The efficacy of maxillary protraction protocols with the micro-implant-assisted rapid palatal expander (MARPE) and the novel N2 mini-implant-a finite element study.

BACKGROUND: Maxillary protraction with the novel N2 mini-implant- and micro-implant-assisted rapid palatal expander (MARPE) can potentially provide significant skeletal effects without surgery, even in older patients where conventional facemask therapy has limited skeletal effects. However, the skeletal effects of altering the location and direction of force from mini-implant-assisted maxillary protraction have not been extensively analyzed. In this study, the application of the novel N2 mini-implant as an orthopedic anchorage device is explored in its ability to treat patients with class III malocclusions. METHODS: A 3D cranial mesh model with associated sutures was developed from CT images and Mimics modeling software. Utilizing ANSYS simulation software, protraction forces were applied at different locations and directions to simulate conventional facemask therapy and seven maxillary protraction protocols utilizing the novel N2 mini-implant. Stress distribution and displacement were analyzed. Video animations and superimpositions were created. RESULTS: By changing the vector of force and location of N2 mini-implant, the maxilla was displaced differentially. Varying degrees of forward, downward, and rotational movements were observed in each case. For brachyfacial patients, anterior micro-implant-supported protraction at -45° or intermaxillary class III elastics at -45° are recommended. For dolicofacial patients, either anterior micro-implants at -15° or an intermaxillary spring at +30° is recommended. For mesofacial patients with favorable vertical maxillary position, palatal micro-implants at -30° are recommended; anterior micro-implants at -30° are preferred for shallow bites. For patients with a severe mid-facial deficiency, intermaxillary class III elastics at -30° are most effective in promoting anterior growth of the maxilla. CONCLUSIONS: By varying the location of N2 mini-implants and vector of class III mechanics, clinicians can differentially alter the magnitude of forward, downward, and rotational movement of the maxilla. As a result, treatment protocol can be customized for each unique class III patient.

Spontaneous improvement of gingival recession after correction of tooth positioning.

A 30-year-old woman sought treatment for malpositioned mandibular incisors; the roots were positioned outside the alveolar bone, related to severe localized gingival recession. She had been previously treated orthodontically and subsequently underwent 2 gingival grafts. The new treatment included torquing the roots back within the alveolar bone and referral to a periodontist for a gingival graft. In this clinical report, the possible spontaneous improvement of gingival recession is discussed. A hypothesis described in the literature is called the "creeping attachment" phenomenon. The literature includes conflicting reports about the cause-and-effect relationship between orthodontics and gingival recession. This clinical example reports spontaneous improvement of gingival recession after correction of tooth positioning in the alveolar bone. A gingival graft can be performed after adequate root positioning in the alveolar bone housing, thus increasing the chance of achieving more favorable results.