Преглед на Локална Анестезия - Техники

Chapter 1
Overview of Local Anesthesia Techniques
Mohammad Ali Ghavimi, Yosef Kananizadeh,
Saied Hajizadeh and Arezoo Ghoreishizadeh
Additional information is available at the end of the chapter
http://dx.doi.org/10.5772/59214
1. Introduction
Down through centuries, efforts have been made to use local anesthesia for treatments. In the
ancient times, the Assyrians applied pressure over the carotid artery in order to obtain a certain
degree of anesthesia, explaining why this artery is called “the artery of sleep” in the Greek
literature. In 1532, the Indians of Peru chewed the leaves of coca shrubs to relieve fatigue and
hunger and to produce a feeling of exhilaration. A chemical with some anesthetic property
was first introduced in the nineteenth century. A German chemist in 1859, however, reported
the anesthetic properties of the coca leaf. In 1859, cocaine was first extracted in its pure form
by Albert Neimann, a German chemist. In the mid-1860s, Sir Benjamin Ward Richardson
introduced the effect of ether spray for skin anesthesia. Around the same time the adverse
effects of cocaine on the mood and psyche were demonstrated. As known today, side effects
of cocaine include cardiac stimulation, peripheral vasoconstriction, excitation of the central
nervous system (CNS) and addiction. In 1943, lidocaine-the first amide local anesthetic was
introduced with greater potency, more rapid onset and less allergenicity as compared to the
previously introduced esters.
Pain control in dentistry presents one of the greatest challenges. Pain leads to increased stress,
release of endogenous catecholamines and unexpected cardiovascular responses. Before
anesthetization, dentists should evaluate the medical history of each patient and document
data on the systemic and psychological status of the patients in order to determine whether
the patient is able to tolerate the treatment with no risk from the systemic and psychological
points of views. Before the injection of the local anesthetic, the dentist should recognize the
potential risks. However, most adverse reactions to local anesthetics are not related to the drug
itself, but to the injection of the drug. The injection of the local anesthesia is the most reported
cause for fear and discomfort of dental patients. Vasodepressor syncope and hyperventilation
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syndrome are the most common reactions. Others include tonic-clonic spasm, bronchospasm
and angina pectoris. Continual research in the field of pain control is still being done in the
quest for novel techniques and safer drugs. [1-4].
2. Anatomy
Management of pain in dentistry requires knowledge about the fifth cranial nerve anatomy-
the trigeminal nerve. It is the largest of the cranial nerves and has three major divisions:
ophthalmic, maxillary and mandibular.
The trigeminal nerve is the major sensory nerve of the face containing both motor fibers for
masticatory muscles and sensory fibers. This nerve exits the brain through the area between
the pons and the middle cerebellar peduncles.
The ophthalmic branch runs through the lateral wall of the cavernous sinus and, through the
superior orbital fissure, enters the orbit, branching again to provide sensation of the lacrimal
apparatus, cornea, iris, forehead, ethmoid and frontal sinuses and the nose. The ophthalmic
nerve –V1- is the smallest of the three divisions, dividing in to three main branches: the
nasociliary, frontal and lacrimal nerves (Figure 1).
The maxillary branch is the second branch of the trigeminal nerve – V2 – passes horizontally
forward, through the lateral wall of the cavernous sinus, exiting the cranium through the
rotundum foramen which is located in the greater wing of the sphenoid bone. Once outside
the cranium, this nerve crosses between the pterygoid plates of the sphenoid bone and the
palatine bone. As the maxillary nerve crosses the pterygopalatine fossa, it gives off branches
to the posterior–superior alveolar nerve, the sphenopalatine ganglion and the zygomatic
region. Branches of this nerve continue through the inferior orbital fissure and infraorbital
foramen, providing sensation of the maxillary sinuses, upper jaw, sides of the nose and the
cheek (Figure 2). [5, 6]
The branches of the maxillary nerve are given off in four regions:
1. Cranium
2. Pterygopalatine fossa
3. Infraorbital canal
4. Face
The branch entering the cranium –the middle meningeal nerve– travels with the middle
meningeal artery to provide sensory innervation of the dura mater.
Several branches are given off in the pterygopalatine fossa namely the zygomatic nerve, the
pterygopalatine nerve and the posterior superior alveolar nerve.
The greater palatine nerve descends through the pterygopalatine canal and through the
greater palatine canal emerges on the hard palate, coursing anteriorly between the osseous
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hard palate and the mucoperiosteum supplying sensory innervation to the bone and palatal
soft tissues as far anterior as the first premolar.
The lesser palatine nerve travels along with the posterior palatine nerve emerging from the
lesser palatine foramen.
The posterior superior alveolar nerve (PSA) branches from the main trunk of the maxillary
division into the pterygopalatine fossa just before the maxillary division enters the infraorbital
canal.
The maxillary division (V2) gives off two significant branches namely the anterior superior
(ASA) and middle superior (MSA) alveolar nerves.
The ASA nerve – given off from the infraorbital nerve – descends within the anterior wall of
the maxillary sinus, providing pulpal innervation of the central and lateral incisors, canine and
the sensory innervation of periodontal tissues, buccal bone and the mucous membrane of the
gums.
