Kamal Maha Nagy Mohamed, Mohammed Haitham Amr, Shokry Abdallah
Removable Prosthodontics Department, Faculty of Dentistry, British University in Egypt (BUE), Elshrouk city, Egypt.
Fixed Prosthodontics Department, Faculty of Dentistry, Fayoum University, Fayoum Government, Faiyum, Egypt.
BMC Oral Health. 2025 May 27;25(1):810. doi: 10.1186/s12903-025-06213-w.
Due to lack of consensus on optimal unilateral attachment retained partial denture design, this finite element comparative analysis study was conducted to measure the stresses induced from four different attachment-retained lower Kennedy class II removable partial denture (RPD) designs around the abutment teeth and the supporting residual ridge.
An educational cast of lower Kennedy class II having the first premolar as the last standing abutment was used. The abutment teeth - canine and first premolar- of the edentulous side were reduced to receive two splinted porcelain veneered metal crowns, while the intact side was prepared to receive a double Aker's clasp and mesial rest seat for indirect retention. Then the cast was scanned, and the partial denture components and the splinted crowns were designed and assembled digitally using Blender4dental software. According to the attachment used; partial dentures were designed as follows: design 1: unilateral PD retained by OT cap attachment, design 2: unilateral RPD retained by double OT cap attachment, design 3: unilateral RPD retained by mini-bar attachment, and design 4: RPD retained by OT cap with major connector crossing the arch for stabilization (conventional RPD). The Meshmex software was used to modify the STL file, and the Abaqus software was used for finite element analysis. On the edentulous side, the first and second molars were subjected to vertical loads of 200 N and tangential loads of 23.5 N, while the first and second premolars were subjected to vertical loads of 140 N and tangential loads of 16.45 N. The von Misses stress levels induced around the abutments and at the residual ridge were measured and compared.
The lowest stresses were found with the conventional RPD design. Regarding von Mises stresses on the prepared abutments; The lowest von Mises stresses were found in design 4, followed by design 1, then design 3, while the highest von Mises stresses were found in design 2. Regarding von-Mises stresses on the residual ridge, the lowest Von Mises stresses were found in design 4, followed by design 3, then design 2, while the highest Von Mises stresses were found in design 1.
The attachment retained RPD with a conventional design offered the lowest stresses applied for the abutment and the residual ridge. OT cap attachment exerts the least stress on the abutments when used in unilateral design RPD, so it is preferable for abutment preservation but contraindicated in weak ridges, however, the double OT cap exerts the highest amount of force on the abutment teeth and could be used with abutments showing perfect periodontal condition.
由于在最佳单侧附着体固位局部义齿设计上缺乏共识，本有限元对比分析研究旨在测量四种不同附着体固位的下颌肯氏II类可摘局部义齿（RPD）设计在基牙和支持性残余牙槽嵴周围产生的应力。
使用以第一前磨牙作为最后留存基牙的下颌肯氏II类教学模型。缺牙侧的基牙——尖牙和第一前磨牙——进行预备以容纳两个联冠烤瓷熔附金属全冠，而健侧则预备以容纳双Aker卡环和近中支托凹用于间接固位。然后对模型进行扫描，并使用Blender4dental软件对局部义齿部件和联冠进行数字化设计与组装。根据所使用的附着体，局部义齿设计如下：设计1：由OT帽附着体固位的单侧局部义齿；设计2：由双OT帽附着体固位的单侧RPD；设计3：由迷你杆附着体固位的单侧RPD；设计4：由OT帽附着体固位且大连接体跨过牙弓以实现稳定的RPD（传统RPD）。使用Meshmex软件修改STL文件，并使用Abaqus软件进行有限元分析。在缺牙侧，第一和第二磨牙承受200 N的垂直载荷和23.5 N的切向载荷，而第一和第二前磨牙承受140 N的垂直载荷和16.45 N的切向载荷。测量并比较基牙周围和残余牙槽嵴处产生的von Misses应力水平。
传统RPD设计产生的应力最低。关于预备基牙上的von Mises应力，设计4中的von Mises应力最低，其次是设计1，然后是设计3，而设计2中的von Mises应力最高。关于残余牙槽嵴上的von-Mises应力，设计4中的Von Mises应力最低，其次是设计3，然后是设计2，而设计1中的Von Mises应力最高。
传统设计的附着体固位RPD对基牙和残余牙槽嵴施加的应力最低。在单侧设计RPD中使用时，OT帽附着体对基牙施加的应力最小，因此对于基牙保护较为理想，但在薄弱牙槽嵴中禁忌使用；然而，双OT帽对基牙施加的力最大，可用于牙周状况良好的基牙。
