Skip to main content
NCBI home page
International Dental Journal logoLink to International Dental Journal
. 2025 Jul 19;75(5):100918. doi: 10.1016/j.identj.2025.100918

The Finite Element Analysis of the Impact of Ferrule Height and Post-Core Materials on Stress Distribution in Incisors

Beibei Yang a,b, Boxuan Wang c, Liangzhi Du a,b, Fang Wang a,b,⁎
PMCID: PMC12296476  PMID: 40684680

Abstract

Objective

Ferrule heights and post-core materials are key factors for post-core restorations, and the interaction between them needs further investigation. This study used finite element analysis to evaluate the stress distribution of post-core models with different materials and varying ferrule heights.

Methods

A 3-dimensional finite element model of the maxillary central incisor was constructed, along with 3 additional groups with different ferrule heights: 2 mm, 1 mm, and 0 mm. Meanwhile, various materials were designed to form the post-core: Zirconia, Titanium, Fiberglass, PEEK, and CFR-PEEK (PEEK reinforced by 30% carbon fiber). A 100 N load was applied at an angle of 45° with the tooth's longitudinal axis on the palatal surface of the crown. The peak von Misses (VM) stress values were recorded.

Results

As the ferrule height increased, a stress reduction was observed at post-core and post-cement interfaces, while the stress in root and cement interfaces increased; meanwhile, the peak VM stress of the post-core decreased among all groups, while that of rigid material groups (Zirconia/Titanium) decreased more significantly; in addition, the peak VM stress at post-core and cement interfaces increased, and that of the 0 mm ferrule PEEK group was the highest.

Conclusion

Ferrule heights and post-core materials affect stress distribution on post-core restorations. A sufficiently large ferrule height can effectively compensate for the stress concentration of highly rigid materials, and PEEK post-core should be carefully used in 0 mm ferrule cases.

Clinical relevance

This study would provide suggestions for dentists to choose appropriate post-core materials according to various ferrule heights.

Key words: Finite element analysis, Post-core, Ferrule height

Introduction

Tooth defects caused by trauma, caries, non-carious hard tissue disorders, and developmental anomalies are common in clinical practice. The repair of severe tooth defects usually requires root canal therapy, followed by the replacement of a post to enhance definitive restoration.1 Compared with vital teeth,2,3 endodontically treated teeth have a 25% to 40% higher susceptibility to fractures; the biomechanical vulnerability is mainly attributed to irreversible loss of dentinal moisture (8%-12% dehydration rate) and subsequent changes in complex distribution patterns.4 Therefore, the design of the “abutment/post-core/crown” composite should provide sufficient strength to all complex components, enabling them to withstand biting forces.

Since endodontically treated teeth are inherently weaker and more prone to fracture than vital teeth, caution must be exercised when selecting post-core materials. According to the study of Jafari et al., when using distinct post-core systems to restore endodontically treated teeth, there are significant differences in the distribution of stress values.5 Traditional metal and ceramic posts have a high elastic modulus and apply a wedge-shaped force onto dental tissues, often leading to root fractures.6 The relatively low elastic modulus of fiber posts effectively mitigates this unfavorable influence, thereby contributing to its increasingly widespread application in clinical scenarios.7 In addition, some in vitro studies have also indicated that the probability of root fractures when using fiber posts is lower than that when using metal posts.8 At present, prefabricated fiber posts become increasingly popular due to their elastic modulus being close to that of dentin, as well as their esthetic appeal, convenience of single-visit treatment, and affordability. Nevertheless, comprehensive long-term clinical studies have shown that the frequency of root fractures remains comparable after the application of both fiber post and metal post restorations. The ideal material for post-core restoration should have physical properties very similar to dentin. However, it must be acknowledged that the elastic modulus of the 3 existing post-core materials currently available exceeds the values observed in dentin. Therefore, scholars have begun to study polyether ether ketone (PEEK) materials, whose elastic modulus is comparable to or lower than that of dentin materials. The unoccupied PEEK material exhibits a comparatively low elastic modulus, with a range approximately between 3 and 4 GPa and a tensile strength of 80 MPa. It is noteworthy that the CFR-PEEK (PEEK reinforced by 30% carbon fiber) material exhibits significant improvement when reinforced with carbon fiber, showing an elastic modulus of 18 GPa and a tensile strength of 120 MPa. Notably, these properties are highly consistent with the physical properties of human dentin, particularly in terms of an elastic modulus of 18.6 GPa and a tensile strength of 104 MPa, highlighting a remarkable resemblance.9

Ferrule is another key factor that significantly affects the outcome of endodontically restoring teeth by post-core crowns. As is well known, the post-restoration biomechanical properties are intricately related to the quantity of residual tooth tissue. Maintaining the integrity of healthy dental tissue, especially the presence of ferrule, is crucial for enhancing the functionality of structurally weakened endodontically treated teeth.10 A ferrule comprises parallel dental walls that extend from the margin of the crown in a direction toward the fractured segment of the tooth.11 The “ferrule effect” represents a recognised and universally acknowledged principle in dentistry. It is the cornerstone for restoring structurally deteriorated teeth.12 Most laboratory studies have reached a consensus that ferrules have a positive impact on enhancing the fracture resistance of teeth that are structurally compromised.13, 14, 15 In addition, official reports indicate that compared to post-core restorations without a ferrule, teeth with a ferrule height of 1.5 to 2.0 mm can significantly reduce the risk of tooth fracture when using post-core restoration after root canal treatment.16

