ch 9: anatomy of local anesthesia

Compare local infiltration with nerve block local anesthesia.
type of injection used determined by type and length of procedure
–local infiltration or nerve block

local infiltration
anesthetizes a small area, including one or two teeth and associated tissue, by injection near their apices
–near terminal nerve endings
–varying degrees of success

nerve block
affects a larger area than local infiltration and thus, more teeth
–agent deposited near large nerve trunks
–higher degree of success than infiltration

Compare the effectiveness of maxillary anesthesia with mandibular anesthesia.
less variation in anatomy of maxillae and palatine bones and associated nerves with respect to local anesthetic landmarks compared to mandible
–maxillary injections more routine, and usually without need for troubleshooting

How effective is local infiltration in the maxillae as compared to the mandible?
most local anesthesia of maxilla more successful than that of mandible because the facial plates of bone of the maxillae are less dense

Posterior superior alveolar block
–Area anesthetized?
–pulpal anesthesia in maxillary third, second and first molars
–buccal periodontium and bone of maxillary molars
–indicated when procedure involves two or more maxillary molars or their buccal tissue

Posterior superior alveolar block
Target area and injection site?
Target: PSA nerve at it enters maxilla through posterior superior alveolar foramina
–up, in and back 45 degrees
–posterior and medial to maxillary tuperosity
–Injection: height of mucobuccal fold superior to apex of maxillary 2nd molar, distal to zygomatic process

PSA
Symptoms and possible complications?
usually none since no soft tissue, only hard
–lip or tongue does not feel numb, so patient may think anesthesia isn’t working
— complications if needle too far distal; may penetrate pterygoid plexus of veins and maxillary arty if overinserted; hematoma
–also anesthesia of branches of mandibular nerve

PSA
How do you avoid complications?
correct angulation; upward/superiorly at 45 degree angle to maxillary occlusal plane and 45 degree angle to midsaggital plane on skull
–syringe barrel exteneded from ipsilateral labial commisure to help with angulation

Middle superior alveolar block
area anesthetized
maxillary premolars and mesiobuccal root of maxillary first molar
–MSA nerve present in only 28% of population
–if need lingual/palatal anesthesia, also use greater palatine block

MSA
Target area and injection site?
Target: at apex of maxillary 2nd premolar
Injection site: height of mucobuccal fold at apex of maxillary 2nd premolar, without contacting maxilla to reduce trauma

MSA
Symptoms and possible complications?
harmless tingling and numbness of upper lip, absence of discomfort during dental procedures
–overinsertion/hematoma complications rare

Anterior superior alveolar block
Area anesthetized?
–pulp of maxillary canine and incisor teeth, facial tissue/gingiva, PDL and bone
–need nasopalatine block if lingual tissue anesthesia desired
–commonly used with MSA instead of using IO block alone
–crossover innervation to contralateral side possible

ASA
Target area and injection site?
Target: ASA nerve at apex of maxillary canine
Injection site: height of mucobuccal fold at apex of maxillary canine, just anterior to and parallel with canine eminence; without contacting maxilla

ASA
Symptoms and possible complications?
–harmless tingling and numbness of upper lip
–absence of discomfort during dental procedures
–overinsertion and hematoma complications rare

Infraorbital block
Area anesthetized?
–anesthetizes both MSA and ASA nerves; and IO
–maxillary premolars, canine and incisors; sometimes mesiobuccal root of 1st molar
–when dental procedures involve more than 2 maxillary premolars or anterior teeth and facial tissue
–need nasopalatine for lingual
–crossover innervation possible, so bilateral injection may be needed

IO block
Target area and injection site?
Target: ASA and MSA nerves as they move superiorly to join IO nerve; keep finger on IO foramen during injection to keep syringe toward foramen

Injection site: height of mucobuccal fold at apex of maxillary first premolar

IO
Symptoms and possible complications?
–branches of IO nerve to lower eyelid, side of nose and upper lip inadvertently anesthetized
–overinsertion and possible puncture of orbit
–hematomas rare

Greater palatine block
–area anesthetized?
–posterior part of hard palate, anteriorly as far as maxillary first premolar and mekially to midline as well as lingual/palatal gingiva tissue
–no pulpal of area teeth
–may also need ASA, PSA, MSA or IO block and sometimes nasopalatine

GP block
Target area and injection site?
target: anterior to where GP nerve enters greater palatine foramen; depression on palatal surface at junction of maxillary alveolar process and hard palate, at apex of maxillary 2nd or 3rd molar

injection site: in palatal tissue anterior to depression of GP foramen; midway between medial palatine raphe and lingual gingival margin of maxillary molar

GP block
Discuss the use of pressure anesthesia on the hard tissue of the palate.
because tissue is dense and adheres firmly to underlying bone, pressure produces a dull ache that blocks pain impulses from needle penetration and reduces patient discomfort

