北海道歯学雑誌 = Hokkaido Journal of Dental Science;第33巻 第2号

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Influence of changes in denture-base fit and connecting rigidity on the load distribution of abutment teeth and the displacement of abutment teeth and denture base in mandibular distal-extension removable partial dentures.

Wada, Tatsunori;Saito, Masayasu;Miura, Yoshifumi;Yokoyama, Atsuro

Permalink : http://hdl.handle.net/2115/52453
KEYWORDS : Denture base fit;Connecting rigidity;Removable partial dentures;Stress distribution of abutment teeth;Displacement of denture-base

Abstract

The purpose of this study was to clarify the influence of denture-base fit and retainer design on the distribution of stress on abutment teeth, and the displacement of abutment teeth and the denture base. A mandibular model with a simulated periodontal ligament and mucosa was fabricated to simulate a partially edentulous case with the right first molar and second molar missing. The edentulous area was made flat to eliminate the influence of residual ridge forms. Two types of removable partial dentures with different direct retainers: 1, a cone crown telescope (CCT); and 2, a modified circumferential clasp with a distal guide plate, a buccal retentive arm and a lingual enlarged bracing arm (MCC), with an embrasure clasp as an indirect retainer, were designed. The following conditions of the denture-base conformity with the simulated mucosa were established: completely suitable( CS), mesial half unsuitable( M-), distal half unsuitable( D-), buccal half unsuitable (B-), lingual half unsuitable (L-), and completely unsuitable (CU). A 200μm clearance area was made between the denture base and simulated mucosa on these unsuitable parts. The stresses at the apical, buccal and distal portions, the distal displacement of abutment teeth and the subsidence of the denture base were investigated. Both the stress on and the displacement of abutment teeth for the partially unsuitable denture base were larger than those for the completely suitable denture bases for the CCT-retained denture. The distal stress and distal displacement of abutment teeth for the completely unsuitable denture base were larger than for the completely suitable denture base with the MCC-retained denture. The buccal stress distribution and the distal displacement of the abutment teeth with the CCT-retained denture were significantly larger than those with the MCC-retained denture under all conditions. When the denture base was completely unsuitable or the distal part was unsuitable, the subsidence of the denture base with the MCC-retained denture was larger than that with the CCT-retained denture. These results showed that the denture base fit influenced the stress and displacement of the abutment teeth for the CCT-retained denture more than that for the MCC-retained denture, and the subsidence of the denture base of the MCC-retained denture was the same as that of the CCT-retained denture when the unsuitable parts of the denture base were only mesial and buccal. Thus, the MCC-retained denture does not cause overloading of abutment teeth and the residual ridge even if the fitness of the denture base decreases.

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