What are the classifications of orthodontic issues and how are they treated?

Orthodontic Classification Systems

Orthodontic malocclusions are primarily classified using Angle's classification system, which categorizes sagittal (front-to-back) relationships of the dental arches into Class I, Class II (Divisions 1 and 2), and Class III, with treatment approaches ranging from non-surgical orthodontics for mild-to-moderate cases to combined orthodontic-surgical intervention for severe skeletal discrepancies.

Primary Classification System: Angle's Classification

Angle's classification remains the most widely used system internationally for evaluating mesio-distal (front-to-back) relationships of dental arches and forms the foundation for malocclusion diagnosis in the sagittal dimension 1, 2.

Class I Malocclusion

• Definition: Normal molar relationship with crowding, spacing, or other dental irregularities 3
• Treatment approach: Typically managed with non-surgical orthodontics including fixed appliances, removable appliances, or extraction therapy depending on severity 1
• Among patients with normal or minor malocclusion (DAI score ≤25), 58% were Class I 1

Class II Malocclusion

• Division 1: Upper front teeth protrude forward 3
• Division 2: Upper central incisors are upright or retroclined with lateral incisors tipped forward 3
• Treatment considerations: Lateral cephalograms (LC) with other orthodontic records significantly influence extraction decisions, particularly for Class II cases 3
• Class II/1 showed the highest percentage of handicapping malocclusions (44% with DAI score ≥36) 1

Class III Malocclusion

• Definition: Lower front teeth are prominent relative to upper teeth; mandible positioned forward relative to maxilla 4
• Etiology: May result from maxillary retrusion, mandibular protrusion, or combination of skeletal and dental factors 4
• Treatment timing: Early intervention (ages 5-13 years) with facemask therapy shows moderate-certainty evidence for immediate improvement 4

Skeletal Classification Parameters

For adult Class III patients, discriminant analysis identifies four critical variables that achieve 92% accuracy in determining surgical versus orthodontic treatment 5:

Decision Algorithm for Class III Treatment

The following equation predicts treatment modality 5:

• Individual score = -1.805 + 0.209(Wits) + 0.044(S-N) + 5.689(M/M ratio) - 0.056(Go lower)
• Wits appraisal is the single most decisive parameter for treatment selection 5
• Anterior cranial base length (S-N) contributes to skeletal assessment 5
• Maxillary/mandibular (M/M) ratio quantifies jaw size discrepancy 5
• Lower gonial angle reflects mandibular morphology 5

Severity Assessment: Dental Aesthetic Index (DAI)

The DAI provides objective severity grading adopted by WHO that links clinical and aesthetic factors 1:

DAI Score Categories

• ≤25: Normal or minor malocclusion - minimal treatment need 1
• 26-30: Definite malocclusion - treatment elective 1
• 31-35: Severe malocclusion - treatment highly desirable 1
• ≥36: Handicapping malocclusion - treatment mandatory 1

Approximately 35% of orthodontic patients present with handicapping malocclusion (DAI ≥36) and 14% with severe malocclusion (DAI 31-35) 1.

Treatment Modalities by Classification

Non-Surgical Orthodontic Treatment

Moderate-certainty evidence demonstrates that non-surgical orthodontic treatments improve overjet by 5.03 mm (95% CI 3.81-6.25) and ANB angle by 3.05° (95% CI 2.40-3.71) immediately post-treatment compared to untreated controls 4.

Effective non-surgical interventions include 3, 4:

• Facemask with or without rapid maxillary expansion (RME) - most commonly reported for Class III 4
• Chin cup therapy 4
• Reverse Twin Block with lip pads 4
• Orthodontic removable traction appliances 4
• Mandibular headgear 4

Critical Limitation of Non-Surgical Treatment

Low-certainty evidence from long-term follow-up shows that improvements from facemask therapy diminish at 3 years (overjet MD 2.5 mm) and appear lost by 6 years post-treatment 4. However, patients receiving facemask treatment were less likely to require jaw surgery in adulthood (OR 3.34,95% CI 1.21-9.24) 4.

Surgical Orthodontic Treatment

Orthognathic surgery is medically necessary only when skeletal deformities contribute to significant masticatory dysfunction and severity precludes adequate treatment through dental therapeutics and orthodontics alone 6.

Indications for Surgical Intervention 6:

• Significant masticatory dysfunction with severe skeletal discrepancies
• Obstructive sleep apnea caused by maxillomandibular deficiency
• Craniofacial syndromes with functional impairment
• Failed non-surgical orthodontic treatment in severe Class III cases

Surgical Approaches

• Maxillomandibular advancement (MMA): Success rates 67-100% for appropriately selected patients; requires 10-15mm advancement 6
• Bilateral sagittal split ramus osteotomies with rigid internal fixation 6
• Le Fort I osteotomy with rigid internal fixation 6
• Surgical miniplates with facemask or Class III elastics: Low-certainty evidence shows substantial improvement (overjet MD 7.96 mm, ANB MD 5.20°) 3

Diagnostic Imaging Requirements

For correct orthodontic diagnosis and treatment planning, panoramic radiography and lateral cephalometric radiography are necessary (Strength A, Evidence Level I) 3.

Imaging Algorithm 3:

• Standard cases: Panoramic radiograph + lateral cephalogram based on malocclusion severity (IOTN) and patient age 3
• Severe dysmorphoses or skeletal Class III: Early radiographic records advisable; if CBCT obtained, standard orthodontic radiographs unnecessary 3
• CBCT indications: Severe dysmorphoses, craniofacial syndromes, impacted teeth, bone anomalies, serious facial asymmetries, condylar aplasia/hypoplasia 3
• CBCT strongly discouraged: For cephalometric diagnosis in moderate-light malocclusion (Strength A, Evidence Level I) 3

Common Pitfall

Using CBCT for routine cephalometric analysis subjects patients to high radiation doses without justifiable benefit when the same information can be obtained with lower-dose techniques 3.

Special Considerations

Skeletal Maturity Assessment

Good agreement exists between hand-wrist (HW) radiographs and lateral cephalograms for skeletal maturity assessment in both boys and girls, though evidence quality is very low 3.

Impacted Canines

• 13% of patients have maxillary canine impactions; 3% have mandibular canine impactions 1
• CBCT justified when canine inclination on panoramic radiograph exceeds 30° or when root resorption of adjacent teeth is suspected 3

Treatment Planning Modifications

Lateral cephalograms influence extraction decisions most significantly for Class II malocclusions and bimaxillary protrusion (very low-certainty evidence) 3. However, for general treatment planning not involving specific extraction decisions, lateral cephalograms provide minimal added value beyond other orthodontic records 3.