Growth and Development, and Craniofacial Anomalies
What the exam tests
Growth questions ask you to separate chronological, dental and skeletal age, predict when a discrepancy will self-correct, and recognise syndromic patterns early. Craniofacial anomalies are tested through embryologic timing, syndrome recognition, and the dental consequences of clefting.
Core rules
- Growth follows cephalocaudal and proximodistal gradients; neural growth is nearly complete by 6-7 years, while somatic and mandibular growth continue into late adolescence (Scammon curves).
- The maxilla grows downward and forward by sutural growth and surface apposition; the mandible grows mainly by condylar cartilage, apposition/resorption and displacement.
- Leeway space is about 1.5 mm per side in the maxilla and 2.5 mm per side in the mandible; it explains why mixed-dentition crowding often improves.
- Cleft lip fusion occurs around 6-7 weeks and palatal fusion around 8-12 weeks; lip repair is done at 3-6 months (rule of 10s), palate repair at 9-18 months.
- Pierre Robin sequence is micrognathia, glossoptosis and a U-shaped cleft palate; Treacher Collins is mandibulofacial dysostosis with malar hypoplasia, coloboma and microtia.
Worked example
An 8-year-old with a repaired unilateral cleft lip and palate has a 4 mm anterior crossbite and a constricted maxilla. Reasoning: scarred palatal tissue restricts transverse growth, so the maxilla is the deficient jaw. Treat with orthopaedic expansion (fan-type appliance, quad helix or RPE) and plan alveolar bone grafting at 8-11 years, before canine eruption. A mandibular setback would treat the wrong jaw.
Traps
Confusing leeway space with E-space; assuming a Class III in a cleft child is mandibular excess; repairing the palate too early and increasing midface hypoplasia; forgetting hearing and speech follow-up.