21--23--LA COMPONENTS AND TECHNIQUE ===2024

Components of Local Anesthetic Cartridge

• Dental local anesthesia techniques involve the trigeminal nerve, which has three branches: ophthalmic (V1), maxillary (V2), and mandibular (V3).
• The superior alveolar, lingual, and inferior alveolar nerves are key nerves in dental anesthesia.

Local Anesthesia in Dentistry

• A standard local anesthetic cartridge contains approximately 1.7 mL of solution.
• A typical cartridge includes a local anesthetic agent (e.g., lidocaine HCl 2%) and a vasoconstrictor (e.g., epinephrine 1:100,000).

Mechanism of Action and Patient Status

• Local anesthetics work by inhibiting the influx of sodium ions through channels in neuronal membranes, preventing neural conduction.
• Sodium channels exist in resting, activated (open), and inactivated states, each affecting the neuron's ability to depolarize.
• Local anesthetics show preferential sensitivity to different neuronal fiber classes based on these channel states.
• Patient's physical, medical, and mental status should be considered.
• Hypertension, diabetes, and allergies to local anesthetic agents or components are important considerations.
• Mental status evaluation is necessary, especially in children and mentally retarded patients, to prevent self-trauma due to anesthesia.
• Long-acting local anesthetics are contraindicated in patients who may traumatize themselves.

Composition of Local Anesthesia

The composition of local anesthesia typically includes:

• Local anesthetic agent: Lignocaine HCL – 2% (20 mg/ml)
• Vasoconstrictor: Adrenaline – 1:80,000 (0.012 mg) or Epinephrine
• Reducing Agent: Sodium Metabisulphite – 0.5 mg
• Preservative: Methylparaben – 0.1% (1mg)
• Isotonic Solution: Sodium Chloride – 6 mg
• Fungicide: Thymol
• Vehicle: Ringer’s Solution
• Diluting Agent: Distilled water
• To adjust pH: Sodium Hydroxide
• Nitrogen Bubble: 1-2mm in diameter to prevent Oxygen from being trapped in the cartridge, which can destroy the Vasopressor or vasoconstrictor.

Local Anesthetic Drugs - Class, Duration, and Dosage

The characteristics of various local anesthetic drugs are as follows:

• Procaine (Ester): Duration 15-60 mins, Dose 7 mg/kg, Max Dose 350-600 mg
• Chloroprocaine (Ester): Duration 15-30 mins, Dose 11 mg/kg, Max Dose 800 mg
• Lidocaine (Amide): Duration 30-60 mins, Dose 4.5 mg/kg, Max Dose 1000 mg
• Lidocaine + Adrenaline (Amide): Duration 120-360 mins, Dose 7 mg/kg, Max Dose 300 mg
• Mepivicaine (Amide): Duration 45-90 mins, Dose 7 mg/kg, Max Dose 400 mg
• Bupivicaine (Amide): Duration 120 – 240 mins, Dose 2.5 mg/kg, Max Dose 175 mg
• Bupivicaine + Adrenaline (Amide): Duration 180 – 420 mins, Dose 2.5-4 mg/kg, Max Dose 225-400 mg
• Prilocaine (Amide): Duration 30 – 90 mins, Dose 8 mg/kg, Max Dose 500-600 mg
• Maximum Recommended Dose (MRD) Calculation: Based on the maximum dose of local anesthetic, patient weight, and concentration.

Vasoconstrictors in Local Anesthesia

• Vasoconstrictors like adrenaline can cause significant drug interactions, with adverse reactions in 2.5-11.2% of cases.
• Local anesthetics are vasodilators; adding a vasoconstrictor provides benefits such as improved onset and duration, reduced bleeding, and decreased systemic absorption.
• Adrenaline is unstable and requires an antioxidant, such as sodium bisulphite, which may cause reactions in patients allergic to sulphites.