GP block
Symptoms and possible complications?
numbness in posterior hard palate and absence of discomfort during dental procedures
–possible gagging if soft palate inadvertently and harmlessly anesthetized

Nasopalatine block
–Area anesthetized?
anesthesia of bilateral anterior part of hard palate, from mesial of maxillary right 1st premolar to mesial of maxillary left 1st premolar
–used when lingual/palatal soft tissue anesthesia required for two or more maxillary teeth
–use pressure!
–may also need MSA, ASA or IO

NP block
Target area and injection site?
target: both right and left NP nerves as they enter incisive foramen of maxilla from the mucosa of anterior hard palate, beneath incisive papilla

injection site: lingual/palatal tissue lateral to incisive papilla, 10 mm lingual to maxillary central incisor;
–never directly into incisive papilla!
–needle 45 degree angle to palate

NP block
Discuss the use of pressure anesthesia on the hard tissue of the palate.
pressure/blanching on palatal tissue on contralateral side of incisicive papilla to reduce pain

NP block
Symptoms and possible complications?
numbness in anterior palate; absence of discomfort during dental procedures
–hematomas rare

Anterior middle superior alveolar block
–Area anesthetized?
soft tisse and pulpal anesthesia of large area covered by ASA, MSA, GP and NP blocks in maxillary arch
–multiple teeth/maxillary 2nd premolar through maxillary central incisor and associated tissue without causing anesthesia to upper lip and face
–with the PSA, will anesthetize a quadrant

AMSA block
What needs to be considered with this injection in regard to devices?
injection best accomplished with a computer-controlled deliver device (CCDD) because it regulates the pressure and volume ration of solution delivered, which is not readily attained with a manual syringe

AMSA block
Target area and injection site?
Target: tissue of hard palate, anterior to middle part of dental plexus, so to anesthetize teeth and facial/lingual tissue of surrounding palate

injection site: area biscecting the apices of maxillary premolars, and midway between median palatal raphe and lingual ginginval margin
–45 degree angle from contralateral premolars; maxilla contacted

AMSA block
Discuss the use of pressure anesthesia on the hard tissue of the palate.
blanching pressure during injection to relieve pain
–if excessive, may cause postoperative tissue ischemia and sloughing.
–slow or stop injection to keep this from happening

AMSA block
Symptoms and possible complications?
–variable numbness of large area that is normally innervated by ASA, MSA, GP and NP blocks
–excessive blanching

Compare effectiveness of mandibular injections with maxillary injections.
infiltration anesthesia of mandible not as successful as that of maxilla because overall the bone of mandible is denser than the maxilla over similar teeth; especially in area of posterior teeth
–nerve blocks preferred to local anesthesia

How effective is an infiltration in the mandible and what part of the mandible is more effective using infiltration?
local infiltrations on facial surface of anterior mandible are more successful than more posterior injections but less successful than injections over maxillae in similar locations
–because of differences in density of facial plates of bone

Inferior alveolar block
–area anesthetized
–most common injection
–mandibular teeth for pulpal anesthesia
–lingual periodontium for all mandibular teeth
–facial periodontium of mandib anterior and premolar teeth
–NOT a complete mandibular block
–need B to get buccal of molars

IA block
Are bilateral injections advisable?
no; because bilateral mandibular injections produce complete anesthesia of body of tongue and floor of mouth, which can cause difficulty swallowing and speech

IA block
Target area and injection site?
Target area: inferior alveolar nerve at mandibular foramen on medial surface of mandibular ramus, inferior to lingula and at same height as coronoid notch

Injection site: mandibular tissue on medial border of ramus; palpated at depth of pterygomandibular space on medial surface of ramus

IA block:
things to remember
–use hard tissue as landmarks to reduce errors!
–being too far inferior to injection site is most common reason for missed IA blocks
–ALWAYS important not to deposit anesthetic agent unless bone is contacted so don’t put in parotid salivary gland
–if insertion/deposition too shallow then only lingual nerve may be anesthetized

if failure of anesthesia of IA block
mainly on mandibular first molar, there may be accessory innervation of mandibular teeth
–need to get mylohyoid nerve
–may need to do Gow-Gates

if a bifid IA nerve detected gy noting a doubled mandibular canal on intraoral radiograph
may get incomplet anesthesia of mandible
–deposit agent more inferior to usual anatomic landmarks

IA block
Symptoms and possible complications?
harmless numbing and tingling of lower lip because mental nerve is anesthetized
–probably means that IA nerve is anesthetized, but not reliable indicator of depth of anesthesia, especially pulpal

IA block
Symptoms and possible complications?
harmless numbness and tingling of body of tongue and floor of mouth
–indicates that lingual nerve anesthetized; not necessarily anesthesia of IA nerve
–most reliable indicator of successful IA block is absence of discomfort

