Stress Distribution Analysis, Research Paper Example

A Finite Element Analysis Comparing Deformation, Strain, Stress on Bone, Implant Components, Crown on Various Types of Crowns-Metal Ceramic, Zirconia and PEEK

Abstract

This study compares the effect of different types of crown material on stress distribution on the bone, implant, abutment, and crown under simulated axial load force using a finite element analysis. The evaluated implants and abutments were made from titanium implants connected to an abutment system. The dental implants were placed in the mandible and abutments screwed into the implants before placing crowns over the abutments. In this study, since implants were placed in the mandible and the crowns used varied and included metal ceramic crown, zirconia crown and PEEK. In each of the six cases, a simulated axial load of 50 N was applied on the system. The finite element analysis developed was based on the physical properties of the implant components and the values of the stresses generated in the mandible, implants, abutment and crown calculated. There was a significant difference in stress distribution between the three systems consisting of metal ceramic crowns, zirconia crowns and PEEK crowns as far as the bone, crown, and abutment were concerned. The metal ceramic crown dental implant system produces less stress on the alveolar bone and the abutment complex, and greater stress on the prosthesis. On the other hand, the zirconia crown dental implant system produces higher levels of stress on the alveolar bone and the abutment complex, and lower stress on the prosthesis. The PEEK system had a higher stress value due to its lower elastic modulus.

Introduction

Dentures and bridges were predominantly used as therapeutic measures to patients with tooth loss due to limited research on improving dental care. Investment in research on dental care led to the discovery of advancement options such as dental implants, which are more efficient in managing dental problems with a success rate of this implant increasing to 98%. Despite this high rate of success, studies reveal that technical complications may arise due to the design of the implant and as a result of excessive axial force with common technical failures including loss and fractured abutments and prosthetics and displacement of the crown (Quaresma et al., 2008). Despite these failures not causing the loss of the implant, they are a constant issue to both clinicians and patients. In addition, they lead to additional costs (El-Anwar et al., 2014). A number of modifications have been devised on implants, and abutments, to mitigate such difficulties. In addition, a variety of crowns have been designed to avert giving patients a variety of options when going for dental restoration procedures.

The design of the implant system characterized by the type of crown used, as well as the implant-abutment combinations is important as it helps in establishing the performance, as well as the maintenance of the implant and prosthesis attached to the implant system (Bramanti et al., 2017). More importantly, the design of the implant system and the type of crown used affects the load transmission on the implant, crown, abutment and surrounding area.

Metal ceramic crowns have been the most common type of prosthetic restorations, which are supported by dental implants and natural teeth. They have continued to be the preferred treatment option despite new ceramics like zirconium oxide emerging and offering encouraging expectation with respect to aesthetics and strength (Kaleli et al., 2018). The longevity of restorations can be determined by fracture resistance with material having a high fracture resistance depicting a higher survival rate under masticatory forces.  With many methods of studying the action of forces on prosthesis having been developed, the finite element analysis is the tool of choice when analyzing the distribution of forces at various points of the surface through created virtual models (Kim et al., 2019). This study compares the effect of various types of crown material on the stress, deformation, and strain on the dental restoration system and surrounding areas.

Materials and Methods

This study applied the in vitro study technique using the finite element analysis (FEA). FEA is a numerical technique for solving structural analysis problems using simulation of a specific physical phenomenon to optimize components in structural design. In vitro studies apply techniques that perform various biological procedures outside the normal biological context and in a controlled environment.  The research consisted of a mandible, implants, abutments, and varied crowns. The six titanium implants are placed in the mandible, the abutments are attached to the implants and crowns made of metal ceramic, zirconia, or PEEK are placed on the attached abutment. The setup consisted of a mandible, six implants, and titanium abutments. Some of the implants were filled with metal-ceramic crowns while others were filled with zirconia crowns.

The study utilized an edentulous mandibular model that is generated using the FEA software. The research was designed to compare the different types of prothesis under controlled environment defined by constant conditions. These constant environmental conditions included; the face-face angle tolerance set at 750 and the trim tolerance at 0.71709 mm, a 10 mm length, and 3.3 mm diameter that were maintained for the implants. Considering that the project was in vitro osseointegration, direct contact between the bone and the implant was assumed. An axial loading technique was used to apply a load of 50 N on the implants. The different metal ceramic, PEEK, and zirconia prostheses were compared based on strain, deformation, and stress on bone, implant components. Data showing the level of deformation, elastic strain and stress were recorded and analyzed. After the application of the 50 N loads, the values for deformation, strain, stress on bone, and implant components upon the variation of crown was recorded.