The biomechanical performance of endodontically treated teeth is significantly impacted by the choice of post material and the height of the ferrule.4, 5, 6,10 Despite progress in research, few studies have investigated the influence of ferrule height and its interaction with diverse post-core materials on stress distribution patterns. Therefore, the main objective of this research is to rigorously examine the interaction between various ferrule heights (ie, 0 mm, 1 mm, and 2 mm) and a diverse array of post materials (including Zirconia Ceramic, Titanium, Fiberglass, PEEK, and CFR-PEEK), as well as monolithic zirconia crowns. This study will use 3-dimensional finite element analysis (FEA) to ensure a comprehensive and precise understanding of the interaction involved. The null hypothesis is that changes in the ferrule height and post-core material do not affect the von Mises (VM) stress in the “abutment/post-core/crown” complex.

Materials and methods

CBCT scan and model generation

The dimensions of the volunteer's right maxillary central incisor were consistent with the standard size for the Chinese normal maxillary central incisor, and CBCT scanning was used for digitisation. The voxel dimension of this scan was 100 µm, ensuring accurate measurement. By utilising the MIMICS software (specifically, version 21) in conjunction with the GEOMAGIC WRAP software (version 17.0), the right maxillary central incisor, including the tooth, enamel, pulp, and adjacent bone structure, was successfully extracted. After data extraction, it was then saved in the STL file format. The processed datasets were imported into SOLIDWORKS software (version 10.0), and the following 4 solid models were successfully assembled. These 4 models are shown in Figure 1.

Fig. 1.

Fig 1:

Open in a new tab

The division and establishment of 3 finite element prototypes: (A) The dimensions of prototypes and (B) the components of constructed geometry models.

Model N: normal right maxillary central incisors

The model consisted of enamel, dentin, root canal, periodontal ligament, cortical bone, trabecular bone, and gingiva. The root length was 22 mm, with a crown-to-root ratio of 31.8%. The periodontal ligament model was defined by extracting a thick shell of 0.2 mm from the root surface, positioned below the cemento-enamel junction (CEJ). The cortical bone thickness is standardised at 1.0 mm, with its upper surface located 2 mm beneath the CEJ.9 The interior of the cortical bone is referred to as trabecular bone.

Model F0: post-core restoration without ferrule

The model included a comprehensive assembly of Zirconia Ceramic crown, post-core, cement layer, gutta-percha, periodontal ligament, cortical bone, trabecular bone, and gingiva. The diameter of the post was carefully designed to constitute one-third of the root diameter, with a conicity of 6%. The tip diameter was accurately gauged to be 1.0 mm, and the insertion depth was standardised at 10 mm, approximating two-thirds of the root length. In addition, the gutta-percha was positioned 5 mm from the root apex, strictly following the established guidelines.17 The cement layer thickness was maintained at 0.1 mm, consistent with previous research findings.9

Model F1: post-core restoration with 1.0 mm ferrule

The ferrule height was precisely measured to be 1 mm, while all other structural components remained unchanged and identical to Model F0.

Model F2: post-core restoration with 2.0 mm ferrule

The height of the ferrule was measured to be 2 mm, while all other structural components remained identical to those of Model F0.

According to the detailed specifications of their constituent post-core materials, models F0, F1, and F2 were systematically classified into 5 discrete subgroups: Zirconia, Titanium, Fiberglass, CFR-PEEK, and PEEK.

Model meshing

The Finite Element Method (FEM) model was obtained by importing the solid model into the ANSYS software (Ansys Inc.), using the IGES format for the import process. All models underwent a rigorous meshing procedure for ease of computational analysis and then were redefined using 8-node parametric elements, each endowed with 3 degrees of freedom. The comprehensive details about the nodes and elements are listed in Table S1.

Contact conditions, boundary conditions, and loading protocol

It was presupposed that the interfaces in the entire model maintain consistent and unchangeable contact boundary conditions, as referenced in the literature.9 Specifically, at the junction where the palatal one-third interfaces with the middle one-third of the central incisor, the incision of the gingiva was precisely at a 45° angle relative to the longitudinal axis of the incisor. As illustrated in Figure 2A, a force of 100 N was applied.

Fig. 2.

Fig 2:

Open in a new tab

(A) Loading applied to the crown of the right maxillary central incisor during simulations. (B) Mesh of Prototypes: a mesh of Model N, Model F0, Model F1, Model F2.

These experiments systematically divided the specimens into 6 well-defined groups: the intact right maxillary central incisor group, the Zirconia post-core group, the Titanium post-core group, the Fiberglass post-core group, the PEEK post-core group; and the CFR-PEEK post-core group. The main objectives of this analysis are 2-fold: to evaluate the stress distribution within both the post-core and the ferrule, and to evaluate the trends in stress distribution within the teeth before and after the restoration process.

