|Year : 2017 | Volume
| Issue : 4 | Page : 245-249
Stress evaluation of titanium-gold and titanium-aluminum-vanadium alloy for orthodontic implants: A comparative finite element model study
Chinglembi Nongthombam1, Sheetal Patani2, Nitin D Gulve3, Amit Nehete2, Mahesh P Pardeshi4, Shivpriya Aher5
1 PG student, Department of Orthodontics and Dentofacial Orthopaedics, M.G.V.'S K.B.H. Dental College and Hospital, Nashik, Maharashtra, India
2 Prof., Department of Orthodontics and Dentofacial Orthopaedics, M.G.V.'S K.B.H. Dental College and Hospital, Nashik, Maharashtra, India
3 Prof. and HOD, Department of Orthodontics and Dentofacial Orthopaedics, M.G.V.'S K.B.H. Dental College and Hospital, Nashik, Maharashtra, India
4 B Tech Mechanical Engineer, Research and Development Department, Mechwell Industries Ltd., Mumbai, Maharashtra, India
5 Lecturer, Department of Orthodontics and Dentofacial Orthopaedics, M.G.V.'S K.B.H. Dental College and Hospital, Nashik, Maharashtra, India
|Date of Submission||27-Jan-2017|
|Date of Acceptance||27-Jun-2017|
|Date of Web Publication||12-Oct-2017|
Luwangsangbam Khunou Leikai, BPO Mantripukhri, Imphal - 795 002, Manipur
Source of Support: None, Conflict of Interest: None
Introduction: With the increased popularity of implants, orthodontists are in search of a better material. Titanium-gold (Ti-Au) is a newer material and could be a choice to replace the currently popular titanium-aluminum-vanadium (Ti-6Al-4Va) alloy. Materials and Methods: Using the finite element analysis method, three-dimensional computer-aided models of a mini-implant was designed. Two cylindrical bone pieces into which the implant was inserted were used. A force magnitude of 5 N was then horizontally and separately applied to the implant head. Results: Comparison of the maximum von Mises stress in the implants of Ti-6Al-4Va and Ti-Au was done. The maximum stress value of 252.356 and 242.415 Mpa, as well as maximum deformation of 0.025 mm and 0.019 mm, on Ti-6Al-4Va and Ti-Au can be observed, respectively. Conclusion: It was found that the maximum stress and maximum deformation values were lower in Ti-Au as compared to Ti-6Al-4Va implant. As the Ti-Au implant has greater resistance to deformation, it can be concluded that this newer alloy has better strength than Ti-6Al-4Va implant.
Keywords: Implants, titanium, titanium-aluminum-vanadium, titanium-gold
|How to cite this article:|
Nongthombam C, Patani S, Gulve ND, Nehete A, Pardeshi MP, Aher S. Stress evaluation of titanium-gold and titanium-aluminum-vanadium alloy for orthodontic implants: A comparative finite element model study. J Indian Orthod Soc 2017;51:245-9
|How to cite this URL:|
Nongthombam C, Patani S, Gulve ND, Nehete A, Pardeshi MP, Aher S. Stress evaluation of titanium-gold and titanium-aluminum-vanadium alloy for orthodontic implants: A comparative finite element model study. J Indian Orthod Soc [serial online] 2017 [cited 2017 Oct 18];51:245-9. Available from: http://www.jios.in/text.asp?2017/51/4/245/216648
| Introduction|| |
Changing trends in orthodontics have increased the use of the implant for treatment as they give miraculous results. With the widespread use of mini-implants, the emphasis is placed on improving its properties. An ideal implant should be biocompatible, should have high strength, and also should resist deformation. Implant should be least invasive in the body offering maximum stability and greater anchorage.
Titanium has very attractive features of good biocompatibility and fine corrosion resistance among other dental materials. Mechanical properties such as higher specific strength and excellent corrosion resistance both in the air and biological fluids have made Ti and its alloys suitable for the application in dental and medical fields.
