Nonextraction treatment of Class II division 2 in an adult patient using microimplant anchorage (MIA) / 대한치과교정학회지

Maxillary anterior teeth were intruded and lingually root torqued with two maxillary anterior microimplants between the lateral incisors and canines. Overerupted maxillary canines were intruded with two other microimplants between the maxillary canines and first premolars. Maxillary posterior teeth and canines were distalized, then the maxillary incisors were retracted with two maxillary posterior microimplants between the first and second molars. The mandibular anterior teeth were intruded and the mandibular posterior teeth were extruded with conventional method such as anterior bite plane, intrusion arch and Class II elastics. The mandible moved slightly forward after the correction of deep bite and retroclination of the upper incisors. Consequently, microimplant anchorage (MIA) provided absolute anchorage for simultaneous correction of Class II canine and molar relationships and deep overbite.

Three-dimensional finite element analysis of the phenomenon produced during retraction of four maxillary incisors / 대한치과교정학회지

This study was designed to investigate force systems and tooth movements produced by retraction archwire during retraction of four maxillary incisors after the maxillary canine retraction into the maxillary first premolar extraction space using the computer-aided three-dimensional finite element method. A three-dimensional finite element model, consisting of 2248 elements and 3194 nodes, was constructed. The model consisted of maxillary teeth and surrounding periodontal membranes, .022" x .028" -slot brackets, and 5 types of retraction archwires(.019" x .025" stainless steel archwire) modeled using the beam elements. The contact between the wire and the bracket slot was modeled using the gap elements because of the non-linear elastic behaviors of the contact between them. The forces and moments, and displacements produced by retraction archwire were measured at various conditions to investigate the difference according to types of loops, magnitudes of activation force, gable angle, and anterior lingual root torque. The results were expressed quantitative and visual ways in the three-dimensional method. The following conclusions can be drawn from this study: 1. When the tear-drop loop archwire was activated, the mesio-distal and lingual translational movements of the teeth helped to close the extraction space, but unwanted movements of the teeth including intrusions and extrusions, and rotational movements in each direction occurred. 2. Activation of T-loop archwire compared with those of other types of retraction archwires produced the least translational movements of the teeth helped to space closure and also the least unwanted movements of the teeth. 3. Increasing amount of activation in the tear-drop archwire led not only to increase of translational movements of the teeth helped to space closure, but also to increase of unwanted movements of the teeth. 4. Addition of gable bend in the tear-drop archwire helped anterior teeth to translational movements in the mesio-distal direction, but increased unwanted movements of the teeth. 5. Addition of anterior lingual root torque in the tear-drop archwire helped central and lateral incisor to improve their facio-lingual inclination, but increased unwanted movements of the teeth.