|Year : 2022 | Volume
| Issue : 2 | Page : 159-164
Impact wear stress distribution and total deformation on dental material under chewing cycles: 3D finite element analysis
Efe Çetin Yilmaz
Department of Control Systems Electrical and Electronic Engineering, Faculty of Engineering and Architecture, Kilis 7 Aralik University, Kilis, Turkey
|Date of Submission||23-Feb-2022|
|Date of Decision||16-Jun-2022|
|Date of Acceptance||25-Jun-2022|
|Date of Web Publication||22-Aug-2022|
Efe Çetin Yilmaz
Department of Control Systems Electrical and Electronic Engineering, Faculty of Engineering and Architecture, Kilis 7 Aralik University, Kilis
Source of Support: None, Conflict of Interest: None
Background: The finite element solution estimates have been improving in recent years in biomedical applications. This method provides many advantages to researchers such as specimen force distribution, total deformation, and strain energy. The data obtained after the experimental methods can be examined for the finite element solutions. Aim: Thus, this study aims to a finite element study of total deformation and strain energy on dental material under chewing impact force simulation after experimental study; prediction of maximum and minimum stress distribution. Materials and Methods: In this study, impact wear stress distribution and total deformation analyses were performed on test samples with different geometries. A cylindrical specimen with a diameter of 12 mm and a square geometry specimen with a size of 8 mm was designed for chewing test procedures. The chewing force was applied to the samples over a while and the effect of this force on the wear surface of the sample was investigated through chewing test procedures. Results: In this study obtained data, the chewing force showed a more homogeneous distribution in the cylindrical sample than in the square sample. Conclusion: In addition, it was observed that the concentration of strength mechanism was present at the time of the maximum chewing force of the sample with square geometry.
Keywords: Chewing simulation, dental material, finite element, stress distribution, wear
|How to cite this article:|
Yilmaz EÇ. Impact wear stress distribution and total deformation on dental material under chewing cycles: 3D finite element analysis. J Dent Res Rev 2022;9:159-64
|How to cite this URL:|
Yilmaz EÇ. Impact wear stress distribution and total deformation on dental material under chewing cycles: 3D finite element analysis. J Dent Res Rev [serial online] 2022 [cited 2022 Sep 28];9:159-64. Available from: https://www.jdrr.org/text.asp?2022/9/2/159/354203
| Introduction|| |
It is a method that has been used recently to analyze the stress, deformation, and thermal behavior of the components of teeth and dental materials placed in the human mouth and bone with computer-aided 3D finite element analysis. This method can often be used in situations where in vivo tests are not possible and in the analysis of complex structures. It is possible to mathematically model the environment in which teeth and dental materials remain during the chewing movement. In previous studies in the literature, studies on mathematical models (finite element method) were carried out on dental implants., In recent years, significant developments have taken place in the field of dental materials. However, mathematical models gain importance in predicting how these developments might behave during the treatment process. Success in modern dental treatment is limited to the life of the material during the treatment process. Ideally, materials placed in the oral cavity aim to achieve the desired level of durability, efficiency, and esthetic behavior. Various mechanical, chemical, and esthetic behaviors of the materials can be predicted by in vitro tests performed in laboratory environments. However, the change of any parameter in the experimental environment necessitates the re-creation of the experimental setup. This disadvantage is eliminated by using the computer-aided finite element technique. The stresses that occur both during function and parafunction are transferred to the elastic and flexible resin matrix from hard and brittle fillers. Stress concentrations at the filler-resin interface can contribute to wear because the failure of this interface causes the filler material to dislodge and rapidly release the resin matrix. In composite materials, such stress concentrations can arise due to water absorption, leakage of filler particles, polymerization shrinkage, and thermal cycling. The superior mechanical and esthetic behaviors of composite materials allow them to be preferred frequently as dental biomaterials. However, it has been reported that composite materials are exposed to various damage mechanisms in long-term clinical studies., In many studies in the literature, simulations of wear test mechanisms have been carried out in vitro.,, Both test methods may have some advantages and disadvantages. Although the in vitro laboratory environment and computer-added model simulation provide advantages in terms of time and cost, the complete realization of the simulation in the oral environment may be weaker than in the in vivo environment. Therefore, a rigorous construction process is required. Thus, this study aims to a finite element study of total deformation and strain energy on dental material under chewing impact force simulation after experimental study; prediction of maximum and minimum stress distribution. Within the scope of this study, the analysis of the chewing force on the specimen wear surface on the cylindrical and square specimens was carried out after chewing test procedures.
