Paul Hoang

University of California, Los Angeles, Los Ángeles, California, United States

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Publications (2)4.64 Total impact

  • P. HOANG · J. PHAM · K. TING · H. LEE
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    ABSTRACT: Objectives: In a patient with unilateral cleft lip and palate (UCLP), the minor segment of the maxilla is normally collapsed and positioned lingual to the ideal dental arch form. Rapid Palatal Expansion (RPE) is performed to place the minor segment into the ideal position. The aims of this study were to develop a 3-dimensional finite element model (FEM) of a complete skull with UCLP to evaluate effects of RPE on the craniofacial complex and to predict points of force application for optimal expansion. Methods: An FEM of a skull with UCLP consisting of 105,357 nodes and 371,605 elements was generated from spiral computed-tomography images using the medical imaging software, Mimics 13.1. This model was imported into the finite element solver, ANSYS 12.0, where transverse and diagonal forces were applied bilaterally to simulate expansion forces of RPE devices. Results: Finite element analysis (FEA) results showed RPE with diagonal force application displaced the minor segment more laterally than RPE with transverse force application, with high stress levels exhibited in the anterior dentoalveolar region of the minor segment. Transverse force applications exhibited greater expansion and higher stress levels in the posterior regions of the maxilla when compared to the anterior region. Application of both diagonal and transverse forces generated high stress concentrations in the zygomatic arch and medial side of the orbit. Conclusions: FEA can be used to study and predict points of force application for optimal expansion in patients with UCLP. Application of diagonal forces using RPE on patients with UCLP results in greater displacement of the minor segment when compared to transverse force application. High stress concentrations in the minor segment, zygomatic arch, and medial side of the orbit are consistent with clinical observations of higher relapse rate of the minor segment and pressure sensations expressed by patients undergoing RPE.
    No preview · Conference Paper · Mar 2011
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    ABSTRACT: Bone morphogenetic proteins (BMPs) are widely used as bone graft substitutes in spinal fusion, but are associated with numerous adverse effects. The growth factor Nel-like molecule-1 (Nell-1) is mechanistically distinct from BMPs and can minimize complications associated with BMP therapies. This study evaluates the efficacy of Nell-1 combined with demineralized bone matrix (DBM) as a novel bone graft material for interbody spine fusion using sheep, a phylogenetically advanced animal with biomechanical similarities to human spine. Nell-1+sheep DBM or Nell-1+heat-inactivated DBM (inDBM) (to determine the osteogenic effect of residual growth factors in DBM) were implanted in surgical sites as follows: (1) DBM only (control) (n=8); (2) DBM+0.3 mg/mL Nell-1 (n=8); (3) DBM+0.6 mg/mL Nell-1 (n=8); (4) inDBM only (control) (n=4); (5) inDBM+0.3 mg/mL Nell-1 (n=4); (6) inDBM+0.6 mg/mL Nell-1 (n=4). Fusion was assessed by computed tomography, microcomputed tomography, and histology. One hundred percent fusion was achieved by 3 months in the DBM+0.6 mg/mL Nell-1 group and by 4 months in the inDBM+0.6 mg/mL Nell-1 group; bone volume and mineral density were increased by 58% and 47%, respectively. These fusion rates are comparable to published reports on BMP-2 or autograft bone efficacy in sheep. Nell-1 is an independently potent osteogenic molecule that is efficacious and easily applied when combined with DBM.
    Preview · Article · Feb 2011 · Tissue Engineering Part A