|Year : 2020 | Volume
| Issue : 1 | Page : 51-54
Effects of contact-stress on wear behavior of zirconia-reinforced lithium silicate glass-ceramic
Efe Cetin Yilmaz1, Recep Sadeler2
1 Department of Mechanical Engineering, Faculty of Engineering, Kilis 7 Aralik University, Kilis, Turkey
2 Department of Mechanical Engineering, Faculty of Engineering, Ataturk University, Erzurum, Turkey
|Date of Submission||04-Dec-2019|
|Date of Acceptance||16-Dec-2019|
|Date of Web Publication||17-Mar-2020|
Dr. Efe Cetin Yilmaz
Department of Mechanical Engineering, Faculty of Engineering, Kilis 7 Aralik University, Kilis
Source of Support: None, Conflict of Interest: None
Background: The purpose of the present study was to investigate effects of contact-stress on direct-contact wear behavior of zirconia reinforced lithium silicate glass-ceramic; in vitro off-axis sliding contact chewing simulation. Methods: In this study, 12 mm diameter X 2 mm thickness in size of lithium disilicate, Vita Suprinity; zirconia-reinforced lithium silicate was used. The test specimens were subjected to 100.000 mechanical loading, 3000 thermal cycles, 1.2 Hz wear frequency, 30° angle 0.7 mm lower jaw movement and different size Al2O3 antagonist material in artificial saliva. The average wear volume loss of the test specimens was obtained after wear test procedure using non-contact 3D profilometer. Furthermore, micro-structure analyzes of the wear surfaces of the test specimens were performed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Results: As a result of this study, ceramic material showed better abrasion resistance with increasing contact surface of abrasive material. Conclusion: However, microstructure analysis has shown that micro cracks occur on the wear surfaces both wear test procedures. These micro cracks may have occurred under the wear surface of the ceramic material.
Keywords: Bioceramic, microstructure, thermal cycle, volume loss, wear
|How to cite this article:|
Yilmaz EC, Sadeler R. Effects of contact-stress on wear behavior of zirconia-reinforced lithium silicate glass-ceramic. Biomed Biotechnol Res J 2020;4:51-4
|How to cite this URL:|
Yilmaz EC, Sadeler R. Effects of contact-stress on wear behavior of zirconia-reinforced lithium silicate glass-ceramic. Biomed Biotechnol Res J [serial online] 2020 [cited 2020 Jul 3];4:51-4. Available from: http://www.bmbtrj.org/text.asp?2020/4/1/51/280863
| Introduction|| |
Biomaterials placed in the human body can be constantly exposed to wear and fatigue mechanisms. These degradation mechanisms can significantly affect the mechanical, chemical, and esthetic behavior of biomaterials placed in the body. Because this continuous and complex structure in the body takes a long time and costly tests on living tissue, researchers have turned to laboratory experiments.,, Wear mechanisms are one of the most prominent degradation mechanisms during chewing cycle tests due to the presence of continuous simultaneous impact and lateral friction mechanisms. Attrition-corrosion wear mechanism is one of the tooth wear types in this process and includes tooth-to-tooth contact in the presence of acids and accordingly contains both mechanical and chemical effects. It is important to understand the nature, mechanical, and chemical behavior of biomaterials as long as it remains in the oral tribology process.
In recent years, various computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic materials have been developed according to the esthetic demands of clinical studies. The development of ceramic materials in this field aims to have better mechanical, chemical stability, and esthetic properties of the material. The use of zirconia as a core in ceramic materials has improved the mechanical properties of all-ceramic restorations. The glass-ceramic material IPS e.max is one of the monolithic ceramic systems, which gives popularity to front and rear single crowns and partial restoration of the coating. Due to their mechanical and esthetic properties.,, IPS e.max glass-ceramic materials can be thermally compressed or obtained using the CAD/CAM production process. IPS e.max ceramic material is first introduced in the literature. As a substrate or core material, characterized by better transparency than high-strength ceramic materials. Monolithic restorations with an anatomical contour can be performed due to different tones of increased transparency and lithium disilicate. This feature gives the IPS e.max glass-ceramic material an esthetic advantage. The process can be summarized as follows; the processed ceramic blocks of lithium disilicate are bluish in color and consist of a metasilicate phase. Finally, the metasilicate phase is transferred to a ceramic structure based on lithium disilicate, obtained by firing during crystallization at 840°C for 25 min.
| Methods|| |
The chemical composition of the ceramic material tested in this study is shown in [Table 1]. The rectangular zirconia-reinforced lithium silicate glass-ceramic test specimens were cut into cubes using a water-cooled low-speed diamond saw (Isomet Buehler GmbH, Düsseldorf, Germany) according to the wear test mechanisms. The cut ceramic samples were polished using silicon carbide abrasive papers. The cut ceramic pieces were then embedded in a 13 mm × 12 mm cylindrical acrylic resin.
