Helmer Loreine M L, Klop Cornelis, Lobbezoo Frank, Lange Jan de, Koolstra Jan Harm, Dubois Leander
Department of Oral and Maxillofacial Surgery, Amsterdam Academic Medical Centers and Academic Centre for Dentistry (ACTA), University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam, the Netherlands; Department of Orofacial Pain and Dysfunction, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam, the Netherlands.
Department of Oral and Maxillofacial Surgery, Amsterdam Academic Medical Centers and Academic Centre for Dentistry (ACTA), University of Amsterdam and Vrije Universiteit Amsterdam, Amsterdam, the Netherlands.
Arch Oral Biol. 2023 Nov;155:105791. doi: 10.1016/j.archoralbio.2023.105791. Epub 2023 Aug 15.
Premature dental contact on the fractured side and a contralateral open bite are signs of a unilaterally fractured condyle of the temporomandibular joint (TMJ). The lateral pterygoid muscle pulls the condyle inwards, causing angulation of the fractured part and shortening of the ramus. This imbalance after fracture might change the load in both TMJs and consequently induce remodeling. The present study aimed to calculate this change in load. It is hypothesized to decrease on the fractured side and increase on the non-fractured side.
For these calculations, a finite element model (FEM) was used. In the FEM, shortening of the ramus varied from 2 mm to 16 mm; angulation, from 6.25° to 50°.
After fracture, load on the non-fractured side increased, but only at maximal mouth opening (MMO). Simultaneously, load on the fractured side decreased, at both timepoints, i.e., MMO and closed mouth. When comparing all simulations at those time points, i.e., from 2 mm and 6.25° to 16 mm and 50°, the load in the fractured condyle declines steadily. However, for both timepoints, a threshold stands out around 6 mm shortening and 18.75° angulation: visualization of the fractured condyle showed, apart from load on the condylar head, a second point of load more medial in the TMJ which was most evident in the 6 mm - 18.75° simulation.
These findings could implicate that the balance between both TMJs is more difficult to restore after a fracture with more than 6 mm shortening and more than 18.75° angulation.
骨折侧过早的牙接触和对侧开牙合是颞下颌关节（TMJ）单侧髁突骨折的体征。翼外肌将髁突向内牵拉，导致骨折部位成角和下颌支缩短。骨折后的这种不平衡可能会改变两个颞下颌关节的负荷，从而引发重塑。本研究旨在计算这种负荷变化。假设骨折侧负荷降低，非骨折侧负荷增加。
为进行这些计算，使用了有限元模型（FEM）。在有限元模型中，下颌支缩短范围为2毫米至16毫米；成角范围为6.25°至50°。
骨折后，非骨折侧的负荷增加，但仅在最大张口（MMO）时。同时，骨折侧在两个时间点，即最大张口和闭口时的负荷均降低。在比较这些时间点（即从2毫米和6.25°至16毫米和50°）的所有模拟时，骨折髁突的负荷稳步下降。然而，对于这两个时间点，在缩短约6毫米和成角18.75°左右有一个阈值：骨折髁突的可视化显示，除了髁突头部的负荷外，颞下颌关节中更内侧还有第二个负荷点，这在6毫米 - 18.75°的模拟中最为明显。
这些发现可能意味着，在缩短超过6毫米和成角超过18.75°的骨折后，恢复两个颞下颌关节之间的平衡更加困难。
