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

2. 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

4. 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

5. 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

6. What about experienced operators?

7. Effectiveness of Conventional IANB as measured by EPT
Childers et al. 1997
lido 2% 1:100K
63%
Clark et al. 1999
73%
Dunbar et al. 1996
43%
Guglielmo et al. 1999
mepiv 2% 1:20K
80%
Reitz et al. 1998
71%
Vital asymptomatic md. 6s: no response to max. EPT, 2 tests within 1 hour
Subjective report of lip numbness at baseline
Wong 2001: 69% weighted success rate

8. 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

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

10. 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

11. Arises within the middle cranial fossa from the trigeminal ganglion—large relay station. Mostly sensory, some motor.
Nerve drops down through foramen ovale and enters the infratemporal region and divides into multiple branches:
Branches from the stem:
3 motor: medial pterygoid, tensor tympani (middle ear), tensor palati (soft palate)
1 sensory: nervus spinosus (sensory): dura of the middle cranial fossa
Branches from the anterior division:
3 motor: masseter, temporalis, lateral pterygoid
1 sensory: buccal branch (long buccal nerve)
Branches from the posterior division:
1. auriculotemporal nerve—mostly sensory but carries autonomic info from the otic ganglion. Auricular, articular, temporal all sensory. Secretory fibres with ANS info.
Otic ganglion: sensory, sympathetic and parasympathetic innervation. Only parasympathetic synapses in the ganglion. Post synaptic sympathetic and parasympathetic fibres hitchhike with the auriculotemporal nerve to the parotid gland.
2. lingual nerve—sensory
3. Inferior alveolar nerve—sensory and motor:
Passes downward along the medial side of the mandibular ramus to the mandibular foramen.
The mandibular foramen lies at the centre point of the internal face of the ramus.
Just about the same height as the occlusal plane. At that point, the nerve to mylohyoid branches off.
Nerve to mylohyoid: motor: passes to the submandibular region. Supplies the mylohyoid muscle and the anterior belly of the digastric.
Intramandibular portion: passes downward and anteriorly through the mandibular canal. Sends small branches to supply the pulps of the teeth.
Mental nerve is a branch that emerges from the mental foramen. Sensory for skin and mucous membrane of the lower lip, skin of the chin, and vestibular gingiva of the mandibular incisors.

12. Theoretically, local anaesthetic deposited at the mandibular foramen should provide anaesthesia to: all mandibular teeth of that side, the vestibular gingiva anterior to the mental foramen, the lower lip, and the chin.

13. 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
Lingula and mandibular foramen

14. 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

15. Inferior alveolar nerve, before entering md
Inferior alveolar nerve, before entering md. foramen branches into mylohyoid nerve.
Mylohyoid nerve runs along medial ramus in mylohyoid groove to provide motor function to mylohyoid muscle.
Foramina found in pm region of md. associated with the mylohyoid.
1972—study—able to elicit pain response by stimulating nerve.
Not anaesthetized by block because of branching—classically thought to be 5 mm above mandibular foramen.
Wilson 1984—mean 14.7 mm, range 5 to 23 mm. LA may not bathe critical length of axon.
Nerve to mylohyoid

16. 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

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

18. 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

19. 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

20. 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

21. 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
Complaint of pain in time with the heartbeat
Potentially need 4 times as much LA to block nerve conduction

22. Effectiveness of Conventional IANB: Irreversible Pulpitis
100% lip anaesthesia
Reisman et al.
1997
1.8 mL lido 2% 1:100K epi
25%
Nusstein et al. 1998
19%
Cohen et al. 2000
1.8 mL lido 2%
1:100K epi
50%
Claffey et al. 2004
23%
Felt pain at any time during the procedure
Clinical diagnosis of irreversible pulpitis based on prolonged response to EndoIce.
After injection, 15 minute wait. Asked pt. about subjective lip numbness. If not present, pt. Excluded.
Therefore, 100% of patients used for data analysis had profound lip anaesthesia.

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

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

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

27. 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

28. 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

29. Maximum Doses LA 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

30. 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/ = 0.001% = g/dL = 0.01mg/mL
A cartridge contains 1.8 mL
Therefore a cartridge of 1: epi contains 0.01 mg/mL X 1.8 mL = mg
(or about 0.02 mg)

31. Maximum Doses Epi Cardiovascular patient 0.04 mg
Healthy patient 0.2 mg

32. Maximum Doses LA 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

34. Pregnant Patients Which Local Anaesthetic to use?
Articaine 4% 1: epi
Lidocaine 2% 1: epi
Mepivacaine 2% 1: levo
Mepivacaine 3% plain

35. 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

36. Pregnant Patients Which Local Anaesthetic to use?
Articaine 4% 1: FDA category C
Lidocaine 2% 1: FDA category B
Mepivacaine 2% 1: FDA category C
Mepivacaine 3% plain FDA category C

37. 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

38. 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

40. Hargraves: bathe more than the 3 nodes of ranvier
Hargraves: bathe more than the 3 nodes of ranvier. May be advantageous to give a gow gates or a high standard block.

