and neck such as trigeminal
neuralgia, postherpetic neuralgia, multiple sclerosis,
Bell’s palsy, owing to the risk of worsening them
(Croll and Simonsen1994; Yap and Ho1996; Yap and
Ong1996; Burke1997; Meechan etal.1998).
● Cochlear implants (Croll and Simonsen 1994; Yap
and Ho1996).
3) Pregnancy, mainly because the effects on the fetus are
unknown (Katch 1986; Hochman 1988; Donaldson
etal. 1989; Malamed et al.1989; Croll and Simonsen
1994; Quarnstrom and Libed 1994; Yap and Ho1996;
Yap and Ong1996; Burke1997; Meechan etal.1998).
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4) Placement of electrodes is totally contraindicated at the
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following sites:
● Skin on the face affected by abnormalities (Croll and
Simonsen1994; Yap and Ho1996; Yap and Ong1996;
Burke1997).
● Eyes (Katch1986; Burke1997).
● Neck, because of stimulation of the carotid barore-
ceptors may induce bradycardia and subsequent
reductions of cardiac output may not be tolerated in
some patients (Yap and Ong1996).
5) Other possible contraindications:
● Fear of electrocution in patients who previously
had a serious electrical accident (Quarnstrom and
Libed 1994).
● Patients with communication barriers since they
must understand the instructions to be able to
cooperate (Donaldson etal.1989; Yap and Ong1996;
Burke1997).
● Arterial hypotension or bradycardia because EDA
can worsen it (Hochman1988).
367
Figure20.4 Dental Electronic Anesthesia System 8670 device
from 3M dental, with adhesive extrabuccal electrodes.
Equipment
Annex 33 shows the main devices used in dentistry. Below,
however, we refer to the Dental Electronic Anesthesia
System 8670, manufactured by 3M Dental (Figure20.4),
since this was specially designed for dental anesthesia. Its
technical features are shown in Table20.3.
The device has a modern and attractive design, uses a 9 V
battery, and is easy to handle, with manual controls:
● Switch, with three positions: M transmits smooth inter-
mittent impulses, R transmits impulses in bursts, and C
transmits continuous impulses and is the most commonly used option.
● Two buttons: R to set the frequency at 140 Hz and W to
set the pulse width at 250
● Current intensity controller. Controlled by the patient,
μs.
with a current that ranges from 0 to 60 milliamperes (mA).
● “On” button. When the device is turned on, a LED light
advises us that the device is operational.
At both sides of the main box, we can find an input for
the cables of the two electrodes. These electrodes are
extraoral (this is an advantage because they do not interfere with interventions in the mouth) and are attached by
means of spongy adhesive patches: green, main electrode,
which is placed on the skin above the treatment area;
brown, complementary electrode. The cables of the electrodes are reusable, therefore they should be cleaned after
use. Each one goes with its respective color (green
or brown).
Table20.3 Technical characteristics ofthe Dental Electronic
Anesthesia System 8670 from3M Dental.
Variable Measurement Value
Cycle frequency Hertz (Hz) 140
Current/amplitude Milliamperes (mA) 0–60
Volts Volts (V) 9
Bandwidth/pulse Microseconds 250
Source: Data obtained from: Croll and Simonsen (1994), Yap and Ong
(1996), Burke (1997), Domínguez etal. (1998), and Cho etal. (1998).
Technique
As stated above, here we address the Dental Electronic
Anesthesia System 8670, manufactured by 3M Dental.
● Pre- operative phase. Explain to the patient how the
device works and show him/her the equipment and the
single- use adhesive electrodes.
● Children. While the child is in the dental chair, apply
the “tell- show- do” technique and show pictures of children with the electrodes. Let the child touch the device
and tell him/her that it “gives you tickles on your face”
(Domínguez etal.1998), which is a nice way of describing paresthesia.
● Place the extraoral adhesive electrodes (with the device off):
○ Clean the skin of the face with alcohol to remove
grease and sweat that might interfere with the transmission of the electrical current.
○ Instruct the patient to open his/her mouth as wide as
possible. This maneuver stretches the skin and brings
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368
the apex of the teeth closer. Thus, we can locate the
area where the electrodes will be placed; the goal is to
approximate the electrodes to the apices of the teeth
being anesthetized.
○ Place the adhesive electrodes on the skin. Each elec-
trode symmetrically on each side of the skin, at least
1
mm apart.
■ In the maxilla:
– Anterior teeth, more forward.
– Posterior teeth, more backward.
■ Mandible, on the skin in the area of the chin:
– Anterior teeth, more forward.
– Posterior teeth, more backward.
■ Try to ensure that the electrode is at the level of the
apex of the tooth to be treated.
● Connect the electrodes to the cables on the box.
○ Green connector. For the green electrode in the area of
the apice of the teeth to be treated.
○ Brown connector. For the electrode on the oppo-
site side.
● Explain to the patient how to use the manual control
(only the on–off button and intensity control button).
Note: In children aged under 8 years, the dentist and/or the
assistant manages the device since children can increase
intensity suddenly. While this does not damage tissue, it
can be uncomfortable and surprise children, thus causing
them to alter their behavior (Jedrychowski and Duperon
1993; Croll and Simonsen1994).
● The patient should increase the intensity (mA) little by
little until he/she feels a slight tingling sensation (Clark
etal.1987; Croll and Simonsen1994). Small muscle contractions (fasciculations) also appear on the face and
muscles near the electrodes (sign that the minimum
therapeutic level has been reached).
○ The fasciculations usually appear at levels 5–10 (Croll
and Simonsen 1994: Yap and Ho 1996; Domínguez
etal.1998), which is between 15 seconds and 2–4 minutes (Yap and Ho1996; Domínguez etal.1998).