Epinephrine

• Epinephrine is a natural hormone from the adrenal medulla, with release increasing 20-40 times under stress.
• Functions include peripheral vasoconstriction, increased heart rate and contractility, increased AV conduction, bronchodilation, and vasodilation of skeletal muscle.
• Peripheral vasoconstriction is related to stimulation of α1 receptors, reducing tissue perfusion and causing local ischemia.
• Intravenous administration should be avoided, and caution is needed in patients with severe hypertension or unstable cardiac rhythm.
• Anesthetics without adrenaline/epinephrine should be used in these high-risk patients.

Calculating Vasoconstrictor Dose

• Vasoconstrictor dosage is expressed as a dilution ratio, not based on weight.
• Common concentrations: 1:80000, 1:100000, and 1:200000.
• 1:1000 adrenaline concentration = 1mg/ml; therefore, 1:100000 = 0.01mg/ml, resulting in 0.018mg adrenaline per 1.8ml cartridge.
• 1:200000 contains 0.005mg/ml, translating to approximately 0.01mg per cartridge.
• Maximum dose: 0.2mg adrenaline per appointment for healthy patients (approximately 10 cartridges of 1:100000).
• Medically compromised patients: maximum 0.04mg adrenaline (two cartridges of 1:100000).

Considerations for Vasoconstrictor Use

• AHA and ADA state that typical vasoconstrictor concentrations are not contraindicated in cardiovascular disease if aspiration is practiced, injection is slow, and the smallest effective dose is used.
• Adrenaline 1:100,000 causes more sympathomimetic side effects than 1:200,000; thus, the lower concentration is preferred when possible.
• Lower concentrations like 1:200,000 do not compromise anesthetic efficacy and are the preferred choice unless significant performance differences exist with 1:100,000.
• For periodontal surgery, 4% articaine with adrenaline 1:100,000 or 1:200,000 provides excellent pain control; 1:200,000 offers better visualization due to less bleeding.

Adrenaline and Drug Interactions/Contraindications

• Adrenaline can interact with non-selective beta blockers, some antidepressants, and street drugs.
• Contraindications: unstable angina, recent myocardial infarction, recent coronary artery bypass surgery, refractory arrhythmias, uncontrolled congestive heart failure, severe hypertension, uncontrolled hyperthyroidism, uncontrolled diabetes, sulphite allergies, steroid-dependent asthma, pheochromocytoma.
• Precautions: Patients taking tricyclic antidepressants, phenothiazine compounds, monoamine oxidase inhibitors, nonselective Beta-blockers, cocaine abusers, patients undergoing general anesthesia with Halothane, and patients taking Digoxin.

Non-Selective Beta Blockers

• Non-selective beta blockers like propranolol and nadolol are used to control hypertension or migraines.
• Vasoconstrictors in these patients can cause uncompensated peripheral vasoconstriction, increasing blood pressure, bradycardia, and headaches.
• Complete avoidance of adrenaline is advised for simple procedures.
• For complex procedures, use minimal vasoconstrictor dose (half a cartridge of 1:100000 or 1:200000), avoid intravascular administration, and monitor vital signs.
• Adrenaline containing retraction cord must be avoided.

Tricyclic Antidepressants

• Tricyclic antidepressants like imipramine and amitriptyline inhibit adrenaline uptake, increasing catecholamine concentrations.
• Maximum dose: 0.04 mg adrenaline (two cartridges of 1:100000 local anesthetic).
• Preferable to use lower concentration of 1:100000 or less (e.g., 1:200000) and no more than one-third the normal maximum dose.
• Interactions with general anesthetics like halothane can increase dysrhythmic effects; inform the anesthetist and restrict the dose.
• Halothane limits: 2.2μg/kg adrenaline.
• Enflurane limits: 3.5μg/kg adrenaline
• Isoflurane limits: 5.5μg/kg adrenaline

Street Drugs

• Common street drugs: marijuana, delta 8 THC, opioids, alcohol, steroids, cocaine, fentanyl, hallucinogens, heroin, etc.
• Methamphetamines and cocaine have sympathomimetic effects and can interact with adrenaline.
• Increased risk of hypertensive crises, stroke, and myocardial infarction.
• Postpone elective dental treatment for at least 24 hours after cocaine use.

