Local anesthesia for oral operations

LOCAL

ANESTHESIA DAVID

I).

BLOOM,

FOR ORAL D.M.D.,

BOSTON,

UPERATIONS MASS.

I

N THIS discussion of local anesthesia for dental needs my purpose is to stress what is axiomatic, that the knowledge of anatomy is basic to any successful invasion of tissue for the purpose of inhibitin g sensory impulses in an area of choice. IKFILTRATION

ANESTHESIA

Let US apply this principle t,o our simplest problem of anesthesia, namely the infiltration of a maxillary anterior tooth. Knowing that the nerve supply enters this incisor through the apex, it becomes evident that the deposition of our anesthetic agent of necessity must be at a height corresponding to that of the root end. If our procedure is to intrude upon the lingual mucosa such as an extraction, the knowledge that the nerve distribution here comes from the inner nerve loop whereas our initial infiltration anesthetizes those fibers of the outer nerve loop supplying the tooth in question with sensation, a subsequent injection is made in the lingual mucosa. Should this tooth be a central incisor which requires operative procedure then it becomes necessary to direct some of our initial anesthetic fluid toward the corresponding central incisor as some innervation crosses from this side. To infiltrate other areas successfully it is essential we have in mind that there exist regions of porosity as well as areas of density in the maxilla and mandible. Only areas of porosity are favorable to infiltration, as here the cortical layer which is composed of compact bone presents numerous foramina thus aiding absorption. Those of you who have attempted infiltration of the mandibular molars are well aware that your att,empts failed for the reason you neglected to apply the above knowledge learned early in your dental educational career. The mandible in general has a more dense and thicker cortical layer than t,he maxilla, and the anterior region of the mandible is its only portion presenting sufficient porosity favorable to the infiltration technique.l In the dense molar region the external oblique line buttressing the body of the mandible is an added factor discouraging absorption. Infiltration for operative needs will be more effective if the injection is made subperiosteally. In this instance it is requisite that our anesthetic fluid reach the pulp, and confining the solution below this membrane obviates permeating the pulp. Furthermore the liquid thus confined is under added pressure enabling it readily to penetrate the cancellous structure, periodontal membrane, and finally to diffuse through the apical foramen into the pulp. Infiltration of all maxillary incisors may be obtained by making the initial puncture over the canine on each side and passin, v the needle horizontally toward City

I,ecture

delivered

Hospital,

Boston.

before

Massachusetts

Dental

5SP

Society

1941

Educational

Course.

Boston

Local

Anesthesia

583

the central incisors infiltrating over the apices of the individual teeth. This is an excellent method of anesthesia for alvcolectomy or gingivectomy in this region, and needless to add infiltration of the lingual mucosa is essential. By this method only two punctures are made labially, and I believe we are indebted to Nevin for this technique. Similarly, should it be desired to anesthetize all the mandibular incisors, only one labial puncture is made. The needle insertion takes place well down in the reflection of mucosa of the inferior frenum and is directed toward one canine fossa. After 1 C.C. of solution is expelled, the needle is withdrawn to a point permitting its course to be directed to the other canine fossa for deposition of the remaining fluid. Massaging the tissues following injection enhances the absorption through the numerous foramina present in these areas. CONDUCTIOK

ASESTHESLi

Where infiltration anesthesia is not indicated due to anatomic, pathologic, or other reasons, we have available the block or conduction method; a direct challenge to our knowledge of anatomy. MANDIBULAR

IiVJECTION

Blocking the inferior alveolar and lingual branches of the third division of the fifth cranial nerve is the method of choice for work in the mandible, and as previously observed, due to anatomic factors, is the only successful procedure posterior to the canines. An excellent technique which establishes the proper height and depth of needle penetration, avoiding at the same time invasion of the internal pterygoid muscle whose lower fibers occupy the region medial to our objective, is as follows. Palpate the greatest depression of the external oblique line with the finger turned radially, keeping the palpatin g finger parallel with the occlusal plane or if teeth are absent with the superior border of the body of the mandible ; direct the needle from the opposite premolars makin g the puncture slightly medial to the fingernail, and at a height corresponding to one-half the width of the nail. Be alert to feeling the osseous structure of the mandible a short distance after the needle is engaged, and, using the inner surface of the bone as a guide, the progress of the syringe point should be terminated by the mandibular sulcus at which point 11/a CC. is deposited. Using the medial surface of the ramus as an indicator will obviate the invasion of the internal pterygoid muscle. The ascending ramus of the inferior maxilla taken as an entity roughly is rectangular in shape, and the mandibular foramen is in a position representing the center of the mass; to allow mandibular movements which will not stretch the nerve and the accompanying vessels entering the foramen. Nature so constructs this bone that the depression on the external oblique line when halved will be on a plane correspondin g to t,he position of the foramen ; consequently the above technique is foolproof when observing the details as described. Blocking the lingual nerve may be accomplished when withdrawing the needle to a point one-half the distance of the engaged portion necessary to reach the mandibular foramen. Innervation of the buccal mucosa in the mandibular molar region comes from the long buccal branch of the mandibular nerve coursing downward in the

