19.2 Malocclusion Classification & Treatment Planning
Key Takeaways
- Angle Class I/II/III describe molar (and conceptually canine) sagittal relationships; subdivisions and skeletal vs dental components must be separated for planning.
- Crowding and spacing are arch-length problems; treatment options include expansion, interproximal reduction, distalization, extraction, or accepting compromise based on profile and stability.
- Crossbites may be dental or skeletal, anterior or posterior, with or without functional shift—early correction of shifting crossbites protects asymmetric growth patterns.
- Open bite may be dental (habits, eruption) or skeletal (vertical growth); etiology drives habit cessation, intrusion/extrusion mechanics, or later surgical options.
- Extraction vs nonextraction is a profile-, space-, and anchorage-based decision, not a universal rule that ‘crowding always means premolar extraction.’
19.2 Malocclusion Classification & Treatment Planning
Quick Answer: Classify malocclusion in three planes. Angle Class I/II/III = sagittal molar relation; add overjet, overbite, crossbite, crowding. Separate dental from skeletal components. Plan by etiology and growth: expand/regain space, correct shifts early, decide extraction vs nonextraction from space + profile + stability, and reserve surgery for severe skeletal problems after growth.
Diagnosis (19.1) feeds a ranked problem list and a phased plan: interceptive, comprehensive, or referral (orthodontist/surgery).
Angle Classification in Orthodontic Context
Edward Angle’s sagittal classes remain the universal shorthand. Use FDI first molars (16/26 and 46/36) as landmarks.
| Class | Molar relationship | Common associations |
|---|---|---|
| Class I | MB cusp of maxillary first molar in buccal groove of mandibular first molar | Crowding, spacing, bimaxillary protrusion, open bite can all occur with Class I molars |
| Class II | Mandibular molar distal relative to maxillary molar | Division 1: large overjet, often proclined upper incisors; Division 2: retroclined upper centrals, deep bite, often laterals proclined |
| Class III | Mandibular molar mesial relative to maxillary molar | Edge-to-edge or negative overjet; true skeletal vs pseudo (shift) |
Canine classification
Canine Class I: maxillary canine sits in embrasure between mandibular canine and first premolar. Canine class often guides finishing; molar class can be finished Class II intentionally in some extraction/camouflage plans (‘Class II molar, Class I canine’ strategies)—concept recognition.
Subdivision
Class II subdivision (or Class III subdivision): Class II (or III) on one side only. Plan must address asymmetry (dental midlines, asymmetric mechanics, or skeletal asymmetry).
Skeletal vs dental Class II/III
| Pattern | Example |
|---|---|
| Skeletal Class II | Retrognathic mandible and/or prognathic maxilla; ANB often increased |
| Dental Class II | Molars Class II with relatively balanced jaws—often mesial maxillary molars or drift |
| Skeletal Class III | Prognathic mandible and/or deficient maxilla; ANB low/negative |
| Pseudo-Class III | Forward mandibular shift on closure due to incisor interference; CR shows more end-to-end or less Class III |
AFK trap: treating only tooth alignment without recognizing a functional shift or severe skeletal problem.
Crowding and Spacing
Crowding etiology
- Tooth-size/arch-length discrepancy (genetics, large teeth, small bases)
- Early loss of primary teeth → mesial molar drift
- Transverse deficiency (narrow arches)
- Soft-tissue pressures and habits
- Supernumerary teeth, transposed teeth, ankylosis-related path problems
Spacing etiology
- Small teeth, large arches
- Missing teeth (hypodontia—common lateral incisors/second premolars)
- Habits, tongue posture
- Midline diastema (normal in mixed dentition ‘ugly duckling’ stage before canine eruption; pathologic if frenum/pathology after permanent canines erupt)
Treatment planning options for crowding
| Strategy | Concept | Cautions |
|---|---|---|
| Arch expansion | Increase perimeter transversely/labially | Periodontal limits, relapse, buccal corridors; skeletal expansion more stable in growing maxilla |
| Incisor proclination | Gains space but increases overjet/profile convexity | Thin labial bone/gingival recession risk |
| Interproximal reduction (IPR) | Enamel slenderizing for mild–moderate crowding | Bolts on tooth morphology, caries risk if poorly finished |
| Distalization of molars | Gain space in arch | Anchorage, cooperation, second/third molar status |
| Extraction | Remove teeth (often premolars) to align and retract | Profile flattening, space closure mechanics, black triangles risk |
| Serial extraction | Guided mixed-dentition extraction sequence | Specialist-level planning; see 19.3 |
Nonextraction preference when profile is flat/concave, soft-tissue drape poor for retraction, or crowding mild with good periodontal support. Extraction consideration when crowding severe, lips procumbent, or camouflage of Class II needs space to retract upper incisors.
