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Occlusal load transfer in full-contour ceramic implant fixed denture

Żmudzki J., Chladek G., Krawczyk C.

Archives of Materials Science and Engineering

2015

Vol. 72, nr 2

61--68

Purpose: Many clinicians use dentures with metallic core due to fears of insufficient strength of ceramic bridges. The aim of work was finite element strength analysis of fullcontour ceramic implant supported denture in lateral region. Design/methodology/approach: Finite element analysis (Solidworks) of occlusal load transfer in all-ceramic implant supported denture for missing second premolar, first molar and second molar teeth was made. Bridgework from zirconia was supported on two implants 4x12 mm (diameter x length) placed in bone with good quality and quantity. Model was loaded with lateral maximal occlusal force of 800 N. Findings: In the bridgework in the connector with premolar tooth Huber-Mises stress reached 375 MPa. Stress in implants was about 1000 MPa and small plastic deformation zones can occur close to the implant edge under pressure of abutment. Stress in abutment screw reached about 800 MPa in the first thread root and up to 400 MPa in the shank. Stress in bone tissues around implant neck and slightly lower of the beginning of the thread exceeded 140 MPa. Research limitations/implications: Linear isotropic behavior of materials and tied contact between components were assumed in the model. Practical implications: Detrimental effect of maximal occlusal force on the osseointegration between implant and bone showed that patients must be warned against loading of the denture over normal mastication. Stress in the abutment screw reached dangerous value and specific design to prevent fatigue failure is required. Originality/value: An impact of torsion and oblique bending are rarely considered in investigations. This result is relevant for the design of bridgeworks and graded materials for ceramic restoration.

The simulation of mastication efficiency of the mucous-borne complete dentures

Żmudzki J., Chladek G., Malara P., Dobrzański L.A., Zorychta M., Basa K.

Archives of Materials Science and Engineering

2013

Vol. 63, nr 2

75--86

Purpose: The aim of this study was to present rules for numerical investigations of mastication efficiency of mucous-borne complete dentures. Design/methodology/approach: Finite element method (FEM) large displacements analysis with denture detaching and sliding at mucous membrane interface was employed. The possibility of a lower denture destabilization under oblique mastication load was modeled. Denture stabilization at balancing contact „at time” and „delayed” was modeled with increasing of a distance to the opposite denture. An unfavorable mucous membrane foundation was assumed. Findings: Pressures beneath dentures during stable vertical occlusal loadings are lower than pain threshold of mucous membrane even when the denture foundation was very unfavorable. Simulation of realistic oblique mastication force results in a denture destabilization. Denture experienced a large slide, completely lost adherence at balancing side and the balancing contact was needed to achieve stabilization. The pressures beneath denture under oblique load increased to values much higher than pain threshold and the „delayed” balancing contact influenced additional increase of pressure values. Research limitations/implications: In the FEM study only characteristic unfavorable denture foundation and conventional denture type were analyzed. Practical implications: Defined values of pressure beneath dentures show that it is necessary to underlay the dentures. The influence of „delayed” balancing contact on significant increase of stress beneath dentures indicates that in case of a problem with stabilization of dentures it is necessary to introduce stabilization on the implants. Originality/value: Universal rules of conducting a numerical experiment and interpreting its results constitute the base and encouragement to complete further practical tasks awaiting engineers and prosthetists.