Pure Mandibular Incisor Intrusion: A Finite Element Study to Evaluate the Segmented Arch Technique.

Leveling the curve of Spee is a commonly-used strategy to correct deep bites. Although several techniques have been proposed to intrude mandibular incisors (MI), flaring of these teeth is often observed and in many instances undesired. A three-dimensional (3D) finite element model (FEM) was used to locate the ideal point of force application (PFA) to achieve pure MI intrusion with the three-piece arches' technique. It comprised (1) a 0.021 × 0.025 in. stainless steel (SS) wire that passively filled the slots of the canine and premolar brackets and the first and second molar tubes, bilaterally; (2) a 0.0215 × 0.0275 in. SS intrusion base arch (IBA) inserted into the MI brackets, that presented a step down distal to the lateral incisors brackets and a posterior extension arm; (3) titanium-molybdenum tip-back springs designed to apply the intrusion force, fitted inside the first molar gingival tube. Four PFA on the IBA were simulated (FEM 1, 2, 3, and 4). FEM 3 resulted in pure MI and was considered the ideal PFA. FEM1 and 2 showed intrusion and buccal crown flaring of the MI, whereas FEM4 resulted in intrusion and lingual crown flaring of those teeth. Clinicians may consider three-piece arch mechanics to achieve pure MI intrusion. However, they must be aware that when force was applied anteriorly or posteriorly to the ideal PFA, the incisors would incline labially or lingually, respectively.

Mandibular Incisor Impaction: A Rare Condition.

The purpose of this case report is to present the management of an impacted permanent mandibular left central incisor using a removable appliance. A minor surgery was done to expose the tooth crown and bond an orthodontic button. The removable appliance was used to apply extrusion forces to the impacted tooth. Over a course of six months, the tooth was fully erupted. To recover the lost space of the primary canine, a fixed appliance was bonded on the mandibular arch and retention was placed until the permanent canine erupted. This report demonstrates the importance of early diagnosis and interceptive treatment in cases of tooth impaction.