The computer-controlled test mechanism was designed and manufactured to evaluate both off sliding (30° angle on lateral) and different contact stress two-wear mechanism. [Figure 1] shows schematics of the dual-axis off sliding wear simulation test mechanism. The zirconia-reinforced lithium silicate glass-ceramic test specimens were subjected to 100,000 mechanical loading, 3000 thermal cycles, 1.2 Hz wear frequency, 30° angle 0.7 mm lower jaw movement, and different size Al2O3 antagonist material in artificial saliva.
|Figure 1: Schematics of the dual-axis off sliding wear simulation test mechanism|
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After the wear tests, the wear regions of the samples were analyzed with noncontact three-dimensional (3D) profilometer, and the wear volume losses were determined. Wear volume loss and depth of test specimens were determined by scanning of 8 μm on the x-axis, 12 μm on the y-axis, and 1000 μm/s on the wear surface using a noncontact profilometer (Bruker-Contour GT 3D Vision 64 simulation software). In addition, random samples were selected in both test groups, and microstructures of the wear area were examined with scanning electron microscopy and atomic force microscopy.
| Results|| |
In this study, zirconia-reinforced lithium silicate glass-ceramic materials were 0.18 (0.08) mm 3 and 0.24 (0.11) mm 3 wear volume loss (for 10 and 6 mm antagonist materials, respectively) after wear test procedures. [Figure 2] shows an example of volume loss calculation 3D and two-dimensional analyzer using noncontact profilometer. Zirconia-reinforced lithium silicate glass-ceramic material showed better abrasion resistance with increasing contact surface of abrasive material. The application of the wear force over a wider area was reduced the effect of the bite force during chewing cycle conditions. [Figure 3] and [Figure 4] show microstructure analyses of zirconia-reinforced lithium silicate glass-ceramic material after wear test procedures (for 6 mm Al2O3 antagonist abrasive material).
|Figure 2: Example of volume loss calculation three-dimensional and two-dimensional analyzer using noncontact profilometer|
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|Figure 3: Microstructure analyses of zirconia-reinforced lithium silicate glass-ceramic material after wear test procedures scanning electron microscopy|
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|Figure 4: Microstructure analyses of zirconia0-reinforced lithium silicate glass-ceramic material after wear test procedures atomic force microscopy|
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| Discussion|| |
This study evaluated and compared effects of contact-stress on direct-contact wear behavior of zirconia-reinforced lithium silicate glass-ceramic; in vitro off-axis sliding contact chewing simulation. The parameters selected in the wear test mechanisms may affect the mechanical and esthetic behavior of ceramic materials. It has been reported in the literature that many chewing simulator devices can model direct contact and abrasive media wear mechanisms.,,,, The mechanical and chemical behavior of biomaterials placed in the body can be predicted in time periods. The abrasion process in oral tribology is complex and stable. In the chewing process, the oral environment, the amount of bite force, the third body particle, the mechanism of lateral movement, the mechanical property of the antagonist material, can positively or negatively affect the wear behavior of the composite material. There is no agreement in the literature as to which material should be used as an antagonist material for wear simulations. OHSU (developed at Oregon Health and Science University in Portland) and Zurich chewing test methods proposed enamel as antagonist material, and other test methods suggested ceramic, aluminum oxide and stainless steel, alumina, and zirconia ceramic balls as antagonist materials.,, The bite force (vertical load force) applied throughout the chewing test method should be similar to the force in intraoral tribology. Studies have reported that the bite force varies between 20 N and 120 N during chewing cycle test procedures.,, However, in many studies, the mean 50 N bite force was used as the reference load during chewing test procedures.,,, In the chewing test procedures, the number of wear cycles has been reported to range from 50,000 to 1,200,000., In the in vivo study, an average of 300–700 mechanical loads per day during chewing cycles was reported. In this study, 100,000 mechanical loads selected during chewing cycles were 1 year on average in the in vivo experiment. The chewing simulator was programmed to perform 2 mm of vertical movement and 0.7 mm of lateral movement at the load cycle frequency during the experiment and at 1.2 Hz. In many studies in the literature, it has been reported that the amount of lateral wear loaded movement varies between 0.3 and 1 mm.,,,, Changing the laterally loaded movement mechanism of the chewing simulator will directly affect the wear surface of the composite material. For this reason, a 0.7 mm lateral movement loaded amount, which is frequently preferred in the literature, was selected in this study.,
In the microstructure analysis, it was found that there were deep wear tracks in the wear area of the zirconia-reinforced lithium silicate glass-ceramic material. These deep wear marks have occurred during particle transport of the lateral movement mechanism during the chewing movement. Consequently, it is possible to say that zirconia particles have two effects on the mechanical and tribological behavior of glass-ceramic materials;First, a strong bonding between the glass-ceramic matrix and the zirconia particles is formed to prevent a separate wear particle during the lateral movement, and second, to prevent the stress distribution mechanism; performing the transfer of the tensile material during the chewing movement during the bite mechanism. As the contact area increases in the wear area of zirconia-reinforced lithium silicate glass-ceramic material, the bite force is spread over a larger area, and the direct effect value is reduced through chewing cycle test procedures. However, it has been observed that both wear test methods have particle transport in the wear areas lateral movement direction. These transported particles are indicative of plastic deformation of the zirconia-reinforced lithium silicate glass-ceramic material during direct contact wear test procedure. This can be explained by the fact that particles separated from the wear surface of the zirconia-reinforced lithium silicate glass-ceramic material from as the third abrasive body. Therefore, the particulate property separated from the surface of the zirconia-reinforced lithium silicate glass-ceramic material directly affected the wear surface through chewing test procedures.
| Conclusion|| |
In this study, it has been determined that the different contact-stress wear mechanism has a significant effect on two-body wear resistance of zirconia-reinforced lithium silicate glass-ceramic material after chewing test procedures. As a result of this study, zirconia-reinforced lithium silicate glass-ceramic material showed better abrasion resistance with increasing contact surface of abrasive material. However, microstructure analysis has shown that micro-cracks occur on the wear surfaces both wear test procedures. These micro-cracks may have occurred under the wear surface of the zirconia-reinforced lithium silicate glass-ceramic material.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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