Department of Orthodontics and Dentofacial Orthopedics, University of Missouri-Kansas City, Kansas, MO, USA.
Department of Oral and Craniofacial Sciences, University of Missouri-Kansas City, Kansas, MO, USA.
Orthod Craniofac Res. 2017 Jun;20 Suppl 1:145-150. doi: 10.1111/ocr.12174.
To determine whether dolichofacial (Frankfort horizontal mandibular plane angle (FHMPA) ≥30°) vs brachyfacial (FHMPA ≤22°) phenotypes differ in temporomandibular joint (TMJ) loads and whether these differences correlate longitudinally with mandibular ramus height (Condylion-Gonion, Co-Go).
Lateral and posteroanterior cephalographs from ten dolichofacial and ten brachyfacial individuals made at average ages of 6 (T1), 12 (T2) and 18 (T3) years and available online (http://www.aaoflegacycollection.org/aaof_home.html) were used.
Three-dimensional anatomical data were derived from cephalographs and used in numerical models to predict TMJ loads for a range of biting angles on incisors, canines and first molars. Two criteria were used to define clinically important between-group TMJ load differences: statistical significance was defined with a two-group t-test, and where differences were also ≥20%. A statistical approach called response surface analysis was used to assess correlation between TMJ loads and its predictors considered in this study.
The two phenotypes had significantly different FHMPA at all ages (P<.05). No differences in TMJ loads were found at T1. Ipsilateral and contralateral TMJ loads at T2 and T3 were significant and ≥20% larger in dolichofacial than brachyfacial phenotypes for specific biting angles (all adjusted P<.05). Regression analysis indicated age and ramus height contribute 53% of the variability in normalized values of TMJ loads. At higher ages, dolichofacial phenotypes had significantly higher TMJ loads which were correlated with shorter ramus heights compared to brachyfacial phenotypes.
Craniofacial mechanics may explain, in part, mandibular growth differences between dolichofacial and brachyfacial phenotypes.
确定长面型（法兰克福水平下颌平面角（FHMPA）≥30°）与短面型（FHMPA≤22°）是否在颞下颌关节（TMJ）负荷方面存在差异，以及这些差异是否与下颌升支高度（髁突-下颌角，Co-Go）纵向相关。
使用平均年龄为 6（T1）、12（T2）和 18（T3）岁的 10 名长面型和 10 名短面型个体的侧位和后前位头颅侧位片，这些头颅侧位片可在网上获得（http://www.aaoflegacycollection.org/aaof_home.html）。
从头颅侧位片获得三维解剖学数据，并将其用于数值模型，以预测在切牙、尖牙和第一磨牙上的一系列咬合角度下 TMJ 的负荷。使用两种标准来定义组间 TMJ 负荷差异的临床重要性：使用两样本 t 检验定义统计学意义，并且差异也≥20%。使用一种称为响应面分析的统计方法来评估本研究中考虑的 TMJ 负荷与其预测因子之间的相关性。
两种表型在所有年龄段的 FHMPA 均有显著差异（P<.05）。在 T1 时未发现 TMJ 负荷的差异。在 T2 和 T3 时，对于特定的咬合角度，长面型与短面型相比，同侧和对侧 TMJ 负荷显著且≥20%更大（所有调整后的 P<.05）。回归分析表明，年龄和升支高度对 TMJ 负荷的归一化值的变异性贡献了 53%。在较高的年龄，长面型的 TMJ 负荷显著更高，与短面型相比，这与较短的升支高度相关。
颅面力学可能部分解释了长面型和短面型之间下颌生长差异的原因。