Adrenaline and Medically Complex Patients

• Adrenaline mimics sympathetic nervous system mediators and provides direct stimulation of adrenergic receptors.
• Clinicians should be aware of its effect on the sympathetic nervous system, especially in medically compromised patients.
• Joint statement of ADA and American Heart Foundation: use extreme care to avoid intravascular injection and use the minimum possible amount of vasoconstrictor.

Cardiovascular Diseases

• Elective dental treatment is contraindicated in unstable angina, recent myocardial infarction (less than six months), or recent coronary artery bypass surgery (less than three months).
• Emergency treatment requires medical consultation; limit adrenaline dosages to one to two cartridges of 1:100000 solution (0.018 to 0.036 mg).
• Limit vasoconstrictors to one to two cartridges in stable angina patients.
• Vasoconstrictors are contraindicated in severe arrhythmias.
• Digoxin can precipitate cardiac arrhythmia when used concurrently with vasoconstrictors.

Severe Local Anesthetic-Induced Cardiovascular Toxicity

• Toxicity may develop within one hour after injection.
• Stop administration immediately if signs of toxicity occur.
• Assess cardiovascular status and initiate cardiopulmonary resuscitation procedures.
• Avoid using lidocaine as anti-arrhythmic therapy.
• If standard procedures fail, use 20% lipid emulsion (Intralipid®) intravenously.
• Initial bolus: 1.5 mL/kg over 1 minute.
• Infusion: 15 mL/kg/hour.
• If no improvement after 5 minutes, give up to two more bolus doses of 1.5 mL/kg.
• Increase infusion rate to 30 mL/kg/hour until stability is restored, or a maximum cumulative dose of 12 mL/kg is given.

Stroke and Hyperthyroidism

• Defer adrenaline use for patients who have suffered a stroke within the last six months.
• After six months, doses should be limited to less than 0.036 mg (two cartridges of 1:100000 adrenaline concentration).
• Avoid or minimize adrenaline use (one to two cartridges) in untreated or poorly controlled hyperthyroid patients.

Corticosteroid-Dependent Asthma and Pheochromocytoma

• Local anesthetic with vasoconstrictors in cortico-dependent asthma patients may result in a higher risk of sulphite allergy. Use anesthetic without vasoconstrictor.
• Pheochromocytoma, a tumor of the adrenaline medulla, is an absolute contraindication to vasoconstrictors.

Bone Irradiation

• Avoid vasoconstrictors with local anesthetic when a patient is receiving bone irradiation.
• Local anesthesia with vasoconstrictors has been implicated with ischemic conditions of the pulp and alveolar bone, which is associated with an increased incidence of osteitis after extractions.
• Local tissue damage at the site of injection is related to or accentuated by the presence of vasoconstrictors.

Vassopressin (Felypressin)

• Felypressin is an analogue of vasopressin, which is a hormone of the posterior pituitary.
• Vasopressin is released in response to high serum osmolarity, stress, inflammatory signals, and some medications.
• Binds to vasopressin V1 receptor in the vascular smooth muscle, producing vasoconstriction and reducing local blood flow.
• Less potent than catecholamines & poorer control of bleeding during operative procedures.
• Acts on the venous side rather than the arterial side.
• Dose: 0.03 IU/ml (0.54 µg/ml)

Felypressin

• Felypressin is a synthetic analogue of posterior pituitary hormone (Octopressin).
• It acts directly on vascular smooth muscle, mainly the venous peripheral vessels, for constriction.
• Increased the diastolic blood pressure of hypertensive patients with controlled blood pressure.
• Patients with high trait anxiety presented increases in systolic blood pressure, suggesting that an increase in blood pressure might also be related to fear or anxiety.