IA block
“lingual shock”
needle passes by lingual nerve during administration; patient makes involuntary movement
–symptom momentary and anesthesia will quickly occur

IA block
transient facial paralysis
–if facial nerve mistakenly anesthetized
–incorrect administration of anesthetic into deeper parotid salivary gland because mandibular bone not contacted
–temporary loss of use of muscles of facial expression; including inability to close eyelid and drooping of labial commisure

IA block
hematoma
–injection has highest positive aspiration rate
–muscle soreness or limited movement of mandible rarely seen
–self-inflicted trauma such as lower lip biting

IA block
paresthesia
–from trauma to lingual nerve
–abnormal sensation from an area such as burning or prickling
–may be due to lack of adequate fascia around lingual nerve or possibly neruotoxicity from local anesthetic agent

Discuss troubleshooting the IA block depending on the contact of the needle with the bone.

What is the accessory innervation that can prevent a successful IA block?
mylohyoid nerve?

Buccal block
Area anesthetized?
–also “long buccal block”
–anesthesia of buccal periodontium of mandibular molars including gingiva, PDL and bone
–not necessary when buccal tissue not impacted by dental procedures performed

buccal block
Target area and injection site?
Target: buccal nerve/long buccal nerve on anterior border of mandibular ramus; through the buccinator muscle before it enters buccal region

injection site: buccal tissue distal and buccal to the most distal mandibular molar in mandibular arch
–advance needle until it contacts mandible and then inject

buccal block
Symptoms and possible complications?
rare because of location and small size of anesthetized area
–only absence of discomfort
–sometimes self-inflicted trauma like cheek bites
–hematomas rare

mental block
Area anesthetized?
facial periodontium of mandibular premolars and anterior teeth on one side, including gingiva, PDL and bone; NO PULPAL!
–need incisive block or IA block if pulpal anestesia necessary
–no lingual tissue anesthesia of involved teeth

mental block
Target area and injection site?
target area:
anterior to mental foramen where mental nerve enters on surface of mandible, usually between apices of mandibular 1st and 2nd premolars

injection site:
anterior to depression created by mental foramen at depth of mucobuccal fold with needle horizontal and resting on lower lip, without contacting mandible; between apices of premolars

mental block
Symptoms and possible complications?
harmless tingling and numbness of lower lip; absence of discomfort
–hematomas rare

incisive block
–area anesthetized
pulp and facial tissue of mandibular teeth anterior to mental foramen, usually mandibular premolars and anterior teeth (canine and incisors)
–also lower lib and skin of chin to midline
–IA if need lingual anesthesia
–useful when crossover innervation from contralateral incisive nerve and still discomfort on mandib anterior teeth after giving an IA block

incisive block
target area and injection site
target: mental foramen (usually between apices of mandib premolars)
–same as mental block; anterior to where mental nerve enters mental foramen to merge with incisive nerve to form IA nerve

insertion site: anterior to depression created by mental foramen at depth of mucobuccal fold with needle horizontal and resting on lower lip, without contacting mandible; between apices of premolars

incisive block
Symptoms and possible complications?
same as symptoms of mental block
–harmless tingling, numbness of lower lip
–do have pulpal anesthesia of involved teeth
–hematomas rare

Gow-gates mandibular block
area anesthetized
G-G block
–inferior alveolar, metnal, incisive, lingual, mylohyoid and auriculotemporal as well as long buccal nerves
–a mandibular block because it anesthetizes entire V3

G-G block
Reasons for use?
quadrant dentistry when need buccal soft tissue anesthetized from most distal mandib molar to midline and lingual soft tissue is necessary
— sometimes when IA block is unsuccessful
–higher success rate than IA block
–success possibly due to additional anesthesia to mylohyoid nerve

G-G block
Target area and injection site?
target: anteromedial border of neck of mandibular condyle, just inferior to insertion of lateral pterygoid muscle

injection site: intraorally on oral mucosa on mesal of mandibular ramus; just distal to height of mesiolingual cusp of maxillary 2nd molar with direction determined by following a line extraorally from intertragic notch to ipsilateral labial commisure

G-G block
Symptoms and possible complications?
inadvertantly, anterior 2/3 of tongue, floor of mouth and body of mandible and inferior ramus, as well as skin over zygomatic bone and posterior buccal and temporal regions

G-G block
2 main disadvantages
1. numbness of lower lip and temporal region
2. longer time necessary for anesthetic to take effect because of larger size of nerve trunk being anesthetized and distance of trunk from site of deposition

G-G block
advantage
injection lasts longer than IA block because area of injection is less vascular and a larger volume of anesthetic may be necessary

