Local anaesthetics in the dental setting – Deborah Lyle

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  Posted by: The Probe      2nd March 2019














Local anaesthetics represent the safest and most effective drugs used in all of medicine for the prevention and control of pain.[1]They form a major part of clinical practice and are the most commonly used pharmaceuticals in dentistry.

Used to keep patients comfortable and free from pain during dental procedures, local anaesthetics produce temporary loss of sensation to a specific area.1,[2]They work by blocking the nerve impulses that transmit the feeling of pain from the point of administration to the brain.1As dental professionals are aware, physical feeling occurs when a nerve is activated as it transmits electrical and chemical signals through a network of neurons to the brain. When local anaesthetic is applied, it prevents the nerves from becoming activated and transmitting those signals, usually with a chemical that interferes with the response of the nerve cells or produces a malfunction in neuron conduction.[3] 

Although remarkably safe when administered within acceptable dosage guidelines, in order to prevent any adverse reactions, it is imperative that dental practitioners obtain a complete medical history and details of any medication used by patient before applying a local anaesthetic. Fundamentally, there are two basic concerns pertinent to the use of local anaesthetics, which are: an existing systemic condition that may be exacerbated by the anaesthetic agent and/or any medication that could adversely interact with it.[4]

Largely,local anaestheticsolutionscontain a high concentration of avasoconstrictor such as epinephrine (adrenaline), which produces localised constriction of blood vessels. This slowsthe rate of vascular uptake and absorptionand concentrates the anaesthetic agent to the site increasingits duration and the quality.[5]Vasoconstrictors also decrease blood loss during surgical procedures and have minimal effects on healthy patients. However, reduced dosages or a local anaesthetic without a vasoconstrictor should be used for patients with significant cardiovascular disease, Type 1 diabetes or hyperthyroidism for example. In addition,local anaesthetics undergo biotransformation in the liver and are excreted by the kidneys therefore; dosages should be kept to a safe minimum in patients with hepatic or renal diseases.7 The dose and type of local anaesthetic must be also carefully considered for pregnant women as pregnancy affect several organs, including the cardiovascular system, liver and kidneys, which may affect the body’s reaction to the anaesthetic. Similarly, although research indicates that local anaesthetics have small direct effects on the foetus and are relatively safe, it may be advisable to delay dental treatment until the later stages of pregnancy when the risk of teraogenic effects (developmental malformation) from drugs is considered to be lower.[6]

Local anaesthetics inhibit specific neuronal pathways and are all central nervous system depressants. Few significant adverse drug reactions or interactions have been reported and most are usually the result of excessive dosing and depression of the central nervous system resulting in lethargy, loss of consciousness and/or respiratory depression.[7]Nevertheless, people with complex medical conditions and drug histories are becoming ever more commonplace in the dental practice and practitioners should be aware that even widely prescribed drugs could present problems. For example, beta-blockers have the potential to inhibit the effect of the vasoconstrictors such as epinephrine, norepinephrineand phenylephrine, used in local anaesthetic solutions, which can lead to hypertensive reactions and simultaneously, reflex bradycardia (decrease in heart rate).[8]Similarly, certain antidepressants particularly the older tricyclic antidepressants (TCAs) and monoamine oxidase inhibitors (MAOIs) –may increase the effect of vasoconstrictors on the circulatory system and careful dose adjustment may be required to reduce the probability of any adverse effects in patients taking these medications.[9],[10]

Local anaesthetics are useful to control preoperative, intraoperative and postoperative pain. However, for reasons that are not fully understood, the efficacy of dental anaesthesia becomes reduced and frequently fails in the presence of inflammation.[11],[12]This may be because inflammation can make the nerves highly sensitive to pain or that the increased blood flow to the area can ‘wash out’ the anaesthetic agent.[13]Yet, what we do know is that inflammation has the potential to cause serious damage to the teeth and gums and may also have a systemic impact.[14]Therefore, dental professionals conscientiously reinforce oral health instructions and encourage all patients to adopt an effective oral hygiene routine to keep the oral environment in optimum health. As part of this, and to ensure that patients are able to clean effectively between the teeth and below the gum line, practitioners can recommend a Waterpik®Water Flosser. Used in addition to tooth brushing, this device makes it quick and easy for patients to floss properly and it is clinically proven to reduce plaque as well as the clinical signs of inflammation.[15]

The efficacy of local anaesthetic has an impact at both ends of the syringe. When pain is controlled successfully, patients are less anxious and more relaxed enabling dental practitioners to provide high quality treatment in a calm and attentive manner.


