|Year : 2022 | Volume
| Issue : 3 | Page : 95-101
Finite element bite force two-body wear analysis of the titanium-based dental biomaterials
Efe Cetin Yilmaz
Department of Control Systems Electrical and Electronic Engineering, Faculty of Engineering and Architecture, Kilis 7 Aralik University, Kilis, Turkey
|Date of Submission||19-Oct-2022|
|Date of Acceptance||16-Nov-2022|
|Date of Web Publication||27-Dec-2022|
Prof. Efe Cetin 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
| Abstract|| |
Background: It has become an increasingly important issue to be able to predict the behavior of biomaterials placed in the human body over the time periods. It is always desirable for the biomaterial to have the ability to show the desired mechanical and esthetic behaviors throughout the determined treatment process. Researchers develop many laboratory and modeling test mechanisms to determine the behavior of biomaterials over time periods. The aim of this study is to perform computer-aided analysis of the mechanical behavior of titanium biomaterial, which is frequently preferred in the human body, under different chewing forces. Materials and Methods: In this study, 20N, 40N, 60N, 80N, and 100N chewing forces were applied to the titanium test specimen prepared in the cylindrical shape. The chewing load analyses obtained after the test were evaluated by comparing with the previous experimental study (mean chewing force as 50N). Results: With the data obtained as a result of this study, it was observed that more plastic deformation occurs when the chewing force increases. It has been predicted that an increased wear area may occur in the test material due to the movement of the chewing mechanism. Conclusion: It can be said that choosing the average chewing force in experimental studies contributes to the occurred of less wear areas on the test material compared to the random chewing forces test procedures.
Keywords: Biomaterial, chewing force, finite element analyses, wear
|How to cite this article:|
Yilmaz EC. Finite element bite force two-body wear analysis of the titanium-based dental biomaterials. J Interdiscip Dentistry 2022;12:95-101
| Clinical Relevance to Interdisciplinary Dentistry|| |
- Determination of mechanical and aesthetic behaviors of titanium-based biomaterials, which are frequently preferred in the treatment process, in chewing test simulation.
- The thermal environment has a significant effect on the wear behavior and researchers should not ignore this parameter in in vitro test experiments.
| Introduction|| |
In recent years, mechanical tests of biomaterials placed in the body can be modeled using computer-aided programs. It is of great importance to be able to predict the mechanical and aesthetic behavior of a material placed in the body over a period of time because of control periods during the treatment process and to estimate the wear cycles of the material in the body. The chewing mechanism has a complex and continuous structure that this structure contains such as wear, fatigue, corrosion, thermal fatigue, and fracture through chewing cycle procedures. For this reason, researchers focus on developing a test method with more than one parameter such as tribo-corrosion, fatigue-corrosion mechanisms.,, To evaluate the mechanical, esthetic, and chemical effects of test parameters on biomaterials, scientists are developing new test models using many in vivo, in vitro, and computer-aided programs. In literature, it has been reported that pure titanium and titanium alloys mechanism biomaterials are exposed to various damage mechanisms in chewing test procedures. However, the fact that the chewing process has a very complex and continuous structure makes it difficult to model this environment. In the literature, researchers have developed many in vitro/vivo and computer-aided finite element chewing simulation models.,,,,, These simulation models have advantages and disadvantages as compared to each other. For example, it can be said that in vivo test methods take a long time and there are etic problems, whereas in vitro test models and computer-aided finite element can be completed in a shorter time in chewing test procedures. The type of study and the results of the selected materials will be an important parameter in the selection of test methods. In addition, the fact that the test parameters selected in the laboratory environment are not suitable for the real environment may cause the results to play a role in reducing the estimates of living tissue. Therefore, as long as researchers can transfer the environmental conditions to which living tissue is exposed to the laboratory environment, the consistency and validity of the test results will increase through test process. The mechanical and chemical structure of the selected test material during the experiment may contribute to its different behavior. For example, the parafunctional stresses that occur during the chewing test are transmitted from the hard and brittle fillers of the composite material to the flexible and flexible resin matrix. Stress concentrations at the filler-resin interface can contribute to wear because failure at this interface leads to displacement of the filler material and rapid release of the resin matrix. In composite materials, such stress concentrations can occur by water absorption, leaching of filler particles, polymerization shrinkage, and thermomechanical cycling. The superior mechanical and esthetic properties of composite materials make these materials more attractive in clinical trials. However, in many long-term clinical trials, composite materials have been reported to be damaged because of fatigue and wear mechanisms., However, being able to test all parameters affecting these behaviors in a laboratory environment can cause great costs and time. For this reason, researchers have developed various computer-assisted analysis programs that can assist laboratory tests. In this study, the effect of the parameters determined by using the ANSYS program, which is frequently preferred in the literature, was tried to be examined in the experimental environment. As a result of, the aim of this study is to perform computer-aided analysis of the mechanical behavior of titanium biomaterial, which is frequently preferred in the human body, under different chewing forces.
