Mechanobehavior distinguishes mandibular growth differences in two facial types

在美国，超过9%的儿童是正畸患者，他们接受了弯曲的牙齿和下巴的治疗。 差异称为咬合不正（AAO，2017）。这种治疗的费用每年超过95亿美元（Guay 等人2008; Laniado等人2017）。通过牙面矫形术管理颌骨生长的适应症超过30%， 正畸患者，但13-36%的下颌骨生长促进疗法未能纠正错牙合 （Hedlund and Feldmann 2016;奥布莱恩et al. 2003）。因此，结果不佳的代价是相当大的。 下颌骨增强的矫形治疗试图促进对负荷敏感的第二下颌骨的生长， 通过颞下颌关节（TMJ）的加载力学和行为的变化，颌骨软骨。 预计下颌骨生长量较少，垂直方向表达更多（Buschang等人，2017; Karlsen 1997），在长面（长窄）儿童中进行矫形治疗的效果较差 与短面（短宽）表型相比（Deen和Woods 2015; Pancherz和Michailidou 2004; Rogers et al. 2018）。然而，不同的TMJ负荷力学和行为（力学行为）， 生长和处理期间的这些表型是未知的。这项研究的长期目标是 提供具有可预测结果的循证牙面矫形治疗。因此，本申请 提出了一项前瞻性的观察研究，在选定的人口长面和短面儿童 在正畸治疗之前、期间和之后。这项研究将有助于改善牙科， 口腔和颅面健康，通过解决三个具体目标： 1.测试长面儿童与短面儿童相比具有能量密度（能量输入）的假设 单位体积的软骨，mJ/mm 3），对于相同的颌骨任务来说明显更大，因此， 下颌骨生长较早。 2.检验长面儿童与短面儿童相比具有占空系数（下颌时间百分比）的假设 肌肉活动/总记录时间）显著较小，因此促进下颌骨生长较少 每一年。 3.检验存在表型牙面亚组的假设，通过机械行为评分进行区分 （（能量密度）2 ×占空因数），这与下颌骨生长的显著差异相对应。 纵向临床治疗记录和通过验证技术收集的数据，包括数字 建模，动态立体测量，实验室和现场肌电图，将用于比较 表型之间的机械行为变量，并测试这些变量是否预测下颌骨生长， 以支高表示。这项研究的新成果将为未来的临床研究奠定重要基础。 这些方法可以改变机械行为，以实现更成功和可预测的骨科治疗， 有下颚畸形的孩子

In the United States, >9% of children are orthodontic patients who are treated for crooked teeth and jaw discrepancies known as malocclusions (AAO, 2017). Costs for this treatment are >$9.5 billion annually (Guay et al. 2008; Laniado et al. 2017). Management of jaw growth via dentofacial orthopedics is indicated in >30% of orthodontic patients but 13-36% of mandibular growth enhancement therapies fail to correct the malocclusion (Hedlund and Feldmann 2016; O'Brien et al. 2003). Hence, the costs of poor results are considerable. Orthopedic therapies for mandibular enhancement try to promote growth of the load-sensitive secondary cartilages of the jaw through changes in temporomandibular joint (TMJ) loading mechanics and behaviors. Mandibular growth is expected to be less in amount and expressed more vertically (Buschang et al. 2017; Karlsen 1997) with poorer prognoses for orthopedic therapies in children with dolichofacial (long-narrow) compared to brachyfacial (short-wide) phenotypes (Deen and Woods 2015; Pancherz and Michailidou 2004; Rogers et al. 2018). However, differences in the TMJ loading mechanics and behaviors (mechanobehavior) in these phenotypes during growth and treatment are unknown. The broad, long-term goals of this research are to provide evidence-informed dentofacial orthopedic therapies with predictable results. Thus, this application proposes a prospective observational study in selected populations of dolichofacial and brachyfacial children before, during and after orthodontic treatment. This study will contribute to the mission of improving dental, oral, and craniofacial health by addressing three Specific Aims: 1. Test the hypothesis that dolichofacial compared to brachyfacial children have energy densities (energy input per volume of cartilage, mJ/mm3) that are significantly larger for the same jaw tasks and, thus, limit mandibular growth earlier. 2. Test the hypothesis that dolichofacial compared to brachyfacial children have duty factors (% time of jaw muscle activity/total recording time) that are significantly smaller and, thus, promote less mandibular growth per year. 3. Test the hypothesis that phenotypic dentofacial subgroups exist, differentiated by mechanobehavior scores ((energy densities)2 X duty factors) that correspond with significant differences in mandibular growth. Longitudinal clinical treatment records and data collected via validated techniques, including numerical modeling, dynamic stereometry, and laboratory and in-field electromyography, will be used to compare mechanobehavior variables between phenotypes and test if these variables predict mandibular growth as indicated by ramus height. The novel outcomes of this research will be critical foundations for future clinical approaches that modify mechanobehavior to achieve more successful and predictable orthopedic therapies in children with jaw discrepancies.