|Year : 2015 | Volume
| Issue : 3 | Page : 196-199
|Stress distribution of posts on the endodontically treated teeth with and without bone height augmentation: A three-dimensional finite element analysis
Sougaijam Vijay Singh1, Saurabh Gupta1, Deepak Sharma2, Nymphea Pandit3, Aruna Nangom4, Harsha Satija1
1 Department of Conservative Dentistry and Endodontics, DAV (c) Dental College and Hospital, Yamuna Nagar, Haryana, India
2 Department of Conservative Dentistry and Endodontics, Jaipur Dental College and Hospital, Jaipur, Rajasthan, India
3 Department of Periodontology and Implantology, DAV (c) Dental College and Hospital, Yamuna Nagar, Haryana, India
4 Department of Oral Medicine and Radiology, DAV (c) Dental College and Hospital, Yamuna Nagar, Haryana, India
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|Date of Submission||04-Jan-2015|
|Date of Decision||16-Apr-2015|
|Date of Acceptance||22-Apr-2015|
|Date of Web Publication||19-May-2015|
| Abstract|| |
Aims: Adequate bone support is an essential factor to avoid undue stress to the tooth. This is important when the tooth is endodontically treated and requires a post. The purpose of the present finite element (FE) analysis study was to evaluate the stress distribution of post on endodontically treated tooth with reduced alveolar bone height support and after bone augmentation. The null hypothesis was that there is no difference between the stress distribution of post on endodontically treated teeth with reduced alveolar bone height support and after alveolar bone height augmented using bone graft substitute.
Materials and Methods: The three-dimensional model was fabricated using ANSYS Workbench version 13.0 software to represent an endodontically treated mandibular second premolar restored with a full ceramic crown restoration and was analyzed using FE analysis. A load of 300N at an angle of 60° to the vertical was applied to the triangular ridge of the buccal cusp in a buccolingual plane. The stresses on the tooth with normal alveolar bone height, reduced alveolar bone height, and after bone augmentation because of reduced bone height were calculated using von misses stresses.
Results: A maximum stress value of 136.04 MPa was observed in dentin with an alveolar bone height of 4 mm from the cemento-enamel junction (CEJ). However, after 2 mm of alveolar bone augmentation, the stress value was 104.32 MPa, which was comparable to the stress value of 105.56 observed with the normal bone height of 2 mm from the CEJ.
Conclusion: Similar values of stresses were observed in teeth with normal and augmented bone height. Increased stresses were observed with alveolar bone loss of 4 mm from the CEJ.
Keywords: Bone augmentation; bone height; carbon fiber; Panavia
|How to cite this article:|
Singh SV, Gupta S, Sharma D, Pandit N, Nangom A, Satija H. Stress distribution of posts on the endodontically treated teeth with and without bone height augmentation: A three-dimensional finite element analysis. J Conserv Dent 2015;18:196-9
|How to cite this URL:|
Singh SV, Gupta S, Sharma D, Pandit N, Nangom A, Satija H. Stress distribution of posts on the endodontically treated teeth with and without bone height augmentation: A three-dimensional finite element analysis. J Conserv Dent [serial online] 2015 [cited 2020 Jan 27];18:196-9. Available from: http://www.jcd.org.in/text.asp?2015/18/3/196/157242
| Introduction|| |
One of the most common challenge faced by the dentist is the restoration of endodontically treated teeth, especially because of its brittleness as compared to natural teeth. ,, The success of endodontically treated teeth is related to the position of the tooth in the dental arch, , occlusal load to be borne by the tooth,  proximal contact,  the amount of remaining tooth structure,  and periodontal condition of endodontically treated teeth. 
The constant equilibrium between the bone formation and bone resorption maintains the alveolar bone height.  This is regulated by various systemic and local factors.  During inflammation, the physiological balance between the bone formation and resorption process is disturbed leading to bone loss.  Studies have shown that the reduction of alveolar bone height can also occur physiologically due to age.  A prompt diagnosis of periodontal disease is a must for the prevention of tooth mobility, tooth loss or fracture.  The changes that accompany the root canal therapy and the thickness of the residual walls and cusps will determine the selection of the restorative materials and procedures for endodontically treated teeth.  Important factors of treatment plan to be considered for a severely damaged tooth  is the evaluation of importance of tooth for occlusion or esthetics, access the remaining tooth structure after removal of all caries and old restorations, canal configuration, and to control of plaque and eliminate periodontal infection.
One of the most common failures for post and core is loosening of teeth and fracture of teeth.  This results because of improper stress distribution along the root. Metal posts were commonly used for the past many years, however with increased demands of esthetics, the use of tooth color post and core were introduced in the market and are becoming popular. 
The purpose of the present in vitro study using finite element (FE) analysis was to evaluate the stress distribution in the tooth endodontically treated with carbon fiber post having normal bone support, reduced bone support, and bone height that has been augmented with a synthetic bone graft substitute. The null hypothesis was that there is no difference between the stress distribution on endodontically treated teeth with reduced bone height and those which have bone height augmented using synthetic bone graft substitute due to bone loss.
| Materials and Methods|| |
The study was conducted using a three-dimensional (3D) FE model and were analyzed using FE analysis. The 3D model was fabricated using commercially available software ANSYS Workbench version 13.0 (ANSYS, Inc, USA) to represent an endodontically treated mandibular second premolar restored with a full ceramic crown restoration. The model was made with a simulated periodontal ligament with the alveolar bone. The measurements used for the tooth model were taken as described by wheeler's  and model was simulated with the help of an intel core i7 processor, with 8 GB RAM, 64 bit operating system. The materials used in this study were assumed to be homogenous and isotropic. The modulus of elasticity and Poisson's ratio for the elements involved in the study are shown in [Table 1].