| Materials and Methods|| |
In this study, different bite force and thermal cycle loading test modeling of dental material 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 thermal analyses. No human or animal tissue was used in this study. Within the scope of this study, the mechanical behavior of titanium biomaterial was defined by mathematical equations and exposed to chewing test experiments. 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 test sample designed for chewing simulations in this study is shown in [Figure 2]. The test specimen was formed in a counter-body shape with a material with higher elasticity to model the bone structure in which the tooth material is placed. Placing the samples in the x-structure models the tooth structure in the human mouth. In literature, counter-body shaped material was made with acrylic resin in composite and ceramic material test experiments. The values in this picture represent the ideal mechanical properties of the material. Bite forces of 20N, 40N, 60N, 80N, and 100 N were applied to the test specimen at 5°C and 55°C temperature cycles thought chewing simulation procedures. Temperature changes are simulated as the lower limit and upper limit in 1 s periods. [Figure 3] represents the mechanical movement process of the chewing simulation. Step 1 upper jaw is open and there is no contact between sample and antagonist material [Figure 3]a. Then, step 2 combines the upper jaw with the lower jaw to form a direct contact area. In this part, the first disintegration of the food pieces takes place during chewing movement [Figure 3]b. Two-body (direct-contact) wear and corrosion-wear will be effective in this mechanism, along with the disintegration of foods. Finally, in the third stage, the grinding process starts by performing lateral movement of the lower jaw [Figure 3]c. Two-body, three-body (noncontact), and corrosive wear will be effective in this mechanism, along with the grinding of foods. This completes a chewing simulation loop testing process. Two/three-body wear frequency through chewing cycles was calculated using the following formula:
|Figure 1: The mechanical properties of the selected titanium alloy material|
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|Figure 2: The test sample designed for chewing simulations in this study (a: Test specimen and b: Counter body)|
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|Figure 3: The mechanical movement process of the chewing simulation (a: Upper jaw no force, b: Direct contact area in bite force and c: Lower jaw movement for grinding process)|
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f (hertz) =1/T (s) (1)
where f represents wear frequency and T represents the period of the time axis. In this study, thermal cycle and wear test frequency were determined as 1 Hertz. It was chosen between 1 Hz and 2 Hz in in vitro studies in the literature.,, The force distribution on the wear surface of the test specimens and the total amount of deformation were determined after each chewing test procedure. The effect of the 20N bite force applied during the chewing test process on the wear surface of the test material was determined [Figure 4]a. It is seen that the bite force is completed within 1 s and this force distribution is linear [Figure 4]b.
|Figure 4: The bite forces that occur on the test material and abrasive material surfaces during the chewing cycle (a: Bite force area and b: Bite force process time)|
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| Results|| |
In the titanium-based test material designed within the scope of this study, it was observed that a more impact wear area was occurred due to the increased bite force through chewing test procedures. [Figure 5] shows the thermal cycling procedures to which the titanium-based test sample was subjected chewing simulation. [Figure 5]a shows control group, [Figure 5]b heating state 65°C, and [Figure 5]c cooling state 5°C under dwell time 1s respectively. [Figure 6] shows the impact wear area occurring in the titanium test material under a 100N bite force. This wear mechanism is occurred by the combination of the upper jaw with the lower jaw while bite process through chewing motion. In this mechanism, the test material is forced to exhibit plastic behavior during the upper jaw contact and this process can continue until the limit cycle. At the end of this process, the test material surface shows plastic behavior and particle separation occurs on the wear surface. As the wear cycle continues, these particles begin to behave like a third body on the surface. Therefore, removal of these particles on the wear surface is an important parameter for the formation of the two-body wear mechanism in experimental studies. In addition, thermal heating and cooling can accelerate particle separation from the wear surface.