Results

The results on deformation, strain, stress on bone and implant components for a metal ceramic crowns were broken down into effects on bone, overall crown, and abutments.

Ceramic Metal Crown on Titanium Abutment

The findings showed that the bone exhibited a high degree of deformation such that the maximum deformation value 9.8887 mm. with an average value of 2.6984 mm. the bone had a 3.5306 mm/mm maximum strain, and an average strain of 3.0681 mm/mm. the bone stress on the bone had a maximum value of 1.9405 MPa, and an average stress of 1.0983 MPa.

The results on deformation, stress and strain on the six implants provided values that were compressed to maximum values, average values and minimum vales for all the implants. The maximum deformation value for the implants was 8.9231 mm, the average value was 7.9342 mm, while the minimum deformation value attained was 6.8358 mm.  the minimum strain value attained was 1.7418 mm/mm, the maximum value of strain on the implants was 4.1837 mm/mm, while the average value of strain was 3.6105 mm/mm. the maximum stress value was 2.8926 MPa, the average stress on implants was 2.3732 MPa, while the minimum stress value was 1.916 MPa.

The ceramic crowns experienced significant level of stress strain, and deformation. These findings showed that the maximum value of deformation on the ceramic crowns was 8.9648 mm, while the average value was 7.9399 mm. the minimum deformation value on the ceramic crowns was 6.4263 mm. the average strain value recorded on the ceramic crowns was 3.0681 mm/mm, the minimum value was 1.6025 mm/mm, while the maximum strain value was 3.2479 mm/mm. the maximum stress on the crowns was 8.4615 MPa, the minimum stress value was 4.1058 MPa, and an average value of 6.7301 MPa

The abutments showcased a maximum deformation value of 8.7057 mm when the ceramic crowns were placed on the. The average deformation value on the abutment was 7.791 mm, while the minimum value of deformation was 6.7338 mm. the abutment also experienced a maximum strain value of 6.5172 mm/mm, an average stress of 6.1387 mm/mm, and a minimum strain value of 5.2376 mm/mm. the maximum stress on the abutment when the metal ceramic crown were placed was 5.4499 MPa, while the average value of stress on the abutment was 4.2606 MPa. the minimum value was 4.1371 MPa.

These findings show that the bone experiences the lowest deformation when metal ceramic crown is placed on titanium implant and abutment. The findings also show that implants, crowns, and abutment experience approximately equal level of deformation when the metal ceramic crown is placed on the abutment. However, the crown experiences the lowest minimum deformation and the implant and the abutment experience the highest level of deformation.

The results show that when metal ceramic crowns are placed on titanium abutment the abutment experiences the highest level of strain while the crown experience the lowest level of elastic strain. Moreover, the implant experiences significantly higher level of strain than the bone.

These findings show that the crown experiences the highest maximum, average and minimum stress when metal ceramic crowns are placed on titanium abutment. The bone experiences the minimum value of both maximum and average stress. While the abutments experiences significantly higher stress than the implants.

Zirconia Crown on Titanium Abutment

The figure displays the deformation effect on the bone, implants, crown, and abutment when a zirconium crown is placed on titanium abutments.

These findings show that zirconium crown results in minimal deformation of 0.1 mm scale and that the abutment experienced the highest level of deformation (0.17521 mm). Moreover, the bone experiences the lowest level of deformation (maximum deformation value of 0.2257).

These findings show that bone and abutment experience lowest amount of maximum strain when zirconium crown is placed on the abutment. The findings also show that on average values, the bone experiences the highest level of strain (4.8233 mm/mm) followed by the implant (4.1709 mm/mm). Moreover, the abutment experiences the least level of average strain (1.4283 mm/mm).

The findings show that abutment experience the highest level of stress (9.6273 MPa), while then bone and the implant experience the lowest value of maximum stress (4.588 MPa). In terms of average stress values, the abutment has the lowest value (1.2607 MPa), while the implant has the highest value of average stress (3.7884 MPa).

PEEK Crown Placed on Titanium Abutment

When the Peek crown was placed on titanium abutment the bone (9.88 68 mm) experienced the highest level of maximum de formation. In this case, crown also recorded the highest average deformation (78.02456) than in the previous cases where metallic crown and zirconia were placed on the abutment. deformation, while the bone had the lowest deformation.

The strain was highest on the abutment, while the implant experienced the lowest strain (3.2389 mm/mm). On overall, the PEEK crowns resulted to the highest level of strain than the Zirconia, and metal ceramic crowns. The crown had higher average (2.3958 mm/mm) strain than the abutment.

