23.2 Management of Class I, Class II, Class III and Skeletal Problems
Key Takeaways
Functional appliances such as the Twin Block or Herbst work best during the pubertal growth spurt, and their effects in Class II division 1 are mostly dentoalveolar with a modest skeletal change.
Early treatment of a large overjet can reduce the risk of incisor trauma, but it gives no lasting skeletal advantage over treatment started in adolescence.
A pseudo-Class III patient can bring the incisors edge-to-edge in centric relation because of a functional forward shift, and is corrected early by proclining the maxillary incisors.
Maxillary protraction with a facemask, often combined with rapid maxillary expansion, is most effective before about 10 years of age in Class III with maxillary deficiency.
Rapid maxillary expansion separates the midpalatal suture in growing patients, while skeletally mature adults need surgically or miniscrew-assisted expansion.
The blueprint lists Class I, Class II, Class III and skeletal problems separately. The questions mostly test timing and the choice between growth modification, camouflage and surgery.
Growth Timing
- The pubertal growth spurt comes about 2 years earlier in girls (around 11-12 years) than in boys (around 13-14 years).
- Skeletal maturity is assessed with the cervical vertebral maturation (CVM) stages on the lateral cephalogram or with hand-wrist radiographs (ossification of the adductor sesamoid precedes the peak).
- Growth modification must be timed to the peak; surgery waits for the end of growth (later in boys and in Class III).
Class I Problems
Class I molar relationship with dental problems: crowding, spacing, bimaxillary protrusion, crossbites, open or deep bite, displaced or impacted teeth. Treatment is usually dental (alignment with or without extractions or interproximal reduction).
Class II Division 1
Features: increased overjet, often a retrusive mandible, lip incompetence, lower lip trap; higher risk of incisor trauma.
| Approach | Details |
|---|---|
| Functional appliances | Twin Block (removable), Herbst (fixed), activator, Frankel; posture the mandible forward; best at the pubertal growth spurt; effects mostly dentoalveolar (retroclined upper incisors, proclined lower incisors) with a modest increase in mandibular length |
| Headgear | Restrains maxillary growth and distalizes molars; cervical pull extrudes molars and suits low-angle cases; high pull limits vertical growth and suits high-angle cases; worn about 12-14 hours a day; needs safety release and facebow locking to prevent eye injuries |
| Camouflage | Extract maxillary first premolars (finish in Class II molars and Class I canines) or upper and lower premolars; Class II elastics (maxillary canine to mandibular molar), which extrude lower molars and procline lower incisors |
| Surgery | Mandibular advancement (BSSO) after growth for severe discrepancies |
Early (two-phase) treatment for a large overjet can lower the incidence of incisal trauma, but it gives no lasting skeletal benefit compared with one course in adolescence (Cochrane review evidence).
Class II Division 2
Features: retroclined maxillary central incisors, often proclined laterals, deep (sometimes complete) overbite, low-angle face, strong lip musculature, high lower lip line.
Treatment: procline the retroclined incisors (converting to division 1), then correct the Class II; reduce the deep bite by intrusion of incisors or eruption of posterior teeth; long-term retention because deep bites tend to relapse. Gingival trauma from a traumatic overbite may need early intervention.
Class III
Pseudo-Class III: the patient can reach an edge-to-edge incisor contact in centric relation, then shifts forward; skeletal pattern near normal. Treat early by proclining the maxillary incisors (removable appliance with springs or a 2x4 fixed appliance).
True skeletal Class III:
| Approach | Details |
|---|---|
| Facemask (reverse headgear) maxillary protraction | For maxillary deficiency; most effective before about 10 years; often with rapid maxillary expansion to loosen circummaxillary sutures; forward and downward force worn about 12-14 hours daily |
| Bone-anchored maxillary protraction | Class III elastics to miniplates in older children (around 11 years and above) |
| Chin cup | Limited ability to restrain mandibular growth; mainly rotates the mandible downward and backward |
| Camouflage | Procline upper incisors and retrocline lower incisors (sometimes lower premolar extractions, Class III elastics); suitable for mild to moderate discrepancies with acceptable profile |
| Orthognathic surgery | Maxillary advancement (Le Fort I), mandibular setback (BSSO) or both, after growth stops; mandibular growth in Class III males may continue into the late teens or beyond |
Class III growth is unpredictable: repeated cephalograms or hand-wrist films are used to confirm the end of growth before surgery, and parents should know that early correction may relapse with late mandibular growth.
Vertical Problems
| Problem | Features | Management |
|---|---|---|
| Anterior open bite | Dental (habit) or skeletal (long lower face, high angle) | Stop habits (habit-breaker appliances), avoid extruding molars, TAD-supported molar intrusion, or Le Fort I impaction in adults |
| Deep bite | Low angle, Class II division 2 | Incisor intrusion, leveling the curve of Spee, bite planes; retention |
Transverse Problems
- Unilateral posterior crossbite with a mandibular shift: usually a bilateral maxillary constriction; correct early with expansion to remove the shift.
- Rapid maxillary expansion (Hyrax, Haas) separates the midpalatal suture; a midline diastema opens temporarily. The suture becomes interdigitated with age, so late adolescents and adults need miniscrew-assisted (MARPE) or surgically assisted (SARPE) expansion.
- Slow expansion (quad helix, W-arch) suits younger children and more dentoalveolar change.
Camouflage or Surgery?
Camouflage moves teeth to hide a skeletal discrepancy and suits mild to moderate problems with a good profile. Surgery is chosen for severe discrepancies, poor facial esthetics, or when camouflage would need excessive tooth movement beyond the alveolar bone. Pre-surgical orthodontics decompensates the incisors, which temporarily worsens the bite and profile.
Exam Traps
- Class II elastics extrude lower molars and procline lower incisors.
- Facemask therapy works best in young children with maxillary deficiency, not adults with mandibular prognathism.
- A child who reaches edge-to-edge in centric relation has pseudo-Class III.
A 12-year-old boy with a skeletal Class II division 1 malocclusion, an overjet of 10 mm and a retrusive mandible is entering his pubertal growth spurt. Which treatment is most appropriate now?
Waiting until age 20 and then planning a mandibular advancement
A functional appliance such as a Twin Block to take advantage of growth
A chin cup to restrain mandibular growth during the growth spurt
Extraction of mandibular first premolars to reduce the overjet fully
An 8-year-old has an anterior crossbite of tooth 21. In centric relation the incisors meet edge to edge, then the mandible slides forward into the crossbite. The skeletal pattern is close to Class I. What is the best management?
Extract tooth 21 and replace it with an implant after growth is complete
Begin chin cup therapy to restrain mandibular growth for several years
Wait for the end of growth and plan orthognathic mandibular setback surgery
Procline tooth 21 with a removable appliance or a 2x4 fixed appliance now
A 25-year-old with a bilateral posterior crossbite caused by a narrow maxilla wants it corrected. Why is a conventional tooth-borne rapid maxillary expander likely to fail?
The adult suture is interdigitated, so skeletal anchorage or surgery is needed
Rapid expansion works only in the mandible, which has a midline suture throughout life
Adults lack a midpalatal suture altogether, so expansion of the maxilla is impossible
Adults have too few teeth to anchor any expander, so all crossbites must be accepted
Sections you finish are checked off in the contents.