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Dental anesthesia

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Dental anesthesia
Specialtydental anesthesiology
MeSHD000766

Dental anesthesia (or dental anaesthesia) is a field of anesthesia that includes not only local anesthetics but sedation and general anesthesia.

Local anesthetic agents in dentistry

The most commonly used local anesthetic is lidocaine (also called xylocaine or lignocaine), a modern replacement for procaine (also known as novocaine). Its half-life in the body is about 1.5–2 hours. Other local anesthetic agents in current use include articaine (also called septocaine or ubistesin), bupivacaine (a long-acting anesthetic), and mepivacaine. A combination of these may be used depending on the situation. Also, most agents come in two forms: with and without epinephrine (adrenaline) or other vasoconstrictor that allow the agent to last longer and also controls bleeding in the tissue during procedures. Usually the case is classified using the ASA Physical Status Classification System before any anesthesia is given.

Types of local anesthesia in dentistry

Nerve block

A common form of local dental anesthesia; blocks the reception of pain in one region of the mouth at a time.

Palatal block given into the hard palate using pressure anesthesia; useful in anesthetizing the palate side of the maxillary teeth.

Infiltration

Given inferior to the root of the tooth involved in the dental work; used usually for minor procedures such as restorations. However, also used for periodontal surgeries, and with the advent of anesthetics that diffuse more readily through the bone, such as articaine, infiltration can be used routinely for most extractions, grafting and even implant placements.

Intraosseous

An injection of local anesthetic given directly into the osseous (bone) structure of the tooth for more involved dental procedures such as surgery or endodontic therapy (root canals).

Intrapulpal

An injection of local anesthetic given directly into the pulp of the tooth to completely desensitize the tooth.

Pressure anesthesia

Pressure with a cotton swab in the area to distract the nerve sensation of pain when the needle enters certain areas such as palatal tissue.[1]

Akinoski Approach

Technique

This approach is a supplementary method to a conventional regional inferior alveolar nerve block, to achieve anaesthesia of the lower posterior teeth. Anatomical landmarks vary slightly in individuals such as the shape & size of their mandible, hence making it challenging to determine the location of the mandibular foramen to accurately administer the anaesthetic at the correct location in a regional block. Supplementary nerve innervations from other sources may not anaesthetized, resulting in failed anaesthesia.

This use of materials in this technique is the same as that of the conventional block - standard anaesthetic cartridge (2% Lidocaine, 1:80,000 adrenaline), long needle (27 gauge), suitable extraction forceps. When the technique is practiced in children, a short needle is advocated.[2]

Anatomy

The patient will be in a semi-recumbent position, and the operator standing in front of the patient. With their mouth opened, identify the pterygo-mandibular fold where it joins the tissues posterior to the upper 3rd molar.[2] With the patient’s cheek retracted, topical anaesthesia may be placed on the mucosa buccal and distal to the upper 3rd molar.

When anaesthetic is administered, the patient has their teeth together, such that the cheek muscles are relaxed and well-retracted to ensure maximum field of view. With the needle parallel to the maxillary occlusal plane, the syringe is advanced and point of entry of the needle will be at the notch between the vertical ramus and maxillary tuberosity, piercing through the buccinator, into the pterygo-mandibular space. 2.5 - 3 cm of the needle will be within the tissues and 1.5 - 2ml of anaesthetic given, and then carefully withdrawn and capped safely.

In close proximity with the pterygo-mandibular space lies the main branches of the mandibular nerve where the anaesthetic can reach easily through diffusion.

The sensory divisions of the mandibular nerve will be anaesthetized, except the auriculotemporal nerve.