Crossbite
Types
| Type | Definition / notes | |---|---|---| | Anterior crossbite | One or more upper anteriors lingual to lower anteriors | | Posterior crossbite | Buccal cusps of upper posteriors occlude lingual to lower buccal cusps (unilateral or bilateral) | | Buccal nonocclusion / Brodie | Upper teeth completely buccal to lower (scissor) | | Dental crossbite | Tooth position problem on adequate bases | | Skeletal crossbite | Often narrow maxilla relative to mandible | | With functional shift | Premature contact drives mandible to one side—asymmetric muscle/jaw loading |
Why early correction often matters
Unilateral posterior crossbite with shift can promote asymmetric mandibular growth and facial asymmetry if prolonged. Simple anterior dental crossbites (single tooth) may be corrected with removable appliances or limited fixed therapy once sufficient root/eruption allows, provided space exists and the opposing tooth is not locking the bite permanently.
Maxillary expansion (removable plate with jackscrew or fixed hyrax-type expander in growing patients) addresses transverse skeletal deficiency; adult skeletal expansion may need surgically assisted approaches—concept level.
Open Bite and Deep Bite
Open bite
Anterior open bite: lack of vertical overlap of incisors. Etiology drives therapy:
| Etiology | Clues | Direction of care |
|---|---|---|
| Digit habit | Thumb/finger; open bite + often flared maxillaries | Habit cessation first; appliances if needed |
| Tongue thrust / posture | Adaptive or primary; speech/swallow patterns | Myofunctional awareness; retention challenges |
| Airway / mouth breathing | Adenoid facies pattern historically taught | ENT evaluation when indicated |
| Skeletal vertical excess | Long face, high mandibular plane, posterior maxillary excess | Growth modification limited; often ortho-surgery later |
| Dental eruption deficiency | Localized ankylosis/impacted teeth | Local dental treatment |
Stability of open-bite correction is historically challenging—etiology control and retention are critical.
Deep bite
Excessive overbite; may traumatize palatal gingiva, wear incisors, or complicate Class II Division 2. Treatment concepts: relative intrusion of incisors, extrusion of posteriors (grows face vertically—careful in long-face patients), or combination. Deep bite with gummy smile needs vertical diagnosis before simple intrusion.
Overjet and Incisor Relationship
| Finding | Planning note |
|---|---|
| Increased overjet | Class II dental/skeletal; trauma risk to upper incisors in active children—consider early overjet reduction in selected cases |
| Edge-to-edge / reverse overjet | Class III spectrum; rule out shift |
| Bimaxillary protrusion | Both arches proclined; extraction-retraction often improves lip competence |
Extraction vs Nonextraction Principles
There is no single rule. Integrate:
- Arch-length discrepancy magnitude
- Soft-tissue profile and lip competence
- Incisor inclination and labial bone
- Growth pattern (high-angle vs low-angle)
- Anchorage needs for Class II/III camouflage
- Missing/carious teeth that may dictate strategic extraction
- Patient goals and compliance
| Typical extraction pattern (teaching) | Rationale sketch |
|---|---|
| All first premolars | Symmetric severe crowding or bimaxillary protrusion |
| Upper first premolars only | Class II camouflage—retract upper anteriors; finish molars Class II |
| Lower incisor | Selected Class III camouflage / severe lower crowding (limited cases) |
| Compromised teeth | Extract poor-prognosis tooth rather than healthy premolar when logical |
Anchorage: resistance to unwanted tooth movement. Maximum anchorage means minimal molar mesial movement while retracting anteriors—reinforced with TADs, headgear, or differential mechanics (specialty detail). Loss of anchorage closes extraction space from behind and leaves residual overjet/crowding.
Vertical and Transverse Planning Summary
| Plane | Key questions |
|---|---|
| Sagittal | Class I/II/III? Skeletal or dental? Growth remaining? Camouflage vs ortho-surgery? |
| Vertical | Open vs deep? Habit vs skeletal? Smile gingival display? |
| Transverse | Crossbite? Shift? Skeletal narrow maxilla? |
| Alignment | Crowding mm? Bolton? Impacted canines? |
| Health | Caries control, perio stability, endodontic status before bands/brackets |
Timing Philosophy
| Phase | Intent |
|---|---|
| Interceptive / limited | Habits, space maintenance/regain, crossbite with shift, severe overjet trauma risk, guidance of eruption |
| Comprehensive adolescent | Full fixed appliances after most permanent teeth (except often 8s) |
| Adult ortho | No growth modification; more perio risk; clear aligners common; surgery for severe skeletal |
| Retention | Lifelong stability planning—starts at diagnosis (19.3) |
Multidisciplinary flags
- Impacted maxillary canines → early pan screening (~age 10–12 teaching window), space, surgical exposure coordination
- Hypodontia → restorative/implant timeline with ortho space opening/closure
- Cleft / syndromes → team care
- Severe skeletal discrepancy → orthodontist + oral surgeon pathway
Section 19.3 translates plans into appliances, interceptive tools, and retention.
Angle Class II Division 2 malocclusion is classically associated with which dental pattern?
A unilateral posterior crossbite with a functional mandibular shift is important to recognize early primarily because:
Which statement best reflects extraction versus nonextraction planning for crowding?
Anterior open bite associated with an active thumb-sucking habit should first emphasize: