Moga Radu-Andrei, Olteanu Cristian Doru, Delean Ada Gabriela
Department of Cariology, Endodontics and Oral Pathology, School of Dental Medicine, University of Medicine and Pharmacy Iuliu Hatieganu, Str. Motilor 33, 400001 Cluj-Napoca, Romania.
Department of Orthodontics, School of Dental Medicine, University of Medicine and Pharmacy Iuliu Hatieganu, Str. Avram Iancu 31, 400083 Cluj-Napoca, Romania.
Dent J (Basel). 2024 Oct 14;12(10):328. doi: 10.3390/dj12100328.
BACKGROUND/OBJECTIVES: This numerical analysis of stress distribution in the dental pulp and neuro-vascular bundle (NVB) of lower premolars assessed the ischemic and degenerative-resorptive risks generated by 2 and 4 N during orthodontic movements (rotation, translation, tipping, intrusion and extrusion) in intact periodontium.
The numerical analysis was performed on nine intact periodontium 3D models of the second lower premolar of nine patients totaling 90 simulations.
In intact periodontium, both forces displayed a similar stress distribution for all five orthodontic movements but different amounts of stress (a doubling for 4 N when compared with 2 N), with the highest values displayed in NVB. In intact periodontium, 2 N and 4 N induced stresses lower than the maximum hydrostatic pressure (MHP) with no ischemic risks for healthy intact teeth. The rotation was seen as the most stressful movement, closely followed by intrusion and extrusion. Translation was quantitatively seen as the least stressful when compared with other movements.
Larger orthodontic forces of 2 N and 4 N are safe (with any expected ischemic or resorptive risks) for the dental pulp and NVB of healthy intact teeth and in intact periodontium. Nevertheless, rotation and translation movements can induce localized circulatory disturbances in coronal pulp (i.e., vestibular and proximal sides) generating ischemic and resorptive risks on previously treated teeth (i.e., direct and indirect dental pulp capping). The intrusion and extrusion movements, due to the higher NVB-induced deformation when compared with the other three movements, could trigger circulatory disturbances followed by ischemia on previously traumatized teeth (i.e., occlusal trauma).
背景/目的：本对下颌前磨牙牙髓和神经血管束（NVB）应力分布的数值分析，评估了在完整牙周组织中，正畸移动（旋转、平移、倾斜、压入和伸出）过程中2N和4N力所产生的缺血和退行性吸收风险。
对9例患者下颌第二前磨牙的9个完整牙周组织三维模型进行数值分析，共进行90次模拟。
在完整牙周组织中，两种力在所有五种正畸移动中均表现出相似的应力分布，但应力大小不同（4N时的应力是2N时的两倍），NVB中的应力值最高。在完整牙周组织中，2N和4N引起的应力低于最大静水压力（MHP），对健康完整牙齿无缺血风险。旋转被视为压力最大的移动，其次是压入和伸出。与其他移动相比，平移在定量上被视为压力最小的移动。
对于健康完整牙齿的牙髓和NVB以及完整牙周组织，2N和4N的较大正畸力是安全的（无任何预期的缺血或吸收风险）。然而，旋转和平移移动可导致冠髓局部循环障碍（即前庭侧和近中侧），对先前治疗过的牙齿产生缺血和吸收风险（即直接和间接盖髓）。由于与其他三种移动相比，NVB引起的变形更大，压入和伸出移动可能引发先前受过创伤牙齿（即咬合创伤）的循环障碍，继而导致缺血。
