Mahross Hamada Z, Atito Ehab M, Mansour Mamdouh M, Badr Wesam E, Osman Mohamed S, Quassem Mohamed A
Removable Prosthodontics Department, Faculty of Dental Medicine, Al-Azhar University, Cairo, Egypt.
Department of Substitutive Dental Sciences, College of Dentistry & Pharmacy, Buraydah Private Collages, Buraydah, Saudi Arabia.
J Prosthodont. 2024 Jul 31. doi: 10.1111/jopr.13915.
To analyze the distribution of stresses for mandibular Kennedy class I removable partial overdentures submitted to different implant lengths and clasp designs.
Twenty-seven heat-cured acrylic resin casts with a uniform soft acrylic layer were constructed from models representing the mandibular Kennedy class I removable partial denture with the first premolars terminal abutment on both sides. The casts were grouped into a control group, group I, and group II with three casts of each for designing a different clasp on the last abutment with Rest, Proximal plate, Aker circumferential (RPA), Rest, Proximal plate, I-bar (RPI), and wrought wire (WW). All casts were submitted to vertical load for stress analysis after preparing channels at the buccal/distal surface of abutments, the crest of the ridge, and the buccal/lingual of the implant for placement of uniaxial strain gauges that can convert the electro-signals to micro-strain by using the software. Kolmogorov-Smirnov normality test, independent t-test, and one-way anlysis of Variance (ANOVA) test followed by Tukey`s Post Hoc for multiple comparisons test were used for statistical analysis.
The control group results revealed more significant stresses on the ridge with RPA and RPI clasps but on the abutment with WW clasp as P < 0.05. In group I, the ridge was significantly stressed more than the implant followed by the abutment when the RPA clasp was used while there was insignificance on the implant with RPA and RPI as p > 0.05. In group II, the stresses were more on the abutment with RPA, RPI, and WW clasps followed by lower on the implant and lowest on the ridge.
Proper implant and clasp type selection are critical for stress distribution on the ridge, abutment, and implant when using removable partial overdenture. The stresses on longer implants are tolerated and more widely distributed than shorter ones.
分析下颌Kennedy I类可摘局部覆盖义齿在不同种植体长度和卡环设计下的应力分布情况。
用均匀的软质丙烯酸树脂层制作27个热固化丙烯酸树脂模型，这些模型代表双侧第一前磨牙为末端基牙的下颌Kennedy I类可摘局部义齿。将模型分为对照组、I组和II组，每组三个模型，分别在最后一个基牙上设计不同的卡环，即支托、邻面板、Aker环形卡环（RPA）、支托、邻面板、I形杆卡环（RPI）和锻丝卡环（WW）。在基牙的颊侧/远中面、牙槽嵴顶以及种植体的颊侧/舌侧制备通道以放置单轴应变片，之后对所有模型施加垂直载荷进行应力分析，应变片可通过软件将电信号转换为微应变。采用Kolmogorov-Smirnov正态性检验、独立样本t检验和单因素方差分析（ANOVA），随后进行Tukey事后多重比较检验进行统计分析。
对照组结果显示，使用RPA和RPI卡环时牙槽嵴上的应力更显著，而使用WW卡环时基牙上的应力更显著，P < 0.05。在I组中，使用RPA卡环时牙槽嵴上的应力明显大于种植体，其次是基牙，而使用RPA和RPI卡环时种植体上的应力无显著差异，p > 0.05。在II组中，使用RPA、RPI和WW卡环时基牙上的应力更大，其次是种植体，牙槽嵴上的应力最小。
在使用可摘局部覆盖义齿时，正确选择种植体和卡环类型对于牙槽嵴、基牙和种植体上应力的分布至关重要。与较短种植体相比，较长种植体上的应力更易耐受且分布更广泛。
