Orthodontics and Pediatric Dentistry: Growth & Development, Malocclusion, Child Oral Health
This domain tests growth and development, cephalometric and space diagnosis, appliance logic, and child-specific care including caries and behaviour management.
Growth and diagnosis
- Cephalometric norms: SNA about 82°, SNB about 80°, ANB 2–4°; ANB above 4° suggests skeletal Class II, below 0° skeletal Class III.
- Cervical vertebral maturation stages estimate the pubertal growth spurt - girls peak around 11–12 years, boys around 13–14.
- Angle classification uses the first molars (mesiobuccal cusp in the buccal groove = Class I), then canines.
Space analysis
- Leeway space is about 3 mm in the maxilla (1.5 per side) and 4.5 mm in the mandible (2.5 per side).
- Incisor liability: permanent incisors are larger than primary incisors, and the difference is met by intercanine growth.
- Moyers' probability tables predict combined canine and premolar width from lower incisor width.
Pediatric care
First primary tooth erupts at 6–8 months, mandibular central incisor first; the first permanent molar erupts at about 6 years. Early childhood caries follows prolonged bottle or night feeding. Pulpotomy (formocresol or MTA), stainless steel crowns and band-and-loop space maintainers are core procedures. Behaviour management relies on tell-show-do and modelling rather than restraint.
Worked example
A 9-year-old has 3 mm of mandibular anterior crowding. Mixed-dentition analysis shows 4.5 mm of mandibular leeway space plus normal intercanine growth will accommodate the erupting canines. The crowding falls within anticipated space gain, so the correct plan is observation while preserving the primary molars as space maintainers - not extraction.
Traps
Using chronological age as the only growth indicator; extracting primary canines prematurely; classifying malocclusion from canines alone; treating early childhood caries as ordinary caries and missing the feeding habit.