# Local Anaesthesia in Paediatric Dentistry > Local anaesthesia in children — BDS Pedodontics notes on weight-based maximum doses, cartridge arithmetic, agent selection, topicals and complications. - Canonical URL: https://prepelephant.com/topics/bds/pedodontics/local-anaesthesia-pedo - Exam / course: BDS · Subject: Pedodontics - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Local Anaesthesia in Paediatric Dentistry", PrepElephant, https://prepelephant.com/topics/bds/pedodontics/local-anaesthesia-pedo ## Direct answer Paediatric local anaesthesia is arithmetic before it is technique: the maximum safe dose scales with weight, not with fear — lidocaine 4.4 mg/kg plain and 7 mg/kg with epinephrine, and a 2 per cent cartridge of 1.8 mL carries 36 mg, so a 20 kg child tops out near four cartridges with epinephrine and barely two without. The default agent is 2 per cent lidocaine with 1:100,000 epinephrine; 3 per cent mepivacaine plain serves short procedures where epinephrine is avoided; articaine 4 per cent is generally not recommended below four years; prilocaine is avoided in infants for methaemoglobinaemia risk. Topical anaesthesia on dried mucosa, a 27-gauge short needle, slow deposition and aspiration are the technique constants, and the commonest complication — the anaesthetised child biting a numb lip — is prevented with words, not drugs. ## What you must remember - **Maximum doses:** lidocaine 4.4 mg/kg plain and 7.0 mg/kg with epinephrine; mepivacaine similar; bupivacaine's long soft-tissue anaesthesia makes it a poor paediatric choice; prilocaine risks methaemoglobinaemia in the very young. - **Cartridge arithmetic:** per cent times 10 gives mg per mL — 2% lidocaine = 36 mg per 1.8 mL cartridge, 3% mepivacaine = 54 mg, 4% articaine = 72 mg; a 15 kg child with epinephrine tolerates about 105 mg, roughly two and a half cartridges, calculated before the syringe is loaded. - **Age rules:** articaine is generally avoided below four years; benzocaine topical is avoided under two years (FDA methaemoglobinaemia warning), making 5 per cent lidocaine gel the paediatric topical. - **Topical discipline:** dry the mucosa, apply for at least one to two minutes, and use euphemisms ("tooth jelly") — pain on injection is the single most fear-generating stimulus in child dentistry. - **Technique constants:** 27-gauge short needle, slow deposition (about a minute per cartridge), aspiration, and the mandibular foramen sitting relatively lower and nearer the occlusal plane in young children, so the inferior alveolar needle aims lower than the adult landmark. - **Buccal infiltration works in young bone:** maxillary teeth and even mandibular primary molars in preschoolers can be managed by infiltration through porous cortical plate; the inferior alveolar block is reserved for mandibular permanent molars and longer procedures. - **Complications:** soft-tissue self-injury (lip and cheek biting) is the most common — warn the caregiver; haematoma after posterior injections; transient facial nerve palsy from deposition near the parotid; needle breakage, guarded by never bending the needle and never burying it to the hub. ## Working the numbers at the chair A four-year-old weighing 15 kg needs two quadrants under 2 per cent lidocaine with epinephrine. Seven mg per kilogram sets the ceiling at 105 mg; at 36 mg a cartridge, that is two cartridges and change — two safe cartridges for the session. Mandibular work is planned around infiltration plus perhaps one inferior alveolar block, not bilateral blocks, which multiply both dose and the self-injury surface; if the plan needs more anaesthesia than weight allows, the answer is staging or pharmacological support — never thinning the margin. The same arithmetic disciplines agent choice: the same child with a cardiac history gets plain 3 per cent mepivacaine for a short procedure — 4.4 mg/kg is 66 mg, barely one cartridge, so the procedure is chosen to fit the dose. Aftercare closes the loop: the mother is shown the numb lip, told it lasts one to two hours, and asked to keep the child from chewing it. ## Where marks are lost MCQs harvest the numbers directly: milligrams per cartridge, maximum mg/kg for each agent, the articaine age cut-off, and the most common complication — soft-tissue trauma from the numb lip. The dose-calculation viva presents a weight and expects the cartridge count out loud. Two traps recur: the "half cartridge for children" folklore, defeated by weight-based arithmetic, and landmark transfer from adults, defeated by the child's lower mandibular foramen. Indian exam conventions add "lignocaine" spelling and the final-year practical where the external asks — "how many cartridges will you give this child, and why?" — expecting the multiplication on the spot. ## Frequently asked questions ### What is the maximum safe dose of lidocaine in a child? 4.4 mg/kg plain or 7 mg/kg with epinephrine — about 36 mg per 1.8 mL cartridge of 2 per cent solution. ### How many cartridges can a 15 kg child receive? With epinephrine, roughly two cartridges (ceiling about 105 mg at 7 mg/kg); plain, barely one — calculated before injecting. ### Why are benzocaine gels avoided in children under two? Benzocaine can induce methaemoglobinaemia in infants and toddlers, prompting an FDA warning; 5 per cent lidocaine topical is the safer choice. ### What is the most common complication of dental local anaesthesia in children? Soft-tissue self-injury — biting the numb lip or cheek — prevented by pre-emptive warning, a cotton roll and supervised discharge. ### Why is articaine restricted in young children? Regulatory labelling and safety data generally restrict 4 per cent articaine to children aged four years and above, favouring lidocaine below that age.