Local Anesthesia in Dentistry

Aims of Local Anesthesia Training

• Deliver safe and effective local anesthesia to patients
• Identify related oral anatomy and nerve supplies
• Safely deliver infiltrations and IDBs (Inferior Dental Blocks)
• Understand the legal framework for LA delivery in dentistry
• Recognize potential complications of LA delivery

GDC (General Dental Council) learning outcomes

• Describe relevant dental, oral, craniofacial, and general anatomy and relate it to managing patients
• Explain relevant physiology and its application to patient management
• Describe the properties of relevant medicines and therapeutic agents and how they apply to patient management
• Be able to manage patient pain and anxiety through communication, reassurance, and behavioral techniques
• Manage patient pain using appropriate analgesia.

Nerve Supply

• The trigeminal nerve has three branches: ophthalmic (V1), maxillary (V2), and mandibular (V3).

Patient Preparation

• First, check the legal requirements include a valid prescription.
• Take a medical history including contraindications, medications, and potential allergies/previous reactions to LA.
• Ask about food intake to prevent vaso-vagal attacks.
• Next, explain the procedure, sensations, and rationale to the patient, addressing their anxiety and using techniques such as distraction, appropriate language and a calm atmosphere.
• Patient positioning, visibility, and ensuring you have the local anesthesia equipment ready are important.

Pain Threshold

• Factors affecting a patient's pain threshold include anxiety, previous experience, culture, age, psychological makeup, the physical environment, and emotional state

Gate Control Theory

• Managing pain involves distraction, hypnosis, a calm atmosphere, and alternative stimuli.

Infiltrations

• Infiltrations are a type of local anesthesia

Steps for Buccal Infiltration

• Estimate the apex position of the tooth
• Pull the surface mucosa taut.
• Insert the needle through mucosa at 25 degrees to the the bone.
• Aim for the apex of the tooth
• Keep the needle roughly parallel to the long axis of the tooth
• Smoothly advance the needle through taut mucosa
• Avoid contacting the bone; if contact occurs, withdraw the needle 1-2mm
• Keep the needle bevel to bone
• Aspirate, especially when injecting around upper second/third molars and check the cartridge for blood
• Deliver the solution gently and slowly
• Use very little pressure on the plunger
• Withdraw the needle smoothly and make the needle safe
• Inject 0.5ml - 1ml of solution per site for infiltrations for perio work.
• Use 2.2ml of solution for restorations.
• Expect pulpal analgesia within 2-5 minutes and soft tissue analgesia within 1-2 minutes before proceeding

Particular Care for Buccal Infiltration Technique

• Labial aspect of upper incisors are very sensitive; use topical anesthetic and inject very slowly.
• There is attachment of mentalis and depressor labii inferioris muscles, so be careful on the labial aspect of the lower incisors.

Supplementary Injections

• Palatal infiltrations
• Lingual infiltrations
• Intrapapillary

Palatal Infiltration

• First, apply topical anesthetic/pressure on the area
• Infiltrate the palatal mucosa of the appropriate tooth
• Inject at 90 degrees to the mucosa, 1-1.5cm from the gingival margin, halfway between the gingival margin and midline of the palate
• It will be difficult due to considerable resistance
• Deposit 0.2 ml of solution
• This technique is used for deep restorations, subgingival PMPR (Professional Mechanical Plaque Removal), and extractions of deciduous maxillary dentition.

Intrapapillary Injection

• It is useful for achieving palatal analgesia in children and nervous patients
• Direct the needle at right angles to the interdental papilla
• Then insert the needle into the center of the papilla at the level of attachment to the periosteum
• Deposit 0.25ml of solution
• Check to ensure that the palatal mucosa has blanched

Inferior Dental Block (IDB)

• This is another type of local anesthesia

Innervation of the Mandible

• Includes the inferior dental/alveolar nerve, mylohyoid nerve, lingual nerve, long buccal nerve, and mental nerve.

Basic Anatomy of the Mandible

• Includes the condylar process, coronoid process, submandibular fossa, sublingual fossa, alveolar process, mental foramen, mental protuberance (chin), body, retromolar fossa, mandibular foramen, and ramus

Pterygomandibular Space

• It contains several important structures, like the parotid salivary gland, sphenomandibular ligament, medial pterygoid muscle, facial nerve, inferior alveolar nerve, lingual nerve, pterygomandibular raphe, medial surface of the ramus of the mandible, coronoid notch of the mandible, and masseter muscle.
• Facial nerve paralysis can result from depositing the anesthetic solution outside the pterygomandibular space into the deep lobe of the parotid gland, causing temporary facial palsy

IDB Technique

• The patient can be supine or upright; an upright position is recommended for patients with a large tongue or those who are obese
• Proper lighting is needed
• Topical analgesia can be used
• The patient's mouth needs to be wide to allow for visual of anatomical landmarks
• The operator will have to sit in an appropriate position relative to the patient.
• Select a needle that is long, 35 mm, and 27 gauge.
• Use a finger or thumb to locate the retromolar fossa and identify the pterygomandibular raphe
• Look for a 'crease' in the mucosa between the finger and thumb
• Position the barrel of the syringe over the contra-lateral premolars
• Identify the level for the mandibular foramen by bisecting the thumb/fingernail and drawing an imaginary line 1cm above the plane.
• Insert the needle slowly into the pterygomandibular space, aiming for the mandibular foramen
• Inject to a depth of 2.0-2.5 cm
• Do not insert the full needle; 5mm of needle must always be visible
• If mandibular bone is contacted, withdraw the needle 1 mm and aspirate

IDB Technique: Positive Aspiration

• If blood is present upon aspiration, withdraw the needle 1 or 2 mm
• Aspirate again, continue with injection if there is no blood
• If the aspiration is again positive, reposition and repeat aspiration

IDB Technique: Final Steps

• Make sure that the tip of the needle is not in a vein, then slowly deliver the anesthetic solution
• Withdraw the needle quickly and smoothly and re-sheath the needle to make it safe
• Sit the patient up for a rinse

IDB Effect

• An IDB makes the yellow area numb

Anatomical Variations and Troubleshooting the IDB

• If bone is struck too soon, withdraw, swing the needle toward the midline, advance for 7 mm, and swing back to the original position to proceed.
• An electric shock sensation in the tongue or lip means the lingual nerve or mandibular nerve, respectively, has been touched by the needle; withdraw 1-2mm from the mandibular nerve

Incisive and Mental Block

• Use this if you want anesthesia of several anterior teeth (incisors, canine, and first premolar)
• Aim for the mental foramen (between apices of first and second premolars)
• Bear in mind it may provide unreliable anaesthesia for the central incisor, and that it could potentially need a lingual infiltration

Incisive and Mental Block Procedure

• Check the position of the mental foramen on a radiograph, if one is available
• Patient needs to be ideally supine with good lighting
• Start with topical LA
• Ask the patient to open wide
• Unsheathe needle (30 gauge short)
• Place the tip of the needle in the reflection of the buccal sulcus between root apices of LL4 and LL5
• Aspirate - if not positive, slowly inject at least 1ml solution
• Withdraw the needle and re-sheath safely
• Articaine should not be be administered for IDBs or Incisive and Mental blocks

Needle Stick Injury: Before Contact with Patient

• There is no transfer of infection if the needle has not contacted the patient
• Double lock cover on needle
• Remove gloves, wash with soap, and dress wound if necessary
• Inform senior tutor on clinic
• Get a new syringe/needle/cartridge and holder
• Put on new gloves
• No additional reporting needs to happen

Needle Stick Injury: After Contact with Patient

• Potential transfer of infection from the patient to the operator
• Double lock cover on needle
• Take you gloves off and wash the wound under running water or rinse mucous membranes appropriately
• Report to senior tutor on clinic
• Check the medical history to confirm if they have known blood-borne viruses
• Contact Occupational Health or A&E (out of hours) for advice
• Take a patient blood sample
• Record in notes
• Then file a Datix incident report

Legal Framework

• LA is a Prescription Only Medicine (POM)
• To comply with the law, a written prescription for each specific agent is needed from a dentist prescriber. The Human Medicines Regulations (2012) applies here.
• A Patient Group Directive (PGD) gives a legal framework allowing registered health professionals, including dental hygienists and therapists, to administer specified medicines without a prescription
• An amendment to the Human Medicines Regulations from June 26 2024 now allows dental hygienists and therapists to supply and administer POMs under exemptions, without needing a prescription from a dentist or a PGD.
• They must undertake appropriate training to ensure competence to use this mechanism.
• Dental therapists and dental hygienists still cannot prescribe.
• A prescription for LA needs the type of LA, the route of administration, the dosage, and date to comply with the regulation.

Post-Operative Instructions

• Never leave a patient after an injection, as an adverse reaction can occur at any time including fainting and anaphylaxis

Instructions to patient

• Anesthesia duration lasts for a few hours
• The patient should avoid hot food/drinks in case they bite their lips and cheeks
• If they poke/prod the area, they must use their finger/tongue
• They shouldn't smoke for the duration of LA

Documentation of LA

• A dated, signed entry must be made on the patient's record every time LA is given. This should include the type of LA agent and vasoconstrictor, amount of solution administered, site of injection, any unusual effects, and post-operative instructions given orally. E.g. LA - 2ml lidocaine 2% with epinephrine 1: 80,000, buccal infiltration UL7, UL4, UL2. POIGV

Complications of LA

• Unwanted effects may occur due to injecting inappropriate solutions, injecting too much solution, or injecting into the wrong site and can be divided into local and general issues

Local Complications

• Failure to go numb
• Pain during injection can due to no topical LA, blunt needle, flaccid mucosa, injecting too fast, site of injection, injecting too much of the solution, injecting something too hot or cold, or psychological component from the patient.
• Bleeding into the tissues from a blood vessel puncture can cause hematoma is a local complication.
• Intravascular injection can cause systemic toxic effects or can cause failure of the anelgesia
• Skin blanching can be caused from vasospasm of the artery
• Bleeding at the point of injection stopping by itself.
• Other complications include infection, lip/soft tissue trauma, Trismus and visual disturbances.
• Serious complications include prolonged impairment of sensation and facial paralysis (IDB), needle breakage, post-anaesthetic reactivation of herpes simplex virus. 1 in 14,000 IDBs cause permanent injury

General Complications

• Psychogenic
• Toxicity of LA agent
• Overdose
• Reduced tolerance
• Intravascular adrenaline
• Allergy- anaphylaxis
• Drug interactions

Bleeding Risk

• ID blocks and lingual infiltrations may be contraindicated depending on the bleeding risk. The risk relates to the act of injection, not the LA agent. For example, patients with genetic bleeding disorders e.g. haemophilia or that are taking anticoagulants/ antiplatelet drugs e.g. warfarin, clopidogrel, alcoholics (reduced liver function) or patients with liver disease.

Failure of Anaesthesia

• This may be as a result of waiting too long, too little solution being used, intravascular injection, inaccurate placement of the needle point, anatomical variations, incorrect choice of technique, the patients fear of an anxiety, or from the poor storage of the local anesthesia
• Never inject into an area of inflammation/infection. Instead, inject mesial and distal to the area, and avoid overdosing and get advice.

Learn the aims of local anesthesia training for dental professionals. This covers safe delivery, oral anatomy, nerve supplies, and legal frameworks. Also covers GDC learning such as pain management and medicines.