Local Anesthetics: Oral Anatomy and Nerve Supplies

Local Anaesthetics Theory - Part 2

• Learning Outcomes:
  • Describe relevant dental, oral, craniofacial, and general anatomy, and explain application to patient management
  • Describe relevant physiology and explain its application to patient management
  • Describe properties of relevant medications and therapeutic agents, and discuss their application to patient management
  • Manage patient anxiety and pain through effective communication, reassurance, and relevant behavioural techniques
  • Manage patient pain through appropriate analgesia use

Aims and Objectives

• Deliver safe and effective local anesthesia to patients
• Describe and identify related oral anatomy and nerve supplies
• Relate how to safely deliver infiltrations and IDBs
• Investigate the legal framework for LA delivery in dentistry
• Highlight potential complications of LA delivery

Nerve Supply

• The trigeminal nerve is the primary nerve responsible for oral sensation.
• Branches include ophthalmic (V1), maxillary (V2), and mandibular (V3)
• Key nerves include:
  • Ophthalmic branch (V1)
  • Maxillary branch (V2)
  • Mandibular branch (V3)
  • Superior alveolar nerve
  • Lingual nerve
  • Inferior alveolar nerve

Patient Preparation

• Legal: Valid prescription, any contraindications, medical history (medication use, previous reactions to LA, presence of food), and vaso-vagal attack prevention
• Patient: History of food intake (recent eating), management of LA anxiety/phobia, distractions, calm atmosphere, accurate explanation, language appropriate to patient
• Operator: Operator visibility, necessary LA equipment positioning

What can affect the patient's pain threshold?

• Anxiety
• Psychological makeup
• Previous experience
• Culture
• Age
• Physical environment
• Emotional state

Approaches to pain management

• Gate Control Theory: The theory postulates there exists a gate in the spinal cord that regulates the transmission of pain signals to the brain. Using techniques such as calm atmosphere, distraction, and hypnosis can potentially influence this "gate" to reduce pain perception.

• Distraction: Shifting attention away from pain through different techniques like conversation or tasks serves as a distraction technique

Infiltrations

• Infiltrative technique steps:
  • Estimate position of tooth apex
  • Pull mucosa taut
  • Insert needle through mucosa at 25 degrees to the bone
  • Aim for tooth apex
  • Keep needle parallel to long axis of tooth
  • Smoothly allow needle to glide through taut mucosa
  • Avoid contacting bone, if contacted, withdraw 1-2 mm
  • Aspirate, especially if injecting around upper second/third molars
  • Check cartridge
  • Deliver solution gently and low
  • Minimal pressure

Additional Considerations (Buccal Infiltration)

• Volume: 0.5–1 mL for perio work, 2.2 mL for restorations
• Timing: Pulpal analgesia within 2–5 minutes, soft tissue analgesia within 1–2 minutes
• Specific areas: Labial aspect of upper incisors is very sensitive, so inject very slowly; and take care when injecting labial aspect of lower incisors relating to attachment of mentalis and depressor muscles

Palatal Infiltration

• Application/pressure on the area first
• Inject at 90 degrees to mucosa
• Inject about 1-1.5 cm from gingival margin halfway between gingival margin and palate midline.
• Needs considerable resistance during insertion
• Deposit 0.2 mL of solution
• Used for: Deep restorations, Subgingival PMPR (Professional Mechanical Plaque Removal), extractions of deciduous maxilla

Intrapapillary Injection

• Direct needle at right angles to interdental papilla
• Insert needle into papilla at level of attachment to periosteum
• Deposit 0.25 mL of solution
• Check palatal mucosa to identify if numbed

Inferior Dental Block (IDB)

• Technique Steps:
  • Have patient positioned supine or upright
  • Use good lighting
  • Topical anesthetic is ideal (if used)
  • Use a 35 mm, 27 gauge needle
  • Locate retromolar fossa and pterygomandibular raphe
  • Position barrel of syringe over contralateral premolars
  • Identify correct level for mandibular foramen using thumb/fingernail and an imaginary line 1cm above the occlusal plane
  • Insert needle smoothly into pterygomandibular space, aiming for mandibular foramen
  • Inject to a depth 2.0 - 2.5 cm
  • Don´t inject the complete needle - leave 5mm of needle visible
  • If bone is contacted, withdraw 1 mm of needle and aspirate.
  • Deliver anesthetic slowly.
  • Remove needle, and re-sheath.
  • Have the patient up/rinse

Incisive and Mental Block

• Procedure -Check position of mental foramen on radiograph -Ideally patient should be supine, good lighting. -Apply topical LA -Patient opens wide -Unsheathe the needle (30 gauge) -Place needle tip in buccal sulcus between LL4 and LL5 root apices. -Aspirate and if not positive - slowly inject at least 1mL solution -Withdraw needle, re-sheath safely

Post-Operative Instructions

• Duration of anesthesia is usually a few hours
• Avoid hot food/drinks, biting lips, cheeks, touching affected area with fingers or tongue during healing
• Avoid smoking for the duration of anesthesia

Documentation of LA

• Every instance where LA is given, a dated signed entry must be made on the patient's record:
• Type of LA agent and vasoconstrictor
• Amount of solution administered
• Site of injection
• Any unusual effects
• Post-operative instructions

Complications of Local Anaesthesia

• Local Complications:
  • Failure to go numb
  • Prolonged impairment of sensation
  • Facial paralysis
  • Needle breakage
  • Post-anesthetic reactivation of herpes simplex virus
• 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 or used with caution depending on bleeding risk
  • Risk relates to the act of injection, not the LA agent: Patients with genetic bleeding disorders like hemophilia, and those taking anticoagulants or antiplatelet drugs (e.g., warfarin, clopidogrel); alcoholics (reduced liver function), patients with liver disease

Failure of Anaesthesia

• Too long a delay before treatment commencement
• Too little solution administered
• Intravascular injection (aspirate)
• Inaccurate placement of needle point (IDBs)
• Anatomical variations
• Incorrect technique
• Anxiety/fear
• Poor storage of LA (too hot/in sunlight)

Presence of Infection

• Never inject LA into area of infection/inflammation.
• Inject mesial or distal to affected area.

If LA Fails

• Don't overdose, get advice

Legal Framework

• LA is prescription only medicine
• Needs a written prescription from a recognized prescriber (dentist)
• Patient group directive (PGD) gives legal framework for health professionals (including Dental Hygienists and therapists to administer specified medications without prescription

Summary of Today's Topics

• Described and identified related oral anatomy and nerve supplies
• Understand how to safely deliver infiltrations and IDBs
• Investigated the legal framework for LA delivery in dentistry
• Highlighted the potential complications of LA delivery

Learn about the trigeminal nerve and its role in oral sensation. Understand safe delivery of infiltrations and IDBs. Explore the legal framework and potential complications of local anesthesia in dentistry.