LA-Local anesthesia in endodontics 24-01-23.pptx

local anesthesia in dental

1. Good Morning

2. Local Anesthesia

3. Contents Definition Requirements Mechanism of action Classification Adverse effects Mandibular anesthesia Maxillary anesthesia Complications Future trends

4. Definition LA has been defined as a loss of sensation in a circumscribed area of body caused by a depression of excitation in nerve endings or an inhibition of the conduction process in peripheral nerves.

5. REQUIREMENTS Nonirritant. Should not produce any local reaction. Should not cause any permanent change in the nerve structure. Should cause minimal systemic toxicity. Should be effective and enough penetrating properties when used topically. Should have short time of onset.

6. The theories explaining the mechanism of action of local anesthesia are   Acetylcholine theory. Calcium displacement theory. Surface charge theory. Membrane expansion theory Specific receptor theory.

7. Specific receptor theory The most favored today, proposes that local anesthetics act by binding    To specific receptors on sodium channel.  Once the local anesthetic has gained access to the receptors, permeability to sodium ions is decreased or eliminated, and nerve conduction is interrupted.to specific receptors on the sodium channel .

8. MECHANISM OF ACTION 1. displacement of calcium ions from the sodium channel receptor site, which permits …  2. binding of the local anesthetic molecule to this receptor site, which produces …  3. blockade of the sodium channel and a …  4. decrease in sodium conductance, which leads to … 5. depression of the rate of electrical depolarization and … 6. failure to achieve the threshold potential level, along with …  7. lack of development of propagated action potentials, which is called … 8. conduction blockade

9. FUNCTIONS LOST WITH LA PAIN TEMPERATURE TOUCH PROPRIOCEPTION SKELETAL MUSCLE TONE

10. Classification BASED ON CHEMICAL NATURE ESTERS These can be further classified as: Esters of benzoic acid e.g. cocaine butacaine. Esters of para-aminobenzoic acid e.g. procaine, propoxycaine. AMIDES e.g. articaine , bupivacine , lidocaine.

11. BASED ON DURATION OF ACTION short acting articaine , lidocaine, mepivacaine, prilocaine. Long acting: bupivacaine, etidocaine, bucricaine

12. BIOTRANSFORMATION Esters are rapidly metabolized in the plasma by cholinestrase Amides are slowly destroyed in the liver by microsomal P450 enzymes

13. Modes of application Topical or surface application Infiltrations Nerve Block Field Block Centrally acting(Spinal)

14. Possible adverse effects Possible adverse reactions to local anesthetics can be divided into six major categories:  Cardiovascular reactions  Systemic effects  Methemoglobinemia  Peripheral nerve paresthesia  Allergic reactions to the anesthetic and/or latex  Reactions to anesthetics containing a sulfite antioxidant

15. Cardiovascular Reactions Tachycardia after injection is primarily a pharmacologic effect. The cardiovascular effects are the result of alphaadrenoceptor stimulation by systemic distribution of the vasoconstrictor throughout the vascular compartment. The patient may also report heart palpitations associated with anxiety or fear and may experience transient tachycardia and changes in blood pressure.

16. Systemic Effects It can include an initial excitatory phase (e.g., muscle twitching, tremors, grand mal convulsions) and a subsequent depressive phase (e.g., sedation, hypotension, and respiratory arrest).  An acute hypotensive crisis with respiratory failure also has been interpreted as the result of hypersensitivity to local anesthetics.

17. Methemoglobinemia  Metabolism of certain local anesthetics (e.g., prilocaine, benzocaine, articaine , and to a lesser extent lidocaine) can produce a metabolite that causes methemoglobinemia; this effect often occurs several hours after injection of the local anesthetic.Typical signs and symptoms include cyanosis, dyspnea, emesis, and headache.

18. Peripheral Nerve Paresthesia Postinjection paresthesia is a rare adverse effect of local anesthetics.1 The incidence of paresthesia (which involved the lip and/or tongue) associated with articaine and prilocaine was higher than that found with either lidocaine or mepivacaine.

19. Allergic reactions to local anesthetics and latex Common reported signs and symptoms include allergic-like reactions, such as urticaria, bronchospasm, and anaphylaxis. Risk factors include an active history of asthma.

20. Effects of systemic diseases on Local anesthetics It has been stated that vasoconstrictors should be avoided in patients with high blood pressure (higher than 200 mmHg systolic or 115 mmHg diastolic), cardiac dysrhythmias, unstable angina, less than 6 months since myocardial infarction or cerebrovascular accident, or severe cardiovascular disease.  Patients taking antidepressants, nonselective beta-blocking agents, medicine for Parkinson disease, and cocaine have a potential for problems.

21. Alcoholics have been found to be more sensitive to painful stimulation.  Any of the commonly available LA are safe for use in pregnant or lactating woman.

22. Failure to achieve Anesthesia in patients with pain Inflamed tissue has a lower pH, which reduces the amount of the base form of anesthetic that penetrates the nerve membrane. Nerves arising from inflamed tissue have altered resting potentials and decreased excitability thresholds. Another factor might be the TTX-R sodium channels, which are resistant to the action of local anesthetics are increased in inflamed dental pulp and are sensitized by prostaglandins. A related factor is the increased expression of sodium channels

23. Reversing the Action of Local Anesthetics Phentolamine mesylate is a recently developed agent that shortens the duration of soft tissue anesthesia. The duration of soft tissue anesthesia is longer than pulpal anesthesia and is often associated with difficulty eating, drinking, and speaking. The best use is after dental procedures when postoperative pain is not a concern.  Therefore,it may be used to shorten the duration of soft tissue anesthesia if the patient presents with an asymptomatic tooth and little postoperative pain is anticipated.

24. Inferior Alveolar Nerve Block For Restorative Dentistry  anesthetic success Anesthetic success for nerve blocks is the percentage of subjects who achieve two consecutive nonresponsive readings on electrical pulp testing within 15 minutes and continuously sustain this lack of responsiveness for 60 minutes.  Anesthetic Failure  Anesthetic failure can be defined as the percentage of subjects who never achieved two consecutive nonresponsive EPT readings at any time during 60 minutes period.

25. Noncontinuous Anesthesia It may be related to the action of anesthetic solution on the nerve membrane . Slow onset Slow onset can be defined as the percentage of subjects who achieved a nonresponsive EPT reading after 15 minutes. Duration The duration of action for pulpal anesthesia in the mandible is very good. If patients are anesthetized initially, anesthesia usually persists for approximately 2.5hours.

26. Alternative anesthetic solutions for inferior alveolar nerve block 3% Mepivacaine     It is used as a local anesthetic when medical conditions or drug therapies suggest caution in administration of solutions containing epinephrine  4% Prilocaine with 1:200,000 and 2% mepivacaine with 1:20,000 levonordefrin      In a study of volunteers without dental pathosis, IAN injection of 4% prilocaine with 1:200,000 epinephrine or 2% mepivacaine with 1:20,000 levonordefrin worked as well as 2% lidocaine with 1:100,000 epinephrine in achieving pulpal anesthesia

27. Articaine with 1:100,000 epinephrine      Articaine has been reported to be a safe and effective local anesthetic. Long acting anesthetics     Ropivacaine and levobupivacaine are being developed as potentially new local anesthetics based on their stereochemistry. Both are S-isomers and are thought to cause less toxicity than the racemic mixture of bupivacaine currently marketed.

28. Buffered Lidocaine     Buffering lidocaine using sodium bicarbonate raises the pH of the anesthetic solution.t buffered lidocaine produced less pain on injection and a faster onset of anesthesia.   Use of Mannitol     Mannitol, a hyperosmotic sugar solution, is thought to temporarily disrupt the protective covering (perineurium) of sensory nerves, allowing the local anesthetic to gain entry to the innermost part of the nerve.

