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    Biomechanical evaluation of chincup treatment with various force vectors
    (MOSBY-ELSEVIER, 2008) Basciftci, Faruk Ayhan; Korkmaz, Hasan Huesnue; Uesuemez, Serdar; Eraslan, Oguz
    The aim of this study was to evaluate the biomechanical effects of chincup treatment by using a 3-dimensional finite element model. Methods: Three-dimensional models of the mandible and the temporomandibular joint were modeled and analyzed. The final mesh consisted of 1572 solid elements with 5432 nodes. The chincup with 500 g of force was applied in a direction from the chin toward the mandibular condyle, the coronoid process, and a point anterior to the coronoid process. Then, the mechanical responses in terms of displacement and von Mises stresses are evaluated. Results: The mandible was displaced backward and downward with the vector passing through the condyle. Forward and upward displacement was recorded with the force vector passing through or anterior to the coronoid process. The mandibular condyle and the coronoid process showed minimal displacement for all force vectors. The highest stress levels were observed in the condylar and posterior ramus regions and increased as the force vector was transferred away from the condyle. Conclusions: With the limitations of modeling, boundary conditions, and solution assumptions, chincups applied in various directions produce different force vectors, which induce different stress locations and displacements. The force vector is an important determinant of the orthopedic effects of the chincup and therefore should be carefully considered. (Am J Orthod Dentofacial Orthop 2008; 134: 773-81)
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    Long-term effects of symphyseal distraction and rapid maxillary expansion on pharyngeal airway dimensions, tongue, and hyoid position
    (MOSBY-ELSEVIER, 2007) Malkoc, Siddik; Uesuemez, Serdar; iseri, Haluk
    Introduction: The aim of this study was to evaluate the effects of mandibular symphyseal distraction osteogenesis (MSDO) followed by rapid maxillary expansion (RME) on the pharyngeal and nasal airway dimensions and the tongue and hyoid positions. Methods: The material consisted of lateral and posteroanterior cephalometric radiographs of 13 female and 7 male patients (mean age, 20.0 +/- 2.3 years). Records were taken before treatment, after distraction (11.4 +/- 2.2 days after surgery), after RME (94.9 +/- 5.8 days after surgery), and at follow-up appointments (24.1 +/- 4.2 months after surgery). MSDO was performed with a custom-made tooth-and-bone-borne device. RME was performed with an acrylic bonded device. The average amounts of mandibular and maxillary expansion were 8.1 +/- 1.7 and 5.9 +/- 1.0 mm, respectively. Results: Posteroanterior cephalometric analysis showed significant transversal width increases between the mandibular canines and molars. No significant pharyngeal or transverse nasal airway changes occurred with MSDO except for a significant decrease in tongue length. However, MSDO followed by RME caused statistically significant but clinically small changes in oropharyngeal width (+1.0 mm), tongue length (-2.2 mm), vertical airway length (-2.3 mm), and vertical position of the hyoid bone (-1.4 mm), which were all stable at the 2-year follow-up. Conclusions: The results suggest that MSDO alone or MSDO followed by RME does not significantly affect the pharyngeal airway dimensions or the hyoid position in adults. Any changes caused by these procedures might have been counteracted by the reflex mechanisms that protect airway potency.