LOCAL ANESTHESIAO.R.GANESH

M.Sc.D ENDO

UNIVERSITY OF THE EAST

LOCAL ANESTHESIAWhat is local anesthesia?• LA has been defined as a temporary loss of sensation in a circumscribed area of the body caused by a depression of excitation in nerve endings or an inhibition of the conduction process in peripheral nerves.•It produces loss of sensation without inducing loss of consciousness

METHODS OF INDUCING LOCAL ANESTHESIA Mechanical trauma Low temp Anoxia Chemical irritants Neurolytic agents ,eg: alcohol,phenol Chemical agents ,eg: local anesthetics

THE NEURON

ELECTRO PHYSIOLOGY 1. Nerve consists “potential”. Here it is negative resting elec.pot

existing across the nerve membrane.

2. A stimulus produces excitation of the nerve, leading to the following sequence of the events.

3 . Initial phase is slow depolarization. The electrical potential becomes slightly less negative.

4. When the elec.pot reaches a critical level. An extremely rapid phase of depolarization occurs- threshold potential or firing threshold

5. The phase of rapid depolarisation results in the reveral of the electrical potential across the nerve membrane. The inside of the nerve is +ve.

6. After depolarization- repolarization occurs.

7. The process requires 1 msec (2 thru 6 stage)

8. Depolarization 0.3sec(2 thru 5)

9. Repolarization 0.7sec( 6 stage)

ELECTRO CHEMISTRY

INITIAL MANAGEMENT1. Psychologic approach : 4c Control Communication Concern Confidence

2. PAINLESS INJECTIONS Patients generally have a fear of dental injections. A good

practice builder and method of winning confidence and cooperation is to master injection techniques that are nearly painless.

Although most injections cannot be pain-free, there can be minimum of discomfort

3.OBTAINING PATIENT CONFIDENCE

Obtaining patient confidence is critical Before injection, a dentist should establish communication and exhibit

empathy .

4. TOPICAL ANESTHESIA As an adjunct to painless injection The most important aspect of using topical anesthesia is not primarily

the actual decrease in mucosal sensitivity but rather the demonstrated concern that everything possible is being done to prevent pain

1. Topical anesthesia gel is used , a small amount on a cotton applicator is placed on the dried mucosa for 1 – 2 mints before the injection.

2. An intraoral adhesive, 20% lidocaine patch. It is placed for 5 mints..later it was shown to reduce the pain of needle stick

Draw back-

poor adhesive to mucosa

extra time

5. SOLUTION WARMING

A common belief is that an anesthetic solution warmed or above

body temp are better tolerated but in clinical trials, patients could not differentiate between prewarmed and room temp.

so it is not necessary to warm the anesthetic cartridges.

6. NEEDLE INSERTION Insert gently in to the mucosa.

7. SMALL GUAGE NEEDLES Misconception --that smaller needles cause less pain. Patients cannot differentiate between 25,27 and 30 gauge. a 27 gauge needle is recommended for conventional dental injections.

8. SLOW INJECTIONS Slow injection decreases pressure and patient discomfort . A technique for slow injection is to use a computer controlled

anesthetic delivery system.

This device delivers 1.4 ml of the An.solu

over 4 mints 45 secs.

9. TWO STAGE INJECTION Decreases the pain of needle placement in infe.alv.nerv.bl . This is in indicated in pediatric , anxious and apprehensive patients.

------ a two stage injection consists of initial very slow administration of a approximately a quarter cartridge of anesthetic just under the mucosal surface.

after regional numbness, the reminder of the cartridge is deposited to the full length at target site

10.GENDER DIFFERENCES women try to avoid pain more than men, accept it less , and fear it more.

11. WHEN TO ANESTHETIZE Instruments can be used painlessly with out anesthesia in canals with

the necrotic pulp and periradicular lesions. But if the vital tissue is present in apical few millimts of the canal, then pain results.

The inflamed tissue contains nerves and is sensitive. so anesthesia should be given at each appointment.

Sometimes pressure is also created and it gives discomfort to patient. Working length can be determined in an non anesthetized patient by

passing an instrument in to a necrotic canal until patient shows an “eye blink response”

Unfortunately ,patient perceptions and responses are too variable for accuracy.

