1 Aetiology and Extractions

Definition: Aetiology of Malocclusion is described by Houston as "an appreciable deviation from the ideal occlusion that may be considered aesthetically or functionally unsatisfactory".
- Ideal Occlusion: Rarely observed in patients; malocclusion itself is not a disease but a deviation from normal.

Skeletal Pattern: Influences overall malocclusion by the facial and jaw structure.
Malposition: Misalignment of teeth contributes to malocclusion.
Space Deficiency: Occurs when there is insufficient space in the arch.
Local Factors: Involves soft tissues and excess conditions affecting occlusion.

Skeletal Relationship: Genetic predisposition primarily controls skeletal structure.
- Trend: Indicates a reduction in jaw size from primitive populations.
Tooth and Arch Size Disproportion: Smaller arch sizes or larger teeth can lead to crowding.
- Tooth size is genetically controlled; examples include Begg and Aboriginal populations.
Genetic and Developmental Disorders: Include conditions like cleft lip and palate, which may influence the position and alignment of teeth.
- Trauma to the TMJ and any growth abnormalities may also impact skeletal relationships.

Early Loss or Prolonged Retention of Deciduous Teeth: Affects permanent teeth alignment and positioning.
Ectopic Teeth: Teeth that erupt in an abnormal position, causing shifts in adjacent teeth.
Absent Teeth and Supernumeraries: Congenitally missing teeth or excessive teeth can disrupt alignment.
Impaction and Delayed Eruption: Teeth may fail to erupt or may be blocked, leading to complications.
Fraenum and Local Pathology: Thick or improperly positioned frena can affect tooth positioning and result in malocclusion.
Dental Trauma: Involves damage that can disrupt the alignment and positioning of teeth, leading to malocclusion.

Factors Affecting Effects:
- Type of Tooth Lost: Ex. Loss of D, E teeth leads to drift of first permanent molars.
- Age at Loss: Earlier losses tend to have more severe effects on alignment.
- Degree of Crowding: Existing crowding can exacerbate space loss and midline shifts.

Common in teeth E or D; may prevent natural loss and alter the expected eruption sequence of permanent teeth. Potential complications include:
- Submerged or infraoccluded teeth due to ankylosis.
- Tipping of adjacent teeth (especially first molars).
- Treatment generally involves observing natural exfoliation unless teeth become submerged.

Refers to conditions such as hypodontia and anodontia, affecting the number and position of teeth. Treatment strategies include:
- Space closure, bridgework, or implants.
- Surgical options where appropriate (e.g., for supernumeraries or absent teeth).

Occurrence is 1-2%; common in the maxilla (80% of cases).
- Can lead to clinical effects such as delayed eruption or crowding.
- Management varies from extraction to observation depending on the case specificity and alignment post-eruption.

Common Types: Include impacted first molars, premolars, and third molars. Impacted teeth may require management strategies ranging from extraction to space creation for proper eruption.
Management Rationale: Often revolves around ensuring dental alignment and preventing crowding from occurring due to impacted teeth.

The interaction of genetic and environmental factors causes most malocclusions. Success in treating local factors and habits is often achievable with basic interventions. More complex cases may require advanced treatment methods based on skeletal patterns and size disproportions.