Orthodontics and Pediatric Dentistry
What this domain tests
Expect questions on normal occlusal development, space analysis in the mixed dentition, interceptive measures, and the management of caries and trauma in children.
Core rules
- Angle classification is based on the first permanent molar relationship: Class I, Class II (division 1 or 2), Class III. Skeletal pattern is assessed cephalometrically with SNA, SNB and ANB.
- The primary dentition normally has primate spaces and a flush terminal plane; the leeway space (about 1.5 mm per side in the mandible, 0.9 mm in the maxilla) helps the permanent molars reach Class I.
- Mixed dentition space analysis uses Moyers' probability tables or the Tanaka–Johnston prediction from the lower incisors.
- Space maintenance after premature primary tooth loss: band and loop for a single posterior tooth, Nance or lingual arch for multiple losses, and a distal shoe for an unerupted first permanent molar.
- Primary tooth pulp therapy: pulpotomy with MTA, ferric sulfate or formocresol for a vital crown with no radicular disease; pulpectomy with a resorbable paste when the radicular pulp is involved.
- Avulsed permanent tooth: handle by the crown, rinse, replant immediately if clean, otherwise store in milk or saline, splint flexibly for about two weeks and refer for root canal treatment. Do not replant a primary tooth.
- Intruded primary tooth: if the apex is displaced toward the permanent germ, extract or allow spontaneous re-eruption with radiographic monitoring.
Worked example
An 8-year-old falls and the upper right central incisor is avulsed; the tooth has been dry for 40 minutes. Reasoning: this is a permanent tooth, so replantation is still considered after rinsing with saline. Splint flexibly, check tetanus status, prescribe appropriate analgesia, and arrange endodontic review because a delayed replantation carries a high risk of inflammatory resorption.
Traps
Replanting a primary tooth; extracting an intruded primary incisor without checking the direction of displacement; using adult local anaesthetic doses in children; forgetting the leeway space when judging crowding.