Local Anesthetic Preparations and Autonomic Nervous System

• Changes in circulatory dynamics during tooth extraction with the two different local anesthetic preparations were the result of a decrease in parasympathetic nervous activity with lidocaine-epinephrine and an increase in sympathetic nervous activity with prilocaine-felypressin.
• One of the complications during local anesthesia include increased blood pressure and vasovagal reflex, which are caused by changes in the autonomic nervous system.
• The commonly used local anesthetic preparations are lidocaine to which the vasoconstrictor epinephrine is added (lidocaine-epinephrine) and prilocaine to which the vasoconstrictor felypressin is added (prilocaine- felypressin); however, their effects during dental treatment are unclear.

Adverse Reactions and Management

• Toxicity is related to the peak circulating levels of local anesthetics.
• Circulating levels are determined by the rates of absorption, distribution, and metabolism.
• The absorption rate depends on the chemical structure, dose, presence/absence of epinephrine, speed of administration, local tissue vascularity, and technique of administration.
• Distribution occurs in three phases: uptake by highly vascular tissues (lungs, kidneys), less vascularized tissues (muscle, fat), and then metabolism.
• Metabolism depends on chemical structure: amino esters are degraded primarily by plasma pseudocholinesterases, while amino amides are cleared primarily by hepatic metabolism with renal excretion.
• Local anesthetics decrease the rate of depolarization of cardiac tissue, which is the rationale behind the use of lidocaine in the treatment of ventricular arrhythmias.

Adverse Reactions - Neurotoxicity and Myotoxicity

• Adverse reactions may occur due to excessive drug administration, injection into vascular sites, or accidental intravascular injection.
• Deaths following local anesthetic administration are usually a result of overdosage.
• Tissue toxicity can be achieved by all local anesthetics.
• Adverse reactions occur primarily in the CNS (neurotoxicity) and cardiovascular system (myotoxicity).
• CNS symptoms may include lightheadedness, tinnitus, circumoral numbness, metallic taste, or double vision.
• Upon examination, the patient may exhibit drowsiness, slurred speech, or nystagmus. At higher levels, anxiety, tremors, seizures, hypoxia, acidosis, and respiratory arrest may occur.

Maximum Recommended Dosage and Safety

• Consideration Maximum Recommended Dosage (MRD) for cardiovascular disease patient = 0.04 mg of adrenaline = 2 dental cartridge of 2ml 1:100000 concentration adrenaline
• Controversy still exists on using adrenaline in controlled cardiovascular diseased patient.
• Uses of small amount available in dental cartridge is better than exposing the patient to failure anesthesia which produce pain and bleeding that can stimulate fear and increase intrinsic adrenaline that may have more dangerous effect than extrinsic adrenaline
• Preservative agent of LA Maintains sterility of the solution
• Caprylhydrocuprienotoxin used for this purpose
• Methylparaben used for vasoconstrictors.
• Reducing agent (in vasoconstrictor containing solution) Antioxidant (reducing agent) used to prevent oxidation of vasoconstrictor that may deteriorate on exposure to sunlight (brown discoloration), Sodium metabisulfite used for this purpose
• On exposure to oxygen it will diffuse through the rubber of the cartridge where sodium metabisulfite will be converted to sodium metabisulfate (oxidized), Oxidized instead of vasoconstrictor
• Fungicide (Thymol)
• Sodium chloride and distilled water (ringers solution) For isotonicity of injected solution to reduce edema and discomfort on inject

Selection of Local Anesthetic Agent

• There are several anesthetic agents available for use in dentistry, each agent has got its own indications,
• The agents are selected on the basis of the needs of each patient, the following factors are to be considered for the selection of particular agent
• 1. Duration of action.
• 2. Need for control of post-operative pain.
• 3. Physical and mental status of the patient.
• 4. Concomitant medications.