Complications

There has thus far been no significant local or systemic complication reported with this technique.[2][3]

Advantages

This technique does not require the patient to open their mouth fully, hence is indicated for use in patients with trismus. It induces significantly less pain[3], because the soft tissues are not taut, upon penetration of the needle. It is much more straightforward to administer as 1 injection allows the main nerves (lingual nerve, IDN, long buccal nerve) to be anaesthetized compared to at least 2 separate needle entries in the conventional block, and it had a more rapid onset of anaesthesia & high success rates.[2] Fewer aspiration incidents are also reported with this technique in comparison to the conventional block.[3]

Disadvantages

This technique may be challenging when there is either an abnormality or tumour in the region of the maxillary tuberosity, or when there are no posterior teeth in the area. However, identifying and targeting the alveolar ridge in the area should be able to overcome this problem.

Lower success outcomes were recorded for children compared to adults, due to the struggle in judging the depth of needle penetration in a child. Achieving anaesthesia was also reported to be slightly slower than a conventional block.[3]

Electrical nerve blocks

Technology that involves using electric current to block the reception or generation of pain signals; the pain control can be transient.

Acupuncture or accupressure

An alternative to chemical or electrical blocks, but is rarely used.

Contraindications

When considering the use of a local anaesthesia there are many factors which should be considered. In terms of contraindications associated with LA there are “absolute” and “relative” contraindications. When something is said to have an “absolute” contraindication this underlines that under no circumstance would that LA be selected to administer to that specific patient as it poses a potential life-threatening risk e.g. allergy. When the LA has a “relative” contraindication the administration of the LA is not preferable and should be avoided, but does not pose a life-threatening risk.

In Relation to the Type

As stated previously Local Anaesthesia used in dentistry can vary significantly as there are various preparations with a multitude of qualities. Each preparation has slight differences in how the anaesthetic effects the body. This is due to the use of different constituents. Local Anaesthetics which contain adrenaline such as Lidocaine (using 1:80,000 of adrenaline) or Articaine (using 1:100,000 of adrenaline) have a direct effect on the cardiac output by increasing the rate and contraction of the heart itself. Due to these effects, if a patient suffers from unstable angina or severe cardiac dysrhythmia, these preparations are often discouraged as they may predispose to unfavourable side effects.[4]

As an alternative, other preparations such as Mepivicaine Hydrochloride or Prilocaine (containing Felypressin) can be used. Prilocaine is especially suitable for a patient who wishes to avoid adrenaline or may have a latex/preservative allergy. The main contraindication of Prilocaine is that it has a short half life and it possesses a mild cytotoxic effect, therefore should be avoided in pregnancy. This cytotoxic effect can influence the uterine tone and interfere with circulation, which can pose detrimental effects on the pregnancy. Mepivicaine Hydrochloride is then considered if Prilocaine is contraindicated. Mepivicaine is the least vasodilatory anesthetic as it has no vasoconstrictors and no preservatives added.[5]

In Relation to the Dose

The dose of local anesthesia is often reduced when a patient has any systemic health implications or habits which may cause an interference. From time to time the local anaesthetic itself should be reduced (therefore reducing the maximum dose). This is particularly done when alcoholism, anaemia (if using Prilocaine), anorexia, bradycardia or GORD is concerned. On other occasions the vasoconstrictor used (often adrenaline) must be reduced when an individual suffers from angina, bradycardia, chronic bronchitis, cardia disarrhythmia, COPD or glaucoma. These include drug abuse, calcium channel blocker containing medications, beta blocker medications or liver disease as this impairs the metabolism.

In Relation to the Technique

The variety of techniques associated when giving a local anaesthetic can affect the success and if done incorrectly lead to a possible fracture of the needle tip. It is extremely rare for the needle to fracture whilst giving an injection intra-orally unless an inadequate technique is adopted. To prevent such an occurrence, especially when performing an inferior alveolar nerve block, it is recommended to not bend the needle, to use the correct needle length and to not insert the needle up to the hub.