|Figure 5: Thermal cycling procedures to which the titanium-based test sample was subjected chewing simulation (a: Control group, b: Heating statement and c: Cooling statement)|
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|Figure 6: Impact wear area occurring in the titanium test material under a 100N bite force. (Top figure: bite force stress region, bottom figure: impact wear and plastic deformation region)|
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[Figure 7] shows the mechanical loading process to which the titanium test specimen is subjected for 1 cycle. When this cycle period is examined, it is seen that loading and unloading process on the test sample takes place in about 1 s. As a result of this cycle corresponds to the 1 Hz period. Maximum wear stress occurs in the bite force contact zone in the chewing test cycle process [Figure 7]a. The plastic behaviors that occur in the material during the chewing cycle occur in this region. [Figure 7]b shows that the bite force in the chewing cycle is decreasing and distribution towards the sample margins. The region where the maximum bite stress and the minimum bite stress of the test specimen occur are shown in [Figure 7]c. It was determined that residual forces accumulated on the wear surface of the test specimen after chewing cycles under 100 N chewing force of this cycle test [Figure 7]d. The formation of these residual forces can be defined as the application of the chewing force to the test material during the cycle and the inability to completely discharge the force on the material. The intensity of these residual forces will contribute to the occurred of an inhomogeneous area in the wear area of the test material. In addition, increasing the chewing force and changing the contact surface in the test parameters will affect the behavior of the wear zone. As a result of, in experimental studies, it is predicted that test materials may show different wear behavior in test mechanisms performed at different frequencies, chewing force, and direct-contact area.
|Figure 7: Mechanical loading process to which the titanium test specimen is subjected for 1 cycle. (Top figure: bite force stress distirbution, bottom figure: maximum and residual stress region)|
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| Discussion|| |
The use of commercially pure titanium and titanium alloys in dental biomaterials is increasing because of its excellent corrosion resistance, good fatigue resistance, and relatively low Young's modulus. However, it is still a problem that pure commercial titanium exhibits poor wear resistance, high coefficient of friction when used as a metallic antagonist material in dental applications. The chewing movement can be defined as a movement that a person must do many times in her daily life. The chewing mechanism can be defined as the process of starting the lateral movement with the combination of the upper jaw with the lower jaw in order to break down the food taken into the human mouth. The bite force exerted by the chewing simulator should be constant and similar to intraoral tribology during the chewing test. It has been reported in the literature that teeth and dental materials are exposed to a bite force between 20 N and 120 N during the mouth movement mechanism. 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 between a wide scale, the researchers chose 50 N as the average bite force.,, Finite element model analysis can play an important role in predicting the situation thermal effect on the different parts of the tooth restored under various wear force loads. Because the wear mechanism that occurs during chewing motion has a complex and continuous structure. Temperature changes are a constant parameter that influences wear mechanisms throughout the environment chewing process. Therefore, estimating the effect of temperature on wear mechanisms in the mouth has a significant impact on the mechanical and esthetic behavior of the material. In [Figure 5], it is shown that the temperature ranges in the test method designed within the scope of this study changes in a period of 1 s. In experimental studies, the period and continuity of temperature change have a significant effect on the consistency of test results. In the literature, it has been reported that the thermal cycling process is an effective parameter on the three-body wear mechanism in experimental in vitro study. In recent years, intraoral tribology continues to improve the wear behaviors of dental biomaterials. However, many studies in the literature have reported that biomaterials may still suffer damage due to contact and contact-free wear mechanisms mechanism.,,, Many chewing simulators have been reported in the literature to simulate intraoral tribology, which performed two-and three-part wear mechanisms.,,, Both chewing simulator models are compared; in the case of a two-body wear mechanism, wear occurs with direct contact between the test samples and antagonist samples, while in the case of a three-body wear mechanism, wear occurs with an abrasive slurry (e.g. poppy seeds or PMMA as the third body) between the test subjects instances and antagonistic instances. However, some literature studies did not take into account the process of changing the thermal cycle in oral motion tribology.,, When considering the tribological process, it becomes clear that the occurrence of a thermal cycle is inevitable when three bodies are worn during chewing tests. The wear process in oral tribology has a complex and constant structure. During chewing, the oral environment, bite force, third body particle, lateral motion mechanism, and mechanical properties of the antagonist material can positively or