|Year : 2020 | Volume
| Issue : 5 | Page : 134-139
Biomechanical evaluation of stress distribution in subcrestal placed platform-switched short dental implants in D4 bone: In vitro finite-element model study
Manchala R Sesha1, Rajashekar Sunduram2, Hossam A Eid Abdelmagyd1
1 Department of Periodontics, College of Dentistry, Gulf Medical University, Ajman, UAE
2 Department of Periodontics, Rajah Muthiah Dental College & Hospital, Annamalai Nagar, Tamil Nadu, India
|Date of Submission||26-Jan-2020|
|Date of Decision||10-Mar-2020|
|Date of Acceptance||10-Mar-2020|
|Date of Web Publication||28-Aug-2020|
Manchala R Sesha
Department of Periodontics, College of Dentistry, Gulf Medical University, Ajman 4184
Source of Support: None, Conflict of Interest: None
| Abstract|| |
The present study was carried out to assess stress distribution in the maxillary posterior bone region (D4 bone) with the help of a short platform switched subcrestal dental implants using the FEM model. Missing teeth surfaces related to the maxillary posterior region were stimulated. The bone model had a cancellous core of (0.5 mm) which represents D4 bone. A 7.5x4.6 mm screw type implant system with 3.5 platform switch abutment was selected. ANSYS WORKBENCH was used to model all the finite element structures. Force of 100 N was tested and adapted at an angle of 0º, 15º, 30º on the tooth model. Overall results from the current study showed that a high amount of stress was seen in cortical than in relation to cancellous bone. Stress values reduced from equicrestal to subcrestal (2 mm) placement of dental implants irrespective of angulation of load from 0o to 30o in both types of bone. However higher stress values were seen when force was applied in an oblique direction (30o) in comparison to a vertical load (0o). Least amount of stress was noticed when platform switched implants were placed 0.5 mm subcrestatlly irrespective of angulations of a load. Platform switched short subcrestal implants reduced the stress in the D4 cortical bone than in contrary equicrestal implant placement. This results in the preservation of marginal bone leading to implant success.
Keywords: FEM, subcrestal, equicrestal, platform switched implants, short implants
|How to cite this article:|
Sesha MR, Sunduram R, Eid Abdelmagyd HA. Biomechanical evaluation of stress distribution in subcrestal placed platform-switched short dental implants in D4 bone: In vitro finite-element model study. J Pharm Bioall Sci 2020;12, Suppl S1:134-9
|How to cite this URL:|
Sesha MR, Sunduram R, Eid Abdelmagyd HA. Biomechanical evaluation of stress distribution in subcrestal placed platform-switched short dental implants in D4 bone: In vitro finite-element model study. J Pharm Bioall Sci [serial online] 2020 [cited 2020 Sep 19];12, Suppl S1:134-9. Available from: http://www.jpbsonline.org/text.asp?2020/12/5/134/292869
| Introduction|| |
Replacement of missing teeth with osseous integrated dental implants has become a regular practice in the current clinical setup. With an improvement in science and technology, a high success rate of approximately 90% has been reported.,, In spite of the high success rate, crestal bone loss has been a concern for many clinicians., In the past, 1.5 mm bone loss in the crestal region in the early years and 0.2 mm in the next consequent years were considered normal., However in regions with poor bone quality, losing that vital bone with reduced bone height is of major concern. Thus, variation in surgical technique (subcrestal placement) and implant designs (platform switching, short wider diameter) have been planned for the preservation of crestal bone.,
Authors have reported three different kinds of stress observed at any bone-implant boundary. They comprise compressive, tensile, and shear stress. Literature reveals improved bone density with compressive stress; on the contrary, tensile and shear stress diminish bone density with shear stress being less helpful. It is the macroscopic implant design that has significance to influence stress distribution on the adjacent bone.,
Short and wider diameter dental implants have been used in the past with various amount of success rate. Clinically short and wider diameter implants have been used in posterior maxillary and mandible region with reduced bone height. Short implants were indicated to avoid additional bone augmentation procedures with reduced bone height. Short implants are used in posterior maxilla owing to changes in surface topography, new surgical techniques thereby improving contact ratio between bone and implant, which in turn reducing stress at the crestal region.,, Previous concept stresses on the need for implant length as it leads to increase in primary stability by increasing in bone to implant contact (BIC),,, but the latest concept is increase in functional surface area (FSA) that could be obtained by short and wider dental implants that result in better distribution of compressive and tensile stress owing to its FSA.,
Platform-switching concept was introduced way back in 1991 to effectively reduce circumferential bone loss with an added advantage of better acceptance by both adjacent hard and soft tissues.,, As a result, this technique could be used in the esthetic zone. Currently, we do not have enough data with regard to platform switch and subcrestal dental implant placement, which lead us to carry out this experiment.
