Finite element analysis (FEA) and photoelasticity are frequently utilized methods in biomechanical research to examine stress distribution within dental structures and materials. This review provides a comprehensive examination of the historical evolution, clinical applications, and comparative advantages of these methods and limitations of FEA with a particular emphasis on endodontic research. While photoelasticity offers intuitive, real-time visualization of stress patterns, it remains limited in analyzing complex three-dimensional (3D) structures. In contrast, FEA enables the simulation of complex 3D anatomical structures and multidirectional loading conditions through numerical computations, making it a powerful tool across various dental specialties. However, FEA presents significant limitations including unrealistic modeling assumptions, oversimplified anatomical geometries with insufficient representation of diversity and lack of material long-term material degradation models. The review proposes recommendations to enhance FEA’s clinical relevance including incorporating anisotropic tissue and material properties, patient-specific parameters, dynamic loading scenarios, and advanced techniques for crack propagation analysis.

dental biomechanics, endodontics, finite element analysis, future directions, photoelasticity, stress distribution

Stress analysis plays a crucial role in understanding the biomechanical behavior of dental structures and materials, aiding in the development of improved restorative techniques and treatment planning.^[1] Two widely utilized methodologies for stress analysis in dentistry and endodontics are finite element analysis (FEA) and photoelasticity. Both techniques offer unique insights into the distribution of stress and strain within dental materials and tissues, yet each possesses distinct advantages and limitations that influence their applicability.

This review aims to bridge the gap between theoretical finite element method and real-world clinical applications by highlighting not only the advantages but also the critical limitations of FEA in dental biomechanics. By comparing it with experimental methods such as photoelasticity and providing targeted recommendations for improvement, this study supports the development of more realistic, validated, and patient-specific simulations, ultimately aiming to enhance treatment planning and clinical outcomes in dentistry.

FEA is a computational numerical method that has gained prominence in dental biomechanics due to its ability to analyze complex structures under various loading conditions. Initially developed in the 1950s for aerospace engineering, FEA was introduced into dentistry in the 1970s as an alternative to experimental stress analysis techniques like photoelasticity.^[2,3] The method involves discretizing a structure into finite elements interconnected by nodes, allowing for the simulation of stress distribution under applied forces.^[4]

One of the key advantages of FEA is its flexibility in modeling intricate dental structures with varying material properties. It enables the visualization of stress contours, which aids in predicting failure points in dental restorations, implants, and endodontic treatments. Additionally, FEA allows for modifications of variables such as material composition, geometry, and loading conditions without requiring physical specimens, making it cost-effective and highly reproducible.^[5]

However, despite its advantages, FEA has notable limitations. The accuracy of the analysis is highly dependent on the assumptions made during model creation, such as the assignment of material properties and boundary conditions. Simplifications or inaccuracies in these assumptions can lead to significant deviations between simulated results and actual biomechanical behavior. In FEA dental tissues are simplified as isotropic and homogeneous, despite their inherently anisotropic nature.^[6] Moreover, FEA models often fail to replicate the viscoelastic behavior of the periodontal ligament (PDL) and the dynamic conditions of occlusal forces, leading to potential discrepancies between simulated results and real clinical scenarios. Additionally, complex models may require significant time and computational power, which requires high investment in workstation-type computers and special software, which mostly requires an annual subscription.

Finite element analysis is a computational tool that divides complex structures into smaller elements to simulate physical phenomena, including stress, strain, and deforma- tion.^[7] In dentistry, FEA has been extensively applied across various specialties to enhance understanding and improve clinical outcomes.

FEA is instrumental in evaluating stress distribution around dental implants, aiding in the optimization of implant designs and placement strategies to ensure longevity and stability. Falcinelli et al., in their systematic review, reported that FEA allows for the assessment of different implant geometries, lengths, diameters, materials, and loading conditions, thereby guiding clinicians in selecting the most appropriate implant systems for patients. It was reported that FEA predictions indicated larger implant diameters resulted in reduced stress magnitudes and smaller stress concentration zones within cortical bone tissue, while increased implant length produced more favorable stress distribution patterns in cancellous bone.^[8]

In prosthodontics, FEA assists in analyzing the biomechanical behavior of various restorative materials and prosthetic designs. Yan et al., in their systematic review, reported that FEA enables the prediction of how different prostheses, such as crowns, bridges, and dentures made from various materials, will perform under masticatory forces, facilitating the development of restorations that are both functional and durable. It was reported that when fixed partial dentures made from different materials and incorporating various connector designs were evaluated under multiple loading scenarios via FEA, connector volume represented a critical factor influencing the maximum principal stress within dentures.^[9]

