Local Anesthesia

Local Anesthesia
Local anesthesia sees regular use in a variety of dental procedures, from cavity and crown work to root planing and scaling for periodontal disease. Common local anesthetic drugs used in dentistry include lidocaine, articaine, prilocaine, mepivacaine, and bupivacaine. These drugs impart a numbing effect that lasts for 30 to 60 minutes.
You may receive a local anesthetic either as a gel rubbed onto your gum tissues or as an injection into the part of the mouth that requires treatment. Once you report a feeling of numbness, your dentist will then proceed with the necessary work. You won't experience any sedation or altered consciousness from these drugs.
General Anesthesia
In contrast to local anesthesia, general anesthesia affects the entire body and produces a state of unconsciousness. This option makes sense for lengthy, extensive oral surgeries that might cause more pain than local anesthesia can address. It also serves to keep patients completely still for procedures that require extreme precision.
General anesthesia may prove useful even for procedures that don't usually call for it. For instance, if you suffer from severe fear and anxiety in the dentist's chair, you may benefit from simply going to sleep and waking up after the procedure has concluded. Autistic patients and others with special health issues may also need it.
If you receive general anesthesia, the dentist will administer a controlled, steady supply of the anesthetic through an IV drip or a face mask. Examples of general anesthetic drugs include propofol, ketamine, diazepam, isoflurane, desflurane, and methohexital. You'll breathe through an endotracheal tube while anesthetized.
Not everyone can or should receive general anesthesia. If you have a history of neurological problems, internal organ disease, acid reflux, or previous bad reactions to anesthetic drugs, your dental team needs to know so that they can monitor your condition with extra care or avoid specific types of anesthetic medication.
Nitrous Oxide Sedation
Nitrous oxide, also known as laughing gas, provides a quick, simple form of sedation. You'll inhale a mix of nitrous oxide and oxygen through a face mask, with the balance of these two gases controlled by the dentist to ensure both safety and optimal results. This mild sedation wears off quickly once you stop inhaling it.
Nitrous oxide sedation works well for younger dental patients and anyone who needs only a mild sedative toward the beginning of a routine dental procedure. Other forms of sedation last longer, may convey deeper effects, and usually require you to arrange for safe transportation home.
Oral Sedation
Oral sedative drugs can provide moderate levels of sedation that can last for hours, with no need for you to breathe through a face mask. You'll receive these oral drugs in advance, taking them about one hour before the actual procedure. Dentists commonly use a Valium-like drug called Halcion for oral sedation.
Under oral sedation, you will feel deeply relaxed and either mildly or extremely groggy, depending on the dosage administered. However, you should still manage to understand and respond to your dentist's questions and instructions. This level of sedation sometimes goes by the name of twilight dentistry.
IV Sedation
IV sedation employs the same kinds of drugs as oral sedation. The main difference involves the speed with which the drugs work. With an intravenous drip sending the sedative directly to your bloodstream, you will experience moderate to deep sedation and will be generally unable to perceive all but the most aggressive stimuli.
As in cases that involve general anesthesia, dentists use great care when administering IV sedation. Rest assured that your dentist will monitor your vital signs and adjust the sedation level as needed to keep you safe.
Local anesthetic agents in dentistry
In dentistry, the most commonly used local anesthetic is lidocaine (also called xylocaine or lignocaine). Lidocaine's half-life in the body is about 1.5–2 hours. As of 2018, Lidocaine is most commonly used in dental procedures to numb the area around a tooth.[1] In root canal treatment, for example, more Lidocaine is required than for a simple filling[1]
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 anaesthetic 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.[citation needed]
Drugs with a short duration of action (approximately 30 minutes of pulpal anaesthesia) include Mepivacaine HCl 3%, and Prilocaine HCl 4% without vasoconstrictor.[2]
Drugs with an intermediate duration of action (enabling pulpal anaesthesia 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 anaesthesia at more than 90 minutes.
Multiple factors affect the depth and duration of local anaesthetics' 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.[2] Hence figures citing the duration of action of local anaesthetics 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 Local anaesthetic can be increased to increase alkalinity using sodium bicarbonate which reduces pain at the injection site and produces a faster onset. Buffered local anaesthetics have a 2.29 times increased success rate compared with non buffered solutions.[3]
Maxillary anaesthesia
Local anaesthesia 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 anaesthesia effect.
Mandibular anaesthesia
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 anaesthesia 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 anaesthesia should be the first choice of method for pulpal and soft tissue anaesthesia 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 anaesthesia with 4% articaine with 1:100,000 epinephrine in obtaining pulp anaesthesia 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 anaesthetic close the near 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
Intraosseous
It is an alternative anaesthetic injection technique that was first published in 1910.[8] Intraosseous anaesthetic injection involves the deposition of anaesthetic solution directly into the cancellous alveolar bone adjacent to the apex of the root of the tooth to be anaesthetised through a small hole. It also can be use more involved dental procedures such as surgery or endodontic therapy (root canals).
Intraligamentary
Intraligamentary or periodontal ligament anaesthesia 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 anaesthetic solution for each root of the tooth’ [9] diffusing into the marrow spaces surrounding the teeth. Clinicians may adopt this technique due to some benefits such as: no soft tissue anaesthesia, use of a smaller amount of anaesthetic and single tooth anaesthesia 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 anaesthesia (by action of anaesthetic agent) and mechanical anaesthesia (by pressure from deposition). Interligamentary anaesthetic may be complicated by poor operator technique where rapid injection and excessive volume is used; this could lead to sensitivity to biting and percussion.[10]
Research has shown that the rate of onset of anaesthesia in the patients was between 15-20 second; this provides an advantage compared to that of inferior alveolar dental block.[11] 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
Inter-pulpal anaesthesia involves the direct placement of anaesthetic 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 anaesthesia as the pulpal tissue is subject to chemical action by the anaesthetic agent and mechanical stimulus due to the pressure applied.[12] 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 anaesthesia is difficult to achieve. Nevertheless, due to the patient discomfort associated with this technique it should not be the primary anaesthetic technique used.
Intra-papillary
Intra-papillary anaesthesia 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 anaesthetic 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.[14]
Akinoski approach
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Electrical nerve blocks
Main article: Nerve block
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.