Neurological complications following the administration of a local anaesthetic can be alarming. By reading reports of such incidents, dentists who find themselves in similar situations will be able to reassure their patients and act accordingly. The authors have reviewed the literature for those neurological complications that have been reported and offer an explanation of their aetiology. Examples of complications covered are facial nerve palsy, transient amaurosis, post-injection paraesthesia, Horner's syndrome, transient paralysis of combined cranial nerves III, IV and VI, sudden unilateral deafness and abducens nerve palsy. A thorough knowledge of the relevant anatomy pertinent to the various injections used in dental surgery is essential and is highlighted in the text.
Over the past century, there is perhaps no greater contribution to the practice of clinical dentistry than the development and application of local anaesthesia. What were once considered painful procedures have now been made routine by the deposition and action of local anaesthetics. This article will serve as a review of basic pharmacological principles of local anaesthesia, subsequent sequelae that can arise from their use, considerations when using local anaesthetics, and recent advances in the delivery of local anaesthetics.
When you undergo a procedure that requires dental local anesthesia, your dentist will prepare your mouth by drying a part of it with cotton or air. Your dentist might also decide to numb the area he/she plans to inject with a gel to numb the skin. This can be helpful if you are afraid of injections.
Applicants for certification in the administration of local anesthesia must complete a course in the administration of local anesthesia which is offered by a dental or dental hygiene program accredited by the Commission on Dental Accreditation of the American Dental Association or approved by the board. The course must include a minimum of 30 hours of didactic instruction and 30 hours of clinical experience, and instruction in:
Upon receipt of a complete application, board staff will add the Local Anesthesia qualification to the license and a new license will be issued. The license is to be prominently displayed at the location where the dental hygienist is authorized to administer local anesthesia.
There are two kinds of local anaesthetics that dentists use to numb your mouth. The first is called a topical anaesthetic, which is swabbed over a small area on the surface of your mouth or gums. In most cases, this is used to numb the area where the dentist plans to inject the other kind of local anaesthetic. The injectable anaesthetic is what we rely on to keep you comfortable and pain-free.
Local anaesthesia is used to make a very small, specific area of your body temporarily unable to feel sensations, including pain. Examples of procedures requiring local anaesthesia include fillings, crown placement and root canals.
A local anaesthetic works by blocking nerve cells in a specific area from sending pain signals to your brain. You can expect this numbness to last for two to four hours, which means you will probably still feel residual numbness after your appointment.
Before you undergo a procedure requiring local anaesthesia, we will ask for information regarding any allergies and the medications you take. There is a possibility you might need a different formula if you have certain medical conditions. Call us if you have concerns or wish to know more about how we use local anaesthesia.
Local anaesthesia does have side effects, but they are usually not serious. One well-known side effect is a temporary rapid heartbeat, which can happen if the local anaesthetic is injected into a blood vessel. One of the chemicals used in the local anaesthetic injection, epinephrine, can travel directly from the blood vessel to the heart. You may also know epinephrine by its other name: adrenaline. It is a naturally occurring substance in your body that can rapidly increase your heart rate. The fast heartbeat it causes can be alarming, but it is not dangerous and should return to normal in a matter of seconds.
Local anaesthetic failure is an unavoidable aspect of dental practice. A number of factors contribute to this, which may be related to either the patient or the operator. Patient-dependent factors may be anatomical, pathological or psychological. This paper considers the reasons for unsuccessful dental local anaesthetic injections and describes techniques which may be useful in overcoming failure.
The provision of many dental treatments depends upon achieving excellent local anaesthesia. Pain-free operating is of obvious benefit to the patient, it also helps the operator as treatment can be performed in a calm, unhurried fashion. Failed local anaesthesia therefore can have effects at both ends of the syringe.
Every dentist experiences local anaesthetic failure. Published studies on local anaesthetic efficacy do not report 100% success;1,2,3,4 normally, failures are readily rectified. However, sometimes a simple remedy, such as repeating the original injection, does not overcome the problem. This article aims to offer practical advice in the approach to overcoming local anaesthetic failure. The most rational method is to consider the reasons why a local anaesthetic injection fails. These causes can be classified as:
Pharmacological causes are not included as modern local anaesthetic solutions, when used appropriately, are reliable. Although there are some drug interactions which theoretically could decrease efficacy, these are not a concern.