41. Efficacy of the Gow-Gates Technique
Author
Year
GG (%)
IANB (%)
Watson and Gow-Gates
1976
98.4
85.4
Gow-Gates and Watson
1977
96.2
85.5
Levy
1981 96 65
Malamed
97.5
Montagnese et al.
1984 35 38
Montagnese et al. 1984
Repeated measures design
40 subjects injected twice at separate appointments—once with GG, once with conventional IANB
EPT after profound lip numbness reported
Results:
Higher reports of tongue numbness with GG
EPT:
GG: 35% no response to maximal stimulation
Conventional IANB: 38% no response to maximal stimulation
No significant difference

42. 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

45. Akinosi Technique Martinez Gonzalez et al. 2003 Cruz et al. 1994
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

46. 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

47. Adjunctive Strategies
Additional Anaesthetic
PDL Injection
Intraosseous Injection
Intrapulpal Injection
Different anaesthetic

48. 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
To overcome the high pressures necessary for the technique using a standard syringe, can use either a short 25 gauge needle (recommended by Melamed OOO 1982) or an ultrashort 30 gauge needle (recommended by Branstromm et al J Dent Child 1982). This will help minimize bending of the needle when it’s driven into the sulcus.

50. 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  

51. 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.”
White 1988:White et al (JOE 1988) found that duration and depth of anaesthesia was widely variable (PDL injection, primary technique). Adequate anaesthesia time was sometimes was as little as 10 minutes. With mandibular molars for example, 80 % were adequately anaesthetized after 2 minutes, but only 20% were still adequately frozen at 10 minutes. With maxillary lateral incisors, only 39% had adequate anaesthesia after 2 minutes, and then rates dropped.

52. PDL Injection: Supplemental Technique
Walton and Abbott 1981:
Inadequate pulpal anaesthesia following IAB
92% overall
included situations where multiple PDL injections required
most critical factor was to inject under strong resistance
Smith, Walton, Abbott 1983:
83% overall with high pressure syringe

53. PDL Injection: Anaesthetic Distribution
Garfunkel et al 1983, Smith and Walton 1983, Tagger et al 1994, Tagger et al 1994*
spread along path of least resistance
influenced by anatomical structures and fascial planes
through marrow spaces
avoided PDL route
appears to be a form of intraosseous injection
Tagger E, Tagger M, Sarnat H, Mass E. (Int J Paediatr Dent 1994) Dog study, primary dentition: Similar protocol to above. The solution usually reached the alveolar bone crest, seeped under the periosteum and alongside vascular channels into bone marrow, reaching natural cavities such as the crypts of tooth buds and the mandibular canal. The ink did not penetrate into the enamel organ or contact the permanent tooth buds. The solution appeared to spread along the path of least resistance, governed by the intricacies of anatomical structures and fascial planes. Therefore the risk of mechanical damage to permanent tooth germs appears to be minimal.

54. PDL Injection: Effects on the Periodontium
Animal histological studies
Most studies: no long term evidence of tissue disruption or inflammation
Roahen and Marshall 1990: evidence of localized external resorption

55. Adjunctive Strategies
Additional Anaesthetic
PDL Injection
Intraosseous Injection
Intrapulpal Injection
Different anaesthetic

56. Intraosseous Injection
Technique for mandibular infiltration
Perforate the cortical plate to introduce LA in medullary bone
Bathes the periradicular region in LA
2 commercial systems available:
Stabident (Patterson)
X-Tip (Tulsa Dentsply)

57. Stabident
Solid 27 gauge wire with a beveled end. Used in a slow speed handpiece to perforate the cortical plate.

58. Stabident
Most apical extent of attached gingival margins of adjacent teeth used as landmark for locating appropriate perforation point (cortical bone in mandibular molar region is thinnest within crestal third of alveolar process); after application of topical anesthetic and infiltration of local anesthetic into gingival mucosa, perforation is performed mesial or distal to tooth; after removal of perforator, injection needle is introduced to deliver local anesthetic into periradicular medullary bone

59. Stabident

60. Stabident

61. X-Tip

62. Success of Conventional IANB + IO as Measured by EPT
Dunbar et al.
2% lido 1:100K
90%
Gallatin et al.
3% mepivacaine plain
100%
Guglielmo et al.
Reitz et al.
94%

63. IANB + IO in Cases of Irreversible Pulpitis
Nusstein et al. 1998
Lido 2% 1:100K
91%
Parente et al. 1998
79%/ 91%
Reisman et al. 1997
Mepivacaine 3% plain
80%/ 98%
Nusstein et al. 2003
82% (X-Tip)
Bigby et al. 2006
Articaine 4% 1:100K
86%