FEA is utilized to study the effects of orthodontic forces on teeth and surrounding periodontal structures. By simulating different orthodontic appliances and force applications, FEA aids in designing treatments that achieve desired tooth movements while minimizing adverse effects on the supporting tissues. In a recent study by Luchian et al., the biomechanical impact of orthodontic forces on anterior mandibular teeth with varying degrees of periodontal involvement was evaluated through FEA, and it was concluded that orthodontic forces applied to periodontally compromised anterior teeth should be limited to less than 1 N to prevent periodontal damage.^[10]

In endodontics, FEA helps in understanding the stress distribution within tooth structures and operative materials during conventional root canal procedures and after repair or regeneration interventions with bioceramic materials or post-endodontic restorations. It evaluates the impact of different instrumentation techniques and bio/non-bio materials on the integrity of the tooth, guiding the development of methods that preserve tooth structure, prevent fractures, and facilitate a complete biomechanical preparation.^[11-14] In a recent FEA study by Smran et al.^[14], stress distributions within root dentin were evaluated following simulated endodontic treatment using AH Plus and BioRoot RCS sealers to identify regions of stress concentration that may predispose to fracture formation. The simulated application of vertical and oblique masticatory loads revealed that BioRoot RCS-obturated specimens generated lower maximum von Mises stress values in root dentin compared to AH Plus-obturated specimens. Maximum von Mises stress locations in the computational model identified regions with the highest probability of crack formation.

FEA is applied to assess the biomechanical behavior of periodontal tissues under various loading conditions. It aids in understanding the effects of occlusal forces on periodontal health and the design of periodontal therapies that distribute stresses favorably to promote healing and regeneration. In a recent study by Shetty et al., the biomechanical effects of normal occlusal forces at different angulations on maxillary first molar periodontal structures were evaluated using FEA. It was found that the highest tensile stresses occurred at 90° angulation, and it was stated that they could impair blood flow and potentially lead to periodontal breakdown, particularly when localized in the cervical and apical regions of the periodontal ligament.^[15]

In surgical planning, FEA assists in predicting the outcomes of reconstructive procedures, such as mandibular resections and orthognathic surgeries. It enables the simulation of different surgical approaches, fixation methods, and materials, optimizing functional and aesthetic results while minimizing complications. In a recent study by Xue et al., the biomechanical performance of 3D-printed customized titanium reconstruction plates with different heights, thicknesses, and screw distributions in comparison to commercial reconstruction plates for segmental mandibular defects was evaluated using FEA to determine optimal design parameters. The study further incorporated a clinical case to verify FEA-based predictions regarding potential complications, including titanium plate fracture and screw loosening.^[16]

FEA plays a crucial role in the development and testing of new dental materials. By simulating the mechanical behavior of novel biomaterials under functional loads, FEA facilitates the design of materials with enhanced properties, such as increased strength and biocompatibility.^[8,17]

FEA is used to study the effects of traumatic forces on dental structures. It helps in understanding how different designs and materials can absorb impact forces, thereby preventing or minimizing dental injuries. In their scoping review, Atif et al. stated that FEA applications not only allowed researchers to visualize internal stress-strain behavior during trauma but also provided quantitative evidence to guide clinical decision-making regarding trauma management, splinting strategies, and the protective role of various mouthguard designs.^[4]

Photoelasticity, an experimental optical method for stress analysis, has been used in dentistry since the mid-20th century to study stress patterns in particularly prosthetic materials and dental implant parts. Its application in dentistry dates back to 1935, when Zak utilized it to study orthodontic movements and their effects on the supporting periodontium.^[18]

The technique relies on birefringent materials that exhibit stress-induced optical changes, producing isochromatic fringe patterns that visually represent stress concentration zones. This qualitative approach provides direct visualization of stress distribution in dental structures subjected to mechanical loads.^[19]

One of the primary advantages of photoelasticity is its ability to capture real-time stress distribution without requiring computational assumptions about material properties. This makes it particularly valuable for analyzing prosthetic designs, implant-supported restorations, and orthodontic forces. Also, photoelasticity provides immediate visual representation of stress patterns, facilitating intuitive understanding. Additionally, the method provides experimental validation for numerical simulations, complementing FEA studies.^[20]

Despite its benefits, photoelasticity has several drawbacks. It requires the fabrication of physical models using photoelastic materials, which may not accurately replicate the biomechanical properties of dental tissues. The need for birefringent materials and the limitation of these materials may not perfectly mimic the properties of actual dental tissues. Furthermore, photoelastic analysis remains limited for complex three-dimensional (3D) structures. The technique still remains constrained by the availability of suitable materials and the complexity of model preparation and possible discrepancies between the printed models and their real-world counterparts.^[19]