Most common local anesthetic procedure

The Inferior alveolar nerve anaesthesia or block or IANB (sometimes termed "inferior dental block", or wrongly referred to as the "mandibular block") probably is anesthetized more often than any other nerve in the body. An injection blocks sensation in the inferior alveolar nerve, which runs from the angle of the mandible down the medial aspect of the mandible, innervating the mandibular teeth, lower lip, chin, and parts of the tongue, which is effective for dental work in the mandibular arch. To anesthetize this nerve, the needle is inserted somewhat posterior to the most distal mandibular molar on one side of the mouth. The lingual nerve is also anesthetized through diffusion of the agent to produce a numb tongue as well as anesthetizing the floor of the mouth tissue, including that around the tongue side or lingual of the teeth.[6]

Several nondental nerves are usually anesthetized during an inferior alveolar block. The mental nerve, which supplies cutaneous innervation to the anterior lip and chin, is a distal branch of the inferior alveolar nerve. When the inferior alveolar nerve is blocked, the mental nerve is blocked also, resulting in a numb lip and chin. Nerves lying near the point where the inferior alveolar nerve enters the mandible often are also anesthetized during inferior alveolar anesthesia, such as affecting hearing (auriculotemporal nerve).[6]

The facial nerve lies some distance from the inferior alveolar nerve within the parotid salivary gland, but in rare cases anesthetic can be injected far enough posteriorly to anesthetize that nerve. The result is a transient facial paralysis, with the injected side of the face having temporary loss of the use of the muscles of facial expression that include the inability to close the eyelid and the drooping of the labial commissure on the affected side for a few hours, which disappears when the anesthesia wears off.[1]

In contrast, the superior alveolar nerves are not usually anesthetized directly because they are difficult to approach with a needle. For this reason, the maxillary arch is usually anesthetized locally for dental work by inserting the needle beneath the oral mucosa surrounding the teeth so as to anesthetize the smaller branches.[7]

Dental syringe

A dental syringe is a syringe for the injection of a local anesthetic.[8] It consists of a breech-loading syringe fitted with a sealed cartridge containing anesthetic solution.

In the UK and Ireland, manually operated hand syringes to inject Lidocaine in to patient's gums.[9][10][8]

Other anesthetics used in dentistry

  • Topical anesthetics benzocaine, eugenol, and forms of xylocaine are used topically to numb various areas before injections or other minor procedures.
  • Nitrous oxide (N2O), also known as "laughing gas", easily crosses the alveoli of the lung and is dissolved into the passing blood, where it travels to the brain, leaving a dissociated and euphoric feeling in most cases. Nitrous oxide is used in combination with oxygen. Often (especially with children) a sweet-smelling fruity scent similar to an auto[clarification needed] scent is used with the gas to inspire deep inhalation.
  • General anesthesia drugs such as midazolam, ketamine, propofol and fentanyl are used to put a person in a twilight sleep or render them completely unconscious and unaware of pain. Dentists who have completed a training program in anesthesiology may also administer general IV and inhalation anesthetic agents.
  • Nebotamine, a drug with similar effects to ketamine, is injected into the anterior lingual glands blocking action potentials from sending signals to the myelinated nerve. The potency of the anesthetic is directly related to its lipid solubility, since 90% of the nerve cell membrane is composed of lipid.
  • Midazolam (Versed), a drug that represses memories of the procedure, is usually given two hours prior to the procedure in combination with Tylenol in general anesthesia so the person will go home with no memories of being in surgery.
  • Sevoflurane gas in combination with nitrous oxide and oxygen is often used during general anesthesia followed by the use of isoflurane gas to maintain anesthesia during the procedure. In children sweet fruity scents are often used with the gases to inspire deep inhalation. Scents come in cherry, apple, bubblegum, watermelon, etc...
  • Propofol, a drug with similar effects to Sodium Pentathol, is often used through intravenous infusion through an IV during general anesthesia after gasses are initiated.
  • Morphine is often used to control pain during the dental surgery under general anesthesia. The morphine is usually administered through IV.
  • Ketorolac is often administered through IV to suppress both pain and inflammation while under general anesthesia.

