Object

Title: The analysis of biomechanical systems of anchorrring frame prostheses used in causes of bilateral free-ends in lower jaws

Abstract:

Claspless prostheses are denture solutions of not only aesthetic values, but are also beneficial from the biomechanical point of view. A frequent type of edentulous areas restored with claspless dentures are bilateral mandibular free-ends. Purpose The purpose of the paper is to analyze the biomechanical operating conditions of various systems of claspless anchorage of dentures, in the aspect of selection of a functionally optimal construction solution for frame dentures applied in cases of bilateral mandibular free-ends. Therefore, it is assumed that the studies performed will allow for answering a question that is important for clinical practice, namely whether if it is necessary while using claspless abutments to interlock the natural abutment teeth and which of the stabilizing and supporting elements allow for achieving the most beneficial clinical effect in using the mandibular alar prostheses. Material and method In the studies performed, the basis for assessment of various construction solutions of dentures was the analysis of load bone by construction elements, particularly the spatial distribution of the load in the most exposed tissues of the mucous and bone base, as well as abutment teeth. Modeling of the load bone and functioning of dentures requires considering the non-linear character of the mechanicalbiological system. The non-linearity is related both to live tissues in the patient, and to the structure and operating principle of prosthesis. In own FEM models, three types of non-linearity were considered: geometric, material and non-linearity related to the change of terminal conditions. Calculations were performed on a PC computer with Intel Pentium IV 3 GHz processor and Strand 7 Software by G+D Computing as the digital environment to generate the numerical model of prosthetic base with bilateral free-ends, namely edentulous molar areas with preserved anterior-lateral arch up to second premolars inclusive. Designing of the model with the finite elements method comprised the following stages: 1) use of numerical bar models as simplified mathematical models, 2) performance of individual models of premolars obtained with tri-dimensional analysis (scanning) of roots of premolars extracted for orthodontic reasons, 3) generalization of mathematic models of the roots of abutment teeth in the form of double cut cones for the purpose of obtaining a 3D model of finite elements of the prosthetic base, 4) performance of the analysis on the axially symmetrical 3D models of prostheses and the analysis on twodimensional models constituting their axial cross-sections. The prosthesis comprised fixed restorations, namely crowns fixed to the patient's own abutment teeth, made of chromium-cobalt alloy. Together with the crown, on the common metal frame, there 7 was a part of the abutments anchoring the removable denture, namely the counter-elements of latches and clips. The other part of the abutment, namely the matrix, strictly matching the counter-element, was placed in the alar prosthesis, also made of chromium-cobalt alloy. The analysis was performed on numerical models of claspless restorations of mandibular frame dentures, in the following variants: using clips, latches with or without interlocking crowns, and using supporting elements in the form of thorns and interlocks®. Models analyzed include: model A – single crowns with cylindrical latches connected to the frame denture, model B – single crowns with lateral clips connected to the frame denture, model C – multi-unit crowns with cylindrical latches connected to the frame denture, model D – multi-unit crowns with lateral clips connected to the frame denture, model E – multi-unit crowns with cylindrical latches and interlocks® placed between the crowns, connected to the frame denture, model F – multi-unit crowns with lateral clips and interlocks® placed between the crowns, connected to the frame denture. ; Results For the purpose of performing a detailed analysis of the variants of construction solutions for alar prosthesis, it was necessary to define a model reference framework, namely the volume of load on the periodontium of abutment teeth and load on the tissues of the mucous and bone base. Having defined the model reference framework, the analysis was performed of the loads on the periodontium of abutment teeth and load on the tissues of the mucous and bone base for various variants of the construction solutions of dentures, according to the models from A to F. The analysis of the model of single crowns with supports and cylindrical latches – model A. The analysis involved the axial crosssection of the 3D model composed of 6975 flat triangular and rectangular elements connected with 27340 nodes. The occlusal load on the mucous and bone base indicates increase in the centrifugal force value, whereas average load (0.0668 MPa) is about twice lower than the comparative load (0.1317 MPa) in the model reference framework. The occlusal load of premolars depends on their situation as compared to the edentulous area, and on average, for first premolars, amounts to 0.0762 MPa, which is twice less than the value in the model reference framework, while for second premolars the average load value is 0.1628 MPa. The analysis of load direction illustrated by comparison of sections AB and BC in particular abutment teeth indicates the predominance of the shifting direction towards the edentulous area. The analysis of the model of single crowns with supports and lateral clips – model B. The analysis involved the axial cross-section of the 3D model composed of 6975 flat triangular and rectangular elements connected with 27340 nodes. The occlusal load on the mucous and bone base is varied, increasing in the centrifugal direction. Average values (0.1469 MPa) exceed the load in the model reference framework (0.1317 MPa). First premolars are not under load, while in second premolars the occlusal load is about twice lower than the model reference framework, with the predominance of values in section BC, which indicates the centrifugal direction of the force, towards the edentulous area. The analysis of the model of multi-unit crowns with supports 8 and cylindrical latches – model C. The analysis involved the axial cross-section of the 3D model composed of 6982 flat triangular and rectangular elements connected by 27368 nodes. The occlusal load on the mucous and bone base is even and has the value (average – 0.0394 MPa) that is three times lower than in the case of model reference framework (average – 0.1317 MPa). The occlusal load transferred on particular abutment teeth has similar values (first premolars - average: 0.1438 MPa, second premolars - average: 0.1462 MPa) and does not exceed the values obtained in the model reference framework (average – 0.1784 MPa). First premolars are under centripetal force, while second premolars - under centrifugal force, which indicates that connection of two teeth with blocked crowns creates a certain type of functional connection, constituting a functional whole that behaves like one tooth, which means that blocked premolars are under even load. The analysis of the model of multi-unit crowns with supports and lateral clips – model D. The analysis involved the axial crosssection of the 3D model composed of 7033 flat triangular and rectangular elements connected by 27512 nodes. The occlusal load on the mucous and bone base is uneven (average – 0.1244 MPa) and grows centrifugally to the value above the load in the model reference framework. Abutment teeth are under load below the value of the model reference framework (average – 0.1784 MPa). First premolars (average – 0,0464 MPa) are under an over three times lower load as compared to the model reference framework, while the load on second premolars (average – 0.1371 MPa) have values similar to the model reference framework.

Level of degree:

2 - studia doktoranckie

Degree discipline:

stomatologia

Degree grantor:

Wydział Lekarski

Promoter:

Stanisław Majewski

Date issued:

2007

Format:

application/pdf

Identifier:

oai:dl.cm-uj.krakow.pl:979

Call number:

ZB-107313

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nieograniczony

Location of original object:

Biblioteka Medyczna Uniwersytetu Jagiellońskiego - Collegium Medicum

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Last modified:

Feb 12, 2020

In our library since:

Nov 21, 2012

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