However, literature highlighted several disadvantages of commercially pure Titanium such as difficulty in welding, machining, and high reactivity with surrounding impurities such as oxygen and nitrogen. Therefore, attempts have been made to develop new Ti alloys with improved mechanical properties and castability by alloying Ti with a variety of elements such as nitinol and titanium-aluminum-vanadium (Ti-6Al-4Va) alloy. The release of metallic ions during the destruction of the passive film can cause side effects in the body. Aluminum is found to be a suspected inducer of Alzheimer's disease, and its special complex has a carcinogenic effect. Vanadium also brings an allergic reaction. Moreover, Ti-6Al-4Va alloy has a slightly lower resistance to corrosion than pure Ti. To overcome the limitations of Ti alloys, the need arises to introduce alloys with improved properties.
Gold is one of the noblest elements known. It does not corrode in the oral environment. When alloyed with titanium, it has a benefit of improved corrosion resistance over pure Ti and its alloys. Rosalbino et al. reported the positive influence of gold addition on the corrosion behavior of Ti. Furthermore, Takahashi et al. examined the mechanical properties of the titanium gold (Ti-Au) alloys and found that the Ti-Au alloys had higher yield strength, tensile strength, and hardness.
This study is an attempt to compare the stress and maximum deformation when the Ti-6Al-4Va and Ti-Au implant were inserted into the bone assemblies.
| Materials and Methods|| |
This study involved the consideration of the following elements during the construction of the three-dimensional (3D) finite element model (FEM) [Figure 1],[Figure 2],[Figure 3].
- Implant design which included the length, diameter, and pitch of the screw
- Establishment of the 3D FEM of the implant - FEM of the implant inserted into the bone
- Material's properties - Poisson's ratio and Young's modulus for the implants which include Ti-6Al-4Va alloy, Ti-Au alloy, and cortical and cancellous bones. The material properties for this study which are shown in [Table 1] and [Table 2] are derived from the related research.
|Table 1: Material properties of Ti-6Al-4Va, cortical and cancellous bone.|
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The design of the study had the implant as a small head-type tapered titanium alloy screw, with an external diameter of 1.3 mm, a length of 8 mm, a threaded deepness flight depth of 0.2 mm, threaded angle of 60°, and thread interval of 0.5 mm.
Two FEMs of the implant with the above-mentioned combinations were designed. 3D cylindrical bone pieces of 7.5 mm in height and 5.6 mm in diameter were established and exported to the FE software.
The assembly meshed with 10 nodes tetra elements. The element is defined by 10 nodes having three degrees of freedom at each node: translation in the nodal x, y, and z directions. The element has plasticity, hyperelasticity, creep, stress stiffening, large deflection, and large strain capabilities. It also has mixed formulation capability for simulating deformations of nearly incompressible elastoplastic materials and fully incompressible hyperplastic materials. The FEM model consisted of 627,017 nodes and 414,162 elements. Bone elements should be designed so as to access the stresses surrounding the implant.
The ANSYS Software PA, USA, was used to mesh the implant and bone models. Two FEMs were generated to perform finite element analysis on the implants of the two titanium alloys with a diameter of 1.3 mm and length of 8 mm. A simulated orthodontic force of 5 N was applied to each of the FEMs, and the amount of stress on the implant–bone interface was analyzed.
| Results|| |
The amount of stress that can be withstood by the implants of two different alloys in this study was evaluated according to the von Mises stress hypothesis in megapascal (MPa). A color code scale served to evaluate quantitatively the stress distribution in bone and the implants. It was evident that the stress distribution was concentrated in the thread area of the neck of the implant and the cortical bone was subjected to higher stresses as compared to the cancellous bone.
The stress value of Ti-6Al-4Va implant in the thread area of the neck was 252.356 MPa and the maximum deformation was 0.025 mm, whereas the stress value in the thread area of the neck and the maximum deformation of the Ti-Au implant was 242.415 MPa and 0.019 mm, respectively [Figure 4] and [Figure 5]. This means that stress value was higher in the thread area when the implant of Ti-6Al-4Va was inserted as compared to the stress value when Ti-Au was inserted. Moreover, the amount of deformation was more when the implant of Ti-6Al-4Va was used. However, both the implants of the two alloys are comparatively safe to withstand the load as per boundary conditions as the overall stresses are below the yield strength.
|Figure 4: von Mises stress for the titanium-aluminum-vanadium. (a) The maximum deformation. (b) Maximum stress concentrating in the thread area of the implant|
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|Figure 5: von Mises stress for the titanium-gold. (a) Maximum deformation; (b) Maximum stress concentrating in the thread area of the implant|
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| Discussion|| |
In the recent years, there has been a tremendous increase in the use of implants in orthodontics for enhancing anchorage. Elastic modulus, strength, and biocompatibility must be considered while choosing an orthodontic implant. The material should have enough mechanical strength to resist the stress developed during insertion and removal without any permanent deformation.
