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

Abstract

To determine the change in the sagittal and vertical position of the mini-implant placed in the maxilla during distal movement of the entire maxillary dentition. Twenty eight mini-implants, fourteen on each side were evaluated in young healthy patients in the age group of 15 years to 25 years. Distal movement of the entire maxillary arch was performed with 1.2 mm x 8 mm stainless steel mini-implants on 0.018" x 0.025" stainless steel wire. CBCT were taken at the start of (T1) and at the end of six months (T2) of distal movement of the maxillary teeth. The vertical and sagittal angulation of the 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 mini-implant 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. Vertically, there was a significant change in the linear distance between the miniimplant and the alveolar crest on the right side (p≤.006) and the mini-implant 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 towards 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). 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 teeth. The linear displacement of the mini-implant was more pronounced in the sagittal direction compared to the vertical direction.