The most appropriate local anaesthetic solution for most dental procedures is lignocaine with adrenaline. In some medically-compromised patients adrenaline-free solutions may be preferred, however for the majority of cases lignocaine with adrenaline is the 'gold standard'. The use of plain lignocaine does not give reliable pulpal anaesthesia and in addition its effect is short-lived.
The most likely defect in technique is faulty needle placement. Failure to aspirate before injection, which could lead to intravascular deposition of solution might also lead to failure of anaesthesia although this has never been proven. Success may be related to the speed at which the solution is deposited. It is easy to imagine the anaesthetic being directed away from a nerve trunk during forceful injection. There is evidence in the surgical literature that the success of some techniques is increased with slower injection speeds.5
This is technically more difficult than the standard direct approach to the inferior alveolar nerve. The method relies upon deposition of local anaesthetic adjacent to the head of the mandibular condyle (fig. 1a).6 The patient has the mouth wide open and the dentist imagines a line drawn from the angle of the mouth to the inter-tragic notch. This is the plane of approach. The needle is introduced across the contralateral mandibular canine and directed across the mesio-palatal cusp of the ipsilateral upper second molar (fig. 1b). The point of mucosal penetration is thus higher than with the conventional block and the needle is advanced until bony contact is made. The point of bony contact is the condylar head. The needle is withdrawn slightly, and after aspirating a full cartridge is deposited. The patient should keep the mouth open for a few minutes until the subjective signs of inferior alveolar anaesthesia are reported.
This method,7which is also known as the Vazirani-Akinosi closed-mouth technique, is useful when conventional block anaesthesia fails (fig. 2a,b). It is simpler than the Gow-Gates method, and uniquely for intra-oral approaches to the inferior alveolar nerve, it does not rely upon contacting a bony end-point. The patient has the mouth closed and the syringe, fitted with a 35 mm needle, is advanced parallel to the maxillary occlusal plane at the level of the maxillary muco-gingival junction. The needle is advanced until the hub is level with the distal surface of the maxillary second molar, by which stage it will have penetrated mucosa at a higher level than with the direct approach to the nerve. At this point a cartridge of solution is deposited.
Other methods of anaesthetising man-dibular teeth include infiltration anaesthesia, incisive and mental nerve blocks, intraligamentary (or periodontal ligament), intra-osseous and intra-pulpal methods.
Buccal infiltration anaesthesia in the mandible can be effective in some areas. Indeed in children this may the preferred technique when treating the deciduous dentition.8 In adult patients buccal infiltrations may be effective in the mandibular incisor region.
When treating the lower premolar and anterior teeth a mental and incisive nerve block may overcome a failed inferior alveolar nerve block. When using this method 1.5 ml should be injected in the region of the mental foramen which is often located between the apices of the lower premolars (available radiographs can be used to accurately localise the foramen).
These techniques rely on the same mechanism to achieve anaesthesia, namely deposition of solution in the cancellous bone of the alveolus. The intraligamentary method gains access to the cancellous space by the periodontium, the intra-osseous technique by way of a perforation through the buccal gingiva. They can be used in either jaw.
This may be used both as a primary or a secondary technique. It has limitations as a principal method of anaesthesia (such as variable duration) but has been used to overcome failed conventional methods.9,10
When administering intraligamentary injections the needle is inserted at the mesio-buccal aspect of the root and advanced until maximum penetration. A 12 mm 30 gauge is recommended although efficacy is independent of needle diameter.9,10 Ideally the bevel should face the bone although effectiveness is not impaired with different orientations.12 The needle does not penetrate deeply into the periodontal ligament but is wedged at the crest of the alveolar ridge. Around 0.2 ml of solution is injected per root. When using an ordinary dental syringe 0.2 ml is the approximate volume of the cartridge rubber bung. The injection must be delivered slowly, at least 10 seconds is recommended. Rapid injection can lead to tooth extrusion, indeed an inadvertent extraction has been reported as a result of this method of anaesthesia.13 59ce067264