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Local Anesthesia/ics

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-MAIN modality to manage dental pain -Most FREQUENTLY used drug in dentistry -Blocks sensations from teeth, tissues, & bone -Provides comfort to clinician/patient -Provides satisfying result to clinician/patient -Increases patient compliance

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What Are Anesthetics & Anesthetic Solutions?

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Drugs or agents that produce analgesia

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Analgesia

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Loss of sensation to a localized or generalized area

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Root Instrumentation WITHOUT discomfort requires?

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Profound pulpal and periodontal tissue level anesthesia

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Pulpal Tissues

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HARD tissues & PULP of teeth

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Soft Tissues

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SOFT tissues of the oral cavity (eg. gingiva, papilla, tongue)

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Do pulpal tissues or soft tissues remain anesthetized longer?

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SOFT tissues remain anesthetized long after the pulpal tissues have recovered sensation

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Landmark

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LANDMARK is where the needle needs to go

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Target

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TARGET is where the anesthetic goes in

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Local Infiltration

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-Small area anesthetized (1-2 teeth & associated structures) -Anesthetic deposited near TERMINAL NERVE ENDINGS -Injection occurs near apices of teeth -Anatomy of area determines success rate

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Nerve Block

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-Large area anesthetized -Anesthetic deposited near LG NERVE TRUNKS -More successful with anesthetization than local infiltration method

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(3) Skull Bones Involved In Local Admin. of Anesthesia

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1) Palatine 2) Maxilla 3) Mandible

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(2) Body Systems You Want To AVOID Injecting Into

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1) Lymph 2) Blood

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Trigeminal Cranial Nerve V

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*Provides sensory information for the teeth and associated tissues *Branches of CN-V MOST COMMONLY anesthetized in dentistry

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Type of Injection Used Is Determined By (2):

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1) Type of procedure 2) Length of procedure

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Is it OKAY to inject into areas of infection?

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To prevent spread of disease, NEVER inject into areas of infection such as: -Abscess -Cellulitis -Osteomyelitis

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True or False: Areas of infection REDUCE the effectiveness of local anesthetics?

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TRUE; Effectiveness is greatly reduced when infection is present -Additional amounts of anesthetic may be needed -Keep MAX recommended dosages in mind

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Reasons You Might Need Increased Amounts of Anesthetic:

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-Presence of infection -Large teeth with unusually long roots -Excessively thick bone surrounding roots of teeth

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Order of Injections

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Posterior to anterior Your work should then follow in the same mannor

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Properties of "IDEAL" Local Anesthetic (1-6)

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1) POTENT 2) REVERSIBLE 3) NO local reactions 4) NO systemic reactions 5) NO allergic reactions 6) RAPID onset

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Properties of "IDEAL" Local Anesthetic (7-12)

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7) INTENDED duration 8) ADEQUATE tissue penetration 9) LOW $ cost 10) LONG shelf life 11) STERILIZED 12) EASY metabolism & excretion

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Do anesthetics constrict or dilate BV?

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Dilate (WHEN USED ALONE)

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What is added to local anesthetics to cause constriction of BV?

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Epinephrine -OR- Levonordefrin (if Mepivacaine is used)

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How do local anesthetics work?

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1) BLOCKs nerve conduction by INHIBITING the influx of Na+ ions into cytoplasm 2) The inhibition of the influx in Na+ STOPS K+ from flowing out 3) **THEREFOR, They INHIBIT the depolarization of the nerve!!

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Actions of local Anesthetic:

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1-DECREASE permeability of nerve cell membrane to Na+ ions 2- REDUCES influx of Na+ into cytoplasm 3- K+ CAN NOT flow out with influx of Na+ *NO depolarization = NO repolarization

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Anesthetic Molecules MUST enter through -WHAT- in order to take effect?

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Nerve cell membrane

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The ability of anesthetic molecules to enter into the nerve cell membranes determines -WHAT-?

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Potency; Onset time; Duration of action

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Esters: TYPES

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Procaine (Novocaine) Propoxycaine Cocaine *Benzocaine Pontocaine

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Amides: TYPES

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Lidocaine Mepivacaine Bupivacaine Prilocaine Articaine

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THREE Structures Esters & Amides Have Chemically In Common:

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1) Aromatic Group 2) Intermediate Chain 3) Amine Group

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Aromatic Group (PENETRATION)

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-Benzene Ring -Allows lipid solubility & the penetration of solution past nerve cell membrane barriers

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Intermediate Chain

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Ester -OR- Amide makeup

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Amine Group (ENTRAPMENT)

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-Allows solution to remain inside nerve cell

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TRUE or FALSE: ALL local anesthetics are weak bases?

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TRUE!

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Normal pH of Body Tissues?

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7.4

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pH of Body Tissues with Active Infection Present?

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5-6 *Shift in pH STOPS anesthetic from entering into nerve cells

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Does local anesthetic take on the pH of the surrounding tissue?

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YES! Local anesthetics will take on the pH of the tissue in which they are injected

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Are small nerve fibers or large nerve fibers more susceptible to local anesthetics?

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SMALL

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Are myelinated or unmyelinated fibers more susceptible to local anesthetics?

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MYELINATED

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ORDER OF SENSORY FUNCTION BLOCK!

