Gharechahi Jafar, Sharifi Esmael, Nosohian Saeid, Aghdaee Nafiseh Asadzadeh
Department of Prosthodontics of the School of Dentistry, Dental Research Center, at Mashhad University of Medical Science in Mashhad, Khorasan Iran.
J Contemp Dent Pract. 2008 Nov 1;9(7):49-56.
One of the most important issues in the design of removable partial dentures (RPD) is the location of retentive arms to provide sufficient support. This is a critical factor in patients with less supporting tissue and abutment teeth. Patients classified as Class IV Aramany need special attention in this area of RPD design to minimize the stress distribution in bone and mucosal membrane. Using the finite element method, the aim of this study was to analyze the distribution stress to supporting tissues when a Class IV Aramany RPD is worn. The data presented in this report are the effects of the stress on bone and mucosal membranes. Results on teeth and the periodontal ligament have been previously reported.
Three dimensional finite element models were constructed using normal dimensions. Exact physiology and morphology of teeth and the remaining palate were simulated to that of a maxillectomy patient. Three RPD designs with circumferential cast retainers were examined: buccal retention and palatal reciprocation (P1); palatal retention and buccal reciprocation (P2); and buccal and palatal retention (P3). After completion of the models and remaining palate, each RPD design was loaded under 53N and stress was applied in three different directions: vertical to the posterior teeth (premolar and first molars) of the RPD (F1); at a 33 masculine angle to the posterior teeth (premolar and first molars) of the RPD (F2); and vertically on the anterior teeth (central incisors) of the RPD (F3). The stress distribution in the RPD models on cortical and cancellous bone and the mucosal membrane was analyzed using von Mises criterion.
The maximum tension in cortical bone (70.84 Mpa) was observed when a 53N force was applied in a vertical direction to posterior teeth (F2) using buccal and palatal retention (P3). Minimum tension (15.73 Mpa) in cortical bone was observed using the F3 load on the P2 design. Similar results were seen in cancellous bone, with the highest stress (8.01 Mpa) observed using F2 load on the P3 design and the lowest stress (3.04 Mpa) observed using the F3 load on the P2 design. For mucosal membrane, the maximum (3.57 Mpa) and minimum (3.05 Mpa) stress was observed using the F3 load on the P3 design and the F1 load on the P2 design, respectively. The average stress in all RPD designs was 3 Mpa.
The design demonstrating the least tension in cortical and cancellous bone and mucosal membrane was the P2 design, a RPD with palatal retention and buccal reciprocation.
Palatal retention and buccal reciprocation (P2 design) is recommended for patients with maxillofacial RPDs.
可摘局部义齿（RPD）设计中最重要的问题之一是固位臂的位置，以提供足够的支持。对于支持组织和基牙较少的患者，这是一个关键因素。被归类为IV类阿拉马尼（Aramany）的患者在RPD设计的这一领域需要特别关注，以尽量减少骨和粘膜膜中的应力分布。本研究旨在使用有限元方法分析佩戴IV类阿拉马尼RPD时支持组织的应力分布。本报告中的数据是应力对骨和粘膜膜的影响。牙齿和牙周韧带的结果此前已有报道。
使用正常尺寸构建三维有限元模型。模拟牙齿和剩余腭部的精确生理和形态，使其与上颌骨切除患者的情况一致。检查了三种带有环形铸造固位体的RPD设计：颊侧固位和腭侧对抗（P1）；腭侧固位和颊侧对抗（P2）；以及颊侧和腭侧固位（P3）。在完成模型和剩余腭部后，对每个RPD设计施加53N的载荷，并在三个不同方向施加应力：垂直于RPD的后牙（前磨牙和第一磨牙）（F1）；与RPD的后牙（前磨牙和第一磨牙）成33°角（F2）；以及垂直于RPD的前牙（中切牙）（F3）。使用冯·米塞斯准则分析RPD模型在皮质骨、松质骨和粘膜膜中的应力分布。
当使用颊侧和腭侧固位（P3）在垂直方向对后牙施加53N力（F2）时，观察到皮质骨中的最大张力（(70.84 Mpa)）。在P2设计上使用F3载荷时，观察到皮质骨中的最小张力（(15.73 Mpa)）。在松质骨中也观察到类似结果，在P3设计上使用F2载荷时观察到最高应力（(8.01 Mpa)），在P2设计上使用F3载荷时观察到最低应力（(3.04 Mpa)）。对于粘膜膜，在P3设计上使用F3载荷时观察到最大应力（(3.57 Mpa)），在P2设计上使用F1载荷时观察到最小应力（(3.05 Mpa)）。所有RPD设计中的平均应力为(3 Mpa)。
在皮质骨、松质骨和粘膜膜中显示出最小张力的设计是P2设计，即一种具有腭侧固位和颊侧对抗的RPD。
对于颌面RPD患者，建议采用腭侧固位和颊侧对抗（P2设计）。