Stress was highest on the crown (19.4 MPa) and the implants (11.5 MPa). The bone had the lowest maximum stress (6.7489 MPa). The stress experienced was much higher than the ones achieved when the zirconia, and the metal ceramic crowns were placed on titanium abutment.

Discussion

This study reveals an important finding as it indicates that a dental restoration system condition of metal ceramic crowns produces lower stress levels on the bone and abutment is comparison to a restoration system consisting of zirconia crowns. The study also revealed that all restorative crown materials and abutment material had similar biomechanical behavior with respect to stress distribution in the peripheral bone and implants. Therefore, the study dismisses a popular hypothesis that PEEK customized crowns produce better stress values in peripheral bone and implants. This study confirms that companies have different responses to masticatory axial forces, which may be attributed to the absent periodontal ligaments that act as elastic buffers (Quaresma et al., 2008).

The complexity of biomaterials, microstructural details and dental anatomy makes it challenging to analyze the biomechanical responses of implants, bones and the surrounding area. However, the standardized parameters of the Finite Element Analysis technique make it a suitable analytic method for evaluating these behaviors within complex geometries (El-Anwar et al., 2014). In the three-dimensional model of analysis, it becomes possible to analyze deformations, stresses and strain with realistic results (Bramanti et al., 2017).

The von Mises stress value was carefully used to prevent exceeding the 550 MPa yield strength limit if titanium implants beyond which failure may occur (Kaleli et al., 2018). The highest overall stress value obtained was 458.8 MPa on the second system comparison of titanium abutment and zirconia crown indicating that there was no implant model that exceeded 550 MPa. The stress distribution on the implant components, crowns and peripheral bone was evaluated using 50 N axial loads.

The present study also indicated that the implant model consisting of a PEEK crown presented a lower level of elastic strain compared to both the metal ceramic crown and zirconia crown models. The PEEK model also demonstrated lower stress valued under axial loading hence indicating that the PEEK model represents the most favorable stress distribution among the three types of restorative crowns. The PEEK customized model has an elastic modulus that is 60 times lower than the zirconia model, which demonstrated in low stress values within the structure but higher stress in the restorative structure (Sadowsky, 2019). Furthermore, a higher von Mises stress values was observed in the titanium base abutment connected to PEEK and metal ceramic systems compared to the zirconia system (Kim et al., 2019: Shwarz et al., 2019).

In conclusion, the dental implant systems with metal-ceramic prosthesis produce less stress on the alveolar bone and the abutment complex, and more significant pressure on the prosthesis. On the other hand, dental implant systems having zirconia prosthesis produce higher levels of pressure on the alveolar bone and the abutment complex and less stress on the prosthesis. While zirconia is advantageous in terms of aesthetics, it has a low resistance to fracture with long-term use which is an important consideration when trying to avoid fractures during chewing.

References

Quaresma, S. E., Cury, P. R., Sendyk, W. R., & K, C. S. (2008). A finite element analysis of two different dental implants: stress distribution in the prosthesis, abutment, implant, and supporting bone. Journal of Oral Implantology, 1-6.

El-Anwar, M. I., El-Mofty, M. S., Awad, A. H., El-Sheikh, S. A., & El-Zawahry, M. M. (2014). The effect of using different crown and implant materials on bone stress distribution: A finite element study. Egyptian Journal of Oral & Maxillofacial Surgery, 5, 2, 58-64.

Bramanti, E., Cervino, G., Lauritano, F., Fiorillo, L., D’Amico, C., Sambataro, S., Denaro, D., & Cicciu?, M. (2017). FEM and Von Mises Analysis on Prosthetic Crowns Structural Elements: Evaluation of Different Applied Materials. The Scientific World Journal, 2017, 1-7.

Kaleli, N., Sarac, D., Kulunk, S., & Ozturk, O. (2018). Effect of different restorative crown and customized abutment materials on stress distribution in single implants and peripheral bone: A three-dimensional finite element analysis study. Journal of Prosthetic Dentistry, 119, 3, 437-445.

Kim, K. T., Eo, M. Y., Nguyen, T. T., & Kim, S. M. (2019). General review of titanium toxicity. International Journal of Implant Dentistry.

Sadowsky, S. J. (2019). Occlusal overload with dental implants: a review. International Journal of Implant Dentistry.

Shwarz, F., Langer, M., Hagena, T., Hartige, B., Sader, R., & Becker, J. (2019). Cytotoxicity and pro-inflammatory effects of titanium and zirconia perticles. International Journal of Implant Dentistry.