"Safe Zone" for Risk-Free Implantation of Skeletal Anchor Plates in Skeletal Class II Malocclusion Patients: An Anatomical Study Using Cone Beam Computed Tomography

Introduction: Successful clinical attempts have been carried out to support fixed functional appliances by using skeletal anchor plates placed in the symphysis to avoid mandibular incisors protrusion. Aim: The purpose of the present study, that used cone beam CT, was to clarify the anatomical features of the mandibular anterior region to help identify a safe zone to apply skeletal anchor plates. Materials and Methods: Study sample consisted of 9 patients with skeletal Class II. Considering the lower occlusal plane as a reference, numerous measurements related to the mandibular anterior region were evaluated in axial and buccolingual cross-sections. Results: The measurements of right and left sides were not significantly different (P >.05). Mental foramen was directed inward and downward in all patients, and close to second premolar root in most cases. Bone height was 11mm below the mental foramen, and 8.2mm below the mandibular canal. Bone height was the biggest below the central incisor root 17.4 mm, and the smallest below the root of canine 12.6mm. The mean cortical bone thickness at the lower margin ranged between 2.9-3.6mm. The bone below the root of the central incisor was characterized by the smallest width 8.9mm, and in the same time the biggest width 13.2mm. The mean of the mesiodistal width of the anterior region was 23.9mm. Conclusion: Safe zone extends distally for 21mm horizontally starting from the midline, and 8mm vertically over the lower margin region of symphysis. The area below the foramen was risky because the presence of the mandibular dental canal. Schlagwörter: Safe Zone, Skeletal Anchor Plates, Symphysis, Mental Foramen, Cone Beam Computerized Tomography