cheek. Consequently surgical endeavor in this region demands a subsequent injection to accommodate this anatomic factor. Entrance of the needle is made in the cheek at the occlusal plant height, and at a point corresponding to the mesial surface of the first molar, directing the needle posteriorly, just under the mucous membrane, injecting as progress is made, and completing the injection posterior to the third molar region. TUBEROSITY

ISJECTION

In the maxilla the molars may be anesthetized by means of the tuberosity injection. Here the objective is to block the posterior superior alveolar nerve which descends from the infraorbital nerve anterior to Meckel’s ganglion coursing downward to gain access to the osseous structure of the posterior surface of the maxilla, entering the bone about one inch above the distogingival margin of the superior third molar. Keeping in mind this point as the area to deposit our anesthetic fluid, the needle insertion is made high in the reflection of mucosa, posterior to the zygomatic process. In other words the zygoma is an obstacle preventing t,he proper progress of the needle, consequently palpating same and injecting posterior to it avoids its obstruction. The bone is used as a guide, and no more than one-half the length of a 15/s inch needle should be engaged. Moving the syringe body laterally enables continuous contact with the bone. A word of caution is necessary for a successful result and avoidance of unnecessary complications in this useful injection. The pterygoid plexus of veins lies about the external pterygoid muscle which may be invaded if the needle is carried too far posteriorly or is not kept in close contact with the bone. This venous arrangement has a connection with the cavernous sinus through the foramen ovale, consequently, it is important not to carry infection into this area. Encroachment of this venous plexus will cause a hematoma, which in the absence of infection is not serious, but nevertheless an undesired postoperative sequel to injection. The mesiobuccal root of the first molar is, in the majority of eases, innervated by the middle superior dent,al branch of the infraorbital nerve which comes down the lateral wall of the antrum to innervate the premolars; consequently, the infiltration of this root is necessary to complete the anesthesia of the first molar. INFRAORBITAL

INJECTION

Blocking the anterior superior alveolar or dental branch of the infraorbital nerve may be accomplished intraorally as follows. The infraorbital foramen may be palpated first orienting the infraorbital ridge and then directing the finger in a line with the second premolar root and the center of the eyelids. The foramen lies slightly below the ridge in this line. Directing the needle in this imaginary line, make the initial insertion, high in the reflection of the mucosa, and be sure to rest the barrel of the syringe on the lower lip. The index finger of the palpating hand remains over the infraorbital foramen while the thumb retracts the lip. When the needle has reached its objective, the escaping fluid is easily detected by the finger and as an aid to absorption is massaged into the foramen. The upward progress of the needle, when properly guided, is without resistance as it passes through a layer of fat lying between the caput infra-

585

Local Anesthesia

orbital muscle and the caninus muscle. The former arises from the infraorbital ridge of the maxilla and passes downward to be inserted into the sphincter muscle (orbicularis oris) of the lip. From t,his it is evident it must of necessity superimpose the infraorbital foramen. The caninus muscle, as its name implies, arises from the canine fossa and passes downward to be inserted at the angle of the mouth. Thus its position is below the foramen and the syringe needle in passing between these muscles to gain access to the infraorbital opening passes through the adipose tissue occupying the space between these muscles. Another anatomic consideration relative to this injection is the position of the anterior facial vein which winds its way down the face from the medial commissure of the eyelids. Consequently, when injecting, it is advisable to aspirate and determine if invasion of the blood stream has taken place. Should this occur, blood in the syringe barrel will indicate the undesired result and necessitate a slight alteration in our pathway. Owing to the presence of a branch of the facial nerve at the infraorbital foramen, we obtain a characteristic drooping of the lip on the injected side. This serves as an indication that our solution has been properly placed. ANESTHESIA