negatively influence the wear characteristics of the composite material. For these reasons, the estimation of the parameters that may affect the chewing movement will play an important role in determining the life of the materials used in the treatment process. The parameters of the thermal cycle test procedure itself (such as dwell time, thermal cycle number, and range of test temperature) affect the mechanical and esthetic behavior of the material. Temperature measurement at specific sites in the human oral cavity has been reported for over a century. Sublingual temperature is routinely used as an indicator of oral temperature and is about 37°C for most people when measured under the certain conditions. However, it cannot be assumed that this represents the true resting temperature for all regions within the oral cavity. The temperature environment in the human oral cavity is dynamic, so it is very difficult to define the temperature range closest to the oral physiology. It is important to consider as many variables as possible that can affect the temperature of the teeth. The main sources of temperature stabilization in the mouth are the cheek, tongue, and periodontal tissue surrounding the teeth, which act as a physical barrier regulating temperature distribution. The liquids that humans ingest during chewing can be drunk in the range of 0°C–100°C, but cooked foods and frozen solids can provide temperatures outside this range to the oral cavity. The temperature ranges that an individual can tolerate may vary among the population and may be affected by variables such as the number of teeth, the amount of dentin present, the degree of keratinization of the oral mucosa, age, and patient's gender.
In the literature, it has been reported that bite force is one of the most important parameters during in vitro chewing tests. The bite force that occurs during chewing varies between individuals in a wide range. Average chewing force varies between 10 N and 120 N during the food and swallowing chewing movement., The maximum forces occur in the anterior region between 190 N and 290 N while in the molar region between 200 N and 360 N. The force profile during chewing is in the form of a half-sine wave ranging from with repetitions of 0.2–1.5 Hz. Therefore, it is important that the chewing simulator devices can simulate the changing chewing forces through mouth motion. In the literature, in many chewing test experiments, the changing of bite force and abrasive medium were ignored for application dental material through chewing simulation. Therefore, the purpose of this study was to effect of chewing force and abrasive medium on wear resistance of different composite materials through chewing simulation. The frequency of the chewing movement and the variability of the bite force had a significant effect on the mechanical and esthetic behavior of the biomaterial. In the literature, it has been experimentally observed that the mechanical behavior can change with the change of the contact area on the wear surface of the test specimen. According to the data obtained from the analyses carried out by the impact wear mechanism method in this study, the plastic and elastic deformation areas on the wear surface have changed with the increase of the contact area. This result shows that choosing similar wear regions in all group test experiments in experimental studies will contribute to the consistency of the experiments. According to the data obtained as a result of this study, the plastic deformation area of the test sample is occurred in the impact wear area. It shows that the particles can be transported from this region with lateral movement during the chewing movement process. In an experimental study in the literature, it has been reported that the 3000 thermal cycling mechanism not only simulates temperature changes in the mouth movement but also allows the removal of wear particles from the wear surfaces of composite materials.
| Conclusion|| |
In this study, the following evaluations can be made within the scope of the data obtained by the computer-aided 3D finite element methods.
The data obtained within the scope of this study showed that the increase in chewing force and contact surface and the impact-wear mechanism were more effective, but there was no linear relationship between chewing force and wear force distribution on the wear surface.
In the 100 N chewing cycle test experiments, significant increases were observed in the maximum force regions on the sample surfaces. Considering the material defects in the experimental studies, it is predicted that various damage mechanisms may occur in these regions.
In the chewing test experiments, it was observed that the plastic deformation mechanism of the test material occurred during the first contact. With this mechanism, it can be seen that particles can break off from the wear surface of the material. In the two-body wear mechanism, these particles can serve as a third abrasive structure. For this reason, these particles must be removed from the wear surface in order for the two-wear mechanism to take place through chewing test procedures.
It is seen as an inevitable situation that biomaterials placed in the human mouth can undergo various mechanical and chemical deformation mechanisms. For this reason, it is very important to predict the mechanical behavior of the biomaterial during the treatment process. In future studies, analyzing the data obtained in the in vitro test method with computer-aided modeling will allow the results to be interpreted more consistently for different chewing test process.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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