Hypersensitivity Reactions

• Although exceedingly rare, hypersensitivity reactions may occur with the use of local anesthetics.
• This is usually a reaction to the anesthetic or the preservative used in the solution.
• Allergic reactions are uncommon in the amino ester group and extremely rare in the amino amide group.
• Most reactions to local anesthetics are actually caused by anxiety, panic attacks, vasovagal responses, or accidental intravascular injection.
• True allergic reactions occur in fewer than 1% of all reactions to local anesthetics.
• The cause of hypersensitivity reactions is believed to be a breakdown product created by the action of serum pseudocholinesterases on the amino ester paraaminobenzoic acid (PABA).
• PABA is very antigenic and is capable of sensitizing lymphocytes and eliciting the formation of antibodies for a humoral immune response.
• Hypersensitivity reactions may be type I reactions manifested by a spectrum of symptoms from local or systemic urticaria to anaphylactic shock, or type IV reactions manifested by contact dermatitis or anaphylactoid reactions.

Hypersensitivity Symptoms, Management, and Alternatives

• The patient may develop hypotension, tachycardia, hives, angioedema, dyspnea, bronchospasm with wheezing, or rhinorrhea.
• Ceasing the operation immediately at the onset of any signs or symptoms of a severe allergic reaction is important.
• Antihistamines and corticosteroids are first-line treatments, to be administered concomitantly with activation of ACLS protocols and the Emergency Medical Services (EMS) system.
• If a patient has a reaction to a local anesthetic, assuming that he or she is also sensitive to other agents in the same class is the safest route.
• Most patients with a hypersensitivity reaction to an amino ester can probably be treated safely with an amino amide.
• However, many commercial amino amide preparations contain methylparaben as a preservative. Methylparaben is chemically similar to PABA and is capable of eliciting a hypersensitivity reaction. The extremely rare cases of hypersensitivity reactions to amino amides are probably related to the methylparaben preservative rather than to the amino amide.
• Mepivacaine commercial preparations do not contain methylparaben and can usually be substituted safely in this situation.

Hypersensitivity Testing

• If any question exists regarding a prior hypersensitivity reaction to local anesthetics, initially administer a test dose prior to proceeding with the intended therapeutic amount.
• Alternatively, referral to an allergist can help elucidate a suspected allergy to a local anesthetic. Skin testing and incremental dose challenges can be performed as recommended by the Joint Council of Allergy, Asthma, and Immunology (JCAAI).
• The JCAAI has shown this strategy to be safe and efficacious.

Common Local Anesthetic Agents

• Articaine HCL 4% with epinephrine 1:100,000
  • Color of Cartridge Band: Gold
• Bupivacaine 0.5% with epinephrine 1:200,000
  • Color of Cartridge Band: Blue
• Lidocaine HCL 2%
  • Color of Cartridge Band: Light blue
• Lidocaine HCL 2% with epinephrine 1:50,000
  • Color of Cartridge Band: Green
• Lidocaine HCL 2% with epinephrine 1:100,000
  • Color of Cartridge Band: Red
• Mepivacaine HCL 3%
  • Color of Cartridge Band: Tan
• Mepivacaine HCL 2% with levonordefrin 1:20,000
  • Color of Cartridge Band: Brown
• Prilocaine HCL 4%
  • Color of Cartridge Band: Black
• Prilocaine HCL 4% with epinephrine 1:200,000
  • Color of Cartridge Band: Yellow

Lignocaine (Lidocaine) - Properties and Pharmacology

• Lignocaine is the most commonly used local anesthetic agent in dentistry and the first non-ester type used.
• Stable and can be stored for a long time at room temperature.
• Withstands boiling and autoclaving.
• Compatible with all types of vasoconstrictors.
• Rapidly diffuses through intestinal tissue into lipid-rich nerves for rapid onset.
• Metabolized in the liver by microsomal fixed-function oxidases.
• Excreted in the urine to some extent by the kidney.
• Potency: 2 times as potent as procaine, used as a standard for comparison.