The MSA nerve provides sensory innervation of maxillary premolars and, perhaps, the
mesiobuccal root of the first molar, periodontal tissues, buccal soft tissues and the bone and
gums in the premolar region.
Branches of the face: through the infraorbital foramen, the infraorbital nerve emerges into the
face dividing into its terminal branches: the inferior palpebral, external nasal and superior
labial.
The mandibular branch (V3) is considered a motor-sensory nerve innervating masticatory
muscles, lower jaw and teeth, parotid and sublingual gland, two third of the tongue and the
ear canal and exits the skull through the ovale foramen. The mandibular division: The
mandibular division – the largest branch of the trigeminal nerve – descends between the medial
ramus and the medial pterygoid muscle, entering the mandible through the mandibular
foramen (Figure 2.).
The inferior alveolar nerve has the largest diameter of 2.4±0.4 mm at the lingula.
The anterior division of the V3 branch provides sensory innervation of the cheek, mucous
membrane in the buccal of the mandibular molars and motor innervation of the masticatory
muscles.
The buccal nerve, passing through the two heads of the lateral pterygoid, reaches the external
surface of the lateral pterygoid muscle, continuing in an anterolateral direction.
The auriculotemporal nerve passes through the upper part of the parotid gland crossing the
posterior portion of the zygomatic arch.
The lingual nerve travels downward and medial to the lateral pterygoid muscle, lying
between the ramus and the medial pterygoid muscle in the pterygomandibular space as it
descends. The sensory tract of the anterior two-third of the tongue, the mucous membrane of
the mouth floor and mandibular lingual gingiva is provided by the lingual nerve.
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Figure 1. The superficial branches of the trigeminal nerve
Figure 2. Branches of the trigeminal nerve
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The mylohyoid nerve branches off the inferior alveolar nerve just before the entrance of the
inferior alveolar nerve into the mandibular canal. This is a mixed nerve providing sensory
innervation of the mandibular incisors, and portions of mandibular molars in some. It also
provides the motor innervation of the anterior belly of the digastrics and the mylohyoid
muscle.
At the mental foramen, the inferior alveolar nerve branches into its terminal branches-- the
incisive and the mental nerves:
The incisive nerve, remaining within the mandibular canal, forms a nerve plexus innervating
the pulpal tissues of the mandibular first premolar, canine and incisors via the dental branches.
The mental nerve innervates the skin of the chin and the mucous membrane of the lower lip.
[1-6]
3. Mandibular anesthesia
There is a great variety of techniques for anesthetizing different regions of the mandible, the
most common and useful ones are described in this section.
3.1. Inferior alveolar nerve block
The inferior alveolar nerve block (IANB) is one of the most important and commonly used
techniques in dentistry. Unfortunately it is also the most frustrating with the highest percent‐
age of failure even when properly administrated [1].The IANB anesthetizes the IAN (a branch
of mandibular division of the trigeminal), incisive nerve, mental nerve and commonly (but not
always) the lingual nerve of the injected side. This block effects the sensation of all the teeth
on one side of mandible, the bone from the inferior portion of ramus to the midline, the lingual
soft tissue and periosteum of the mandible, buccal soft tissues anterior to the mental foramen
and anterior two thirds of the tongue and floor of the oral cavity [2].
In one technique, the patient is positioned supine (recommended) or semi-supine. The thumb
of the free hand is placed on the coronoid notch retracting the soft tissues. The insertion point
of the needle is about 6 to 10 mm above the occlusal plane and at the 3/4 of the anterior posterior
distance from the coronoid notch to the pterygomandibular raphe (visual in the oral cavity).
The syringe is advanced from across the lower premolar teeth of the opposite side. A long
dental needle is used; the bone must be touched while advancing about 25mm of the 35 mm
needle into the tissue. After contacting bone the needle is withdrawn slightly, aspiration
performed and if negative in two directions 1.5 to 1.8 ml of solution is deposited over a
minimum of 60 seconds (Figure 3).. [1]
Two problems occur very commonly with this technique [7]:
1.Contacting the bone too soon: to solve this problem the needle is withdrawn halfway, still
remaining in the soft tissue, then the barrel of the syringe is swung over the mandibular
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teeth of the side being anesthetized, then the needle is advanced about 2.5 mm and the
solution is deposited. This is a modification of IANB (the indirect technique) [8].
2.The bone is not contacted after 30 mm of needle insertion: the needle should be withdrawn
halfway back then the barrel of the syringe is swung over the molar teeth of the opposite
side being anesthetized, and then advanced to touch the bone and then continued as
described. When the bone is not touched the solution should not be deposited because the
needle could be in the parotid gland near the facial nerve and an injection there could lead
to transient paralysis of the facial nerve [1].
One of the most common causes of failure of IANB is depositing the solution too low (below
the mandibular foramen) in this case it can be corrected by re-injecting at a higher site,
approximately 5 to 10 mm above the previous site.
Mylohyoid nerve is the most common nerve which provides mandible teeth with accessory
sensory innervation (most commonly the mesial portion of mandibular f