Camacho Marisol C, Gallardo Yolanda R, Stegun Roberto Ch, Costa Bruno, Sesma Newton
Department of Prosthodontics, Dental School, Científica del Sur, Peru.
Department of Prosthodontics, Dental School, Sao Paulo University, Av. Prof. Lineu Prestes, 2227- Cidade Universitária- Butanta, São Paulo, CEP: 05508-000, Brazil.
Heliyon. 2018 Mar 15;4(3):e00575. doi: 10.1016/j.heliyon.2018.e00575. eCollection 2018 Mar.
The purpose of this study was to evaluate the behavior of mandibular canines acting as abutment teeth and indirect retainers of a Kennedy class II according to different designs: lingual rest and lingual rest associated with a reciprocal arm.
MATERIALS & METHODS: A resin cast with two simulated canine teeth was made in Ni-Cr alloy, representing a Kennedy class II mandibular arch. With the objective of simulating the resilience of the periodontal ligament, a polyurethane layer was added at the canine tooth's root. A metallic framework of Co-Cr alloy was fabricated with a T bar clasp and a lingual rest associated with a reciprocal arm. To obtain the second framework, the reciprocal arm was removed using a tungsten bur. Each framework was submitted to tensile force using a VersaTest machine. The magnitude and direction of canine movement during removal of the framework was measured using two dial gauges (mm). The axial tensile force required to remove the experimental framework (N) was also evaluated. The data were compared using the paired t-test with 95% confidence intervals. Differences were considered significant at P < .05.
The mean retentive force of the modified design framework with the reciprocal arm was significantly higher (P < .0001) than that of the framework with the lingual rest. The abutment teeth showed movement in the lingual and mesial directions, and this movement was less when associated with the reciprocal arm design.
The reciprocal arm in association with a lingual rest in the framework decreased the movement of the abutment teeth when analyzed in the bucco-lingual and mesio-distal directions and contributed to increased retention by friction.
本研究旨在根据不同设计评估下颌尖牙作为基牙和Kennedy II类间接固位体的行为：舌侧支托以及与对抗臂相关的舌侧支托。
用镍铬合金制作带有两颗模拟尖牙的树脂模型，代表Kennedy II类下颌牙弓。为模拟牙周韧带的弹性，在尖牙牙根处添加一层聚氨酯。用钴铬合金制作一个带有T形卡环和与对抗臂相关的舌侧支托的金属支架。为获得第二个支架，用钨钢钻去除对抗臂。每个支架使用万能试验机施加拉力。在去除支架过程中，使用两个百分表（毫米）测量尖牙移动的大小和方向。还评估了去除实验支架所需的轴向拉力（牛顿）。使用配对t检验和95%置信区间对数据进行比较。P <.05时差异被认为具有统计学意义。
带有对抗臂的改良设计支架的平均固位力显著高于（P <.0001）仅带有舌侧支托的支架。基牙在舌侧和近中方向出现移动，与对抗臂设计相关时这种移动较小。
在支架中，对抗臂与舌侧支托相结合，在颊舌向和近远中向分析时减少了基牙的移动，并通过摩擦力有助于增加固位力。
