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

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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.