|Year : 2012 | Volume
| Issue : 1 | Page : 19-25
Effect of length and diameter on stress distribution pattern of INDIDENT dental implants by finite element analysis
Bobin Saluja1, Masood Alam2, T Ravindranath1, A Mubeen3, Nidhi Adya1, Jyoti Bhardwaj4, A Dhiraj4
1 Institute of Nuclear Medicine and Allied Sciences, Min of Defence DRDO, India
2 Department of Applied Sciences and Humanities, Jamia Millia Islamia University, New Delhi, India
3 Mechanical Engg, Jamia Millia Islamia University, New Delhi, India
4 Cognizant Technology Solutions, Teaneck, New Jersey, USA
|Date of Web Publication||24-May-2012|
3E/15 Jhandewalan Extension, New Delhi
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Context: Dental implants are subjected to a variety of loads when placed in function. The implant dimensions influence the magnitude and profile of stresses within the bone. The greater the magnitude of stress applied to a dental implant system the greater the difference in strain between the implant material and bone. An optimum stress profile is required in order to maintain a strong and healthy bone.
Materials and Methods: The design efficacy of the Indigenous titanium Dental implant "INDIDENT" developed by INMAS was studied using finite element stress analysis. Abacus software has been chosen for the analysis and the models are constructed as three-dimensional Solid models. The boundary conditions for each case are same. The amount of load applied is equal for all the cases as 100 N. The study involved the modeling of mandible and the dental implant meshed together. The stress generated was calculated by Finite element method using Abacus software. The different parameters used in this study for FEA simulation were stresses developed due to variation in length and diameter variation.
Results and conclusion: The results indicated that the stress concentration and distribution was not effected by the length variation of the Implants. Stress concentration was same at the neck of hole and which can be reduced after suitable chamfering of the hole. The stress distribution on the effect of diameter variation indicates that if the diameter of implant was increased the contact surface also increases and simultaneously stress pattern was reduced.
Keywords: Finite element analysis, indigenous dental implant, stress distribution
|How to cite this article:|
Saluja B, Alam M, Ravindranath T, Mubeen A, Adya N, Bhardwaj J, Dhiraj A. Effect of length and diameter on stress distribution pattern of INDIDENT dental implants by finite element analysis. J Dent Implant 2012;2:19-25
|How to cite this URL:|
Saluja B, Alam M, Ravindranath T, Mubeen A, Adya N, Bhardwaj J, Dhiraj A. Effect of length and diameter on stress distribution pattern of INDIDENT dental implants by finite element analysis. J Dent Implant [serial online] 2012 [cited 2022 Jan 25];2:19-25. Available from: https://www.jdionline.org/text.asp?2012/2/1/19/96561
| Introduction|| |
A dental implant as a screw-type biomaterial is a functional load transfer structure to substitute for lost or partially damaged teeth. Despite the high success rates reported by a vast number of literatures, time dependent marginal bone resorption around implants is still unavoidable. The biomechanical factors related to implant failures can be related mostly to the implant design (e.g., length, diameter). Masticatory forces acting on dental implants can result in undesirable stress in adjacent bone, which in turn can cause bone defects and the eventual failure of implants.
Indident dental implant
The high cost of globally available implants warrants their design and development in our own country. The present research work was aimed at indigenizing the implant system, taking into account the economic requirements and working conditions of a developing nation. These new indigenous dental implants can be expected to revolutionize the treatment procedure in dentistry in general and prosthetic dentistry in specific. As an effort to overcome these aforesaid difficulties, Institute of Nuclear Medicine and Allied Science, Defence Research and Development Organization, DRDO Ministry of Defence has come with suitable cost-effective/affordable dental implants INDIDENT to meet these growing needs of the dental patients.
As a part of a research project, an extensive study was carried out by the Department of Dental Research of the Institute of Nuclear Medicine and Allied sciences vis-a-vis metal selection, scientific designing, in vivo and in vitro biological studies, multi-centric trial and also the prosthetic procedures before finalizing the design of the implants and the related armamentarium. Using the above methodology we would evaluate the design efficacy of the Indigenous titanium Dental implant "INDIDENT" developed by INMAS using Finite Element Stress analysis. The study involves the modeling of mandible and the dental implant meshed together and to calculate the stress generated by Finite element method using Abacus software. The Titanium Dental Implant used in this study were designed and fabricated by Institute of Nuclear Medicine and Allied Sciences, Defence Research and Development Organization under the name and style "INDIDENT".
Three different types of implants used were
- External Hex implant
- Internal Hex Implant and
- Ball and Socket type
The three-dimensional model of the Indident Dental implant was created using VISI software. The physical and mechanical properties of titanium were employed to generate a three-dimensional model of the implant. The 3D model represented the exact replica of the implant used in this study [Figure 1].
| Materials and Methods|| |
Effect of implant length
Study of variation of implant length has been done in abaqus 6.7; the assembly of implant is made by the titanium metal. As per the study of availability the implant length are generally available in lengths from about 6mm to as much 20 mm. We have analyzed the lengths of INDIDENT implant as 8, 10 and 12 mm. The surrounding bone is considered a block. The implants are inserted in the bone. Abacus software has been chosen for the analysis and the models are constructed as three-dimensional models. The boundary conditions for each case are same. The amount of load applied is equal for all the cases as 100 N.
The main objective of the study is optimization of the implant length with respect to diameter [Figure 2], [Figure 3] and [Figure 4].