OF

THE

ENTIRE

OUTER

NERVE

LOOP

It is possible to anesthetize the complete outer nerve loop. Using an cxtension hub so bent as to place the needle at a right angle relation to the syringe barrel, the puncture is made at the same place advised when making a tuberosity injection. Our objective is to diffuse sufficient solution about the second division of the fifth cranial nerve as it crosses the pterygopalatine fossa in its attempt to reach the floor of the orbit and gain access to the infraorbital canal. As the floor of the orbit is the upper surface of the body of the maxilla, and as we are aiming at a position which is posterior to its posterior boundary, the zygomatic surface of the maxilla furnishes a guide and the puncture is made so as to reach this surface and to avoid the zygomatic process which would obstruct the needle. Visualizing the path of the nerve it becomes apparent that our syringe is guided not only upward along the osseous posterior surface of the maxilla, but inward toward the pterygopalatine fossa. Nevin advises the use of a 4 cc. syringe to be sure of sufficient anesthetic fluid for diffusion in case we are not in the position nearest the nerve trunk. About lrh inch of the needle is engaged. A necessary caution is to avoid directing the syringe too far posteriorly as this will be in the direction of the lateral surface of the external pterygoid plate and invasion of the musculature, the pterygoid Venus plexus or both may result. Another caution is to be as close t,o the posterior surface of the maxilla as possible. EXTRAORAL

INJECTIONS

Conditions may be encountered indicatin, v the use of local anesthesia, but on account of pathologic conditions preclude an intraoral approach. Therefore, mention of the extraoral inject,ion becomes pertinent. The infraorbital injection from this access allows for easier entrance into canal. Using a fine brush and a coloring fluid such as weak tincture of iodine, tincture of metaphen, etc., outline the infraorbital ridge and draw a short line

David

D. Bloom

downward at right angles on the imaginary line whose points are the center of the eyelid and the second premolar root. Approximately l/4 inch down on this line, marks the foramen, and our puncture is made the same distance below

Fig.

Fig.

1.

Fig. l.-Extraoral infraorbital injection by iodine. (From Thoma, Om2 Anesthesia.) Fig. 2.-Extraoral mandibular injection the mandibular foramen. 0, place for insertion

Fig.

S.-Insertion

of

needle

for

mandibular Thoma,

showing showing of the

insertion

of

landmarks to needle. (From

injection at Oral Anesthesia.)

a

Site

2.

needle

at

determine Thoma,

prepared

with

an

area

prepared

the location Oral Anesthesia.)

iodine.

of

(From

this point expelling a few drops of fluid to allow painless progress of the needle (Fig. 1). The needle used is a 1 inch 25.mm. gauge and is directed upward aspirating to ascertain invasion of the blood stream. After the avoidance of the

infraorbital vein is assured, carefully seek the orifice of the foramen and advance the needle for a short distance into the canal, again aspirating to determine entrance into the blood stream. Should the latter not have occurred, expel the remainder of the fluid. Extraoral injection for the inferior alveolar nerve according to Thomaz may be made as follows : a line is drawn from the tragus of the ear to the inferior-anterior angle of the masseter muscle. This line is divided equally to determine the point marking the position of the mandibular sulcus. A line is drawn downward from this point of division parallel to the posterior border of the ramus. The length of this line determines the amount of needle necessarily engaged to reach the mandibular foramen (Fig. 2). This length is then indicated on a 60-mm. needle. The needle is inserted beneath the lower border of the ramus and directed upward through t,he internal pterygoid muscles along the inner surface of the mandible parallel with the posterior border of the ramus according to the line previously drawn (Fig. 3). In all estraoral injections, it is needless to caution that strict surgical procedure is essential. In closing, I call your attention to the importance of having the anatomic objective in mind, and then by a careful consideration of those structures which it is necessary to invade, a technique can be used which best meets your skill and judgment. REFERENCES 1. Nevin

and Dent. 2. Thoma, K. 412

Conduction, Infiltration, and Puterbaugh: Items Interest, Ed. 3, Brooklyn, 1927. H.: Oral Anesthesia, Ed. 2, Philadelphia,

BEACON

STREET

General 1920,

Anesthesia Lea

and

Febiger,

in

Dentistry, page

148.