Investigation of the removable partial denture design based on the in vivo 3-D force analyses on the abutment tooth of the removable partial denture

本研究的目的是通过自行研制的压电式三维力测量装置来研究基牙在载荷作用下的行为。对于局部义齿的设计，包括基牙和咬合方案的选择，了解载荷是很重要的。该测力装置由形成金属核的内部部分、力传感器和形成金属牙冠的外部部分组成。受试者为自然牙列的年轻男性和部分无牙列的老年女性。在充分解释这项研究之后，获得知情同意。实验牙为有义齿受试者的上颌左第二磨牙和部分无义齿受试者的下颌右第二前磨牙，当部分无义齿受试者戴义齿时，基牙所承受的载荷较不戴义齿时明显减小。当部分无义齿受试者佩戴义齿时，内侧托槽最大咬合时，载荷方向角较不戴义齿时明显减小。而与内侧支撑位和远端支撑位的夹角有显著差异。当部分无义齿受试者戴用远中支托义齿时，载荷方向的角度比戴用内支托义齿时明显增大。内侧和远端的力矢量指向最外侧，内侧的力矢量指向最下方。4种不同状态在正位面上的方向差异无统计学意义，牙科受试者MVC时最大震级为173.3±15.3N。随着压力大小的增大，载荷方向发生三维变化。在咀嚼粘性食物的整个过程中，都记录了牵引力。

The purpose of this study is to clarify the behavior of the load applied to the abutment tooth by means of the 3-dimensional force measuring device with a piezo-electric transducer that we have developed. It is important to know that load for partial denture design including the selection of the abutment tooth and occlusal scheme. The custom-made force measuring device comprised an inner part forming a metal core, a force transducer, and an outer part forming a metal crown.The subjects were a young male with natural dentition and an old female with partial edentulous dentition. Informed consent was obtained after full explanation of this study. The experimental teeth were the maxillary left second molar of dentulous subject and mandibular right second premolar of partial edentulous subject.When the partial edentulous subject wearing the denture with distal rest clenched maximally, the magnitude of the load applied to the abutment tooth decreased significantly than without the denture. When the partial edentulous subject wearing the denture with medial rest clenched maximally, the angle of the load direction was decreased significantly than without the denture. On the other hand, there was significant difference between the angles with the medial rest and with the distal rest. When the partial edentulous subject wearing the denture with distal rest clenched maximally, the angle of the load direction was increased significantly than the denture with medial rest. The force vector with the medial and distal rests directed most laterally, and that with the medial rest directed most downward. There was not significant difference among the directions of four different conditions in the frontal plane.In the dentulous subject, The maximum magnitude was 173.3±15.3N during MVC. As the magnitude of the compressive force increased, the load direction changed three dimensionally. Tractive forces were recorded throughout the chewing the sticky food.