Use of topical and local anesthesia (LA) is the workhorse of all aspects of dentistry. There was a time in the past when dentistry was performed without any local pain control. Owing to this there are patients with dental anxiety and fear of a dental office. The media portraying dentistry as being painful, or showing a dentist with needles, enlists fear and distrust of dentists. In contrast, pain is what brings the patient to the dental office and with local pain control measures a dentist is able to alleviate the patient’s cause of pain.
Key points
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The goal for topical anesthesia is to blunt the effect of administration of local anesthesia.
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Local anesthetics are divided into esters and amides, amides being commonly used.
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Local anesthesia is dose dependent. Maximum dosage should be calculated to prevent toxicity in pediatrics and adult patients.
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Amide local anesthesia is safe for breastfeeding women.
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Advances in local anesthesia administration can make the experience more tolerable for the patients.
Introduction
Use of topical and local anesthesia (LA) is the workhorse of all aspects of dentistry. There was a time in the past when dentistry was performed without any local pain control. Owing to this there are patients with dental anxiety and fear of a dental office. The media portraying dentistry as being painful, or showing a dentist with needles, enlists fear and distrust of dentists. In contrast, pain is what brings the patient to the dental office and with local pain control measures a dentist is able to alleviate the patient’s cause of pain.
Topical anesthetics
The role of topical anesthetic is to minimize painful stimuli or dull the effect of the procedure. A painful stimulus can be a procedure, injections, or to blunt gag reflexes. LA can be administered as gels, cream, ointment, liquid, sprays, or lotions.
Benzocaine is one of the most common topical anesthetics; it can be purchased over the counter or prescription based. Benzocaine is an ester derivative topical anesthetic. The pharmacophysiology of benzocaine is that it binds selectively to the intracellular surface of sodium channels to block influx of sodium into axons. The role of benzocaine in dentistry is to provide relief from dental pain or to lessen the painful experience of injection of LA. There are different formulations, combinations, and brands of topical anesthesia. Cetacaine is a combination of benzocaine, tetracaine, butyl aminobenzoate, and benzalkonium chloride. Cetacaine is available as a spray, and it is commonly used before dental impressions to control the gag reflex.
Tetracaine is an ester-type local anesthetic. Ester is metabolized in the plasma and in the liver by plasma pseudocholinesterase. Tetracaine should not be used in patients with liver disease. Tetracaine is commonly used in medicine for spinal anesthesia, and LA to the eye and nose for diagnostic examinations; it is not commonly used in dentistry.
Flurori-methane is a topical local anesthetic spray that aids in myofascial pain in patients with temporomandibular dysfunction. The goal of the local anesthetic spray is to assist in stretch therapy after application of the spray. The spray should be 12 in away from the muscle, and care should be taken to cover the patient’s eyes before application.
Lidocaine is probably the most common topical and local anesthetic; it is classified as an amide. Topical lidocaine is available as 5% base and 2% water soluble. When lidocaine is used in its viscous state (0.5%, 1.0%, and 2.0%) form, the goal is to help patients with pain in mucositis secondary to chemotherapy and radiation therapy. The topical application also helps patients suffering from autoimmune blistering disease such as pemphigus and pemphigoid of the oral cavity. Most obstetricians and gynecologists prefer lidocaine applications in their patients because it is classified as a category B drug. In the pediatric population the clinician must be aware of the maximum dosage of lidocaine that should be considered, which is 4 mg/kg without epinephrine.
Local anesthetics
The goal for LA is to provide loss of sensation at the area of the body by depression of excitation in nerve endings and inhibition of the conduction process in peripheral nerves. LA takes its effect by decreasing the permeability of the ion channels to sodium therefore decreasing the rate of depolarization. All the local anesthetics have an aromatic ring that gives them lipid solubility. Adequate LA has been found to reduce the need for inhalation anesthetics for patients undergoing general anesthesia Local anesthetics are divided into amides and ester.
Ideal properties for local anesthetics are they should not be an irritant, and they should not be neurotoxic, which can lead to permanent alteration of nerve structures. The systemic toxicity should be low. Their efficacy is comparable when injected into deep tissue as well as mucous membranes. The duration of onset is short. The duration of LA is based on the drug selected, which is based on the length of the procedure. There is potency for anesthesia without the use of harmful concentration. One should also choose a local anesthetic that does not cause an allergic reaction. The drug is able to undergo biotransformation in the body.
Amide local anesthetics are metabolized in the liver and no para -aminobenzoic acid (PABA) is formed. The amine terminal end gives these local anesthetics their water solubility. Common amide local anesthetics include lidocaine, mepivacaine, prilocaine, articaine, etidocaine, and bupivacaine. The dosage of amide local anesthetic should be adjusted for patients with medical comorbidities ( Table 1 ).
| Drug | Facts , | Comments |
|---|---|---|
| Lidocaine |
|
|
| Mepivacaine |
|
|
| Prilocaine |
|
|
| Articaine |
|
|
| Bupivacaine |
|
|
| Etidocaine |
|
|
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