Lignocaine (Lidocaine) - Toxicity, Action, and Availability

• Toxicity: 2 times as toxic as procaine.
• Time of onset of action: Rapid (2-3 min).
• Effective dental concentration: 2%.
• Anesthetic half-life: 1.6 hours.
• Maximum recommended dose: 4.4 mg/kg body weight with or without a vasoconstrictor.
• Availability in dentistry: Dental cartridge of 2% lidocaine with epinephrine 1:80,000.

Factors Affecting Local Anesthetic Action

The action of local anesthetics can be influenced by different factors:

• pKa: Lower pKa = more rapid onset of action due to more uncharged molecules diffusing through the nerve sheath.
• Lipid solubility: Increased lipid solubility = increased potency.
• Protein binding: Increased protein binding = increased duration due to firmer attachment to proteins at receptor sites.
• Non-nervous tissue difficulty: Increased diffusibility = decreased time of onset.
• Vasodilator activity: Greater vasodilator activity = increased blood flow, resulting in rapid removal of anesthetic molecules and decreased potency and duration.

Mepivacaine

• Same potency as lidocaine
• Similar to lidocaine in metabolism and excretion
• Same onset, slightly extended duration (weak vasodilatation)
• PKa = 7.6
• Less toxic than lidocaine
• Used for child and geriatric patient when vasoconstrictor contraindicated
• MRD = 4.4 mg/Kg = 300mg
• 2% → 7.5 cartridge
• 3% → 5 cartridge

Prilocaine (citanest)

• Same potency to lidocaine
• Less toxicity
• Less vasoldilating activity
• PKa = 7.9
• MRD = 6mg/kg
• 3% → ?? cartridge
• 4% → ??? Cartridge
• Metabolism occur mostly in liver into orthotolidine which can cause methemoglobulinemia in susceptible individual (patient with hemolytic anemia) if used in large dose → poor oxygen carrying capacity resulting in cyanosis
• Clinically patient may have cyanosis in the lip, mucous membrane and skin. Patient may also have respiratory distress in severe cases
• Treatment by methyline blue 1% injection 1-2 mg/kg IV/5min

Articaine

• Slightly more potent than lidocaine
• Similar toxicity, and vasodilating activity
• Some literature present a cross allergisity with sulfate so it is best to be avoided in patient allergic to sulfonamide
• MRD = 7mg/kg
• 4% → 7 cartridge
• Similar to prilocaine in producing methemoglbulinemia
• Common and Rare Side Effects for articaine-epinephrine:
  • Dizziness,Muscle Tremors,Loss Of Skin Color,Headache,Heart Throbbing Or Pounding,Nausea,Vomiting,Nervousness,Generalized Weakness,Anxious Feelings,Fast Heartbeat
• 4% articaine causes more nerve damage than 2% lidocaine, although some authors advise caution when using this agent. All studies suggested that dental practitioners exhibit caution when choosing to use 4% articaine in an inferior alveolar nerve block until further scientific research has been performed

Bupivicaine

• Bupivacaine is an anesthetic (numbing medicine) that is used as a local (in only one area) anesthetic. Bupivacaine is given as an epidural injection into the spinal column to produce numbness during labor, surgery, or certain medical procedures. Bupivacaine is also used as an anesthetic for dental procedures
• Four times more potent than lidocaine and 4 times less toxic
• Slower onset (5-10 min) and extended duration lasting for 90-180 min
• MRD = 1.3mg/kg 0.5% → 10 cartridge
• Dental Indication
  • 1. Prolonged dental procedure , Expected post operative pain
  • 2-bupivacaine lasted 27% longer than lidocaine and 45% longer than etidocaine
• Contraindication
  • 1. Child and mentally retarded patient
• Dosage Modifications
  • Renal impairment ,Pharmacokinetics not evaluated,Substantially excreted by the kidneys; may increase bupivacaine exposure and risk of systemic toxicities in patients with renal impairment,All severities: Use with caution; consider frequent monitoring for adverse reactions
  • Hepatic impairment, Pharmacokinetics not evaluated, Owing to inability to metabolize local anesthetics normally, patients with hepatic impairment at risk of increased bupivacaine plasma levels and systemic toxicities Moderate-to-severe: Use with caution; consider reducing dosage and closely monitor

