Mandibular Anterior Alignment

An evaluation of changes in mandibular anterior alignment from I0 to 20 years postretention

Little et al 1998
AJODO 1988 93 423-8

The purpose of this study was to evaluate adolescent orthodontic treatment by evaluating post-retention change at several decades of adult life and, if possible, to determine when and if relapse progression had stopped.

There may be an assumption once the majority of growth is completed the dento-occlusal changes will be minimal, and therefore retention may not be required.

Littles previous study (10 yr post retention) concluded

  1. Long-term alignment was variable and unpredictable.
  2. No descriptive characteristics-such as Angle Class, length of retention, age of the initiation of treatment, or gender - nor measured variables-such as initial or end-of-active- treatment alignment, overbite, overjet, arch width, or arch length - were of value in predicting the long-term result.
  3. Arch dimensions of width and length typically decreased after retention, whereas crowding increased. This occurred in spite of treatment maintenance of initial intercanine width, treatment expansion, or constriction.
  4. Success at maintaining satisfactory mandibular anterior alignment is approx 30% with nearly 20% of the cases likely to show marked crowding many years after removal of retainers.

Study Type: Retrospective
Population: Pts treated at UW
Sample: 31 cases
Inclusion: 4 bi exo cases. * the quality iof treatment finish was not considered in the selection process

Data: All cases had records at 4 different time points 1. Pre Rx; 2. Post Rx; 3. 10 yrs. post retention; and 4. 20 yrs. post retention
Analysis: Littles Irregularity index was used for analysis of mandibular models


  • At 10 yrs post Rx there was an Irr index of 5mm with a wide range. 
  • Most changes from 10-20 yrs were slight ( approx.- 1mm)
  • At 20 yrs  only 3 cases out of 31 (10%)  were determined to be clinically acceptable..
  • Arch constriction continues well after the cessation of pubertal and “active growth”
  • There is a marked individual variation.


  • The only way to ensure continued satisfactory alignment post treatment probably is by the use of fixed or removeable retention for life.
  • Patients should be fully informed about the liability of post treatment changes and one should assume that instability is likely. Therefore a plan to prevent these undesirable changes is prudent. 


  • Heterogenous sample with considerable pre-treatment discrepancy.  
  • Authors noted Incisors were finished in a “non-procumbent position”, but one must remember these patients were treated by Grad students, and therefore the results may have been different in an experienced clinicians practice.
  • Individual variation in etiology of malocclusion and biological and physiological response to tooth movement.
  • We know that teeth have a propensity to return to their original position prior to orthodontic treatment. This is explained to some degree by Proffits paper on equilibrium. 
  • No fiberotomies for rotated teeth.
  • Normal facial development support continues characterized by mesial migration of mandibular dentition as we age resulting in crowding

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