Dental Anesthesia Concepts

• LA Theory
• Analgesia is the loss of pain sensation, but other forms of sensibility are still intact.
• Anesthesia involves the loss of all forms of sensation, including pain, touch, and pressure.
• Individual reactions to the same stimulus can vary among different people.
• The same patient may also react differently to the same stimulus at different times.

Nerve Impulse/Action Potential

• Electrical impulses are created by nerve cells.
• Impulses travel in one direction only.
• Nerves can only send one message at a single speed, but their frequency or number of pulses can differ.
• Ion channels in the axon are voltage-gated.
• Depolarization at one axon segment causes nearby ion channels to open.
• Action potential spreads along the axon as a 'wave' of depolarization.
• Resting neurons have high sodium (Na+) levels in the extracellular fluid.
• Resting neurons have high potassium (K+) levels in the intracellular fluid.
• The process starts with a resting neuron or nerve cell and is followed by an excitatory stimulus.
• Sodium channels open next followed by sodium ions which enter the neuron from extracellular fluid, leading to depolarization and triggering action potential.
• Subsequently, potassium channels open and potassium leaves the neuron resulting in a recharging phase known as repolarization which brings the neuron back into its resting state.

Blocking Nerve Conduction

• Local anesthetic (LA) agents function by blocking the transmission of impulses in sensory nerves.
• The aim of dental treatment is to contain active disease and prevent its recurrence.
• LA agents work by binding to specific receptors in sodium channels, thus blocking the inward passage of sodium ions during impulse conduction.
• They also cause non-specific expansion of nerve cell membranes, causing physical obstruction of the (Na+) channels.
• Agents diffuse through the lipid membrane of nerve fibers.
• Ideal LA is effective and reversible, non-irritating, capable of sterilization, has an adequate shelf life, is isotonic, allows for a combination with a vasoconstrictor, provides adequate working time, and is highly safe.
• An analgesic agent blocks nerve conduction and examples include Lidocaine, Prilocaine, Articaine, and Mepivacaine.
• A vasoconstrictor increases the depth and duration of analgesia and examples include Epinephrine/adrenaline and Felypressin.
• A reducing agent is used to prevent the oxidation of the vasoconstrictor, such as Sodium metabisulphite.
• A vehicle carries the other agents and ensures the solution is isotonic with sterile saline.

Local Anesthetics

• Lignospan 2% with epinephrine 1:80,000 is the gold standard for dental procedures due to its effectiveness, rapid onset, suitability for pulpal and soft tissue analgesia and low toxicity.
• Scandonest 2% with epinephrine 1:100,000 and Scandonest 3% plain (no vasoconstrictor) shares similar properties with prilocaine, but has shorter analgesia if used as infiltration.
• It should not be used on pregnant women or children under 4.
• Citanest 3% with octapressin and Citanest 4% plain (no vasoconstrictor) has a shorter duration of action than lidocaine, is less potent and rapidly dispersed and cleared with very low incidence of side effects.
• Septanest 4% Articaine hydrochloride with epinephrine 1:100,000 and Septanest 4% Articaine hydrochloride with epinephrine 1:200,000.
• Articaine is a powerful, rapid onset local anesthetic suitable for longer soft tissue analgesia.
• It is rapidly metabolized in plasma and should not be used as an inferior dental block.
• Exercise caution with patients who are pregnant and breastfeeding. Xylonor gel, a 5% lidocaine topical gel should be applied with a cotton wool roll on mucosa prior to injections.
• Epinephrine/adrenaline increases depth and duration of anesthesia, occurs naturally in the body and controls haemorrhage.

Systemic Effects of LA

• LA is not easily absorbed through intact skin.
• When applied to mucous membranes, it is absorbed into the bloodstream allowing for distribution, metabolism, and elimination.
• LA has reversible blockage of conduction in nerve endings, smooth muscle relaxation, myocardial depression and depresses the central nervous system.
• Absorption causes the LA action to wear off and depends on the anesthetic, dose/concentration, tissue vascularity and presence/absence of a vasoconstrictor as well as accidental intravascular injection.
• Most LA agents get metabolized in the liver and are excreted in the urine with decreased liver and kidney function, requiring less agent for safety.
• Signs of toxicity are tingling and numbness of lips, visual and hearing disturbances, mood changes, light headedness/dizziness, increased respiration rate, drowsiness, convulsions and/or cardiac and respiratory arrest.
• A strategy for reducing systemic toxicity is avoiding intravascular injection by aspirating slowly with the use of safe doses.
• Choosing less toxic drugs and using vasoconstrictors also contributes to a strategy for reducing systemic toxicity.