Many think that after cleaning and shaping ,there is no need of anesthetizing the tooth but during obturation, pressure is created and small amounts of sealer may be extruded beyond the apex which is quite uncomfortable.

12.ADJUNCTIVE THERAPY Sedation may enhance local anesthesia, particularly in patients who

want to co operate but are extremely apprehensive

CONVENTIONAL ANESTHESIA1. MANDIBULAR ANESTHESIA

2. MAXILLARY ANESTHESIA

MANDIBULAR ANESTHESIA1. Anesthetic agents Most commonly used agent is 2% lidocaine with

1: 100,000 epinephrine Lidocaine is safe and effective drug

2. Related factors

a. Lip numbness- 5 to 7 mints, it indicates that injection blocked the nerves to the soft tissues of the pulp.

b. Onset of pulpal anesthesia- 10 to 15mints

c. Duration - persists apprx 2 and half hours

d. Success - the incidence of successful mandibular pulpal anesthesia tends to be more frequent in molars and premolars and least in anteriors

ALTERNATIVE TECHNIQUES Increasing the volume:

increases the volume of anesthetic from 1 – 2 cartridges will not increase success rate .

Increasing the epinephrine concentration :

there is no improvement in anesthesia with a higher concentration of epinephrine in an inf.alv.nerv.blk.

Alternating solutions: lasts atleast 1hr

1. 2% mepivacaine with 1: 20,000 levonordefrin

2. 4% prilocaine with 1: 200,000 epi

3. Solutions without vaso constrictors

Articaine : recently introduced in united states. Safe and effective Clinical trials failed to detect any superiority of articaine over lidocaine.

(mand. Block) Incidence of paresthesia is rare Alternative injection techniques: Neither Gow Gates nor vizarani akinoski technique is superior to standard

inf.nerv.block . They are usefull only when normal approaches cannot be used

Incisive nerve block at the mental foramen:

This is successful in anesthetizing the premolars but not central and lateral Infiltration injections:

1. labial or lingual infiltrations alone are not effective for pulpal anesthesia in mandible

2. Combination of labial and lingual are effective- lower ant. Teeth

3. Articaine is effective than lidocaine for buccal infiltration Long acting anesthetics:

1. bupivacaine and etidocaine provide prolonged analgesic period and are indicated when post operative pain is anticipated.

2. Bupivacaine has slower onset than lidoccaine but has double the duration of pulpal anesthesia in mandible … apprx 4 hrs.

Accuracy of needle placement :

1. Accurate anatomic positioning is no guarantee of a successful block.

2. Even after locating the inf.alv.nerve with ultra sound before the injection did not improve success.

Needle deflection:

1. This deflection has been theorized as a cause for failure with infe. Alv.nerv block

2. Needle bevel does not effect the success of the inf.alv.nerv.blk Accessory innervation

1. An experimental study using mylohyoid injection lingual and inferior to retro molar fossa in addition to an inf .alv.nerv.blk showed no enhancement of pulpal anesthesia

2. The contribution of mylohyoid nerve to pulpal sensitivity is insignificant.

Cross innervation :

1. cross innervation from the contra lateral inferior alveolar nerve has been implicated in failure to achieve anesthesia in ant.teeth after an inferior alveolar injection

2. Cross innervation does not occur in incisors Pain and inflammation :

patients who have symptomatic pulpal or periapical pathosis present additional problems.

MAXILLARY ANESTHESIA1. Anesthetic agents

2%lidocaine with 1:100,000 epi

2. Related factors

a. Lip numbness: in few mints.

b. Success: high incidence of successful pulpal anest.

c. Onset : of pulpal anesthesia occurs in 3-5mints.slower in molars.

d. Duration: problem in max.infiltration pulpal anesthesia in ant.teeth declines after 30mints and loses by

60mints In premolars and 1st molars no pul.anes at 45mints

and half losing by 60mints

ALTENATIVE TECHNIQUE Volume:

1. increasing the volume increases the pulpal

anesthesia.

