Orthodontics and Pediatric Dentistry
This domain spans growth and development, occlusal classification, simple biomechanics, and the behavioural and restorative management of children. Pediatric doses and eruption timing appear frequently because they are objectively checkable.
Growth, eruption and space
- Primary teeth erupt from about 6 months; the first permanent molar at 6 years, mandibular central incisors at 6-7, premolars at 10-12, second molars at 12.
- Leeway space in the mandible and primate spaces in the primary arch are normal and must not be misread as pathology.
- Mixed dentition space analysis uses tables such as Moyer's; arch length discrepancy determines whether space maintenance, serial extraction or expansion is needed.
- Peak mandibular growth can be gauged from cervical vertebral maturation on a lateral cephalogram.
Diagnosis and biomechanics
- Angle Class I, II and III describe the first molar relationship; cephalometric norms approximate SNA 82 degrees, SNB 80 degrees and ANB 2 degrees.
- Light continuous force moves teeth biologically; anchorage control, friction and force direction determine the side effects more than force magnitude alone.
- Fixed retention or a removable retainer is required after treatment because relapse from PDL and gingival fibre reorganisation is predictable.
Child behaviour and local anaesthesia
- Frankl scale rates cooperative behaviour; tell-show-do, positive reinforcement and, when indicated, nitrous oxide form the first-line approach.
- Maximum local anaesthetic doses: lidocaine 4.4 mg/kg (maximum 300 mg), mepivacaine 4.4 mg/kg, articaine 7 mg/kg (maximum 500 mg). Calculate by weight, not by age.
Pediatric restorative and trauma care
- Caries risk assessment drives prevention: fluoride varnish, diet advice, and silver diamine fluoride for arresting cavitated lesions.
- Pulpotomy with a calcium silicate or formocresol, or pulpectomy with a resorbable paste, preserves primary teeth until exfoliation.
- Avulsed primary teeth are never replanted because of the risk to the developing permanent germ; intruded primary teeth are usually allowed to re-erupt if not displaced into the follicle.
Worked example
A 20 kg four-year-old needs a mandibular primary molar restored under local anaesthesia. Lidocaine 2% with 1:100,000 epinephrine contains 20 mg/mL, and the limit is 4.4 mg/kg = 88 mg, that is 4.4 mL. A single cartridge of 1.8 mL is well inside the limit, but the volume must still be calculated rather than assumed.
Traps
- Replanting an avulsed primary tooth.
- Dosing local anaesthetic by age rather than weight.
- Treating leeway space as crowding.