Etidocaine

• More toxic than lidocaine
• MRD= 8mg /kg available in1.5% → 13 cartridge
• In general surgery both indicated in prolonged procedure when uses of vasoconstrictor is contraindicated systemically or locally
• The PKa of etidocaine (7.74) is similar to that of lidocaine (7.86).
• However, etidocaine possesses a greater degree of lipid solubility and protein binding capacity than does lidocaine.
• Duranest (etidocaine hcl) Injections are sterile and, except for the 1.5% concentration, are available with or without epinephrine 1:200,000.
• Single dose containers of Duranest (etidocaine hcl) Injection without epinephrine may be re autoclaved it necessary b

Ropivacaine

• Ropivacaine is a long-acting amide local anaesthetic agent and first produced as a pure enantiomer. It produces effects similar to other local anaesthetics via reversible inhibition of sodium ion influx in nerve fibres.
• Ropivacaine is less lipophilic than bupivacaine and is less likely to penetrate large myelinated motor fibres, resulting in a relatively reduced motor blockade. Thus, ropivacaine has a greater degree of motor sensory differentiation, which could be useful when motor blockade is undesirable. The reduced lipophilicity is also associated with decreased potential for central nervous system toxicity and cardiotoxicity.
• Ropivacaine causes reversible inhibition of sodium ion influx, and thereby blocks impulse conduction in nerve fibres. This action is potentiated by dose-dependent inhibition of potassium channels.Ropivacaine is less lipophilic than bupivacaine and is less likely to penetrate large myelinated motor fibres; therefore, it has selective action on the pain-transmitting A β and C nerves rather than Aβ fibres, which are involved in motor function
• The maximum recommended dose of ropivacaine is 3 mg kg−1, which means that the patient with weight 50 kg should have been given 30 ml of 0.5% as a maximum. Was there any case of toxicity or any other side-effects in the lower weight patients in this study

Calculating Concentrations

• Local Anesthetic:
  • Multiply the percentage (%) concentration by the number of ml in the cartridge to calculate the mg of an agent contained in the cartridge.
  • Example: 2ml of 2% local anesthetic solution contains 40 mg of local anesthetic agent because 2$% = 20 mg/ml by 2 (the number of ml in the cartridge)) = 40 mg of local anesthetic agent.
• Epinephrine:
  • Convert the ratio to a %: 1 in 100 is 1% and 1 in 1000 in 0.1%.
  • Multiply the % by 10 to get mg/ml.
  • Example: 1:1000 epinephrine is 1mg/ml.

Dental Cartridge

• Glass cylinder containing the local anesthetic drug, among other ingredients.

• The glass cylinder itself can hold 1.8, 2 ,2.2 mL of solution; however, as prepared today, the dental cartridge contains approximately 1.8 mL of local anesthetic solution.

• Local anesthetic cartridges list their volume

• The dental local anesthetic cartridge is, by common usage, referred to by dental professionals as a carpule.

• Plastic cartridges have several negative features, primarily leakage of solution during injection, the requirement for considerable force to be applied to the plunger of the syringe (e.g., periodontal ligament [PDL], nasopalatine), and the fact that the plunger does not “glide” down the plastic cartridge as smoothly as it does down the glass cartridge, leading to sudden spurts of administration of local anesthetic under increased pressure, which can produce pain in the patient.

• Another problem with plastic cartridges is that they are permeable to air. Exposure to oxygen leads to more rapid degradation of the vasoconstrictor in the cartridge and to a shorter shelf life.