Three-dimensional (3D) finite-element model (FEM) is a mathematical model used to evaluate stress distribution in dental implants as well as the shrouding bone. FEM has become a vital instrument in evaluating bone to implant boundary with mechanical load application. It is a computerized 3D model that has added advantages as compared to other models in implant dentistry. Hence, owing to limited information concerning the effect of platform-switched short implants and subcrestal placement, this study was carried out to estimate the influence of platform-switched subcrestal short dental implants on stress distribution in the D4 bone using FEM model. To test null hypotheses, we assume that (1) no difference exists in stress distribution between platform-switched short implants when placed equicrestally and subcrestally and (2) stress distribution is not governed by the angulation of load.
| Materials and Methods|| |
Missing teeth surfaces related to maxillary posterior region were stimulated. The bone model had a cancellous core of 0.5 mm, which represents D4 bone. Diameters of implant length, implant body, and implant platform are 7.5, 4.6, and 3.5 mm, respectively. ANSYS Workbench version 17.5 was used to model all the finite-element structures. Regarding material properties, all materials used in this study were isotropic, homogeneous, and linearly elastic. Literature search was done concerning elastic properties, [Table 1]. Loads of 100N were tested at an angle of 0º, 15º, and 30º. Center of the abutment was area where force was applied. The parameters analyzed were von Mises stress.
|Table 1: D4 bone mechanical properties as well as materials used in finite-element model analysis|
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| Results|| |
Following results were obtained through FEM. Force of 100N was applied in axial and oblique direction at the center of the occlusal surfaces. The mean and standard deviation values of maximum principal stress on buccal and lingual surfaces of cortical and cancellous bone are shown in [Figure 1] and [Figure 2]. [Table 2] represents the maximum von Mises stress in cortical and cancellous bone. The overall stress distribution is greater in cortical bone than in the cancellous bone [Figure 3]. Stress values reduced from equicrestal to subcrestal (2 mm) placement of dental implants irrespective of angulation of load from 0o to 30o in both types of bone [Figure 4]. However, higher stress values were seen when force was applied in an oblique direction (30o) in comparison to a vertical load (0o). Least amount of stress was noticed when platform-switched implants were placed 0.5 mm subcrestally irrespective of angulations of a load [Figure 3].
|Figure 1: The von Mises stress (MPa) in cortical bone under force of 100N in vertical (0c) and oblique (15c and 30c) direction in implants placed at equicrestal or subcrestally|
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|Figure 2: The von Mises Stress (MPa) in cancellous bone under force of 100N in vertical (0c) and oblique (15c and 30c) direction in implants placed at equicrestal or subcrestally|
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|Table 2: Average von Mises stress produced in cortical and cancellous bone under vertical and oblique load of 100 N|
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|Figure 3: Maximum stress concentrations in cortical and cancellous bone when load of 100N applied in vertical and oblique direction when implants placed at 0.5 mm subcrestally|
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|Figure 4: Maximum stress concentrations in cortical and cancellous bone when load of 100N applied in vertical and oblique direction when implants placed at 2 mm subcrestally|
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| Discussion|| |
Stress distribution around endosseous dental implants and the supporting bone were closely pertinent to the angulations of load and placement of platform-switched short dental implants either equicrestal or subcrestal. To precisely animate and design the stress state of bone and dental implants, three different angulations of load and five types of implant positions in bone have been considered. To the best of our knowledge, this is the first report to analyze subcrestal or equicrestal platform-switched short dental implant and FEM. This study also centered on the collective outcome of platform-switched short and subcrestal dental implants on stress distribution in the cortical and cancellous bone under the force of 100N at three different angulations. We believe this approach safeguards the crestal bone that intern prevents implant expose and peri-implantitis.
Our results show that stress distribution in cortical and cancellous bone under similar loading conditions was greater when the angulations of forces shifted from 0o to 30o (from vertical to oblique force).,, This is mainly because vertical forces distribute the stress more uniformly along the implant length and to the adjacent bone. On the contrary, oblique load creates shear forces and lateral movements on the implant, thus leading to more stress on the surrounding bone.,
In comparison with equicrestal to subcrestal [Figure 3], platform-switched short dental implants, the cortical bone showed less stress concentration at 0.5 mm subcrestally irrespective of angulations of force applied. Also, cortical bone showed overall stress reduction when short dental implants were placed subcrestally [Figure 4]. This is largely due to the opinion that cortical bone is responsible for the distribution and transmission of occlusal forces to the adjacent bone. A secondary reason is based on the mechanism of stress principle that is whenever two different materials are placed together and when a load is applied on one (implant), we can observe stress concentration where the two materials first come in contact. In this case, it would the cortical bone. Other reason could be, short wider diameter implants have better stress distribution as it improves implant strength and fracture resistance at the bone crest.,,, However, in the cancellous bone least stress reduction was observed at 2 mm when short implants placed subcrestally regardless of angulations of force applied. Mainly attributed to cancellous bone lesser elastic modulus, bone implant contact (BIC) and implant are placed 2 mm below the crest. Furthermore, the apex of the implant exhibits maximum stress in the cancellous bone in comparison with cortical bone. The results of this study coincide with other studies that short dental implants affect the peak stress concentration in the cancellous bone as stress values are influenced by implant length., Short and subcrestal dental implants have similar survival rate to regular implant, but the marginal bone loss was lower in short dental implants. Although platform switch and insertion depths are two independent variables for the marginal bone loss, its synergistic effect can be effective in minimizing crestal bone loss by reducing inflammatory infiltrate and increasing implant–abutment interface from the marginal bone. All of which could be helpful in clinical scenario.,
| Conclusion|| |
Within the limitations of this study, designs mimicking bone and implants have considered measuring peri-implant bone stress. However, till date there is no evidence on the level of stress at which bone remodeling ends and resorption begins. Platform-switched short subcrestal implants reduced stress in the cortical bone as compared with equicrestal implant placement. This results in preservation of marginal bone leading to implant success. Further studies need to assess the critical stress value that leads to bone resorption.
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]
[Table 1], [Table 2]