G-G block
contraindicaitons
in cases with limited ability to open mouth

The skull bones involved in local anesthetic administration by dental professionals prior to dental care are the maxilla, the mandible, and the
palatine bone

To increase the reliability of local anesthesia procedures, the dental professional MUST learn to rely MAINLY on both visualization and palpation of
hard tissue

Which structures should the dental profession AVOID inadvertently injecting?
major blood vessels and glandular tissue

Which nerve branches are anesthetized before MOST dental procedures?
trigeminal nerve

Which of the following are NOT considerations that need to be followed when working with a patient with an oral infection?
will need less amounts of local anesthetic agent;

The effectiveness of local anesthetic agents is greatly reduced when administered adjacent to areas of infection, so additional amounts of local anesthetic agent may be needed keeping the maximal recommended dosage always in mind for each patient.

What SHOULD always be attempted in all injections before administration in order to avoid injection into blood vessels?
aspiration

What complication can occur if the needle is advanced too far distally into the tissue during a posterior superior alveolar block?
extraoral hematoma

What structure can be initially involved in a spread of infection if the needle is contaminated during a posterior superior alveolar block?
cavernous sinus

Which of the following structures are NOT usually anesthetized during a posterior superior alveolar block?
lip and tongue

Which of the following nerves may involve crossover-innervation after administration of the local anesthetic agent in many patients?
anterior superior alveolar nerve
–so bilateral injections of the ASA block or local infiltration over the contralateral maxillary central incisor may be indicated.

What structure can be punctured if the dental professional does NOT keep the needle in contact with the bone at the roof of the infraorbital foramen to prevent overinsertion when administering an injection in that area?
orbit

Which of the following is NEVER anesthetized during an administration of the greater palatine block?
pulpal anesthesia

Which of the following injections need to have pressure anesthesia used in order to administer a MORE pain-free block?
greater palatine block

Which of the following injections is the MOST commonly used during dental procedures even if it is NOT always successful?
Inferior alveolar block

Which of the following structures need to be contacted for a successful and safe inferior alveolar block?
mandibular bone

1. An extraoral hematoma can result from an incorrectly administered posterior superior alveolar local anesthetic block because the needle was overinserted and penetrated which of the following?
pterygoid plexus of veins

PSA: up, in, back at 45 degrees each way

2. Which of the following local anesthetic blocks has the same injection site as the incisive local anesthetic block?
mental block

–at depth of mucobuccal fold anterior to the depression created by mental foramen, WITHOUT contacting mandible!

3. Which of the following nerves is NOT anesthetized during an IA local anesthetic block?
buccal

–buccal only gets buccal gingiva of molars

4. Which of the folloing local anesthetic blocks uses pressure anethesia of the tissue to reduce patient discomfort?
greater palatine block

5. Which of the following are usually anesthetized during an infraorbital local anesthetic block?
upper lip, side of nose, lower eyelid

6. If the mesiobuccal root of the maxillary first molar is NOT anesthetized by a posterior superior alveolar local anesthetic block, the dental professional should administer a
MSA/middle superior alveolar block

7. Which of the following is an important landmark to locate before performing an inferior alveolar local anesthetic block?
coronoid notch

8. The injection site for the greater palatine local anesthetic block is usually located on the palate near which of the following?
maxillary second or third molar

9. If an extraction of a permanent maxillary lateral incisor is scheduled, which of the following local anesthetic blocks can be administered instead of the infraorbital block?
nasopalatine block

(with ASA)

10. Transient facial paralyses can occur with which incorrectly administered local anesthetic block?
inferior alveolar block
IA
–have to contact bone first!
–it goes into parotid salivary gland instead

11. Which local anesthetic block anesthetizes the largest intraoral area?
inferior alveolar block

12. Which of these situations can occur if bone is contacted early during an inferior alveolar local anesthetic block?
needle tip is too far anteriorly on ramus

13. In which of the following locations is the outcome MOST successful when using local infiltrations of local anesthetic?
anterior maxillary?

14. If working withing the mandibular anterior sextant, which local anesthetic block is most successful and comfortable for the patient?
bilateral incisive

15. Which of the following local anesthetic blocks anesthetizes the buccal tissue of the mandibular molars?
buccal block

16. The mental foramen is usually located between the apices of which of the following mandibular teeth?
first and second premolars

17. To have complete anesthesia of the maxillary quadrant, which of the following local anesthetic blocks needs to be administered along with the anterior middle superior alveolar block?
posterior superior alveolar block

18. Which of the following can serve as a landmark for the anterior middle superior alveolar local anesthetic block?
premolar teeth

19. Which of the following is considered a mandibular local anesthetic block because it anesthetizes MOST of the mandibular nerve?
Gow-gates block

20. Which of the following landmarks are noted when administering a Gow-Gates mandibular local anesthetic block?
maxillary second molar

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