Both FEA and photoelasticity offer valuable insights into dental biomechanics, but their complementary nature makes them most effective when used in conjunction for experimental validation. Photoelasticity offers direct experimental observation of stress patterns, serving as a practical tool for validating FEA digital twin designs and mechanic models.^[21] FEA provides precise numerical data and predictive capabilities, making it ideal for simulating various clinical conditions and treatment scenarios.^[5] However, its reliance on assumed material properties and boundary conditions can introduce errors. On the other hand, photoelasticity offers direct experimental visualization of stress distribution but is constrained by material limitations.^[22]

Literature comparing these methods suggests that while FEA is superior for analyzing complex structures and long-term simulations, photoelasticity remains a critical tool for validating computational models.^[21] Integrating both approaches can enhance the accuracy and reliability of stress analysis in dentistry, leading to better clinical outcomes and the development of more durable dental materials and restorations.

While finite element analysis and photoelasticity share several applications in dentistry, photoelasticity has unique advantages in certain areas where direct experimental validation, real-time stress visualization, and qualitative stress analysis are particularly beneficial.^[2] The following areas highlight applications where photoelasticity offers additional insights beyond FEA.

In implantology, photoelasticity proves particularly useful in examining different implant-abutment connection types, such as external and internal, highlighting their roles in stress distribution. Photoelastic analysis is also effective in assessing the biomechanics of mini-implants and short implants, which differ from standard implants. This technique has been applied to investigate the effects of implant diameter and implant thread geometry on stress modulation within cortical bone.^[23,24]

In prosthodontics, photoelasticity proves particularly beneficial in comparing the biomechanical behavior of different implant-abutment connection types, such as external hexagon and Morse taper connections, offering insights into their influence on load distribution and prosthesis stability.^[25] Moreover, photoelasticity has been applied to evaluate different prosthesis retention mechanisms, such as screw-retained versus cemented restorations, under functional loading.^[26]

In orthodontics, this technique is utilized usefully in evaluating the biomechanical effects of different molar uprighting mechanics, such as the use of miniscrews, cantilever springs, T-loop springs, and open-coil springs.^[27]

In endodontics, this technique proves particularly useful in assessing the biomechanical effects of different rotary instrumentation systems with varied tip and taper sizes.^[28] Moreover, it has been utilized to analyze the influence of type of motion, reciprocating versus continuous rotation, and the metallurgical properties of the instruments, such as heat treatment, on the stress patterns observed during canal preparation.^[29]

In periodontology, photoelasticity can effectively illustrate how occlusal forces are transmitted through the tooth-PDL-bone complex and show the stress concentrations in the cervical region of the supporting bone and root sur-face.^[30]

In oral and maxillofacial surgery, photoelasticity has been utilized to assess the stress distribution around different osteosynthesis systems, conventional and locking, used in mandibular fracture repairs.^[31] Additionally, photoelastic analysis has been applied to study the effects of various orthognathic surgical procedures on stress distribution in the jawbones.^[32]

In dental materials research, photoelastic analysis provides a valuable experimental approach for assessing the biomechanical performance of various dental materials. Photoelasticity has been utilized to assess the stress distribution around dental implants restored with various ceramic materials.^[33]

1. Unrealistic nature of modeling assumptions

• Limitation: Most FEA studies assume dental tissues are isotropic (having the same physical properties in all directions) and homogeneous. However, dentin and enamel are actually anisotropic and show microstructural differen- ces.^[6,34]

• Recommendation: FEA models should better represent the anisotropic and heterogeneous properties of dental tissues. Multi-scale modeling techniques supported by nano-mechanical tests should be used.^[35]

2. Inadequacy of periodontal ligament (PDL) and surrounding tissue simulations

• Limitation: FEA models generally treat PDL as a homogeneous and linear elastic structure. However, PDL shows viscoelastic and nonlinear behavior, meaning it responds to loading at different time scales.

• Recommendation: Nonlinear and viscoelastic material models should be used to simulate the realistic behavior of PDL. Time-dependent deformations should be considered in dynamic loading scenarios.^[36]

3. Unrealistic adhesion simulations

• Limitation: Most FEA studies often consider adhesive interfaces as perfectly bonded. While the effect of factors such as polymerization shrinkage, temperature changes, and masticatory loads on the distribution of the generated stress on the adhesive bond was investigated with FEA^[37], it is neglected that the effect of root canal disinfectants and dentinal fluid may weaken the bond strength in endodontic and restorative polymer/composite restorations.