Material properties

The data are presented in Table S2.17, 18, 19, 20, 21, 22 The material and structure of the model are presumed to be composed of continuous, homogeneous, and isotropic linear elastomers.

Abbreviations

VM stress: von Mises stress.

FC interface: The interface between the ferrule and the cement layer is defined as the ferrule-cement interface; PC interface: The interface between the post and the cement layer is defined as the post-cement interface (Figure 3A).

Fig. 3.

Fig 3:

Open in a new tab

(A) FC interface and PC interface. (B) Distributions of VM stress in the FC interface and PC interface.

Cement layer c: the cement layer around the crown; cement layer p: the cement layer around the post.

FEA

The VM stress was calculated for the models (Figure 2B). Meanwhile, a comprehensive record of the stress distribution was maintained for a systematic evaluation of the impacts of ferrule height and material on the biomechanical properties of the PC interface, FC interface, post-core, root, cement layer c, and cement layer p.

Results

Mesh densities of convergence test

During the experiment, the integration of the convergence tools within the ANSYS Workbench platform was successfully achieved. To facilitate the convergence analysis, 4 distinct grid densities were established. The number of cells associated with each mesh density and the peak stresses expressed in VM stress units (MPa) were fully recorded and visually illustrated in Figure 4. To conduct convergence testing, the element sizes were systematically halved, and a criterion was established to ensure that the difference between consecutive stress results did not exceed 10% or 20%. Based on these comprehensive findings, a mesh density of 0.05 mm was considered appropriate and selected as the optimal mesh size for the subsequent FEA (Figure S1).

Fig. 4.

Fig 4:

Open in a new tab

Distributions of VM stress at the post-core in Models F0, F1, and F2.

VM stress distribution within FC and PC interfaces

The peak VM stress distributions at the FC and PC interfaces are shown in Table S3. In Models F0, F1, and F2, the peak VM stress at the FC interface increases: Zirconia < Titanium < Fiberglass < CFR-PEEK < PEEK. Meanwhile, the relationship between the peak VM stress at the FC interface and the ferrule height is: Model F0 < Model F1 < Model F2, whereas for PEEK, it is Model F0 < Model F2 < Model F1. The peak VM stress at the PC interface is: Zirconia > Titanium > Fiberglass > CFR-PEEK > PEEK. The relationship between the peak VM stress at the PC interface and the ferrule height is: Model F0 > Model F1 > Model F2. In addition, the VM stress at the PC interface is significantly larger than that at the FC interface. As illustrated in Figure 3B, the peak VM stress at the FC interface is located on the buccal side of the interface in Models F0 and F1, whereas in Model F2 it is located on the palatal side of the interface.

VM stress distribution within the post-core

In Model F0, the peak VM stress for Zirconia, Titanium, Fiberglass, CFR-PEEK, and PEEK are 136.07 Mpa, 118.99 Mpa, 82.957 Mpa, 51.04 Mpa, and 40.04 Mpa, respectively. In Model F1, the peak VM stress for Zirconia, Titanium, Fiberglass, CFR-PEEK, and PEEK are 110.57 Mpa, 95.168 Mpa, 66.231 Mpa, 40.646 Mpa, and 18.35 Mpa, respectively. In Model F2, the peak VM stress for Zirconia, Titanium, Fiberglass, CFR-PEEK, and PEEK are 81.106 Mpa, 71.379 Mpa, 50.977 Mpa, 32.748 Mpa, and 15.37 Mpa, respectively. The relationship between the peak VM stress of the 5 types of post-core materials and the ferrule height is: Model F0 > Model F1 > Model F2. Compared to Model F0, the reduction rates for Model F2 are: Zirconia (54.964 Mpa), Titanium (47.593 Mpa), Fiberglass (31.98 Mpa), CFR-PEEK (18.292 Mpa), and PEEK (20.67 Mpa). As the height of the ferrule increases, the peak VM stress of the post-core decreases, but the stress value of rigid materials (Zirconia/Titanium) decreases more significantly. As the elastic modulus of the material decreases, the peak VM stress of the post-core also decreases. As illustrated in Figure 4, the stress is mainly concentrated in the 1/3 cervical region of the post.

