Dental anesthesia (or dental anaesthesia) is the application of anesthesia to dentistry. It includes local anesthetics, sedation, and general anesthesia.
Local anesthetic agents in dentistry In dentistry, local anesthetic medications (LA) are often used to control any potential pain that may occur with procedures. Local anesthetic injections are given in specific areas of the mouth, rather than the whole body. Although several different medications are available, the most commonly used local anesthetic to prevent pain in the area around a tooth is lidocaine (also called xylocaine or lignocaine). Lidocaine's half-life in the body is about 1.5–2 hours. The time it takes for the anesthetic medication to prevent pain in the area (speed of onset) and length of time that the area does not have painful sensations are considerations when choosing an appropriate approach to dental treatment. Other considerations include procedural considerations, the presence of inflammation, techniques used to administer the anesthetic medication, and adverse effects. In root canal treatment, for example, more Lidocaine is required than for a simple filling.
Other local anesthetic agents in current use include articaine (also called septocaine or Ubistesin), bupivacaine (a long-acting anesthetic), prilocaine (also called Citanest), and mepivacaine (also called Carbocaine or Polocaine). Different types of local anesthetic drugs vary in their potency and duration of action. A combination of these may be used depending on the situation. Some agents come in two forms: with and without epinephrine (adrenaline) or other vasoconstrictor that allow the agent to last longer. This controls bleeding in the tissue during procedures. Usually the case is classified using the ASA Physical Status Classification System before any anesthesia is given.
Drugs with a short duration of action (approximately 30 minutes of pulpal anesthesia) include Mepivacaine HCl 3%, and Prilocaine HCl 4% without vasoconstrictor.
Drugs with an intermediate duration of action (enabling pulpal anesthesia for roughly 60 minutes) include Articaine HCl 4% + epinephrin 1:100,000, Articaine HCl 4% + epinephrin 1:200,000, Lidocaine HCl 2% + epinephrine 1:50,000, Lidocaine HCl 2% + epinephrine 1:80,000; Lidocaine HCl 2% + epinephrine 1:100,000 and Prilocaine HCl 4% + epinephrine 1:200,000.
Bupivicaine HCl 0.5% + epinephrine 1:200,000 gives a long duration of action of pulpal anesthesia at more than 90 minutes.
Multiple factors affect the depth and duration of local anesthetics' action. Examples of these factors include the patients individual response to the drug, vascularity and pH of tissues at the site of drug administration, the type of injection administered etc. Hence figures citing the duration of action of local anesthetics is an approximation, as extreme variations may occur among patients.
Commercially used LA in dental practice has a low pH of 3–4, this is advantageous as it will extend the shelf life of the product and prevent early oxidation. However, low pH LA's may produce a burning sensation, have a slower onset and decrease clinical efficacy. The pH of a local anesthetic can be increased using sodium bicarbonate which reduces pain at the injection site and produces a faster onset. Buffered local anesthetics have a 2.29 times increased success rate compared with non buffered solutions.
Maxillary anesthesia Local anesthesia is deposited at the buccal (cheek) side of the maxillary alveolus which can diffuse through the thin cortical plate of the maxilla, then further into the pulp of the tooth in order to achieve dental anesthesia effect.
Mandibular anesthesia Both regional block and infiltration techniques are considered the first choice injections for anaesthetising the mandibular teeth.
Different techniques are chosen based on different factors: Patient age Infiltration anesthesia is a preferable method to anaesthetise deciduous/primary teeth in children. The method is similar to the maxillary buccal infiltration. Ensure the lip/ cheek is stretched in a lateral and inferior direction instead of superiorly and the needle is then penetrated 45' with the buccal cortical plate of the bone through the taut tissue of the muccobuccal fold. Tooth to be anaesthetised Infiltration anesthesia should be the first choice of method for pulpal and soft tissue anesthesia of mandibular permanent incisors in adults. Regional block injections are sometimes ineffective due to crossover innervation from the opposite side of inferior alveolar nerve. It is recommended to deposit at least 0.5mL at each buccal and lingual site in the apical region of the tooth of interest. The use of infiltration anesthesia with 4% articaine with 1:100,000 epinephrine in obtaining pulp anesthesia of the mandibular permanent first molar is getting more common these days due to its successful formulation.
Regional block techniques
Inferior alveolar and lingual block The inferior alveolar nerve block is probably one of the most common methods used by dentist to anaesthetise the mandibular teeth in adults. This technique aims to inject the needle and deposit local anesthetic close to the nerve before it enters the mandibular foramen, which locates on the medial aspect of the mandibular ramus. This is to block the nerve transmission in the inferior alveolar nerve before entering into the bone through the mandibular foramen.
