orthodontics

The Problem of Overbite in Class II, Division 2 Malocclusion (Mills, 1973)

Anisha ValliLeave a comment

Overview

  • Class II Division 2 malocclusion is characterized by a deep overbite with retroclined maxillary incisors.
  • The etiology is multifactorial, involving:
    • Dental factors
    • Skeletal factors
    • Soft-tissue influences
  • Deep bite is not caused solely by retroclined upper incisors.
  • Mills (1973) evaluated 60 treated Class II Division 2 cases to determine factors influencing overbite and its stability.

Characteristic Features

  • Mild Class II skeletal pattern with considerable individual variation.
  • Markedly increased inter-incisal angle (most consistent finding).
  • Retroclined maxillary central incisors.
  • Frequently associated retroclined mandibular incisors.
  • Increased lip cover (higher lower lip line over upper incisors).
  • Reduced lower anterior facial height in many patients.
  • Deep overbite is produced by the combined effect of:
    • Increased inter-incisal angle
    • Soft-tissue pattern
    • Vertical facial proportions

Factors Influencing Overbite

  • Inter-incisal angle
    • Strongest correlation with overbite depth.
    • Greater the angle → deeper the overbite.
  • Lip cover
    • Positively correlated with overbite.
    • Increased lower lip pressure helps maintain incisor retroclination.
  • Lower anterior facial height
    • Reduced facial height contributes to deep bite.
    • Correlation weaker than inter-incisal angle.
  • Deep overbite results from the interaction of multiple factors, rather than any single variable.

Mechanism of Overbite Reduction

  • Successful correction associated with:
    • Reduction in inter-incisal angle
    • Proclination of lower incisors
    • Increase in lower facial height during growth
    • Improvement in facial proportions
  • Lower incisor proclination was more effective than upper incisor proclination.
  • Simple incisor intrusion alone showed limited long-term effectiveness.
  • Mandibular rotation contributed only in selected patients.

Clinical Implications

  • Do not treat the overbite in isolation.
  • Evaluate:
    • Inter-incisal angle
    • Lower facial height
    • Lip posture (lip cover)
    • Growth potential
  • Utilize remaining growth whenever possible.
  • Treatment mechanics should emphasize:
    • Controlled lower incisor proclination
    • Correction of incisor inclination
    • Improvement in facial proportions
  • Vertical intrusion alone is usually insufficient for stable correction.

Stability and Relapse

  • Stability depends on correcting the underlying incisor relationship.
  • Relapse is likely if:
    • Inter-incisal angle remains excessive.
    • Facial pattern remains unfavorable.
  • Stable results achieved when:
    • Lower incisal edges contact the cingulum of the upper incisors.
    • A self-retaining incisor relationship develops.
  • Growth contributes significantly to long-term stability.

Treatment Principles (Mills, 1973)

  • Class II Division 2 may represent a natural compensation for a mild skeletal Class II pattern.
  • Mild cases:
    • Preserve acceptable central incisor relationship.
    • Relieve crowding without excessive bite opening.
  • Severe growing cases:
    • Use anterior bite planes.
    • Employ staged orthodontic therapy.
    • Allow favorable repositioning of incisors under soft-tissue influence.

Key Conclusions

  • Deep overbite is multifactorial.
  • Inter-incisal angle is the strongest determinant of overbite depth.
  • Lip posture and lower facial height significantly influence the malocclusion.
  • Long-term success depends on:
    • Growth
    • Incisor reorientation
    • Favorable facial development
  • Lower incisor proclination is generally more effective than upper incisor proclination.
  • Intrusion alone provides poor long-term stability.
  • Stable correction requires establishing a self-maintaining incisor relationship.

References

  • Mills JRE. The Problem of Overbite in Class II, Division 2 Malocclusion. 1973.
  • Erik Backlund. Overbite and the Incisor Angle. 1958.
  • Arne Björk. Prediction of Mandibular Growth Rotation. 1969.
  • William J. B. Houston. Cephalometric analysis of Class II Division 2 malocclusion. 1967.
  • Kevin G. Isaacson. Overbite and Facial Height. 1970.

Leave a comment