Experimental measurements for the numerical simulation verification of mechanical actions of upper alar chrome-cobalt partial denture with separated kinematics
Journal Title: Prosthodontics - Year 2011, Vol 61, Issue 4
Abstract
Introduction. The verification of the numerical representation of mechanical actions of alar frame chrome-cobalt partial denture with separated saddle kinematics required the metrological evaluation of experimental measurements, taking into account strength parameters estimated in the laboratory tests.Aim of the study. To determine the characteristics of connectors stress, depending on displacements of the saddle pressed to the base tissues that reflected changes in the level of simulated occlusion force transmitted from the alar part of denture on the abutment teeth.Material and methods. A test replica of clinical denture for wide posterior teeth loss in the jaw, limited by tooth 21, was measured. Separation of the kinematic influence of the alar partial denture on the base tissues was achieved by separating the saddle between artificial teeth 22 and 23 and cutting out big connector along clasp line between abutment teeth 21 and 17. To determine connectors stress, depending on denture displacements, four tensometric strain converters were used in typical Wheatstone’s bridges arrangement with a sensor of linear saddle displacements in the Spider-8 measurement system. The measured linear deformations were recalculated into stresses based on flexural elasticity module Eg and longitudinal elasticity E estimated in strength measurements at the level of approx. 180 GPa at stress limit Rg 0.2 ≈ 530 MPa and maximum bending moment Mg ≈ 1 Nm.Results. The measurements were taken on a paralellometric miller at loads increasing then decreasing by 0.96 N in the range of 0.00↔19.62 N applied statically to individual saddle teeth, from 23 to 27, perpendicularly to the occlusion plane. In each series of 41 measurement points for each of four tensometric strain converters a stress characteristics as a function of saddle deflection was determined. Calculated coefficients of linear regression R assumed values from 0.987 to 0.999 at increasing load and from 0.982 to 0.998 at decreasing load being close to one in both cases. Thus, it can be stated that the observed differences between increasing and decreasing connectors stress, depending on the saddle deflection for similar load level did not significantly affect mutual proportionality of changes in their values.Conclusions. The determined stress level relative to the linear deformation in flexural state of connectors, depending on saddle displacement, was sufficiently accurate for the proportional estimation of occlusion force bending moment distribution and their influence on abutment teeth in approximation to clinical conditions of the experiment.
Authors and Affiliations
Wojciech Michalski
Keywords
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