| Materials and Methods|| |
In this study, test specimens with cylindrical and square geometry of pure titanium and titanium alloy were designed under chewing test procedures. In our previous study, chewing test experiments of titanium and titanium alloys were carried out in vitro. In the experimental test mechanism in vitro, the parameters were determined as cylindrical form (12-mm diameter 2-mm thickness) test specimens were subjected to wear tests under 100.000 mechanical loading, 50 N mechanical force, 2.0 Hz wear frequency, 6-mm diameter Al2O3 antagonist ball, 0.7 mm lateral movement, 5°C/55°C thermal change conditions immersed in poppy seed slurry as a third-body medium. For this finite element study, a cylindrical specimen with a diameter of 12 mm and a square geometry specimen with a size of 8 mm was designed for chewing test procedures. The chewing force was applied to the samples over a while and the effect of this force on the wear surface of the sample was investigated through chewing test procedures. In this study, stress distribution, total deformation, and strain energy on dental material loading test modeling were carried out using the ANSYS 19 Workbench academic version program. For this reason, the mesh amount is set to a maximum of 30.000 which this ratio is in a range of values sufficient for the analysis performed on stress distribution, total deformation, and strain energy on dental material loading test modeling. The material was chosen as a titanium alloy from the general material library of the ANSYS program. The mechanical properties of the selected titanium alloy material are shown in [Figure 1]. The values in this picture represent the ideal mechanical properties of the material. The test specimens with cylindrical and square geometry designed in this study are shown in [Figure 2]. Samples with both geometries have meshed into equal numbers of pieces for chewing test procedures. Test procedures similar to the experimental study were applied to the test specimens. The wear surfaces of the specimens with both geometries were analyzed after the wear test procedures.
|Figure 1: The mechanical properties of the selected titanium alloy material|
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|Figure 2: The test specimens with cylindrical and square geometry designed in this study|
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| Results|| |
The distribution of the bite force in both samples in the wear area during chewing motion is shown in [Figure 3]. The chewing movement begins with the contact of the upper jaw with the lower jaw this initial contact process is called bite force. The force distribution in the cylindrical test sample showed a more homogeneous distribution compared to the test sample with square geometry. The load distribution of the test specimens in the wear area with the increase in the bite force during chewing behavior is shown in [Figure 4]. With the increase in bite force during chewing, both samples showed an increase in stress density through chewing test procedures. In [Figure 5], the stress intensity, maximum principal stress, minimum principal stress, and directional deformation distribution mechanisms that occur during the bite force applied to different parts of the samples with cylindrical and square geometry are shown through chewing test procedures. [Figure 5] (a) shows the stress intensity that occurs during the chewing motion of the wear surface of the test specimen. [Figure 5](b) shows the maximum stresses occurring in the wear area. In this area, there is a continuous transfer of stress from the direct contact node to the wear node thrıyght chewing cycle process. [Figure 5] (c) shows the minimum stress areas in the absence of direct contact load during chewing cyle process. Finally, [Figure 5] (d) shows the areas of directional deformation during the chewing motion of the wear surface of the test specimen. The wear areas occurring in the test sample with square geometry after the chewing test procedure were estimated and these results were compared with the experimental 3D profilometer study results in [Figure 6]. In addition, the wear area where the maximum force accumulates and the wear depth occurs in the wear region has been analyzed after chewing test procedures. When [Figure 6] detailed that there show wear areas occuring in the test specimen with square geometry after the chewing test procedures (a) Bite force in the direct contact area that occurs during the chewing movement, (b) direct contact area in the wear mechanism, (c) surface change analysis of the wear area, (d) 2D analysis of the wear area and (e) lateral ve vertical axis surface changes in the wear mechanisms.
|Figure 3: The distribution of the bite force in both samples in the wear area during chewing motion|
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|Figure 4: The load distribution of the test specimens in the wear area with the increase in the bite force during chewing behavior|
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|Figure 5: (a) The stress intensity, (b) Maximum principal stess, (c) Minumum principal stress and (d) Directional deformation distribution mechanisms recpectively|
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|Figure 6: Wear areas occurring in the test specimen with square geometry after the chewing test procedures. (a) bite force stress distribution, (b) impact wear area, (c) wear area surface analysis, (d) 2D wear area and (e) lateral and vertical axis changes in the wear|
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| Discussion|| |
The chewing movement begins with the contact of the upper jaw with the lower jaw this initial contact process is called bite force. The bite force may vary according to the mechanical properties of the material exposed to the chewing movement in the mouth. For example, there will be different forces between biting a carrot and biting a piece of bread. Although it is reported in the literature that the bite force varies on a wide scale, the researchers chose 50 N as the average bite force., It was observed that the stress accumulation in the test specimens increased with the increase in chewing force. Therefore, the amount of bite force selected in vitro has a significant effect on the mechanical behavior of the dental material. In this study, more stress accumulation was observed in the test sample with square geometry than in the cylindrical sample in finite element analyses. This showed that the geometry of the test specimen had a significant effect on the mechanical behavior of in vitro chewing test procedures. The stress area shown in [Figure 5]d represents an area where the test material will likely suffer damage in the chewing test procedure. If these chewing motion tests were carried out to the stress life limit of the material, these test materials would likely have been exposed to various damage mechanisms in the stress regions.
