Orthodontics and Interceptive Orthopedics
What the exam tests
Interceptive questions ask whether you should maintain, regain or refer, and when.
Core rules
- Space maintenance: band-and-loop or SSC-and-loop for single primary molar loss; Nance or lingual arch for multiple losses. Place soon after loss, before drift.
- Space regain: mild crowding can be regained; severe crowding needs extraction or serial extraction planning.
- Habits: pacifier or digit sucking needs a palatal crib if it persists beyond 4 years and affects occlusion; reassure below that age.
- Crossbite: a single anterior tooth can be corrected with a removable appliance or 2x4; posterior crossbite needs expansion with a quad helix or RPE.
- Class II: functional appliance (Twin Block) or headgear in a growing child; Class III: face mask with RPE before 10 years.
- AAO first orthodontic examination at age 7; ectopic first molar and infraoccluded primary molar need early referral.
Worked example
A 7-year-old loses the mandibular second primary molar early and the first permanent molar drifts mesially 2 mm. Reasoning: this is space loss with drift, so space maintenance alone is insufficient; regain space first or refer, then place a lingual arch. A band-and-loop would lock in the loss.
Traps
Placing a space maintainer after the space has closed; extracting a primary canine too early for crowding; using headgear in a non-compliant child; ignoring an ankylosed primary molar.