Angle's Classification of Malocclusion Flashcards

Angle's Classification of Malocclusion

• Classifies dentoalveolar relationships, particularly the anteroposterior alignment of upper and lower first permanent molars.

Normal Occlusion

• Defined by a normal molar relationship (Angle Class I) with teeth arranged along a smooth, curving line of occlusion.

Angle Class I Relationship

• Identified by the mesio-buccal (MB) cusp of the maxillary first molar fitting into the MB groove of the mandibular first molar.

Malocclusion

• Refers to deviations in the intramaxillary and/or intermaxillary relationships of teeth compared to normal occlusion.

Intra-maxillary Deviations

• Include malaligned teeth, rotations, spacing issues, and crowding of teeth.

Inter-maxillary Deviations

• Characterized by conditions like crossbite, overjet, overbite, and molar relationship abnormalities.

Crossbite

• Occurs when one or more upper incisors occlude lingually to lower incisors; can result from occlusal or skeletal problems, such as a disproportionately large lower jaw.

Overjet

• The horizontal distance by which the upper central incisors protrude over the lower counterparts; a normal overjet is 0 mm and may indicate a small lower jaw if excessive.

Overbite

• Refers to the vertical overlap of upper incisors over lower incisors; normal is approximately one-third. Complete overbite may impede the gingiva.

Class I Malocclusion

• Similar to normal occlusion but with crowding and malposed teeth. The MB cusp of the upper molar is in the lower molar's MB groove, often manageable.

Class II Malocclusion

• Known as distocclusion; occurs when the MB cusp of the maxillary first molar is situated mesial to the MB groove of the mandibular first molar, often leading to increased overjet and crowded incisors.

Divisions of Class II Malocclusion

• Based on the positioning of maxillary central incisors into Class II Division 0 (normal inclination), Division 1 (proclined incisors with increased overjet and overbite), and Division 2 (retroclined incisors which may require extensive treatment).

Half Cusp Relationship

• Defined as a cusp that does not fit into its respective groove.

Common Malocclusion

• Class II malocclusion is the most frequently encountered type.

Class III Malocclusion

• Known as mesiocclusion; identified when the MB cusp of the maxillary first molar articulates distal to the MB groove of the mandibular first molar, leading to a reverse overjet and potential anterior crossbite, sometimes necessitating jaw surgery.

Cuspid Relationships

• Class I (neutrocuspid), Class II (distocuspid), and Class III (mesiocuspid) relationships correspond with their respective Angle classification.

Subdivision

• Refers to Class II and Class III malocclusions exhibiting Class I molar relationship effects on only one side.

Mutilations

• Changes in occlusion resulting from early tooth loss and subsequent tooth drift, classified by the original molar position.

Limitations of Angle's Classification

• Fails to consider etiology, skeletal and muscular patterns, vertical and transverse issues.

Terminal Plane Percentages (Deciduous Molar Relationships)

• Flush terminal plane: 76%
• Mesial step: 14%
• Distal step: 10%

Flush Terminal Plane Outcomes

• 56% result in Angle's Class I molar relationship; 44% develop into Angle's Class II.

Mesial Step Outcomes

• A mesial step of 1 mm leads to 76% becoming Angle's Class I and 24% transitioning to Class III, demonstrating that an increase in mesial step raises the likelihood of Class III outcomes.

Distal Step Outcomes

• Always results in a 100% Angle's Class II molar relationship.

Leeway Space on Maxillary Arch

• The second primary molar is 1.5 mm wider than its second premolar, yielding a total leeway space of 3 mm in the upper arch.

Leeway Space on Mandibular Arch

• The first primary molar is 0.5 mm wider than its first premolar, and the second primary molar is 2 mm wider than its second premolar, resulting in a total leeway space of 5 mm.