29. Attempts to increase success of Inferior alveolar nerve block Increasing volume of anesthetic Increasing epinephrine concentration Addition of hyaluronidase Carbonated anesthetic solutions Diphenhydramine as local anesthetic agent Addition of meperidine to lidocaine

30. Factors In Failure Of Inferior Alveolar Nerve Block Accessory Innervation: Mylohyoid Nerve         Mylohyoid nerve is the accessory nerve most often cited as cause of failure of mandibular anesthesia. As these branches passing through accessory canals may provide an escape pathway for pain. Accuracy of injection Inaccurate injection contributes to inadequate anesthesia  but a number of studies determined that the use of ultrasound, a peripheral nerve stimulator, or radiographs to guide needle placement for IAN blocks did not result in more successful pulpal anesthesia

31. Needle Deflection                                                                                                                Needle deflection has been proposed as a cause of failure with the IAN block.  Several in vitro studies have shown that beveled needles tend to deflect toward the nonbeveled side Speed of Injection                                                                                                                     A slow inferior alveolar nerve block increases success over a fast injection.

32. Cross Innervation                                                                                                                     Cross-innervation from the contralateral inferior alveolar nerve has been implicated in failure to achieve anesthesia in anterior teeth after an IAN injection.

33. Enhancement of Mandibular Anesthesia Supplemental articaine infiltrations Supplemental intraosseous anesthesia Supplemental intraligamentary anesthesia

34. Maxillary Anesthesia  the most commonly used injection for anesthetization of maxillary teeth is infiltration with a cartridge of 2% lidocaine with 1:100,000 epinephrine. Infiltration results in a fairly high incidence of successful pulpal anesthesia Pulpal anesthesia usually occurs in 3 to 5 minutes The duration of pulpal anesthesia is a problem with maxillary infiltrations. Pulpal anesthesia of the anterior teeth declines after about 30 minutes, with most losing anesthesia by 60 minutes. In premolars and first molars, pulpal anesthesia is good until about 40-45 minutes and then it starts to decline.

35. Complications Local complications Systemic complications

36. Local Complications • needle breakage  • prolonged anesthesia (paresthesia) • facial nerve paralysis  • ocular complications  • trismus  • soft tissue injury 

37. • hematoma  • pain on injection  • burning on injection  • infection  • edema  • sloughing of tissues  • postanesthetic intraoral lesions

38. Systemic Complications Overdose Allergy

39. Overdose predisposing factors Patient Factors  Age  Weight  Other drugs  Sex  Presence of disease Genetics  Mental attitude and environment

40. Drug Factors  Vasoactivity   Concentration  Dose  Route of administration  Rate of injection  Vascularity of the injection site  Presence of vasoconstrictors

41. Management P…POSITION ↓  Unconscious…supine with feet elevated slightly  Conscious…based on patient comfort  A…AIRWAY ↓  Unconscious…assess and maintain airway  Conscious…assess airway

42. B…BREATHING ↓  Unconscious…assess and ventilate if necessary  Conscious…assess breathing   C…CIRCULATION ↓  Unconscious…assess and provide chest compression if necessary  Conscious…assess circulation D…DEFINITIVE CARE Diagnosis Management: emergency drugs and/or assistance

43. Allergy Sodium Bisulfite allergy Epinephrine Allergy Latex Allergy Topical Anesthetic allergy

44. Management Emergency protocol no.1    The most practical approach to this patient is to provide no treatment of an invasive nature.  Emergency protocol no. 2    Use general anesthesia in place of local anesthesia for management of a dental emergency Emergency protocol no. 3    Histamine blockers used as local anesthetics should be considered if general anesthesia is not available Emergency protocol no.4     Electronic dental anesthesia or other non drug techniques as hypnosis

45. Future Trends  Centbucridine Ropivacaine EMLA Ph Altration Hyaluronidase Ultra long acting LA Electronic dental anesthesia

46.    THANK YOU