○ With children, it is a good idea to use a mirror so that
they can see the fasciculations.
● The patient can increase the intensity during the treat-
ment. Most do so to levels 10–20in 3–5 minutes. Smooth
increases every 20 seconds are recommended.
● If the effect of the anesthesia is not sufficient during
treatment, then we can use the following:
○ Nitrous oxide (N
O/O2), which provides sedation and
2
enhances analgesia (Donaldson etal.1989; Croll and
Simonsen1994).
○ Let the children listen to their favorite music through
headphones, thus providing a distraction and increasing the pain threshold (Croll and Simonsen1994).
○ Administer injections of conventional local anes-
thetic, which do not hurt now because the patient is
already feeling the anesthetic effect of EDA (Croll and
Simonsen1994; Quarnstrom and Libed1994; Meechan
and Winter1996).
● When treatment has finished:
○ Switch off the device. Warn the patient that he/she
may feel fasciculations for another few minutes.
○ Remove the electrodes from the skin of the face. The
skin may be red. Explain to the patient that this will
disappear in a few minutes (10–20
minutes).
Complications ofthis Technique
● During treatment:
○ Increased salivation. This can be resolved easily by
using a rubber dam, isolating with cotton wool (Croll
and Simonsen1994), or increasing suction.
○ Muscle twitching may appear in the eyes and eyelids
(Yap and Ong1996; Yap and Ho 1996). This has no
clinical relevance.
● After treatment:
○ Reddening of the skin the electrodes were adhered to
(Burke 1997) caused by increased blood flow to the
area. This situation may occur in around 15% of cases
(Yap and Ho 1996) and usually disappears in
15–20 minutes (Domínguez etal.1998). Burns on the
skin have been reported rarely, although these were
with older EDA devices (Katch1986).
○ The sensation of soft tissue anesthesia on the face,
where the electrodes were placed, lasts a few minutes
longer in over 35% of patients (Yap and Ho1996).
Computer- Controlled Injection Systems
(The Wand®)
The first computer- controlled injection system was The
Wand, whose prototype appeared and was first examined
in a clinical trial in 1997 (Hochman etal.1997), the same
year that the clinical model for professionals also appeared
(Friedman and Hochman1997), before being acceptance
by the American Dental Association (ADA) in 1998
(Anonymous2002).
The main objective of this system (and of the variants
discussed below) is that the injection is painless or involves
minimal discomfort (Lee et al. 2004), as corroborated in
clinical trials with The Wand (Annex 32). The system manages to separate the rate of injection from the pressure
(impossible with a manual syringe), thus enabling an
extremely low injection rate.
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The Wand is a genuine novelty and an alternative to con-
(c)
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ventional injection techniques. Below, we describe the
device in detail, the specific anesthetic techniques developed (palatal approach to the anterior and middle superior
alveolar nerves [Panterior superior alveolar nerve [P-
AMSA] and palatal approach to the
ASA]), as well as some
variations with conventional techniques when they are
applied using The Wand.
Description ofthe Device
Although the device is basically the same as when it first
appeared, a series of modifications have been introduced
(Clark and Yagiela2010):
369
● 1997. The Wand. The first device.
● 2000. The Wand plus. With some modifications in the
foot control.
● 2005. CompuDent Wand. With a high- speed injection
function.
● 2007. The Wand STA (Single Tooth Anesthesia). With a
modification for optimizing periodontal ligament injection (STA2015).
● The features of The Wand are continuously updated with
regular minor modifications.
Central Processing Unit
The central processing unit (CPU) is as large as a thick book,
with an attractive, brightly colored design (Figure 20.5). It
contains a microprocessor with an electric motor to control
the injection of local anesthetic solution, thus removing the
need for manual pressure from the operator to administer
the injection. This ensures the following:
1) A constant flow, regardless of tissue resistance because
the microprocessor automatically adjusts the pressure
on the plunger in such a way that if the resistance
increases, the force on the plunger increases, although
the same injection rate is maintained at all times,
therefore there is less tissue distension and less pain.
As the maximum pressure of the device is 450 psi
2
(31.6 kg/cm
) (STA2015), it does not break glass cartridges (Froum etal.2000) (Table18.2, Chapter18). It
is important to note that with the hand, it is impossible
to maintain a constant flow with increased resistance
(Hochman etal.1997).
2) Very slow injection rate of approximately one drop per
second (Friedman and Hochman 2001; Nusstein
etal.2004a,b) to ensure that the anesthetic is injected
below the pain threshold. Such a rate is almost impossible to achieve with the conventional manual technique owing to factors such as muscle fatigue.
(a) (b)
Figure20.5 The Wand STA: (a) foot control pedal; (b) central
processing unit, and (c) handpiece (The Wand).
Table20.4 Injection rate inmilliliters (ml) injected per unit
oftime (seconds, s or minutes, min) andseconds per milliliter
withThe Wand.
Milliliters
(ml) per
Rate
Very fast
TurboFlo
Fast
RapidFlo
Slow
ControlFlo
Approximate date (±15%).
Source: Data from Friedman and Hochman (2001), Nusstein etal.
(2004b), and STA (2015).
second
0.06 17 23 s 30 s
0.031 35 45 s 1 min
0.005 207 4 min, 45 6 min
Seconds per
milliliter
(ml)
Injection time
1.4 ml 1.8 ml
The system initially had three rates (Table 20.4),
although the slow rate is truly novel: the plunger
advances at 1/200 in. per second (0.005 in. per second=0.1235 mm) (Hochman etal.1997).
Studies have shown that control of the injection, a slow
injection rate, and control of pressure are impossible with
manual systems based on conventional metal syringes
(Tzafalia and Sixou2011).
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