Comparative Evaluation of Teeth Displacement and Stress Generated with Orthodontic Mini-Implant and Infra-Zygomatic Crestal Implant during Intrusion in the Maxillary Arch − A Three Dimensional Finite Element Analysis

Introduction: This study aims to evaluate and compare the stress distribution in bone and sutures surrounding the mini-implant and the teeth displacement pattern in the maxillary arch during full arch intrusion using a mini-implant, IZC implant, and an IZC implant with a mini-implant. Materials and Methods: Three individual finite element models of the craniofacial complex were generated for full arch intrusion with mini-implants and IZC implants using ANSYS 12.1 software. For group 1, five titanium mini-implants of 1.5 × 8 mm and 1.5 × 6 mm were placed 14 mm above the occlusal plane between the second premolar and the first molar, lateral incisors, canine, and between two central incisors, respectively, with forces application of 150 g posteriorly and 80 g anteriorly using a NiTi coil spring. For group 2, two stainless steel IZC implants of 2 × 14 mm were placed 16 mm above the occlusal plane between the first and second molars with a force application of about 300 g using a NiTi coil spring. In group 3, the placement of the IZC implant was similar to that in group 2, with an additional anterior mini-implant of 1.5 × 6 mm between two central incisors. An evaluation of the stress distribution and tooth displacement was carried out. Results: An increased amount of teeth displacement was observed in group 3 (IZC implant with mini-implants). Significant anterior intrusion was achieved in group 1 (mini-implants) whereas anteriors in group 2 (only IZC implants) experienced extrusion. A high amount of stress was observed in group 2. Conclusion: Therefore, IZC implants can be useful in cases of vertical maxillary excess where full arch intrusion is recommended. The anterior mini-implant helps to counteract the unwanted movement (extrusion) caused by the clockwise rotation of the maxilla. High stress levels are associated with an IZC implant without an anterior min-implant but they are within the confines of the physiologic limit of the bone.