Objective:  

 To investigate the factors related to changes in alveolar bone thickness during upper incisor retraction.

 Materials and Methods:  

 The subjects consisted of 23 ongoing orthodontic patients (mean age 20.4 ± 2.7 years) whose upper incisors were bound for retraction. Changes in alveolar bone thickness in the retracted area were assessed using preretraction (T0) and postretraction (T1) cone-beam computed tomography images. Labial bone thickness (LBT), palatal bone thickness (PBT), and total bone thickness (TBT) were assessed at the crestal, midroot, and apical levels of the retracted incisors. Paired t-tests were used to compare T0 and T1 bone thickness measurements. Spearman's rank correlation analysis was performed to determine the relationship of changes in alveolar bone thickness with the rate of tooth movement, change in inclination, initial alveolar bone thickness, and the extent of intrusion.

 Results:  

 As the upper incisors were retracted, the LBT at the crestal level and TBT at the apical level significantly increased (P < .005). Changes in alveolar bone thickness were significantly associated with the rate of tooth movement, change in inclination, and extent of intrusion (P < .05) but not initial alveolar bone thickness (P > .05).

 Conclusion:  

 Rate of tooth movement, change in inclination, and extent of intrusion are significant factors that may influence alveolar bone thickness during upper incisor retraction. These factors must be carefully monitored to avoid the undesirable thickening of alveolar bone.

 Source: The Angel Orthodontists

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