Contraindications and Cautions of LA

• Lidocaine is contraindicated in patients with hypersensitivity and heart palpitations and should be used with caution in patients taking beta blockers (Propanolol).
• Mepivacaine is contraindicated in patients with hypersensitivity, during pregnancy and in children under the age of 4 and breastfeeding and should also be used with caution in patients taking beta-blockers (Propanolol).
• Articaine is contraindicated for use by children under the age of 4 and with plasma cholinesterase deficiency.
• Use should be avoided for inferior dental (ID) blocks.
• it should be used with caution during pregnancy and breastfeeding and in patients who are taking Beta-blockers (Propanolol). Prilocaine is used with caution in patients who take sulphonamides or beta-blockers (Propanolol). Limit usage to 2 x 2.2ml cartridges per day, but for renal failure/dialysis/liver failure to 1 x 2.2ml cartridge per day.
• Consultation with a GP may be needed when dealing with LA administrations.
• Epinephrine/adrenaline is contraindicated in patients with cocaine use within the last 24 hours and must be used with caution in patients taking tricyclic or mono-amine oxidase inhibitors, Beta-blockers, calcium-channel blockers, diuretics or those with cardiac conditions, hypertension, circulatory problems and previous strokes.
• Extra short needles (30G 10mm), short needles (30G 25mm) and long needles (27G 35mm).

Patient Preparation

• Prior to administering, ensure you obtain a valid legal prescription.
• Check the patient's medical history to identify contraindications and previous adverse reactions to local anesthetics.
• Ensure the patient ate food prior as well as explaining procedure to reduce discomfort.
• Help reduce anxiety by using distraction techniques and maintaining a calm atmosphere.
• Positioning of both patient and equipment for visibility is also an important consideration.
• Consider anxieties, previous experience, culture, age, emotional state and psychological makeup as well as environmental factors.

Positioning and Application of Topical

• Ensure they are supine, comfortable, and well-supported.
• The dentist should position the patient at a proper/correct height.
• Light should be directed into the sulcus area to ensure clear visibility.
• To apply topical, dry the mucosa, apply cotton wood roll and leave in place for 2-3 minutes.
• Molars are posterior 6-8 (Not MB root 6's).
• Premolars and 1st molar MB root get Anterior 3-3.

Buccal Infiltration

• You should estimate the position of the apex of the tooth as well as pulling the mucosa taut.
• When inserting, use a short needle through the mucosa at a 25 degree angle as well as checking that the bevel indicator faces the bone.
• You should aim for the apex of the tooth and keep it parallel to the long axis of the tooth and bone.
• Check that you can smoothly glide through Taught mucosa.
• Avoid contating the bone, as well as aspirating and checking the cartridge.
• Deliver the anesthetic gently and slowly.
• Withdraw needle at safe range, and wait.
• Perio work requires 0.5 - 1 ml per site, restoration 2.2ml at site.
• Soft tissue is achieved in 1 - 2mins and pulpal is achieved in 2 - 5mins.

Palatal Infiltration and Intrapapillary Injection

• Palatal infiltration requires topical application and pressure on area first.
• Infiltrated in the palatal mucosa of the tooth.
• Short needled inject at 90 degrees towards the mucosa, in the gingival margin.
• Apply 0.2 ml of solution, with considerable resistance.
• For deep restoration and extraction, it is effective to apply sub gingival injection as well as in intrapapillary to get to interdental papilla.
• At right angles, insert at center of papilla at level of attachment to preiosteum.

Maxillary & Palatine Nerve Overview

• Anterior superior alveolar covers anterior incisors and canines.
• Middle superior alveolar covers pre-molars and 1st molar MB root.
• Posterior superior alveolar covers upper molars (not MB Root 1st Molar).
• Nasopalatine nerve reaches anterior incisors and canines gingivae.
• The nasopalatine foramen is behind incisors.
• Greater palatine nerve covers Palatal gingiva in pre molars and molars.
• The greater palatine foramen is posterior to 2nd molar.

Inferior Dental Block (IDB)

• When performing IDB, it is best to check that the patient mouth is wide open as well as locating retromolar fossa.
• Try and identify the position of raphe and palpate outer oblique ridge.
• Check outer crease between thumb and position syringe barrel.
• To inject the depth must be 2-2.5cm, and should enter smoothly after the insertion.
• Then inject into the prelygomandibular - be slow, and remove needle quickly.
• Withdraw if it goes midline, swing needle round to midline.
• Electric shock sensation in tongue/lip means that the nerve has been touched.
• It is critical if inserting Articaine for IDB incisions on other major blocks.
• It's important to always have aspirate when perfoming the block.

Incisive and Metal Block Technique

• Position patient to be inline to be supping and use topic anesthetic with 30 short needle.
• May be unreliable and will require lingual info at the very least.
• Useful for bilateral anesthesia, can administer solution with some anterior. However, if going to deep, blocks the facial. In lingual goes to inferior.
• The inferior/metal nerve controls branches, incisions, cavines as well as gingivae.
• Anesthesia causes too deep in location.

Cautions

• Maxillary incisors have sensitive areas which are located labial.
• You can also find sensitive labial areas in mandibular.

Legal Frame Work

• You should keep everything legal.
• This includes prescriptions, a note of the amount, how you inject the drug, which areas that are in affect.
• Reactions can occur, due to patient being allergic and have long term effects.
• One should never inject in wrong area, with an inappropriate solution or too much solution.
• Duration, smoke (harm to tissue), avoid heat + poking.
• Always write anything down.
• Some complications is infections, sensation damage and failure to go numb.