Effect of implant diameter
Implant diameter is the dimension measured from the peak of the widest thread to the same point on the opposite side of the implant. Solid models for five different types of diameters for dental implant were created. The diameters taken up in the study were 3.5, 3.8, 4.2 and 5 mm. The Abacus software has been used to evaluate the stress on different diameters of the implant using Finite Element Method [Figure 5], [Figure 6], [Figure 7] and [Figure 8].
| Results and Discussion|| |
Effect of implant length
The implant dimensions influence the magnitude and profile of stresses within the bone. The study of effect of length variation of implants has been studied for 8, 10 and 12-mm implants using Finite element Stress Analysis by Abacus Software. The stress distribution on top and stress distribution in section for all the three lengths of implant have been presented in this study [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13] and [Figure 14].
In the above case the results indicate that the stress concentration and distribution is not effected by the length variation of the implants. Stress concentration is same at the neck of hole and which can be reduced after suitable chamfering of the hole.
There has been insufficient research focusing on the pattern of load transfer and the failures with the effect of implant length that correlated with the force transmission area of implant bone interface. It has been an axiom in implant dentistry that longer implants guarantee better success rates and prognosis. Finite element analysis has shown that the occlusal forces are distributed primarily to the crestal bone, rather than evenly throughout the entire surface area of the implant interface.  Since masticatory forces are light and fleeting, these forces are normally well tolerated by the bone. This may be the reason that implant length is not linearly related to biomechanical stability.
The relationship between implant length and survival is limited. A study of fixed single unit restoration demonstrated that a relationship between implant length and success may not exist. 
No relationship between initial mobility and implant length has been established and mechanical analysis has supported the view that increasing the implant length may only increase success rate to a certain extent. A finite element analysis supports the hypothesis that implant length is a secondary parameter for stress distribution. The FEA results done by Basile Georgiopoulos  indicated a tendency toward stress reduction on the implant when the length was increased. In a study done by Sertgoz there was no statistically significant change associated with the length of implants.  Chun investigated and found that the maximum effective stress decreased as implant length increased.
The implant length and diameter has a significant influence on the stress distribution, within the surrounding jawbone. Finite element simulation of stress distribution around implants can be used to determine the optimum length and diameter of the implants that would best dissipate stresses induced by the implantation.
Himmlova et al.,  used FEA to compute values of von Misses stress at the implant-bone interface for all variations in length and diameter of implants. Maximum stress areas were identified to be located around the implant neck. The maximum decrease in stress (31.5%) was found for implants with a diameter ranging from 3.6 to 4.2 mm. Further stress reduction for the 5.0-mm implant was only 16.4%. An increase in the implant length also led to a decrease in the maximum von Misses equivalent stress values; the implant length, however, was not as influential as that of implant diameter. Note that the length of implant ranges from 8 to 18 mm.
Guan et al.,  investigated the stress characteristics in the bone when various combinations of bone and implant parameters are considered. In general, it was found that an increase in length (L) reduces the stress, within both cancellous and cortical bone, for a wider range of parameters as compared to increasing the diameter (D).
Effect of implant diameter
The diameter measures the outside dimension of the thread. Implant diameter is not synonymous with the implant platform which is measured at the interface of the implant connected with the abutment. A wide-platform implant is not coincidental with an increased diameter of the implant thread. Implant diameter may be more important than implant length in the distribution of loads to the surrounding bone. Most implants are approximately 4 mm in diameter. At least 3.25 mm in diameter is required to ensure adequate implant strength. Implant diameters up to 6mm are available, which are considerably stronger, but they are not so widely used because sufficient bone width is not so commonly encountered. Four different diameters were taken in the study. These diameters are 3.5, 3.8, 4.2 and 5 mm [Figure 15], [Figure 16], [Figure 17], [Figure 18], [Figure 19], [Figure 20], [Figure 21] and [Figure 22].
The stress distribution on the effect of diameter variation indicates that if the diameter of implant is increased, the contact surface also increases and simultaneously stress pattern is reduced. Increasing the implant diameter effectively increase the contact area between the implant and the bone, and thus increase the stability of the implant.
The known advantage of using wide-diameter implants include providing more bone to bone contact,  biocortical engagement, immediate placement in failure sites and a reduction in abutment stresses and strain. 
A study conducted by Iplikcioglu showed lower tensile and compressive stress values for wider implants.  Shyh-Chour Huang  investigated and showed that the increased implant diameter reduces the stresses. The contact area between implant and bone is increased thus the stress concentration effect is decreased Also, with increased implant diameter the bone loss is decreased and as a consequence the success rate is improved. Increasing implant diameter is very helpful in decreasing the stress.
A wide-diameter implant can also be used as an alternative to bone grafting in severely resorbed maxilla.  Improved implant strength and resistance to fracture can be attained by increasing the diameters of implant.  Strain test show that by increasing the diameter of an implant, there is a decrease in the abutment strain for a given load.  Wide-diameter implants may also have a more favorable distribution of masticatory forces. 
Increasing the surface of the platform theoretically reduces stress on any point of the osseointegrated interface on occlusal loading. 
Since occlusal loading is implicated in crestal bone loss around implants, it is postulated that wider implants may reduce the stress around the crestal bone and potential bone loss.  Wide-diameter implants also have a significant advantage in immediate implant placement in premolar and molar regions, where the defect created by tooth extraction will result in an oversized osseous preparation.
The study done by T. Li1,  was aimed to create a 3D finite element model for continuous variation of implant diameter and length, thereby identifying their optimal range in type IV bone under biomechanical consideration. These results indicate that in type IV bone, implant length is more crucial in reducing bone stress and enhancing the stability of implant-abutment complex than implant diameter. Biomechanically, implant diameter exceeding 4.0mm and implant length exceeding 9.0mm are the combination with optimal properties for a screwed implant in type IV bone.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16], [Figure 17], [Figure 18], [Figure 19], [Figure 20], [Figure 21], [Figure 22]