VM stress distribution within the root

In Model F0, the peak VM stress for Zirconia, Titanium, Fiberglass, CFR-PEEK, and PEEK are 13.394 Mpa, 13.765 Mpa, 14.564 Mpa, 15.319 Mpa, and 16.142 Mpa, respectively. The peak VM stress at the root of the tooth increases as the elastic modulus of the post-core material decreases. In Model F1, the peak VM stress for Zirconia, Titanium, Fiberglass, CFR-PEEK, and PEEK are 17.293 Mpa, 17.03 Mpa, 18.417 Mpa, 19.139 Mpa, and 19.816 Mpa, respectively. The trend of the peak VM stress at the root is the same as that of Model F0. In Model F2, the peak VM stress for Zirconia, Titanium, Fiberglass, CFR-PEEK, and PEEK are 18.79 Mpa, 18.915 Mpa, 19.108 Mpa, 19.146 Mpa, and 18.684 Mpa, respectively. From Zirconia to CFR-PEEK, the peak VM stress of the root increases as the elastic modulus of the material decreases but the peak VM stress of the root decreases and reaches its minimum in the PEEK group. Except for the PEEK, the relationship between the peak VM stress of the tooth root and the ferrule height is: Model F0 < Model F1 < Model F2, whereas for the PEEK, the relationship is: Model F0 < Model F2 < Model F1. In addition, as shown in Figure 5, the distribution of the peak VM stress at the root varies with the height of the ferrule. In models F0 and F1, the peak VM stress is distributed on the labial side of the root at the cervical one-third. Nevertheless, in Model F2, the peak VM stress is transferred to the region where the ferrule contacts the interface with the post-core.

Fig. 5.

Fig 5:

Open in a new tab

Distributions of VM stress at the root in Models F0, F1, and F2.

VM stress distribution within the cement layer c

In Models F0, F1, and F2, the peak VM stress of the cement layer c increases as the elastic modulus of the material decreases. Specifically, in Model F0, the peak VM stress of the cement layer c for the Zirconia, Titanium, Fiberglass, CFR-PEEK, and PEEK are 7.4854 Mpa, 7.6819 Mpa, 8.1089 Mpa, 8.526 Mpa, and 9.0111 Mpa, respectively. In Model F1, the peak VM stress of the cement layer c for the Zirconia, Titanium, Fiberglass, CFR-PEEK, and PEEK are 5.5472 Mpa, 5.7312 Mpa, 6.0565 Mpa, 6.3753 Mpa, and 6.726 Mpa, respectively. In Model F2, the peak VM stress of the cement layer C for the Zirconia, Titanium, Fiberglass, CFR-PEEK, and PEEK are 4.114 Mpa, 4.2261 Mpa, 4.4659 Mpa, 4.7 Mpa, and 4.9728 Mpa, respectively. As the elastic modulus decreases, the peak VM stress of the cement layer c increases, while it decreases as the height of the ferrule increases. Among all groups, the peak VM stress of the PEEK post-core group is the highest in model F0. From Figure 6, it can be seen that the peak VM stress in cement layer c is located at the labial ferrule bonding interface.

Fig. 6.

Fig 6:

Open in a new tab

Distributions of VM stress at the cement layer c in Models F0, F1, and F2.

VM stress distribution within cement layer p

In Models F0, F1, and F2, the peak VM stress of the cement layer p increases as the elastic modulus of the material decreases. Specifically, in Model F0, the peak VM stress of the cement layer p for the Zirconia, Titanium, Fiberglass, CFR-PEEK, and PEEK are 4.3295 Mpa, 4.4696 Mpa, 4.7729 Mpa, 5.0598 Mpa, and 5.3461 Mpa, respectively. In Model F1, the peak VM stress of the cement layer p for the Zirconia, Titanium, Fiberglass, CFR-PEEK, and PEEK are 2.6863 Mpa, 2.8294 Mpa, 3.1023 Mpa, 3.357 Mpa, and 3.5986 Mpa, respectively. In Model F2, the peak VM stress of the cement layer P for the Zirconia, Titanium, Fiberglass, CFR-PEEK, and PEEK are 1.8841 Mpa, 1.9811 Mpa, 2.1911 Mpa, 2.3999 Mpa, and 2.6443 Mpa, respectively. As the elastic modulus decreases, the peak VM stress of the cement layer increases, while it decreases as the height of the ferrule increases. Among all groups, the peak VM stress of the PEEK post-core group is the highest in model F0. From Figure 7, it is evident that the peak VM stress of the cement layer p is located at the labial ferrule bonding interface.

Fig. 7.

Fig 7:

Open in a new tab

Distributions of VM stress at the cement layer p in Models F0, F1, and F2.

Discussion

Due to the extensive loss of hard tissue structure, teeth treated with root canal therapy are prone to fracture due to biomechanical changes. To avoid compromised integrity of these teeth, post-core restoration is commonly required to provide additional support and stabilisation for the final crown.23,24 The prognosis of root canal treatment for teeth depends on several factors, including sufficient coronal reconstruction, the position of a tooth within the dental arch, the type of ultimate restoration, the length and thickness of the post, the material of the post-core, as well as the existence of a ferrule.25,26 According to the literature, the presence of a ferrule is to protect the tooth from wedging pressure after restoration.27 In addition, the stress in the post-core is related to the elastic modulus of the post-core material and ferrule heights. Thus, this study evaluated the effect of different post-core materials with varying ferrule heights on the stress distribution within the post-core crown recovered teeth.

