Change in the Spatial Position of Mini-implants During Distal Movement of the Entire Maxillary Dentition: An Observational CBCT Study

Purpose: To determine the change in the sagittal and vertical position of mini-implants placed in the maxilla during distal movement of the entire maxillary dentition. Materials and Methods: Overall, 28 mini-implants (1 placed on each side in 14 patients) were evaluated in healthy patients aged 15 to 25 years old. CBCTs were taken immediately after leveling and aligning prior to distalization (T1) and after 6 months (T2) to evaluate the distal movement of the maxillary teeth and position of the mini-implants. The vertical and sagittal angulation of each mini-implant was measured at T1 and T2. The linear distance between the mini-implant and the alveolar crest, the maxillary sinus, the maxillary second premolar, and the maxillary first permanent molar were measured. The change in angulation and the linear displacement of the miniimplant were evaluated in the vertical and sagittal plane. Wilcoxon signed rank test was performed to determine if there was a statistically significant change in the position of the mini-implant. Results: Vertically, there was a significant change in the linear distance between the mini-implant and the alveolar crest on the right side (P ≤ .006) as well as the miniimplant and the maxillary sinus on the left side (P ≤ .003). Sagittally, there was a statistically significant rotation of the miniimplant occlusally (left side P ≤ .004 and right side P ≤ .002). The head and tip of the mini-implant were displaced toward the maxillary second premolar and away from the maxillary first permanent molar, respectively. There was a significant relative displacement of the mini-implant anteriorly away from the maxillary first permanent molar (left side P ≤ .026 and right side P ≤ .041) and closer to the maxillary second premolar (left side: P ≤ .011 and right side: P ≤ .002). Conclusions: There was a statistically and clinically significant rotation of the mini-implant in the vertical and sagittal direction during distal movement of the entire maxillary arch. The linear displacement of the mini-implant was more pronounced in the sagittal direction than the vertical direction.