Management of Local Anaesthesia in Endodontics

Management of Local Anaesthesia in Endodontics Halton-Peel Dental Association Andrew Moncarz BSc, DDS, Dip. An, MSc, FRCD(C) March 22, 2007

Objectives • Review of: • Reported rates of profound anaesthesia • Anatomical variations • Maximum doses of local anaesthetics • Pulpal inflammation as a complicating factor • Adjunctive strategies for profound mandibular LA

Reported Reasons for Mandibular Anaesthesia Failure • Operator Inexperience • Armamentarium: Deflection of the needle tip • Patient factors: • Variations in anatomy • Accessory innervation • Unpredictable spread of LA • Local infection • Pulpal inflammation • Psychological issues

What about experienced operators?

Effectiveness of Conventional IANB as measured by EPT

Always use a long 25 gauge needle (the red one) • 2 reasons: • 1. Less deflection • 2. Less false negative aspiration

Ultrasound Guidance • Hannan et al. 1999: • Repeated-measures design • 40 subjects injected twice at separate appointments—once with landmarks, once with ultrasound guidance • EPT after profound lip numbness reported • Anaesthetic success 38%-92%, no difference between the techniques • Conclusion: accuracy of needle placement is not the primary reason for failure of IANB

Nerve to mylohyoid

Berns et al. 1962: injected radiopaque material into pterygomandibular space • Spread is unpredictable • Suggestion: inject more LA

Decrease in the pH locally • Can influence the amount of LA available in the lipophilic form to diffuse across the nerve membrane • Result is less drug interference of sodium channels • Less likely to influence mandibular block anaesthesia

Pulpal Inflammation • Causes activation and sensitization of peripheral nociceptors • Causes sprouting of nerve terminals in the pulp • Causes expression of different sodium channels: TTX-resistant class of sodium channels are 4 times as resistant to blockade by lidocaine and their expression is doubled in the presence of PGE2

Effectiveness of Conventional IANB: Irreversible Pulpitis 100% lip anaesthesia

Adjunctive Strategies • Additional Anaesthetic • PDL Injection • Intraosseous Injection • Intrapulpal Injection • Different anaesthetic • Retest using the CC

Adjunctive Strategies • Additional Anaesthetic • Higher injection • Gow Gates • Akinosi • Nerve to mylohyoid • PDL Injection • Intraosseous Injection • Intrapulpal Injection • Different anaesthetic

Maximum Doses LA • % means g/dL • Example: • 1% = 1 g/dL • 1% = 10g/L • 1% = 10 mg/mL • Therefore: • 2% = 20 mg/mL

Maximum Doses LA • A cartridge contains 1.8 mL • Therefore a cartridge of 2% local anaesthetic contains 20 mg/mL X 1.8 mL = 36 mg of local anaesthetic

Maximum Doses LA • How much LA can you give? • 193 lb 33 yo male • Lidocaine 2% 1:100K • Articaine 4% 1:200K • 2.2 lbs = 1 kg • 193 lbs = 88 kg

Lidocaine 2% Max dose = 7 mg/kg 7mg/kg X 88=616 mg 36 mg/1.8 mL 616mg/36mg/cart.= 17 cartridges ** Articaine 4% Max dose 7 mg/kg 7 X 88 = 616 mg 72 mg/1.8mL 616 mg/72 mg/cart. = 9 cartridges Maximum Doses LA

Maximum Doses Epi • % = 1/100 = g/dL • Therefore: • 1/100 = 1% = 1g/dL = 10 mg/mL • 1/1000 = 0.1% = 0.1 g/dL = 1 mg/mL • 1/10000 = 0.01% = 0.01 g/dL = 0.1 mg/mL • 1/100000 = 0.001% = 0.001 g/dL = 0.01mg/mL • A cartridge contains 1.8 mL • Therefore a cartridge of 1:100 000 epi contains 0.01 mg/mL X 1.8 mL = 0.018 mg (or about 0.02 mg)

Maximum Doses Epi • Cardiovascular patient 0.04 mg • Healthy patient 0.2 mg

Lidocaine 2% Max dose = 7 mg/kg 7mg/kg X 88=616 mg 36 mg/1.8 mL 616mg/36mg/cart.= 17 cartridges ** 10-11 cartridges (epi) Articaine 4% Max dose 7 mg/kg 7 X 88 = 616 mg 72 mg/1.8mL 616 mg/72 mg/cart. = 9 cartridges Maximum Doses LA

Pregnant Patients • Which Local Anaesthetic to use? • Articaine 4% 1:200 000 epi • Lidocaine 2% 1:100 000 epi • Mepivacaine 2% 1:20 000 levo • Mepivacaine 3% plain

FDA categories (based on risk of fetal injury) • A: controlled studies in humans—no risk to fetus demonstrated • B: animal studies show no risk, no human studies; or animal studies have shown a risk but human studies have shown no risk • C: animal studies show risk, no human studies; or no animal or human studies

Pregnant Patients • Which Local Anaesthetic to use? • Articaine 4% 1:200 000 FDA category C • Lidocaine 2% 1:100 000 FDA category B • Mepivacaine 2% 1:20 000 FDA category C • Mepivacaine 3% plain FDA category C

Advantages of Injecting “Higher” • Failure to achieve profound local anaesthesia attributed to being “too low” and “too far forward” • Injecting superiorly and more distally may block accessory innervation • 3 nodes of Ranvier may not be true

Gow-Gates Technique • Landmarks: • Corner of the mouth (contralateral side) • Tragus of the ear • Disto palatal cusp of the maxillary second molar • AIMING FOR THE NECK OF THE CONDYLE

Efficacy of the Gow-Gates Technique

Akinosi Technique • Closed-mouth technique • Does not rely on a hard-tissue landmark • Parallel to occlusal plane, height of the mucogingival junction • Advanced until hub is level with distal surface of maxillary second molar • Delayed onset of anaesthesia

Akinosi Technique • Martinez Gonzalez et al. 2003 • Pain to puncture less with Akinosi • Onset slower • 17.8% failure vs. 10.7% IAB/LB • BUT-incomplete LB considered failure • Cruz et al. 1994 • Gow Gates more effective, but Akinosi most acceptable to patients

Nerve to Mylohyoid • Deposit ¼ cartridge of LA on lingual surface of tooth in alveolar mucosa • Goal is to bathe the nerve as branches of it enter the lingual surface of the mandible

Adjunctive Strategies • Additional Anaesthetic • PDL Injection • Intraosseous Injection • Intrapulpal Injection • Different anaesthetic

PDL Injection • Technique: • needle inserted into the gingival sulcus at a 30 degree angle towards the tooth • bevel placed towards bone • advanced until resistance felt • anaesthetic injected with continuous force for about 15 seconds. • approx. 0.2 mL of solution • 25 vs. 30 gauge needle

PDL Injection • Conventional vs. specific PDL syringes: • Malamed (1982): • similar rates of success • D’Souza et al (1987): • no sig. difference in anaesthesia achieved. • using the pressure syringe resulted in more spread of anaesthetic to adjacent teeth

PDL Injection: Primary Technique • Melamed 1982: 86% overall • Faulkner 1983: 81% overall • White 1988: variable, short duration esp. md. molars • Walton 1990: “In reviewing the clinical and experimental literature…the periodontal ligament injection does not meet all of the necessary requirements for a primary technique.”

Management of Local Anaesthesia in Endodontics