This study employed a 3D finite element model to simulate the effects of ferrule heights and post-core materials on the stress distribution in a tooth restoration system. The geometrical parameters of the model were based on CBCT scan data, and the material properties were derived from experimental values in literature, assuming isotropy, homogeneity, and linear elastic behavior. Although the viscoelasticity of the periodontal ligaments was not considered, the stability of the model was ensured through mesh convergence validation. The advantage of FEA is that it allows the use of the same model to compare the mechanical distribution characteristics of different materials and quantify the stress distribution characteristics by changing the parameter settings. It makes it possible to observe the stress distribution of each part of the model from any angle, which helps to analyse the stress distribution more intuitively. Consequently, FEA is commonly used to simulate and analyse the effects of restoration design on dental stress and restoration, providing a theoretical basis for clinical design.28

In this experiment, a bonding layer was constructed around the crown and post-core during occlusal loading, and a fixed contact was set up, consistent with clinical practice. To avoid the influence of different cements on the experimental results, glass ionomer cement was used for the post-core and resin cement for the crowns in all groups in this experiment. Research has indicated that teeth treated with root canal therapy with a higher ferrule show lower stress at the bonding interface, which may reduce the likelihood of clinical failure.4 This study obtains similar results, that is, the bonding layer of the post-core decreases as the ferrule height increases, regardless of the material used for the post-core. Meanwhile, when stress was applied to the crown, compressive stress was observed on the labial side of the bonded layer at a neck height of 0 mm. However, as the ferrule height increases, the stress on the bonding layer gradually decreases. Especially, when the ferrule reaches a specific height (2 mm), the peak stress point on the bonding layer will move toward the ferrule area. These results suggest that the presence of the ferrule effectively reduces the stress on the bonding layer and contributes to a more uniform stress distribution, providing key insights for optimising occlusal contact design. In addition, the bonding interface is the weakest part of the tested model, and the PC interface exhibits greater failure susceptibility than the cement-dentin, a phenomenon related to both the adhesive properties of the bonding system and the mismatch of elastic modulus between the post-material and dentin.29,30 In this experiment, the stress at the PC interface is considerably larger than that at the FC interface, also verifying that the interface between the post-core and the cement is more prone to debonding than the interface between the cement and the dentin. Moreover, in the experiments with a ferrule height of 0 mm, the stress at the post-cement layer was larger than in the other groups after using a PEEK post-core, implying a higher risk of debonding. This may be because the low elastic modulus of PEEK (5.1 GPa) is significantly lower than dentin (18.6 GPa), which increases stress concentration at the marginal area and promotes cement fracture under functional loads. Furthermore, Naif Ghanem's research has also indicated that PEEK posts appear to be inferior to prefabricated fiber posts in terms of mechanical properties and bonding with resin cements.31 As a result, the bonding properties of PEEK materials should be considered in clinical applications.

The “ferrule effect” is affected by several parameters, including its height, thickness, and completeness. This study shows that in a ferrule group of 0 mm, the post-core stress is larger and mainly distributed in the cervical 1/3 of the root, especially more pronounced in rigid post materials (such as Zirconia and Titanium). This agrees with the literature, and the absence of a ferrule structure may result in an increased risk of root fracture due to the lack of stress dispersion capability toward the coronal side.32., 33, 34 Therefore, ideally, it is recommended that the ferrule height should be at least 1.5 to 2 mm to improve fracture resistance and the overall stability of the restoration.35 Meanwhile, most experiments and clinical studies have confirmed that preparing a ferrule with a height of 1.0 to 2.0 mm at the cervical root can enhance the ferrule effect of tooth fracture resistance.36 In this study, when the ferrule was 1 mm, the stress peaks of the post-core, tooth root, and bonding interface were all reduced compared to the 0 mm group, supporting the clinical recommendation of “at least 1 mm ferrule”. When the ferrule height was 2 mm, the stress distribution was further optimised such that the stress in the apical region was reduced and the stress distribution shifted towards the ferrule, indicating that the ferrule may improve the stability of the recovery through mechanical retention and hoop effect. However, due to the lingual contour of the anterior tooth, the height and thickness of the ferrule are a pair of contradictory parameters. It is necessary to consider the biomechanical advantage of the minimally invasive restoration. Some studies have also indicated that the thickness of the ferrule, usually 1 mm or greater, helps to distribute functional stress and reduce the risk of tooth fracture.37

The mechanical properties of a material are essentially determined by its internal microstructure, which dictates stress distribution, deformation behavior, and failure resistance under functional loads. For example, the semicrystalline structure of PEEK (typically 30%-35% crystallinity) affects its elastic modulus and yield strength, while CFR-PEEK’s carbon fiber reinforcement (30% w/w) forms a composite structure architecture that increases stiffness and tensile strength from 4 GPa to 20 GPa, optimising stress redistribution in the post-core system.38 In contrast, Zirconia's high elastic modulus (∼210 GPa) is due to its dense tetragonal crystalline structure, while its transformation toughening mechanism (stress-induced phase change from tetragonal to monoclinic) improves crack resistance.39 However, this high stiffness concentrates stress at rigid interfaces. This microstructure-property interdependence explains why material selection must consider structural heterogeneity beyond bulk elastic modulus.