2. Anterior teeth and premolars – give two cartridges initially or one, and inject another apprx after 30mints

3. Molars- two cartridges initially will sped up the the onset and prolong the duration.

Alternative solutions:

1. Prilocaine , mepivacaine, Articaine and lidocaine act similarly.

2. Solutions without vasoconstrictors provide shorter duration.15 – 20 mints

3. Long acting anesthetics do not provide prolonged pulpal anesthesia ( as they do in mandibular block)

Other techniques:

1. Posterior superior alveolar nerve block anesthetizes the 2nd,3rdand 1st molars.

2. Middle.sup.alv.nerv. does not supply the 1st molars

3. An additional mesial infiltration injection may be necessary to anesthetize 1st molar.

4. PSA in indicated when all the molar teeth require anesthesia .

5. For single tooth – infiltration is enough

Infra orbital nerve blk:

1. Similar to infiltration over premolars

2. results in lip numbness

3. does not anesthetize incisors pulp

4. Anesthetizes premolars but duration is less than an hour Second division blk:

1. Anesthetizes pulp of the molars and some 2nd premolars

2. Does not anesthetize anterior pulps

3. High tuberosity technique is preferred to greater palatine approach because it is easier and less painful

Palatal ante.sup.alve.nerv.blk:

1. Anesthetize all maxillary incisors with a single palatal injection in to the incisive canal

2. Did not provide predictable anesthesia for ant.teeth .

3. Often painful. Anterior mid.sup.alv.nerv.blk:

1. Unilaterally anesthetizes the maxillary central and lateral incisors,canines,1st and 2nd premolars with a single palatal injection in to the premolar region

2. Did not provide predictable anesthesia for anterior teeth

3. Often painful.

ANSTHESIA DIFFICULTIES1. The anesthetic solution may not penetrate to the sensory nerves that

innervate the pulp, especially in the mandible.

2. The anesthetic solution may not diffuse in to the nerve trunk to reach all nerves to produce an adequate block.

3. Lowered pH of inflamed tissue reduces the amount of the base form of the anesthetic available to penetrate the nerve membrane. Consequently, there is less of ionizes form within the nerve to achieve anesthesia.

the injection site is distant from the area of inflammation, changes in tissue pH would be unrelated to the anesthesia problem

4. Hyperalgesia of nociceptor is more plausible explanation. This theory states that the nerve arising in inflamed tissue have altered

resting potentials and decreased excitability thresholds. These changes are not restricted to the inflamed pulp itself but effect the

entire neuronal membrane , extending to the central nervous system . Local anesthetic agents are not sufficient to prevent impulse transmission,

owing to these lowered excitability thresholds

5. Patients in pain often are apprehensive , which lowers their pain threshold.

6. The dentist may not allow sufficient time for anesthetic to diffuse and block the nerves.

SUPPLEMENTAL ANESTHESIA Indications:

1. If the standard injection is not effective

2. Only useful to repeat if the patient is not showing the classical signs of soft tissue anesthesia

3. There are 3 supplemental injections

a. Intraosseous

b. Periodontal ligament

c. intrapulpal

IO and PDL are preferred approaches

IP injection reserved for special situations

Anesthetic agents:

2% lidocaine with 1:100,000 epi

INTRA OSSEOUS ANESTHESIA Used in cases like pulpitis in mandibular posterior teeth IO injection allows a placement of a local anesthetic directly in to the

cancellous bone adjacent to the tooth.IO with 2 components – on part is slow speed hand piece driven perforator ,

which drills a small hole through the cortical plate. the anesthetic solution is delivered in to the cancellous bone through a

matching 27 gauge ultra short injector needle

Another IO system uses as a guide sleeve that remains in the perforation .this serves as a guide for the needle and may remain in place through out the procedure.

Another innovation is an IO system that combines a slow speed hand piece with an anesthetic cartridge dispenser system and a rotating needle or drill.

Technique : the area of perforation and injection site is on a horizontal line of buccal

gingival margins of the adjacent teeth and a vertical passing through the interdental papilla distal to the tooth to be injected.

A point 2mm below the intersection of these lines is selected as perforation site.

Soft tissue 1st anesthetized by infiltration.The perforator is placed through the gingival perpendicular to the cortical

plate.

Then with light pressure , resting against the bone the handpiece is activated with full speed.