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[1]Singh P. An emphasis on the wide usage and important role of local anesthesia in dentistry: A strategic review. Dent Res J (Isfahan). 2012 Mar-Apr; 9(2): 127–132.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3353686/#ref3[Accessed 30thOctober 2018]

[2]Kumar M. et al. Topical anesthesia. J Anaesthesiol Clin Pharmacol. 2015 Oct-Dec; 31(4): 450–456. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4676230/[Accessed 30th October 2018]

[3]Tsuchiya H. Interaction of Local Anesthetics with Biomembranes Consisting of Phospholipids and Cholesterol: Mechanistic and Clinical Implications for Anesthetic and Cardiotoxic Effects. Anesthesiology Research and Practice2013(2):297141 https://www.researchgate.net/publication/258205078_Interaction_of_Local_Anesthetics_with_Biomembranes_Consisting_of_Phospholipids_and_Cholesterol_Mechanistic_and_Clinical_Implications_for_Anesthetic_and_Cardiotoxic_Effects[Accessed 30th October 2018].

[4]Budenz A. Local Anesthetics and Medically Complex Patients. J Calif Dent Assoc. 2000 Aug;28(8):611-9. https://www.scribd.com/document/327984276/Local-Anesthesia-and-Med-Compromised-Pts-Jcda-2000[Accessed 30th October 2018]

[5]Sisk A.L. Vasoconstrictors in local anesthesia for dentistry. Anesth Prog. 1992; 39(6): 187–193. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2148619/?page=3[Accessed 5th November 2018]

[6]Lee J.M. et al. Use of local anaesthetics for dental treatment during pregnancy; safety for parturient. J Dent Anesth Pain Med. 2017 Jun; 17(2): 81–90. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5564152/[Accessed 30thOctober 2018.]

[7]Hersh E.V. Adverse drug interactions in dentistry. Periodontology 2000 Feb 2008: 46(3):109-42. https://www.researchgate.net/publication/5650893_Drug_interactions_in_dentistry[Accessed 30th October 2018]

[8]Hersh E.V. et al. Three serious drug interactions that every dentist should know about. 2015 Jun;36(6):408-13; quiz 414, 416. https://www.ncbi.nlm.nih.gov/pubmed/26053779[Accessed 30th October 2018]

[9]Chioca L.R. et al. Antidepressants and local anesthetics: drug interactions of interest to dentistry. RSBO. 2010 Oct-Dec;7 (4) 466-473. https://www.researchgate.net/publication/49583079_Antidepressants_and_local_anesthetics_drug_interactions_of_interest_to_dentistry[Accessed 30th October 2018]

[10]Lambrecht L.T et al. Antidepressants relevant to oral and maxillofacial surgical practice. Ann Maxillofac Surg. 2013 Jul-Dec; 3(2): 160–166. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3814665/[Accessed 30thOctober 2018]

[11]Ueno T. et al. Local anaesthetic failure associated with inflammation: verification of the acidosis mechanism and the hypothetic participation of inflammatory peroxynitrite. J Inflamm Res. 2008; 1: 41–48.

[12]TsuchiyaH. Dental Anaesthesia in the Presence of Inflammation: Pharmacological Mechanisms for the Reduced Efficacy of Local Anesthetics. Int J ClinAnesthesiol Oct 2016.4(3): 1059. https://www.jscimedcentral.com/Anesthesiology/anesthesiology-4-1059.pdf[Accessed 30th October 2018]

[13]Meechan J.G. How to overcome failed local anaesthesia. BDJ Jan 1999. 186;(1)15-20. https://www.nature.com/articles/4800006.pdf[Accessed 5th November 2018]

[14]Hasturk H. et al. Activation and resolution of periodontal inflammation and its systemic impact. Periodontol 2000. 2015 Oct; 69(1): 255–273.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4530469/[Accessed 5th November 2018]

[15]Cutler C.W. et al. Clinical benefits of oral irrigation for periodontitis are related to reduction of pro-inflammatory cytokine levels and plaque. J Clin Periodontol Feb 2000; 27:134-143. https://www.ncbi.nlm.nih.gov/pubmed/10703660[Accessed 30th October 2018]


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