This study indicates that the higher the elastic modulus of the post-core material, the more stress is concentrated in the post-core. When using materials with an elastic modulus close to dentin (such as Fiberglass posts, CFR-PEEK, and PEEK), the stress distribution in the post-core is more uniform. A perfect post-core system material should have enough elasticity to adapt to the natural flexion of the teeth or have an elastic modulus similar to that of the teeth. When subjected to force, the rigid metallic post-core resists the natural movement of the teeth, generating tensile and shear stress areas at the dentin and post-bonding agent-dentin interface.17 Boschian et al. also emphasised the influence of elastic modulus on the post-core material.40

This study implies that there is an interaction between various ferrule heights and a diverse array of post-core materials. With the increase in the ferrule height, the peak VM stress of the post-core decreases, but the stress value of rigid materials (Zirconia/Titanium) decreases more significantly. Although PEEK has a lower elastic modulus than dentin, the stress values at the post-cement layer in the 0 mm ferrule group are larger than that in the other PEEK groups, indicating a higher risk of debonding due to the larger stress concentration region. The observed results are mainly attributable to 2 interrelated factors: (1) Compensation for mechanical mismatch: sufficient ferrule height can share the functional load, thereby compensating for the stress concentration. As a result, the presence of a dent in ferrule provides crucial compensation for the mechanical mismatch associated with high elastic modulus materials. (2) Stress redistribution: the ferrule changes the force transmission pathway, while the elastic modulus of the material determines stress distribution within the root or the post-core. Without a ferrule, the post-core becomes the main load-bearing structure, and the material's strength (fracture resistance) determines the failure mode (PEEK/CFR-PEEK/Fiberglass posts are prone to post fracture, and Zirconia/Titanium posts are prone to causing root fracture). In further studies, dynamic loading cycles and fatigue loading should be performed to further clarify the interaction between ferrule heights and post-core materials.

Conclusions

The interaction between ferrule heights and a diverse array of post materials needs to be considered in clinical decision-making. A sufficiently large ferrule height can effectively compensate for the stress concentration of highly rigid materials. Due to its low elastic modulus, PEEK post-core should be carefully used in 0 mm ferrule cases.

Conflict of interest

None disclosed.

Acknowledgments

Funding

This work was supported by the Shaanxi Laboratory of Advanced Materials (2024ZY-JCYJ-04-12); The Youth Innovation Team Project of Shaanxi Universities (No.23JP148); General Project - Social Development Field, Shaanxi Province(S2023-YF-YBSF-1616); National Training Program of Innovation for Undergraduates(202510698236).

Author contributions

All authors reviewed the manuscript. B.Y.: conceptualisation, methodology, software, validation formal analysis, writing and editing. B.W.: conceptualisation, formal analysis, investigation, writing. L.D.: conceptualisation, methodology, software, validation, investigation, resources, data curation, funding acquisition, formal analysis. F.W.: conceptualisation, formal analysis, investigation, writing (original draft and review and editing).

Acknowledgements

We acknowledge the support provided by Department of Medical Imaging of College of Stomatology, Xi’an Jiaotong University.

Footnotes

Supplementary material associated with this article can be found in the online version at doi:10.1016/j.identj.2025.100918.

Appendix. Supplementary materials

mmc1.doc (80KB, doc)

