Giving a Good Shot
Paul D. Eleazer, DDS, MS University of Alabama at Birmingham
Wake County Dental Society, September, 2007
Disclaimer: The opinions given are those of the author and should not necessarily be
taken as final authority on controversial matters.
Goal: To use pharmacology and neuroanatomy to select the proper anesthetic for various
clinical situations.
Introduction: What is it worth to be 5% better (miss fewer blocks)
Hot teeth are harder to numb
Clin. Tip: Test anesthesia with cold
1. History
a. 1890 Cocaine
b. 1904 Novocain
c. WWII Xylocaine
2. Neuroanatomy
a. Nerve transmission
b. Henderson-Hasselbach equation
c. Sodium channel
d. Pulpal nerves
i. A delta = large, myelinated, peripheral pulp, fast trans., sharp pain
ii. C = small, unmyelinated, central pulp, slow trans., dull pain
1. may be harder to numb
iii. IAN = 5000 fibers, molar fibers peel off first
Clin. Tip: Molars get numb before chin
e. Paresthesia – Lingual nerve more often
Probably should not reuse needle (barb)
Clin. Tip: Do NOT inject where patient feels a shock
Anesthetic is Neurotoxic and Myotoxic
f. Nodes of Ranvier
Clin. Tip: Bathe 10 mm of nerve (=3 nodes)
3. Pharmacology
a. pH
i. Clin. Tip: Less acidic solution burns less (Citanest plain)
b. pKa
c. Dissociation examples
i. Clin. Tip: Use block when abscess lowers pH
ii. Clin. Tip: Select anesthetic with lowest pKa (Carbocaine)
d. Pulpal anesth.: Septocaine 64% vs. Citanest 51% (Haas, Anesth Prog
1990)
e. V2 Block
f. Infraorbital Block
g. Nasopalatine Block
h. Epinephrine – the chemical tourniquet
i. Use for longer duration
ii. Use for vasoconstriction
iii. Use to lessen systemic uptake of anesthetic
iv. Causes anxiety
v. Needs acidic pH
vi. Needs sulfite preservative
vii. Yellow solution = too old to use
i. Individual variation
Citanest plain = least painful
Methemaglobinemia, Paresthesia
Carbocaine = best anesthesia
Neo-Cobefrin = less tachycardia
Lidocaine = best topical
Sedative
Marcaine = longest lasting
Cardiotoxicity
Septocaine = best penetration
Paresthesia
Don’t inject at “shock point”