64. Adjunctive Strategies
Additional Block (higher injection)
PDL Injection
Intraosseous Injection
Intrapulpal Injection
Different anaesthetic

65. Intrapulpal Anaesthesia
VanGheluwe and Walton 1997:
under back-pressure, efficacy of LA=saline injection
Conclusion: back-pressure is the key to intrapulpal anaesthetic success

66. Adjunctive Strategies
Additional Anaesthetic
PDL Injection
Intraosseous Injection
Intrapulpal Injection
Different anaesthetic

68. Articaine
Reputation for improved local anaesthetic effect—short linear molecule
Amide local, contains a thiophene ring instead of a benzene ring
Partial hydrolysis by plasma esterases
4% solution—concern with toxicity
Potential for methemoglobinemia (like prilocaine)

69. Articaine More effective than other local anaesthetics?
No difference found:
Haas et al (vs. prilocaine)
Vahatalo et al (vs. lidocaine)
Malamed et al (vs. lidocaine)
Donaldson et al (vs. prilocaine)
Claffey et al (vs. lidocaine)
Mikesell et al (vs. lidocaine)

70. Articaine Claffey et al. 2004:
Articaine vs. lidocaine IANB for irreversible pulpitis of mandibular teeth
Articaine 9/37 (24%)
Lidocaine 8/35 (23%)
(all subjects had subjective lip anaesthesia)

71. Articaine Paraesthesia?
Haas and Lennon 1995: higher incidence of paraesthesia associated with prilocaine and articaine. Attributed to the higher concentration of drug required for comparable clinical effect
14/ injections
Statistically higher
Clinical relevance? Claffey et al 2004 “clinically rare event”
Abstract JDR 1994: Miller and Lennon. 5X greater incidence

72. Articaine Paraesthesia? Dower 2003 (Dentistry Today) Review article
Paraesthesia rates up to 2-4% when using articaine for lingual blocks or IANBs

74. RCDSO Dispatch Summer 2005 pg. 26
“Until more research is done, it is the College’s view that prudent practitioners may wish to consider the scientific literature before determining whether to use 4% local anaesthetic solutions for mandibular block injections.”

77. College Registrar Replies Dispatch Fall 2005 vol. 19, #4
“This college received legal advice from our general counsel, and from outside counsel, before publishing what we did…The advice we received was that it was certainly within our obligation to advise members to be aware of the literature…”

78. Articaine Hillerup and Jensen 2006:
Danish population—all cases in Denmark referred to authors for evaluation
54 injection injuries in 52 patients
54% of all nerve injuries associated with articaine
Substantial increase in number of injection injuries following introduction of articaine to Danish market in 2000.

79. Articaine What about a mandibular infiltration?
Recommended by Steve Buchanan
Kanaa et al. 2006
Cross-over design comparing articaine and lidocaine for mandibular infiltration for first molars
Anaesthesia measured by maximal EPT X2
Lidocaine 38% effective
Articaine 65% effective

80. 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

81. Kleinknect and Bernstein 1978: positive correlation between anxiety and reported pain during dental treatment

82. Topical Anaesthetic Benzocaine or Lidocaine Effectiveness?
Gill and Orr 1979: 15 second application no more effective than placebo
Stern and Giddon 1975: 2-3 minutes=profound soft tissue anaesthesia

83. Topical Anaesthetic Recommendations: Dry mucous membranes first
2-3 minutes, but concern with tissue sloughing
Tip of the tongue

84. Topical Anaesthetic Benzocaine Spray
RCDSO Dispatch 21, 1, Feb/Mar 2007 pp.28-29
Advice to Dentists
Benzocaine Sprays and Methemoglobinemia (MHb)
Health Canada—9 suspected cases, none fatal

85. Topical Anaesthetic Benzocaine spray/Methemoglobinemia
Recommendations:
Avoid in patients with a history of MHb
Consider lidocaine as an alternative
Broken/inflamed tissue may promote uptake
Use only amount deemed necessary
If suspicious, send patient to hospital for methylene blue tx
O2 won’t help, but give it anyways

86. Methemoglobinemia
Fe2+ ion of the heme group of the hemoglobin molecule is oxidized to Fe3+
Hemoglobin converted to methemoglobin, a non-oxygen binding form of hemoglobin that binds a water molecule instead of oxygen.

87. Conclusions: 1. Consider topical anaesthetic
2. Re-test using patient’s chief complaint
2. Inject again
Higher
More Local Anaesthetic
Nerve to Mylohyoid
3. Consider PDL/Intraosseous Anaesthesia
4. Consider Intrapulpal Anaesthesia
5. If they say it hurts, it hurts

88. Thank you Questions? Please feel free to contact me: 416-223-1771