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. 2021 May 28;14(11):2925.
doi: 10.3390/ma14112925.

Analysis of the Statistical Comparability of the Hardness and Wear of Polymeric Materials for Orthodontic Applications

Ivo Domagała  1 , Krzysztof Przystupa  2 , Marcel Firlej  1 , Daniel Pieniak  3 , Leszek Gil  3 , Anna Borucka  4 , Ireneusz Naworol  5 , Barbara Biedziak  1 , Mariana Levkiv  6
Affiliations

Analysis of the Statistical Comparability of the Hardness and Wear of Polymeric Materials for Orthodontic Applications

Ivo Domagała et al. Materials (Basel). .

Abstract

Background: Clinical success depends on the contact strength and wear resistance of medical devices made of polymer materials. The scientific goal resulted from the problem of using different methods of surface evaluation of materials used in the production of orthodontic appliances. The purpose of the work was an experimental comparative assessment of indentation hardness and scratch hardness and the sliding wear of four selected polymeric materials used in the manufacture of orthodontic appliances.

Methods: Four commercial materials were compared. Shore hardness tests and a scratch test with a Rockwell indenter were performed. A sliding wear test was performed using the ball-on-disc method. Statistical PCA and correlation analyses were performed.

Results: The results of scratch hardness measurements using a contact profilometer correlated with the Shore hardness to a greater extent than measurements made using an optical microscope. PCA showed that Shore hardness explains 45% of the total variance in all the results across the materials.

Conclusions: The scratch hardness method allows for a more explicit ranking of orthodontic polymeric materials when measurements are made with a profilometer. The ranking of sliding wear resistance should be made separately.

Keywords: dental biomaterials; microhardness; scratch resistance; sliding wear; thermocycling.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
A patient 35 years old with bruxism. Tooth wear with attrition facets.
Figure 2
Figure 2
(a) Occlusal splint for the treatment of bruxism; (b) Splint placed on the model; (c) Model with marking of places where the splint damage occurs; (d) Worn splint during bruxism treatment.
Figure 3
Figure 3
Scratch test and samples used in the test: (a) sample in an MCT holder for scratch test; (b) the width of sample used in the scratch test; (c) and scratch width measurement (SWmic) using an optical microscope.
Figure 3
Figure 3
Scratch test and samples used in the test: (a) sample in an MCT holder for scratch test; (b) the width of sample used in the scratch test; (c) and scratch width measurement (SWmic) using an optical microscope.
Figure 4
Figure 4
SEM image of topographic pile-up of the polymer material.
Figure 5
Figure 5
Measurement of the gap width (SWprofil) as the distance between the highest points of plastic pile-up (width of the green field) and the cross-sectional area of the gap, Sar.
Figure 6
Figure 6
Ball-on-disc wear-testing machine (a) and schematic representation (cross section) of sliding wear test (b).
Figure 7
Figure 7
Box plot of hardness in different material groups.
Figure 8
Figure 8
Test scratch on the surface of the 4A material.
Figure 9
Figure 9
Box plot of scratch hardness results based on the measurements made using the optical microscope (Hsmic) in individual material groups.
Figure 10
Figure 10
Box plot of the scratch hardness results based on the measurements made using the optical profilometer (Hsprofil) in individual material groups.
Figure 11
Figure 11
Box plot of measurement of the cross-sectional area of Sar scratches based on the measurements made using the optical profilometer in individual material groups.
Figure 12
Figure 12
Box plot of tribological wear in individual material groups.
Figure 13
Figure 13
Scree plot.
Figure 14
Figure 14
Vectors of original variables.
Figure 15
Figure 15
Dependence between scratch hardness Hsmic and Shore hardness ShD (r—correlation).
Figure 16
Figure 16
Dependence between scratch hardness Hsprofil and Shore hardness ShD (r—correlation).
Figure 17
Figure 17
Dependence between cross-sectional area Sar and Shore hardness ShD (r—correlation).
Figure 18
Figure 18
Dependence between cross-sectional area of sliding wear track War and Shore hardness ShD (r—correlation).
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