REFERENCES

  • 1.Kathuria A., Kavitha M., Khetarpal S. Ex vivo fracture resistance of endodontically treated maxillary central incisors restored with fiber-reinforced composite posts and experimental dentin posts. J Conserv Dent. 2011;14(4):401–405. doi: 10.4103/0972-0707.87211. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 2.Dietschi D., Duc O., Krejci I., et al. Biomechanical considerations for the restoration of endodontically treated teeth: a systematic review of the literature–Part 1. Composition and micro- and macrostructure alterations. Quintessence Int. 2007;38(9):733–743. [PubMed] [Google Scholar]
  • 3.Tang W., Wu Y., Smales RJ. Identifying and reducing risks for potential fractures in endodontically treated teeth. J Endod. 2010;36(4):609–617. doi: 10.1016/j.joen.2009.12.002. [DOI] [PubMed] [Google Scholar]
  • 4.Juloski J., Apicella D., Ferrari M. The effect of ferrule height on stress distribution within a tooth restored with fibre posts and ceramic crown: a finite element analysis. Dent Mater. 2014;30(12):1304–1315. doi: 10.1016/j.dental.2014.09.004. [DOI] [PubMed] [Google Scholar]
  • 5.Jafari S., Alihemmati M., Ghomi A.J., et al. Stress distribution of esthetic posts in the restored maxillary central incisor: three-dimensional finite-element analysis. Dent Res J (Isfahan) 2021;18:10. [PMC free article] [PubMed] [Google Scholar]
  • 6.Meira J.B., Esposito C.O., Quitero M.F., et al. Elastic modulus of posts and the risk of root fracture. Dent Traumatol. 2009;25(4):394–398. doi: 10.1111/j.1600-9657.2009.00772.x. [DOI] [PubMed] [Google Scholar]
  • 7.Junqueira R.B., de Carvalho R.F., Marinho C.C., et al. Influence of glass fibre post length and remaining dentine thickness on the fracture resistance of root filled teeth. Int Endod J. 2017;50(6):569–577. doi: 10.1111/iej.12653. [DOI] [PubMed] [Google Scholar]
  • 8.Owen T.A., Barber M. Direct or indirect post crowns to restore compromised teeth: a review of the literature. Br Dent J. 2018;224(6):413–418. doi: 10.1038/sj.bdj.2018.218. [DOI] [PubMed] [Google Scholar]
  • 9.Yu H., Feng Z., Wang L., et al. Finite element study of PEEK materials applied in post-retained restorations. Polymers (Basel) 2022;14(16) doi: 10.3390/polym14163422. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 10.Juloski J., Radovic I., Goracci C., et al. Ferrule effect: a literature review. J Endod. 2012;38(1):11–19. doi: 10.1016/j.joen.2011.09.024. [DOI] [PubMed] [Google Scholar]
  • 11.Assiri A.Y.K., Saafi J., Al-Moaleem M.M., et al. Ferrule effect and its importance in restorative dentistry: a literature review. J Popul Ther Clin Pharmacol. 2022;29(4):e69–e82. doi: 10.47750/jptcp.2022.977. [DOI] [PubMed] [Google Scholar]
  • 12.Bhuva B., Giovarruscio M., Rahim N., et al. The restoration of root filled teeth: a review of the clinical literature. Int Endod J. 2021;54(4):509–535. doi: 10.1111/iej.13438. [DOI] [PubMed] [Google Scholar]
  • 13.Tan P.L., Aquilino S.A., Gratton D.G., et al. In vitro fracture resistance of endodontically treated central incisors with varying ferrule heights and configurations. J Prosthet Dent. 2005;93(4):331–336. doi: 10.1016/j.prosdent.2005.01.013. [DOI] [PubMed] [Google Scholar]
  • 14.Ma P.S., Nicholls J.I., Junge T., et al. Load fatigue of teeth with different ferrule lengths, restored with fiber posts, composite resin cores, and all-ceramic crowns. J Prosthet Dent. 2009;102(4):229–234. doi: 10.1016/S0022-3913(09)60159-1. [DOI] [PubMed] [Google Scholar]
  • 15.da Silva N.R., Raposo L.H., Versluis A., et al. The effect of post, core, crown type, and ferrule presence on the biomechanical behavior of endodontically treated bovine anterior teeth. J Prosthet Dent. 2010;104(5):306–317. doi: 10.1016/S0022-3913(10)60146-1. [DOI] [PubMed] [Google Scholar]
  • 16.Ng C.C., Dumbrigue H.B., Al-Bayat M.I., et al. Influence of remaining coronal tooth structure location on the fracture resistance of restored endodontically treated anterior teeth. J Prosthet Dent. 2006;95(4):290–296. doi: 10.1016/j.prosdent.2006.02.026. [DOI] [PubMed] [Google Scholar]
  • 17.Lanza A., Aversa R., Rengo S., et al. 3D FEA of cemented steel, glass and carbon posts in a maxillary incisor. Dent Mater. 2005;21(8):709–715. doi: 10.1016/j.dental.2004.09.010. [DOI] [PubMed] [Google Scholar]
  • 18.Genovese K., Lamberti L., Pappalettere C. Finite element analysis of a new customized composite post system for endodontically treated teeth. J Biomech. 2005;38(12):2375–2389. doi: 10.1016/j.jbiomech.2004.10.009. [DOI] [PubMed] [Google Scholar]
  • 19.Li L.L., Wang Z.Y., Bai Z.C., et al. Three-dimensional finite element analysis of weakened roots restored with different cements in combination with titanium alloy posts. Chin Med J (Engl) 2006;119(4):305–311. [PubMed] [Google Scholar]
  • 20.Spazzin A.O., Galafassi D., de Meira-Junior A.D., et al. Influence of post and resin cement on stress distribution of maxillary central incisors restored with direct resin composite. Oper Dent. 2009;34(2):223–229. doi: 10.2341/08-73. [DOI] [PubMed] [Google Scholar]