The models included a porcelain crown with 2 mm thickness, dentin, composite core, alveolar bone 2 mm from the cemento-enamel junction (CEJ), 4 mm from the CEJ and augmented with 2 mm bone graft, Gutta-percha filling 5 mm at the apex and carbon fiber post with post diameter 1.3 mm at coronal, 1.15 mm at middle and 1 mm at 5 mm from the apex and with 2 mm of ferrule height. The geometry of the model was made as shown in [Table 2]. Discretization was done by generating mesh containing 982,759 nodes and 656,093 elements for model of 2 mm alveolar bone height from CEJ, 948,119 nodes and 635,849 elements for model with reduced bone height at 4 mm from the CEJ and 1,021,243 nodes and 681,625 elements for model with augmented bone height. The base of the alveolar bone was kept static, and a load of 300N at an angle of 60° to the vertical was applied to the triangular ridge of the buccal cusp in a buccolingual plane. The relationship of alveolar bone height at 2 mm, 4 mm and after augmentation with 2 mm bone graft was calculated using von Mises stresses. Model was made with material properties ,,, as shown in [Table 1].
| Discussion|| |
Previously, other methods have been used to analyze stress concentration in the tooth structures like the photoelastic studies.  The advantage of FE analysis is that the experimental condition can be kept identical in all the models, which is not possible in the experimental human study. In the present study, the FE analysis showed changes in the stress distribution between the two models at 2 mm bone height from CEJ, 4 mm alveolar bone height from CEJ and bone height after augmentation with 2 mm of bone graft of 2 mm augmentation with a bone graft substitute.
In this study, a load of 300N was applied although a higher load may be observed in the clinical conditions. The maximum load in the present study was observed in the dentine and the minimum load was seen in the cement.
The major finding, in this study is that the bone height was a significant factor in the stress distribution. The stress in the dentin, post, and the cement was much higher in the model with the alveolar bone height of 4 mm from CEJ compared to model with bone support of 2 mm alveolar bone height from the CEJ. This shows that the height of the bone plays an important factor in tooth stability. The present study shows that the stress distribution in teeth with post after bone height augmentation was similar to the stress distribution in teeth with normal bone height of 2 mm from the CEJ as shown in [Figure 1] and [Figure 2].
|Figure 1: (a) Stress distribution in dentin with an alveolar bone height of 2 mm from the cemento-enamel junction (CEJ). (b) Stress in cement with an alveolar bone height of 2 mm from CEJ. (c) Stress in the carbon fiber post with an alveolar bone height of 2 mm from CEJ. (d) Stress in dentin with a carbon fiber post with an alveolar bone height of 4 mm. (e) Stress in cement with a carbon fiber post with an alveolar bone height of 4 mm. (f) Stress in carbon fiber post with alveolar bone height of 4 mm|
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|Figure 2: (a) Stress in dentin with a carbon fiber post with augmented alveolar bone height. (b) Stress in cement with a carbon fiber post with augmented alveolar bone height. (c) Stress in carbon fiber post with augmented alveolar bone height|
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In the present study, carbon fiber post was used as postmaterial as studies have shown that the postmaterial with a higher modulus of elasticity than dentin is capable of causing dangerous and nonhomogenous stress in the root dentin. A material with a higher modulus of elasticity altered the natural biomechanical behavior of the tooth, eventually leading to root fracture.  Stress distribution in dentin with normal bone height was 107.37 MPa and with reduced bone height (i.e., 4 mm from CEJ increased to 138.48 MPa the stresses decreased again when the 4 mm bone height from the CEJ was augmented with 2 mm of bone graft, resulting in a stress value of after augmentation with bone graft, resulting in a stress value of 106.88 MPa, which was comparable to normal bone height, that is, 2 mm from the CEJ. Stress distribution in the cement layer was 35.385 MPa with normal bone height and increased to 48.499 MPa when bone height was reduced by 2 mm. Stresses became normal when bone height was augmented with 2 mm of bone graft that is, (34.808 MPa) stress distribution in the post was 46.046 MPa when bone height was normal that is, 2 mm from the CEJ, it increased to 67.394 MPa when bone height was reduced to 2 mm from the CEJ and increased to 44.405 MPa when bone height was augmented with 2 mm of bone graft, which was comparable to the stresses with normal bone height.
The internal canal architecture of the tooth may be modified because of severe carious involvement and during root canal instrumentation resulting in greater canal diameter. Therefore, it is important that the selection of the cementing medium for the post be carefully evaluated. It has been observed that the modulus of elasticity of the cement layer is more important to the stress concentration of root filled teeth than the thickness of the cement layer.  Moreover, cements with elastic modulus similar to dentin could reinforce weakened root and reduced stress in dentin.  Therefore, in this study Panavia F (Kuraray America, Inc.) was chosen for post cementation, which has a modulus of elasticity of 18.3 which was almost similar to the dentin [Table 1].
| Conclusion|| |
Within the limits of the present FE analysis study, it is observed that:
- Stress distribution in dentin was related to bone height level. Stress was observed more in alveolar bone height level of 4 mm from CEJ than 2 mm alveolar bone height level from CEJ and which had been augmented with a bone graft substitute
- Stress distributions were almost similar in models with a normal bone height of 2 mm from the CEJ and augmented bone height 2 mm from the CEJ
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Dr. Sougaijam Vijay Singh
Department of Conservative Dentistry and Endodontics, DAV (c) Dental College and Hospital, Yamuna Nagar - 135 001, Haryana
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2]
[Table 1], [Table 2]
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