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2 Archives of Materials Science and Engineering

2 2008

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Loading of overdenture attachments under simulated biting forces

Żmudzki J., Chladek W., Krukowska J.

Archives of Materials Science and Engineering

2008

Vol. 32, nr 1

33-36

Purpose: The basis for effectiveness evaluation of over-denture attachments is the determination of loads on supports, and denture mobility. In cases of denture stabilized on two prosthetic supports, for most of the attachments constructions that are available on the market, the margin of dentures mobility is limited to rotation around axes of the attachments. Design/methodology/approach: Determining attachments loadings during bearing of biting forces that accompany chewing processes was carried out by means of Finite Element Method model analysis. A three-dimensional model of a denture supported on mucous membrane and joint supports assumes to be fixed in places of denture anchoring to implants. This model was loaded on one side with unilateral oblique 100 N force at molars zone. Findings: Maximum loading at pillar accompanies biting forces acting in a lateral direction toward buccal side. Research limitations/implications: Researches were carried out exclusively for attachments not showing any resilience in any direction, without any rotational constrains. Hence, in further researches, at the first place, determined should be the influence of the vertical resiliency used in some of the commercial attachments on loads bearing. Practical implications: Appropriate determining of loadings levels on over-denture attachments, requires necessarily that the oblique biting forces will be taken into account. In case of an assumption of only vertically oriented biting forces, there is a significant underestimation of the most dangerous horizontal loadings of prosthetic supports. Originality/value: Presented displacements of denture and pillars loading as vertical and horizontal reactions causing pillar bending and leverage at the bone, constitute a starting point for evaluation of denture’s behavior and strength estimation of analyzed types of attachments for implants and the surrounding bone.

Estimation of stresses in layers of dentures' relining materials

Żmudzki J., Chladek W., Krukowska J.

Archives of Materials Science and Engineering

2008

Vol. 30, nr 1

21-24

Purpose: Durability tests of materials relining dentures should be carried out in conditions reflecting the real loading that accompanies bite force transmission. The influence of geometry resulting from a denture foundation shape on real stresses in relining has not been so far found. Design/methodology/approach: Using FEM modeling, identified were the stress levels in relining layers in conditions reflecting biting loading for two opposite cases of bone foundation atrophy. Findings: The equivalent Huber-Mises` stresses have not reached their critical values, although tangential stresses on the interfacial where relining is bonded with denture base have reached 440kPa, which, for some of the commercial types of relining denotes the bonding strength. Research limitations/implications: The linear elastic mechanical characteristics were assumed. Hence, during further research, taken into account should be the “stiffening” of characteristics in the upper loadings range, which is typical for silicones. Practical implications: In case of a convex foundation the biggest danger will be caused by any bond defects occurring in the central area because in that area shear of bond has reached the highest values. Originality/value: Values of stresses components identified in this paper reflect the real shear conditions of relining bonding with denture base and might constitute a determinant for strength tests.