Other drugs used in combination with general anesthesia in dentistry

  • Decadron a steroid is often administered through IV to suppress inflammation and swelling resulting during the surgery while under general anesthesia.
  • Ondansetron brand named Zofran is often administered to prevent nausea during the surgery which may result from the blood draining into the stomach while under general anesthesia, or it is given after the procedure for postoperative nausea which may result from the anesthesia itself which was administered.

Local anesthesia and the pregnant patient

Provided a dentist performs proper aspiration to avoid intravenous injections, local anesthetics containing epinephrine (adrenaline) are safe to use during pregnancy. lignocaine and prilocaine are assigned a category B ranking by the FDA and are therefore safe for use during pregnancy. Lignocaine and prilocaine are sold as 2% and 4% formulations, respectively. It is therefore safer to use the lignocaine so as to administer a lower concentration of the drug to the pregnant patient.[11]

Mepivicaine, articaine, bupivicaine are given an FDA category C ranking and so should be avoided. Benzocaine, the ingredient of most topical anesthetic formulations, is also ranked as category C and should be avoided. Lignocaine should be used as topical anesthetic instead.[11]

Epinephrine in high doses is harmful to a pregnant woman in that it affects uterine blood flow. However its use in low dose with local anesthetic administration is warranted. The epinephrine causes vasoconstriction which in turn reduces systemic distribution of the anesthetic as well as prolongs its action in addition to decreasing bleeding at the operating site. Lidocaine 2% with 1:100,000 adrenaline is the local anesthetic of choice in the treatment of pregnant women.[11]

See also

References

  1. ^ a b Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012, page 216
  2. ^ a b c d Akinosi, J.O. (1977). "A new approach to the mandibular nerve block". British Journal of Oral Surgery. 15 (1): 83–87.
  3. ^ a b c d Lenka, Sthitaprajna & Jain Kumar, Nikil & Mohanty, Rajat & Singh, Dhirendra & Gulati, Minkle (2013). "A Clinical Comparison of Three Techniques of Mandibular Local Anaesthesia". Journal of Research and Advancement in Dentistry. 2: 61–67.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  4. ^ https://books.google.co.uk/books?id=xRgnDwAAQBAJ&pg=PA52&dq=dental+anaesthesia+contraindications&hl=en&sa=X&ved=0ahUKEwjkmOnbmqHZAhUQ2qQKHX2DAUEQ6AEIJzAA#v=onepage&q=dental%20anaesthesia%20contraindications&f=false
  5. ^ https://books.google.co.uk/books?id=dmxjDQAAQBAJ&pg=PA151&dq=dental+anaesthesia+contraindications&hl=en&sa=X&ved=0ahUKEwjkmOnbmqHZAhUQ2qQKHX2DAUEQ6AEILDAB#v=onepage&q=dental%20anaesthesia%20contraindications&f=false
  6. ^ a b Local Anesthesia for the Dental Hygienist, Logothetis, Elsevier, 2012
  7. ^ Local Anesthesia for the Dental Hygienist, Logothetis, Elsevier, 2012[page needed]
  8. ^ a b "Lidocaine Hydrochloride (Local) Monograph for Professionals - Drugs.com".
  9. ^ Zakrzewska, J. M.; Boon, E. C. (23 August 2003). "Use of safety dental syringes in British and Irish dental schools". British Dental Journal. 195 (4): 207–209. doi:10.1038/sj.bdj.4810445 – via www.nature.com.
  10. ^ Zakrzewska, J. M.; Greenwood, I.; Jackson, J. (27 January 2001). "Cross-infection control: Introducing safety syringes into a UK dental school – a controlled study". British Dental Journal. 190 (2): 88–92. doi:10.1038/sj.bdj.4800891 – via www.nature.com.
  11. ^ a b c Ouanounou, A.; Haas, D. A. (April 2016). "Drug therapy during pregnancy: implications for dental practice". British Dental Journal. 220 (8): 413–417. doi:10.1038/sj.bdj.2016.299. ISSN 1476-5373.
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