ACTION CONTINUED TILL THE BREAK THROUGH IN TO THE CANCELLOUS BONE(2-5sec)

Pen gripping fashion – syringe to be held Anesthetic solution is slowly delivered over 1-2mints with light pressure. If back pressure encountered then needle should be rotated apprx a quarter

turn and deposition is reattempted.

Injection discomfort:

1. when Io injection is used as primary injection, neither perforation ,needle insertion nor solution deposited is painful for most patients

2. If used in irreversible pulpitis then moderate pain may occur. Selection of perforation site:

1. Distal perforation and injection – best anesthesia

2. Exception in 2nd molars – mesial site is preferred

3. Lingual approach may also be successful

Anesthetic agents:

1. 2%lidocaine with 1:100,000 epi

2. 2%mepivacaine with 1:20,000 levonordefrin

3. 1%etidocaine with 1:200,000epi

4. Etidocaine and 0.5%bupivaciane should not be used because of adverse cardiovascular reactions.

Onset of anesthesia

Rapid and no waiting period Success

1. As primary injection success rates are good

2. For 3%mepivacaine success rates are low

3. For irreversible pulpitis success rates are high(sup.inj)

Failure :

if the anesthetic solution squirts out of the perforation then there will be a failure.

Duration :

1. As Primary IO injection pup.anes declines over an hour

2. Supplemental IO injection (to IA block ) is painless and duration is very good.

3. 3%mepivacaine –shorter duration

4. For irreversible pulpitis, the IO injection should provide anesthesia for entire debridement appointment.

Post operative problems:

with primary and supplemental techniques ,the majority of patients report no pain or mild pain

Systemic effects:

1. With both primary and supplemental techniques using anesthetics with a vaso constrictor, most patients perceive an increased heart rate.

2. No significant heart rate is increase occurs with 3% mepivacaine plain.

3. The venous plasma levels of lidocaine are the same for an IO injection as for infiltration injection. Therefore same precautions for IO injection.

Medical contrandications:

1. Moderate to severe cardiovascular disease

2. Tricyclic anti depressants

3. Non selective β adrenergic blocking agaents

4. 3%mepivacaine is preferred

PERIODONTAL LIGAMANET INJECTION

1. The PDL injection is useful if the conventional injection is unsuccessful.

2. The technique is clinically effective and is a valuable adjunct

3. Particularly useful when a rubber dam is in place

Technique:A standard syringe or pressure syringe is equipped with a 30 gauge ultra

short needle or 27 or 25 gauge short needle.The needle is inserted in to the mesial gingival sulcus at 30 degree angle to

the long axis of the tooth.

The needle is supported by fingers or hemostatHeavy pressure is slowly applied on syringe needle for apprx 10-20sec or

trigger is slowly squzeed once or twice with resistanceBack pressure is important.

Mechanism of actionThe PDL injection forces anesthetic through the cribriform plate in to the

marrow spaces and in to the vasculature in and around the tooth

Injection discomfort: as primary injectionIn anteriors – painfulIn posteriors- insertion and injection are mildly uncomfortable Onset

Rapid –no waiting period SuccessAs primary injection – good success ratesHigh success rates in posteriors teeth than in anterior teethWithout vasoconstrictors or with less vasoconstrictors are not effective

As supplemental injection – good success ratesAnd reinjection increases success rateUse of computer controlled local anesthetic delivery system for supplemental

injection was successful in irreversible pulpitis. Duration :10 – 20 mints of pulpal anesthesiaDentist must work quickly and be prepared to reinject Post operative discomfort:When PDL injection is used as primary technique ,post operative discomfort

usually occurs with a duration of 14hours to 3 days

Selective anesthesia:It has been suggested that PDL injection may be used in differential

diagnosis of poorly localized painful irreversible pulpitis.How ever adjacent teeth are often anesthetized with PDL injection of a single

tooth.Therefore this injection is not useful for differential diagnosis. Systemic effects:Some authors have found that PDL increases heart rate , human studies

have shown that PDL injections do not cause significant changes in heart rate.