Long buccal nerve block
Results of a systematic review with meta-analysis, showed that the anesthetic efficacy of 4% articaine buccal infiltration is comparable to 2% lidocaine inferior alveolar nerve block for mandibular first molars with symptomatic irreversible pulpitis.
Supplementary techniques
Intraosseous Intraosseous anesthesia is an alternative anesthetic injection technique that was first published in 1910. Intraosseous anesthetic injection involves the deposition of anesthetic solution directly into the cancellous alveolar bone adjacent to the apex of the root of the tooth to be anaesthetised through a small hole. Additionally, more complex dental procedures like surgery or endodontic therapy (like root canals) might make use of it.
Intraligamentary Intraligamentary or periodontal ligament anesthesia is a technique used primarily for endodontic treatment and to supplement inferior dental blocks where they may have failed. This technique involves 'the deposition of at least 0.2ml of local anesthetic solution for each root of the tooth' diffusing into the marrow spaces surrounding the teeth. Clinicians may adopt this technique due to some benefits such as: no soft tissue anesthesia, use of a smaller amount of anesthetic and single tooth anesthesia however use may be contraindicated due to claims that patients report sharp pain upon administration of interligamentary aesthetic. However the use of a high-pressure syringe and ultra fine needle provide both chemical anesthesia (by action of anesthetic agent) and mechanical anesthesia (by pressure from deposition). Interligamentary anesthetic may be complicated by poor operator technique where rapid injection and excessive volume is used; this could lead to sensitivity to biting and percussion.
Research has shown that the rate of onset of anesthesia in the patients was between 15 and 20 second; this provides an advantage compared to that of inferior alveolar dental block. Other advantages include a decrease in overall trauma in comparison to conventional blocks therefore being an ideal procedure for extractions and endodontic treatment in children.
Intrapulpal Intrapulpal anesthesia involves the direct placement of anesthetic agent using a small needle (of 25 or 27 gauge) into the pulp chamber; it is injected under pressure leading to brief yet intense discomfort. This particular technique provides effective pulpal anesthesia as the pulpal tissue is subject to chemical action by the anesthetic agent and mechanical stimulus due to the pressure applied. This method is usually adopted when all other techniques have been unsuccessful and must include pre-operative warnings of sharp pain. However it may prove useful for pulpal extirpation or endodontic treatment on any tooth where anesthesia is difficult to achieve. Nevertheless, due to the patient discomfort associated with this technique it should not be the primary anesthetic technique used.
Intra-papillary Intra-papillary anesthesia is used as a supplementary technique to infiltrations in order to increase comfort for the patient and is primarily used to replace palatal or lingual infiltrations. This is exceptionally successful in paediatric patients and works to replace or increase comfort for particularly uncomfortable infiltrations such as palatal or lingual infiltrations. The technique involves direct deposition of anesthetic agent into the papilla with associated tissue blanching at site of injection. The point of penetration should lie in attached gingiva 2mm apical of the papilla
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.
Akinoski approach
Electrical nerve blocks
Technology that involves using electric current to block the reception or generation of pain signals; the pain control can be transient.
Jet injection A jet injection aims to create a release of pressure strong enough to push a liquid medication dose through a small orifice. This is usually done with the help of an energy source which is mechanical. With this, a thin column of fluid is created which has the force to penetrate soft tissues, thus a needle is not required.
Advantages: Faster drug absorption at injection site Easy to use Little/no pain Less tissue damage
However, in dentistry, the effectiveness of this technique has been reported to be limited.
Examples of jet injections include: Syrijet, MED-JET H III and iCT injection SE by Dentium.
Dosage References: DrugnameUKTrade nameConcentration(%)Maximum dose(mg/kg)Articaine with adrenalineBartinest Septanest47BupivacaineMarcain0.252.5Lidocaine132Lidocaine with adrenalineUtilycaine
Lignospan Special
Xylocaine172MepivacaineScandonest21.36 (3 mg per pound), less than 400 mg in adults3Prilocaine with FelypressinCitanest0.571Prilocaine PlainCitanest Plain16
Contraindications When considering the use of a local anesthesia 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.
Type
As stated previously, local anesthesia used in dentistry can vary significantly as there are various preparations with a multitude of qualities. Each preparation has slight differences in how the anesthetic affects the body. This is due to the use of different constituents. Local anesthetics 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 has unstable angina or severe cardiac dysrhythmia, these preparations are often discouraged as they may predispose to unfavourable side effects. Studies found that both articaine given by infiltration and lidocaine given by inferior block were equally efficient when used for routine dental treatments in pediatric patients, however, articaine injections caused less post-operative pain.