前歯における合くぎならびに歯根部歯質の応力解析

Abstract

A study was made of the behavior of postcores and tooth structures under various post lengths and post diameters with the strain gauge method and the finite element method.Endodontically treated upper central incisors under various post lengths and post diameters of metal postcore were loaded with a horizontal 1kg weight at the lingual surface and strains at the cervical root surface were analyzed.Two-dimentional finite element models of porcelain jacket crowns on the upper central incisor were developed. The finite element analysis 1 was carried out of 6 sizes of post length (5.0mm, 6.0mm, 7.0mm, 8.0mm, 9.0mm and 10.0mm) and 3 sizes of post diameter (1.0 mm, 2.0mm and 3.0mm).For the purpose of making more clear as to mechanism of fracture of the post-core and the tooth struc ture, the finite element analysis 2 and 3 were carried out. The cervical cement layer (under the analysis 2) and the whole cement layer (under the analysis 3) between the post-core and the tooth structure were assumed to be elastic rubber materials to have the model behavior more emphatically.The model was loaded with a statically concentrated horizontal 1kg weight at the linguo-incisal edge from the lingual side.The results obtained as follows:1. Under the results of the tooth model experiment, severe compressive stress generated at the labio-cervical root surface.And stresses grew gradually higher in every part of the cervical root surface with decreased post length and increased post diameter.2. Comparison among the finite element analysis 1, 2 and 3 suggested that stresses generated in the post-core and the tooth structure were increased, even if the rigidity of the abutment tooth was grown up according as post length and diameter were increased.