  • 21.Nahar R., Mishra S.K., Chowdhary R. Evaluation of stress distribution in an endodontically treated tooth restored with four different post systems and two different crowns- a finite element analysis. J Oral Biol Craniofac Res. 2020;10(4):719–726. doi: 10.1016/j.jobcr.2020.10.004. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 22.Kharboutly N.A., Allaf M., Kanout S. Three-dimensional finite element study of endodontically treated maxillary central incisors restored using different post and crown materials. Cureus. 2023;15(1) doi: 10.7759/cureus.33778. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 23.Bacchi A., Caldas R.A., Schmidt D., et al. Fracture strength and stress distribution in premolars restored with cast post-and-cores or glass-fiber posts considering the influence of ferule. Biomed Res Int. 2019;2019 doi: 10.1155/2019/2196519. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 24.Martino N., Truong C., Clark A.E., et al. Retrospective analysis of survival rates of post-and-cores in a dental school setting. J Prosthet Dent. 2020;123(3):434–441. doi: 10.1016/j.prosdent.2019.05.003. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 25.Ayad M.F., Bahannan S.A., Rosenstiel SF. Influence of irrigant, dowel type, and root-reinforcing material on fracture resistance of thin-walled endodontically treated teeth. J Prosthodont. 2011;20(3):180–189. doi: 10.1111/j.1532-849X.2011.00687.x. [DOI] [PubMed] [Google Scholar]
  • 26.Santos-Filho P.C., Verissimo C., Soares P.V., et al. Influence of ferrule, post system, and length on biomechanical behavior of endodontically treated anterior teeth. J Endod. 2014;40(1):119–123. doi: 10.1016/j.joen.2013.09.034. [DOI] [PubMed] [Google Scholar]
  • 27.Eraslan O., Aykent F., Yücel M.T., et al. The finite element analysis of the effect of ferrule height on stress distribution at post-and-core-restored all-ceramic anterior crowns. Clin Oral Investig. 2009;13(2):223–227. doi: 10.1007/s00784-008-0217-5. [DOI] [PubMed] [Google Scholar]
  • 28.Atif M., Tewari N., Reshikesh M., et al. Methods and applications of finite element analysis in dental trauma research: a scoping review. Dent Traumatol. 2024;40(4):366–388. doi: 10.1111/edt.12933. [DOI] [PubMed] [Google Scholar]
  • 29.Eskitascioglu G., Belli S., Kalkan M. Evaluation of two post core systems using two different methods (fracture strength test and a finite elemental stress analysis) Journal of Endodontics. 2002;28(9):629–633. doi: 10.1097/00004770-200209000-00001. [DOI] [PubMed] [Google Scholar]
  • 30.Mahmoudi M., Saidi A.R., Amini P., et al. Influence of inhomogeneous dental posts on stress distribution in tooth root and interfaces: three-dimensional finite element analysis. J Prosthet Dent. 2017;118(6):742–751. doi: 10.1016/j.prosdent.2017.01.002. [DOI] [PubMed] [Google Scholar]
  • 31.Ghanem N., Ali H., Bahrli N., et al. Clinical performance of custom-milled polyetherketoneketone (PEKK) posts and cores: a 12-month follow-up randomized controlled pilot study. Clin Exp Dent Res. 2024;10(2):e854. doi: 10.1002/cre2.854. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 32.Haralur S.B., Alalyani A.F., Almutiq M.A., et al. Effect of inadequate ferrule segment location on fracture resistance of endodontically treated teeth. Indian J Dent Res. 2018;29(2):206–211. doi: 10.4103/ijdr.IJDR_134_17. [DOI] [PubMed] [Google Scholar]
  • 33.Alberto L.H.J., Zhang Z.X., Duan Y.Y., et al. Effect of ferrule design on stress distribution of maxillary incisor rehabilitated with ceramic crown and PEEK post-core material: a 3D finite element analysis. Ceramics-Switzerland. 2023;6(4):2256–2268. doi: 10.3390/ceramics6040137. [DOI] [Google Scholar]
  • 34.Tanaka R., Yamaguchi S., Takahashi Y., et al. Mechanical behavior of endodontically treated teeth: a three-dimensional finite element analysis using displacement vector. J Prosthodont. 2025;34(3):281–289. doi: 10.1111/jopr.13810. [DOI] [PubMed] [Google Scholar]
  • 35.Magne P., Lazari P.C., Carvalho M.A., et al. Ferrule-effect dominates over use of a fiber post when restoring endodontically treated incisors: an in vitro study. Oper Dent. 2017;42(4):396–406. doi: 10.2341/16-243-l. [DOI] [PubMed] [Google Scholar]
  • 36.Kumar S.S., Viswanathan M., Rajkumar K., et al. Comparative study on fracture resistance of endodontically treated tooth in relation to variable ferrule heights using custom-made and prefabricated post and core: an in vitro study. J Pharm Bioallied Sci. 2020;12(Suppl 1):S554–S5S9. doi: 10.4103/jpbs.JPBS_166_20. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 37.Fontana P.E., Bohrer T.C., Wandscher V.F., et al. Effect of ferrule thickness on fracture resistance of teeth restored with a glass fiber post or cast post. Oper Dent. 2019;44(6):E299–E308. doi: 10.2341/18-241-l. [DOI] [PubMed] [Google Scholar]
  • 38.Kurtz S.M., Devine JN. PEEK biomaterials in trauma, orthopedic, and spinal implants. Biomaterials. 2007;28(32):4845–4869. doi: 10.1016/j.biomaterials.2007.07.013. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 39.Kelly J.R., Denry I. Stabilized zirconia as a structural ceramic: an overview. Dent Mater. 2008;24(3):289–298. doi: 10.1016/j.dental.2007.05.005. [DOI] [PubMed] [Google Scholar]
  • 40.Boschian Pest L., Guidotti S., Pietrabissa R., et al. Stress distribution in a post-restored tooth using the three-dimensional finite element method. J Oral Rehabil. 2006;33(9):690–697. doi: 10.1111/j.1365-2842.2006.01538.x. [DOI] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

mmc1.doc (80KB, doc)

Articles from International Dental Journal are provided here courtesy of Elsevier

RESOURCES