In recent years, titanium material has been increasingly preferred as a biomaterial due to its superior mechanical and biocompatibility behaviors. However, any biomaterial placed in the oral cavity is involved in a very complex and continuous process. During the treatment process, the biomaterial is expected to exhibit the desired mechanical, chemical, and esthetic behaviors. Many in vitro test experimental setups have been developed in the literature to model the treatment process to determine biomaterials' mechanics and esthetic behavior.,,, However, there is a trend among researchers toward in vitro studies due to the time-consuming, costly, and ethical reasons for in vivo studies. More importantly, the complex and continuous nature of intraoral tribology can be modeled in in vitro test environments. For example, the bite force produced during the chewing motion is a parameter in the mouth. Many chewing simulators simulating two- and three-part wear mechanisms have been reported in the literature.,,, When these two test modeling methods are compared, while the dental material and abrasive material are in direct contact in the x wear mechanism, a third abrasive environment is included in this environment in the y wear mechanism. The third corrosive environment was provided in the laboratory using materials such as poppy seeds or polymethyl methacrylate. In addition, a thermal exchange environment inevitably occurs due to the food taken during the chewing movement. However, some literature studies have not considered thermal cycling and the process of changing the third body environment in intraoral tribology., For this reason, it is very difficult to find a correlation between studies carried out in the literature. Because the test material can exhibit very different mechanical and esthetic behavior when any of the test parameters are changed or neglected in chewing test procedures. It will also increase the consistency of the test results if the researchers establish the essential conditions for the test mechanisms. For example, the occurrence of thermal cycling during chewing behavior is inevitable, and when this parameter is neglected in the test mechanism, the test sample will not be affected by this environment. As a result, the test sample will not have reacted to the thermal exchange environment during the chewing test procedure.
In chewing test experiments, the wear volume loss in biomaterials is analyzed by contact or noncontact profilometer, digital microscope, optical sensor, and laser scanning. In the literature, in a study, volume and vertical loss variables were evaluated using various methods such as profilometer, optical sensor, and scanning in the analysis of volume loss in the wear area of a material. As a result, the evaluation of horizontal and vertical volume loss in the analysis of wear loss is important in evaluating the mechanical behavior of the material. It can be said that the wear mechanism of pure titanium and its alloys, such as the biomaterials used, occurred in two stages of in vitro chewing tests. In the first stage, the biomaterial will show elasticity and plasticity when exposed to bite force. In the second step, abrasion marks will form on the wear surface during the chewing motion. Therefore, it is important to analyze the wear area of the biomaterial both in terms of wear depth and along the lateral axes. The use of 6 mm cylindrical balls as antagonist abrasive material in finite element analyses and experimental methods in this study contributed to the similarity of the horizontal and vertical wear area of the test specimens [Figure 6]d and [Figure 6]e. The cylindrical geometry of the antagonist abrasive material occurred a homogeneous force distribution to the wear area of the test specimens during the bite force (step 1 bite force). Then, the volume of the wear area was increased with the lower jaw movement in the chewing motion. In addition, in this step, the particles separated from the test material with the bite force and plastic behavior were transported vertically and transferred to the antagonist material. If these particles are not removed from the wear surface of the test specimen, the two-body wear mechanism will become a three-body wear mechanism. Because the direct contact surface will be eliminated due to the particles breaking off from the wear surface. The surface of the sample is sprayed with water at room temperature in short time intervals to solve this problem in experimental methods.,, As a result, intraoral tribological time is a continuous and complex structure, and test parameters should be simulated similarly to the real environment in experimental studies.
| Conclusion|| |
The following evaluations can be made within the limitation of the results obtained in this study.
- In this study obtained data, the chewing force showed a more homogeneous distribution in the cylindrical sample than in the square sample
- It was observed that the concentration of strength mechanism was present at the time of the maximum chewing force of the sample with square geometry
- The geometry of the selected test sample in vitro laboratory environments affects the wear behavior of the material
- The preparation of cylindrical specimens in vitro chewing test environments will contribute to the homogeneous distribution of the biting stress on the material surface in the chewing test procedures. For this reason, test specimens should have cylindrical geometry to estimate the effect of stress distribution on wear more accurately through chewing test procedures
- Teeth and dental materials are inevitably exposed to mechanical and thermal stress through chewing simulation test procedures. This mechanic and thermal stress can cause the wear mechanisms to lose more volume of the material. In addition, it may contribute to the formation of some problems in terms of material integrity and esthetics. As a result, being able to predict these parameters by modeling in the laboratory environment will contribute to the formation of more satisfactory treatment processes.
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Conflicts of interest
There are no conflicts of interest.
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