• Components The prefilled 1.8-mL dental cartridge consists of four parts

  • cylindrical glass tube
  • stopper (plunger, bung)
  • aluminum cap
  • diaphragm

• The stopper (plunger, bung) is located at the end of the cartridge that receives the harpoon of the aspirating syringe. The sharp harpoon is embedded into the silicone (non–latex-containing) rubber plunger with gentle finger pressure applied to the thumb ring of the syringe. The plunger occupies a little less than 0.2 mL of the volume of the entire cartridge. Today, local anesthetic stoppers are treated with silicone, eliminating both the paraffin and the glycerin that were used in years past. “Sticky stoppers” (stoppers that do not move smoothly down the glass cartridge) are rare today.

• Recent years have seen a move toward the use of a uniform black rubber stopper in all local anesthetic drug combinations. Virtually gone are the color-coded red, green, and blue stoppers that aided in identification of the drug.

Composition of Local Anesthetic Agent (Revisited)

• Local anaesthetic agent : eg Lignocaine HCL – 2% (20 mg/ml)
• Vasoconstrictor : Adrenaline – 1:80,000 (0.012 mg) or Epinephrine
• Reducing Agent: Sodium Metabisulphite – 0.5 mg
• Preservative: Methylparaben – 0.1% (1mg)
• Isotonic Solution: Sodium Chloride – 6 mg
• Fungicide: Thymol
• Vehicle: Ringer’s Solution
• Diluting Agent: Distilled water
• To adjust pH: Sodium Hydroxide
• Nitrogen Bubble: 1-2mm in diameter and is present to prevent Oxygen from being trapped in the cartridge and potentially destroying the Vasopressor or vasoconstrictor.

Actions of Local Anesthetic Components

• Vasoconstrictor Function:
  • Decrease blood flow to the site of injection, absorption of local anesthetic into the cardiovascular system is solved, decrease the risk of local toxicity, higher volume of local anesthetic agent remain in and around the nerve for longer period, thereby increasing the duration of action, vasoconstrictor decreases bleeding at the site of their administration.
• Preservative:
  • Stability of modern local anesthetic solution is maintained by adding caprylhydro-cuprienotoxin which includes xylotoxand methyl paraben.
• Reducing Agent:
  • These act as preservatives for vasoconstrictor agents. Vasoconstrictors are unstable in solution and may oxidize, especially on a prolonged exposure to sunlight. Sodium metabisulphite which competes for the available oxygen is added in the concentration between 0.05% and 0.1%
• Vehicle:
  • All the above solutions and local anesthetic agent are dissolved in a modified ringer solution. This isotonic vehicle minimizes discomfort during injection

Function of Nitrogen Bubble

• The bubble size 1-2mmin diameter and is present to prevent .Oxygen from being trapped in the cartridge and potentially destroying the Vasopressor or vasoconstrictor, so this is the function of Nitrogen Bubble in the LA cartridge.
• We see many patients who ask “what do dentists use to numb teeth or mouth” before performing a procedure and the answer is dental anesthetics which help in making dental procedures painless be it related to the tooth or the gums and other soft tissue in the mouth or oral cavity. Having proper knowledge about the Allergic Reactions to LA and also we should have good knowledge about the amount of LA to be given to avoid

Importance of Dental Local Anesthesia Skills

• The most important skill required of all dental practitioners is the ability to provide safe and effective local anesthesia (LA).
• The injection of local anesthetic is perhaps the greatest source of patient fear and inability to obtain adequate pain control with minimal discomfort remains a significant concern of dental practitioners.
• The achievement of good local anesthesia requires knowledge of the agents being used, the neuroanatomy involved, and best techniques and devices available.
• The agents and anesthetic delivery equipments available today provide the practitioner an array of options to effectively manage the pain associated with dental procedures.
• Local anesthesia forms the backbone of pain control techniques in the dental profession.
• Local anesthetics represent the safest and most effective method for managing pain associated with dental treatment. They are the only drugs that prevent the nociceptive impulse from reaching the patient's brain.
• Local anesthetics need to be deposited as close to the nerve as possible so that optimal diffusion of the drug may occur, providing profound anesthesia and a pain-free dental experience.

Patient and Dentist Perceptions

• The importance of this is demonstrated by the fact that