Commercially pure Ti has been widely used as implant material because of proven biocompatibility with human tissues, high corrosion resistance in air and body fluids, lack of allergic reactions, high specific strength, and low elastic modulus. However, orthodontic implants are smaller than conventional dental implants and must bear high orthodontic loads. This factor has led to the possible fracture of commercially pure Ti implants during placement and removal. Therefore, Ti-6Al-4Va implants have been developed to overcome such problems as they have greater strength and fatigue resistance.
Despite the various advantages of Ti-6Al-4Va, there still appeared several disadvantages. Morais et al. reported that while using the Ti alloy, despite the tendency of greater ion release the detected concentration of vanadium did not reach toxic levels in the animal model. Gioka et al. measured in vitro traces of vanadium released from Ti-6Al-4Va orthodontic brackets, and it was considered that vanadium release was minimal. Iijima et al. used implants where they found that the greater strength of Ti was achieved by the addition of vanadium, iron, and manganese. They concluded that adding these elements decreased biocompatibility as vanadium in Ti-6Al-4Va alloy may cause cytotoxic and adverse tissue reactions. Furthermore, the acute and chronic toxic effects of vanadium when absorbed in greater amounts have been well documented. In addition, aluminum may induce Alzheimer's disease. However, there has been an enormous increase of the use of this alloy in the recent years because of their favorable mechanical properties. Therefore, the ideal implant material that has combined mechanical strength with a high level of biocompatibility has yet to be manufactured.
In this paper, gold has been used as the alloying element. Historically, gold has been used in dentistry for more than 4000 years due to its good biocompatibility and versatility. Lee et al. measured the effect of gold addition on the corrosion behavior of Ti alloys and reported that the Ti-Au alloys exhibited improved corrosion resistance than commercially pure Ti. Rosalbino et al. correlated the positive influence of Au on the corrosion resistance of Ti. Oh et al. studied the cytocompatibility and electrochemical properties of Ti-Au alloy and reported that the cytotoxicities of the alloy were similar to that of pure Ti. Therefore, gold has been employed as the strengthening element to improve the performance of pure Ti and its existing alloys.
In the current study, Ti-6Al-4Va and Ti-Au implants were compared and evaluated for better stress-bearing capacity and strength using the FEM-based study. The results of the study revealed that the stress value and the maximum deformation were found to be much lower when the Ti-Au implant was used, indicating that this alloy has better stress-bearing capacity and higher strength. This result is in accordance with Takahashi et al. where the mechanical properties of Ti-Au alloys were examined and found that the Ti-Au alloys had higher yield strength, tensile strength, and hardness.
As shown by previous study and this study, Ti-Au has better strength than Ti-6Al-4Va. Previous study has shown that a reduction in implant diameter possessed greater fracture risk. This factor may lead to a reduction in the success rate as well as the mechanical stability of the implants. Jolley and Chung revealed that the mean peak torque value at fracture correlated positively with the diameter of the screw. Besides, a diameter of smaller size implants may be advantageous to reduce the risk of damaging adjacent tooth's root. Currently, the commercially available implants vary in diameter from 1 to 2.3 mm. Later, a smaller diameter Ti-Au implants can be manufactured which can provide a better solution for such problem. Even though the cost of the material (Ti-Au) will be comparatively higher, further studies are required to evaluate the cost/benefit ratio for future use.
| Conclusion|| |
This study helped us to study and compare the stress concentration and maximum deformation of different implant materials (Ti-Au implant) using finite element analysis before implementing on the patient. It was found that the maximum stress, as well as maximum deformation values, was lower in Ti-Au as compared to Ti-6Al-4Va implant. As the Ti-Au implant has greater resistance to deformation, it can be concluded that this newer alloy has better strength than Ti-6Al-4Va implant. In future, this model can be developed into an implant material and further perform biocompatibility and the corrosion resistance properties.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2]