Angle's Classification System Overview

Angle's Classification System

• Class I molar relationship: MB cusp of upper molar (UM) articulates with buccal groove of lower molar (LM).
• Canine relationship in Class I: Upper canine (UC) articulates between lower canine (LC) and lower first premolar (LP1).
• Excludes skeletal and muscular factors in occlusion assessment.
• Despite limitations, widely used in orthodontic classification.

Class 1 Occlusion

• Also referred to as Neutroocclusion, indicating a normal occlusal relationship.

Class I Malocclusion

• Defined by the normal molar relationship, but an improper line of occlusion.

Normal Occlusion

• Classified as a range, not a singular point, balancing subjective and objective diagnostics.

Dewey Subclassification System

• Recognizes molar drift; emphasizes repositioning molars to correct spaces.
• Dewey Types:
  • Type 1: Anterior crowding
  • Type 2: Anterior protrusion
  • Type 3: Anterior crossbite
  • Type 4: Posterior crossbite
  • Type 5: Molar mesial drift

Extensive Classification of Class I Malocclusion

• Types 1-12 cover various crowding, spacing, inclination, and bite characteristics:
  • Type 1: Anterior crowding
  • Type 2: Posterior crowding
  • Type 3: Anterior spacing
  • Type 4: Posterior spacing
  • Type 5: Anterior proclination
  • Type 6: Anterior retroclination
  • Type 7: Anterior openbite
  • Type 8: Posterior openbite
  • Type 9: Anterior deepbite
  • Type 10: Anterior crossbite
  • Type 11: Posterior crossbite
  • Type 12: Bimaxillary protrusion

Class II Malocclusion

• Also called Distocclusion, characterized by upper dentition positioned forward relative to lower dentition.
• Can manifest as full, half, or quarter cusp Class II situations.
• Divisions of Class II:
  • Division 1: Maxillary incisors proclined.
  • Division 2: Maxillary incisors retroclined or lateral incisors protruded with central incisor retroclined.
  • Subdivisions: Unilateral Class II molars.

Class III Malocclusion

• Defined by mandibular dentition positioned forward relative to maxillary, characterized by edge-to-edge bite or negative overjet.
• Includes True Class III (skeletal) and Pseudo Class III (muscular).

Simon System

• A comprehensive system examining occlusion in the sagittal, transverse, orbital, and Frankfurt planes.

Lischer's Nomenclature

• Classification of tooth positions using terms such as mesioversion and distoversion.

Aetiological Classification

• Categorizes malocclusions based on osseous, muscular, and dental factors.

Diagnostic Classification of Malocclusion

• Involves evaluating facial proportions, dental arch alignment, and skeletal/dental relationships.

Measurement Techniques

• Overbite measured in mm or percentage with appropriate tools.
• Overjet signifies the horizontal distance, while overbite indicates vertical overlap between incisal edges.

Types of Crossbites

• Defined as variations based on occlusal relationships, including edge-to-edge and lingual non-occlusion.

Andrew's Six Keys of Normal Occlusion

• Specifies conditions for optimal occlusion:
  • Class I molars
  • Crown angulation and torque
  • Absence of rotated teeth
  • Tight contacts
  • Flat Curve of Spee

Space Considerations

• Primate spacing occurs mesial to upper canines and distal to lower canines; important for dental arch development.
• Leeway space results from primary molar replacement by smaller premolars, providing additional arch space.
• Loss of Leeway space can occur due to early primary tooth extractions or caries.

Eruption and Growth Theories

• Pressure and traction theories explain tooth eruption processes influenced by biological and environmental factors.
• Molar shifts during permanent dentition succession involve anterior force and space adaptation for interdigitation.
• Eruption patterns of maxillary and mandibular teeth follow specific sequences.

Evolutionary Aspects

• Dental arch evolution relates to growth patterns, arch size adjustments, and the coordination of occlusion and aesthetic functions.