Safety to peridontium: Minor local damage is limited to the site of needle penetration .This subsequently undergoes repair In rare cases infection occur Safety to the pulp:No adverse effects on pulp after PDL injection Safety to the primary teeth:Minor enamel hypoplasia of succedaneous teeth has been reported.Caused by the cyto toxicity of the local anesthetic rather than the injection

INTRAPULPAL INJECTION: Indications:When IO and PDL do not produce profound anesthesia.Pain persists when pulp is entered.Without giving IO and PDL 1st , IP should not be administered because it

leads to pain.The IP injection may also be useful in injecting into the individual canals ,

when anesthesia is not adequate or touch up anesthesia would be helpful.

Advantages and disadvantages:The advantage is predictability of profound anesthesia if the IP injection is

given under back pressure Onset is immediate No special syringes or needles requiredDifferent approaches are necessary Disadvantages:Needle is inserted directly in to the vital and sensitive pulpEffects of injection are not predictable if it is not given under pressure.

duration of the anesthesia is only 5 – 20 mints

Therefore bulk of the pulp must be removed Another disadvantage is that the pulp must be exposed to permit direct

injection . Mechanism of action: Strong back pressure has been shown to be major factor in producing

anesthesiaDepositing anesthetic passively into the pulp chamber is not adequate. The

solution will not diffuse throughout the pulp .So it depends on pressure

Technique:The patient must be informed that a little extra anesthetic will ensure comfort

and that there will be a sharp sensation.One technique creates back pressure by stoppering the access with a cotton

pellet to prevent backflow of anesthetic Other stoppers – gutta percha,waxes, pieces of rubber dam have been used.

If possible, the roof of the pulp chamber should be penetrated by a half round bur, thus the needle will then fit snugly in the bur hole

another approach is an injection in to each canal after the chamber is unroofed

A standard syringe is usually equipped with a bent sharp needle with fingers support the needle shaft to prevent buckling.

The needle is positioned in the axis opening then moved down the canal.Max.pressure 5- 10 sec

ANESTHETIC MANAGEMENT OF PULPAL OR PERI RADICULAR PATHOSIS

Irreversible pulpitis:Most difficult to anesthetize is mand.molars, mand and max. premolars,

max.molars,Mand and max. ant teeth.(in order)The vital inflamed pulp must be invaded and removed The pulpal tissue has a very concentrated sensory nerve supply particularly

in the chamber.

In some cases, inflamed vital tissue exists only in the apical canals and the tissue in the chamber are necrotic and does not respond to pulp testing. But when a dentist attempts to place a file in to the canal ,Pain is encountered .

Irreversible pulpitis must be differentiated from a symptomatic apical pathosis because IO , PDL. IP are contra indicated.

General considerationsConventional anesthesia using primary techniques is administered.

Mandibular posterior teeth:Conventional inf.alv.injections is administrated, usually in conjunction with a

long buccal injection. Mandibular ant.teeth: An inf.alv.injection is given. If pain is felt IO is administrated. If IO is unsuccessful then IP is administered.. Maxillary post teeth: Approaches are the same as those outlined under general considerations

except that the initial dose is doubled for buccal infiltration(3.6ml)

Maxillary anterior teeth:Labial infiltration Is administratedOccasionally palatal infiltration for rubber dam retainer.IO injection needed rarelyAnd PDL injection is also not very effectiveDuration less than one hour

SYMPTOMATIC PULP NECROSIS This diagnosis indicates pain and swelling and therefore peri radicular

inflammtion. Mandible – long buccal and inf. Alv . Nerve bloc Maxillary- if no swelling then conventional infiltrations or block If soft tissue swelling is present( cellulites or abscess) – regional block +

infiltration. Access is begun slowly –pulp chamber is entered without discomfort if the

tooth is not torqued.

File placement and debridement also can be performed without much pain f the instruments gently.

IO,PDL and IP injec are contraindicated. although effective for vital pulps these injec are painful and ineffective with apical pathosis.

In patients with severe preoperative pain without driange from the tooth----- long acting anesthetic may help control post operative pain in mandibular teeth.

ASYMPTOMATIC PULP NECROSIS

Asymptomatic teeth are the easiest to anesthetized Mandible- conventional injec-inf alv nev,blc and long buccal

infiltation. Maxillary-infiltration or PSA block If patient is uncomfartable than IO or PDL are adminstered. IP is contraindicated .

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