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1st- PAIN 2nd- COLD 3rd- WARMTH 4th- TOUCH 5th- PRESSURE *The pain of the cold was relieved when a warm hand touched my cheek and applied gentle pressure

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Rate of Local Anesthetic Absorption Depends On -WHAT- when it is injected into tissues??

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-Tissue Vascularity -Degree of Inflammation present -Vasodilating properties of anesthetic -Presence of heat -Use of massage

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What TWO organ systems carry local anesthetic throughout the body?

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1) Cardiovascular 2) Lymphatic

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Alternating between hot and cold patches will do what to an anesthetized area?

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Speed up the removal of anesthetic in area and thus a faster return of sensation

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Where are esters metabolized at?

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Blood plasma *pseudocholinesterase Liver *liver esterases --Be careful with those who have an atypical form of pseudocholinesterase, because they can not metabolize it and systemic toxicity may occur --Be careful with those taking cholinesterase inhibitors (eg. Alzheimer's patients) --Be careful with those who have a genetic deficiency in plasma cholinesterase

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Free Base

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Form of anesthetic in tissues Penetrates nerve tissue Alkaline Unstable Viscid liquid or solid Uncharged Unionized Lipid soluable

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Salt

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Form of anesthetic in cartridge Active form at site of action Acidic Stable Crystalline solid Charged Ionized Cation Water soluable

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What does the addition of vasoconstrictors accomplish? (3)

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1- Reduce bleeding 2- Limits systemic absorption 3- Reduces systemic toxicity

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Is it true that highly vascular organs attract higher concentrations of anesthetic?

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YES!!

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Can local anesthetics cross the placenta and blood brain barriers?

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YES!!

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PABA

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Metabolite responsible for allergic reactions

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Where are Amides metabolized?

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*Liver --Watch out for liver diseases, alcoholism, and hepatitis

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Uses For Local Anesthetics

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-Reversible blockage of peripheral nerve conduction -Antiarrhythmic

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Local Anesthetics: Adverse Reactions

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-Toxicity -Allergic reaction -Muscle twitching, unconsciousness, convulsions, respiratory or Cardiac depression, then coma (>10 mcg/ml dosages) -Local effects (hematoma-- too much too quickly) -CNS: light headed, dizzy, tinnitus, unfocused, visual/auditory disturbances, disorientation, drowsiness

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Reasons For Toxicity:

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-Amount of vasodilation drug produces -How much of drug is in circulation -Topical & Intravenous injection -Fast rate of injection -Vascularity of tissues -Patient weight create different blood levels -Rate of metabolism & excretion

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What TWO groups of people are MORE susceptible to Toxicity of local anesthesia?

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1- Elderly 2- Children

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Injection of local anesthetics causes initial CNS ---- then CNS ----

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Initial CNS excitation, then CNS depression (may cause tremors, convulsions, cardiovascular, or respiratory depression)

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What local anesthetic is safe for pregnant women?

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Lidocaine (in the smallest effective dose possible!)

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Inotropic

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Influences the CONTRACTILITY of muscle tissue

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Chromotropic

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Influences rate & timing of physiological processes (eg. HEART RATE)

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Composition of Anesthetic (5)

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1) Vasoconstrictor; 2) Antioxidant; 3) Sodium hydroxide; 4) Sodium Chloride; 5) Methylparaben/Propylparaben

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Vascoconstrictor

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(eg. Epi) slows absorption, reduces systemic concentrations, reduces toxicity, prolong duration, prolong depth, reduce hemorrhage

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Antioxidant

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Preservative; slows oxidation of epi; prolongs shelf life -Sodium metabisulfite -Sodium bisulfite -Acetone sodium bisulfite

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Sodium Hydroxide

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Adjusts pH to 6/7

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Sodium Chloride

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Makes injectable solution isotonic (equal in osmotic pressure)

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Methylparaben/Propylparaben

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Preservatives Prevent bacterial growth May be responsible for some allergic reactions *NO methylparaben in dental cartridges

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Isotonic

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Equal osmotic pressure

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Vasoconstrictors

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Adrenergic agonists or sympathomimetics

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MAX safe dose of vasoconstrictor for cardiac patients

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.04 mg epi .2 mg levo

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MAX safe dose of vasoconstrictor for healthy patients

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.2 mg epi 1.0 mg levo

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BAD Drug Interactions With Use of Vasoconstrictors

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-Tricyclic antidepressants -Non selective beta blockers -MAOI's -Cocaine

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Adverse of Vaso & Tricyclic Antidepressant

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Epi = Three fold increase in BP Levo = Six-eight fold increase in BP

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Adverse of Vaso & Non Selective Beta Blockers

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Epi = hypertension & reflex bradycardia

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Adverse of Vaso & MAOI's

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Epi = Increased risk for disarrhythmias

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Adverse of Vaso & Cocaine

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Cocaine may increase effect of vasoconstriction Dysrhythmia, MI, or stroke

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TWO most common topical anesthetics:

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1) Lidocaine (Amide) 2) Benzocaine (Ester) Higher concentration than injectable anesthetics Watch for toxicity/allergy Come in liquids, gels, sprays

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Why should you NOT rub topicals into tissue?

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Will cause tissue damage and sloughing

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