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The results from clinical tests of single implant-retained dentures (SIDs) are quite promising. However, the biomechanics of SIDs are still insufficiently determined. The aim of the study was to compare the implant loads and pressures beneath one and two implant-retained dentures (TIDs) under oblique mastication forces. The finite element method was used to conduct a model analysis in order to compare loading of the denture attachment onto the implant that accompanies oblique mastication forces in the cases of SIDs and TIDs. The possibility of a denture detaching and sliding on the mucous membrane surface was simulated. The SID solution faced a more remarkable tilt in the direction of the mastication forces, a higher pressures on the mucous membrane surface, and higher implant loadings. The hingelike restraints in the TID favored utilization of the support in the posterior area. The higher pressure values for the SID can be confusing and could lead to inaccurate conclusions about the acceptability of the SID. In the TID, the same areas of the mucous membrane were persistently loaded, independent of the occlusal force direction. In contrast, in the SID the full freedom of rotational movement enhances alternating use of the mucous membrane. This finding explains the more frequent sores in the mucous membrane beneath the TID than beneath the SID.

The results of mechanical characteristics of attachments used for retaining and stabilizing overdenture have been analysed. Two commercially used attachments (a ball attachment and a bar attachment) and elastic frictional attachments designed by the research team with Professor Chladek as the leader have been investigated. The diagrams of force-displacement characteristics have been registered. Retention forces (F(R)) have been determined and total work (W(T)) disconnecting the attachments has been calculated on the basis of these diagrams. The analysis of total work corresponding to different types of attachments made it possible to distinguish some characteristic areas which illustrate specific features of particular designs. It has been revealed that determining the retention force allows us to compare only the attachments which work on similar bases. In order to conduct a purely objective comparison of the efficiency of different designs, it is necessary to analyze complete force-displacement characteristics as well as to determine on this basis the subsequent phases of separating the parts of attachments and to find the value of the work which in fact determines their quality. The comparison of selected commercially used designs and the presented elastic frictional attachments (taking into account the criterion of work) gives clear evidence that the introduced design of attachment enables us to create very good conditions of retaining overdenture.

The paper presents the results of the study of the titanium implant-elastomeric membrane attachment, conducted from the point of view of potential utilization of the results in forecasting the durability of retention elements representing a new solution of dentures based on implants. The examination was carried out using a device designed by the author, which allowed the simulation of the process of inserting and removing dentures. Titanium counter specimens, simulating implants, were subjected to surface modification through their sandblasting with 350 um and 500 um abrasives, so as to diversify their roughness. The elastomeric membranes constituting a retention element of the attachment were made of a silicone material, Molloplast B. The influence of the number of cycles (one cycle meaning one insertion and removal of a denture) on the attachment's retention force was studied. In order to better reflect the natural conditions, the device was equipped with a chamber which made it possible to perform the examination in an artificial saliva environment. The study has shown that the application of the polymer material Molloplast B for constructing the new type retention elements of dentures based on implants ensures practically constant values of the attachment's retention force in the required 6-month utilization period. After the time of denture usage, being eight times longer than originally assumed, the loss of retention force does not exceed 43% in any of the attachments investigated and the retention force values still allow the attachments to operate, although their effectiveness is partly reduced.

This paper presents the results of a study of the friction coefficient of titanium-elastomer couple. The study was carried out with a view to potential future utilization of its results for constructing retentive elements of implanted prostheses. Changes in the friction force were recorded while removing titanium specimens placed between two silicone counter specimens made of Ufi Gel. The influence of the titanium specimen movement speed in relation that of to the counter specimens and the influence of clamping force on the friction force were assessed. Additionally, the surface roughness of titanium specimens differed; in one case, titanium was coated with polyethylene. The effect of introducing artificial saliva between the cooperating surfaces on the friction force and friction coefficient was analyzed as well. Based on the characteristics recorded, the possibilities of shaping the friction coefficient have been assessed, since it is the friction coefficient that determines effective operation of a friction couple through increasing the titanium specimen roughness. The artificial saliva being introduced between the specimens reduces considerably the friction coefficient through a change of the phenomenon model. An increase in the pressure force for the specimens of high roughness entails a reduction of the friction coefficient. The study carried out allows us to identify the roughness parameters, which in turn will enable obtaining the prescribed retention force for friction/membrane couplings.

Implant and a tooth supported dentures are avoided by dentists because of uneven distribution of occlusal loads between a stiffer implant and a more pliable tooth. The hypothesis was that a 3-point all-ceramic bridge supported on a natural second premolar tooth and a two-pieces typical implant bears safely mastication loads. The finite element analysis showed that the implant splinted by all-ceramic zirconium bridge with the second premolar was safe under lateral mastication load, but there was found an overload at wide zone of bone tissue around the implant under the load of 800 N. The patients can safely masticate, but comminution of hard food should be avoided and they should be instructed that after such an indiscretion they need to contact a dental professional, because, in spite of integrity of the prosthesis, the bone tissue around the implant may fail and there is a hazard of intrusion of the tooth. [ABSTRACT FROM AUTHOR]

The primary clinical assessments show that single implant-retained dentures (SIDs) are not worse than two implant-retained dentures (TIDs), although the determination of SID biomechanics is still insufficient. The aim of this work was to determine the loading of commonly used denture attachments that occurs while bearing occlusal forces on SIDs. Finite element method analyses, which took into account the possibility of dentures detaching and sliding on the mucous membrane surface, were used. In the contact calculations conducted, an augmented multiplier Lagrangian method with a classical linear friction model was used. We assumed denture-loading conditions that included oblique mastication forces. The distribution of the occlusal loads between the mucous membrane-bearing area and a denture attachment was examined for economical denture solutions with solitary attachments. Variations in denture movement restrictions among the most typical ball, stud, and axially resilient attachments only insignificantly influenced lateral loads borne by single implantological supports. Axial mobility does not reduce the load on the attachments because mastication loads induce denture settlement that is oblique to the implant axis. The assumption of denture loading with vertical forces leads to a serious underestimation of the loads on implantological supports. [ABSTRACT FROM AUTHOR]