• Recommendation: Improved FEA models of adhesion should be developed to include the combined effects of polymerization shrinkage, dentinal fluid, and disinfectant solutions on bond strength. Comprehensive experimental validations should be performed.^[38]

4. Lack of consideration for micro cracks and defects in FEA models

• Limitation: Most FEA models assume that enamel and dentin are completely flawless (crack-free). However, dental tissues may contain microcracks and porosities.^[34]

• Recommendation: The modeling of microcracks should be ensured using the Extended Finite Element Method (XFEM) or crack propagation analyses.^[39]

5. Unrealistic simulation of the effects of occlusal forces and trauma

• Limitation: In current FEA studies, static and single-point loading is mostly used, ignoring dynamic loadings such as bruxism, trauma, and eccentric chewing movements. However, teeth are exposed to dynamic and multidirectional forces.

• Recommendation: Multi-point loading, cyclic loading, and dynamic analyses should be used. Force distribution should be modeled to better reflect clinical reality. More complex biomechanical models incorporating bruxism and chewing cycles should be developed.^[40]

6. Lack of sufficient clinical validation

• Limitation: Most FEA studies include only theoretical simulations and are not validated with experimental or clinical results.

• Recommendation: FEA results should be compared with advanced laboratory tests and long-term clinical studies, and the consistency of the results with real clinical data should be analyzed.^[41]

7. Inadequacy of in-vitro test methods for long-term performance of dental composites

• Limitation: In-vitro test methods for dental composites fail to replicate the complex, dynamic, and multifactorial conditions of the oral environment and often overlook the synergistic effects of cyclic mechanical loads, enzymatic activity, thermal variations, and chemical interactions that contribute to degradation over time. As a result, they offer limited predictive value for long-term clinical performance.

• Recommendation: Complex FEA models mimicking the long-term clinical scenarios, including multifactorial conditions of the oral environment with dynamic changes in stress, should be developed to predict the durability and clinical performance of dental restorative materials.^[42]

8. Insufficient representation of root canal morphological diversity

• Limitation: Current FEA models predominantly simplify root canal systems, typically using standard or idealized canal geometries as a simple conical form, and overlook the extensive morphological diversity documented in clinical settings, including anatomical complexities such as C-shaped configurations, accessory canals, apical deltas, and isthmuses. Such oversimplifications can lead to misleading biomechanical insights and reduce the clinical relevance, as anatomical irregularities and variations may significantly influence instrument behavior, shaping outcomes and irrigant flow dynamics and cleaning efficiency in vivo.^[43,44]

• Recommendation: Variations of root canals and anatomical irregularities should be 3D reconstructed in high detail from micro-CT and CBCT scans to reflect clinically realistic root canal geometry and should be incorporated into novel FEA models to enable clinically realistic analyses representing the diversities in population.^[45]

9. Inadequate analysis of endodontic post and core systems

• Limitation: The biomechanical effects of post-core systems are frequently analyzed in FEA; however, factors such as the bonding strength of adhesive cement, polymerization shrinkage, and thermal expansion, which may jeopardize the endurance of post-core systems, are often overlooked.

• Recommendation: Advanced FEA models incorporating polymerization shrinkage and thermal stresses to post-core systems, and analyzing their durability in the long-term should be developed.^[46]

10. Unrealistic simulation of vertical root fractures (VRF)

• Limitation: Vertical root fractures are often related to excessive canal preparation, improper condensation techniques, and traumatic occlusion. Despite their clinical importance, most FEA studies do not sufficiently simulate the detailed stress accumulation within the root canal system that contributes to such fractures.^[47]

• Recommendation: Future models should incorporate crack initiation and propagation simulations using the Extended Finite Element Method (XFEM) to more accurately reflect the biomechanical conditions leading to VRF. Moreover, the stresses generated during gutta-percha condensation (vertical and lateral) should be quantitatively analyzed through advanced FEA models.^[39]

11. Lack of modeling of gutta-percha and sealer interactions with root canal walls

• Limitation: Current FEA models often overlook the dynamic interactions between gutta-percha fillings and root canal walls by overlooking the thermal and hydraulic behavior of gutta-percha, the influence of sealer expansion properties, and the microstructural effects at the sealer–dentin interface.

• Recommendation: In the future, finite element analysis modeling should integrate the thermomechanical behavior of gutta-percha and hydraulic sealers under both warm and cold compaction techniques. Additionally, this modeling should incorporate temperature-dependent material properties, distinctive sealer flow dynamics, and the mechanical interaction at the gutta-percha/sealer/dentin interfaces.^[48]

12. Lack of modeling for long-term deformation and leakage of bioceramic root canal filling and repair materials

• Limitation: Bioceramic root canal filling materials can be affected over time by factors such as thermal changes, water absorption, and chemical degradation. While stresses and strains in composite restorative materials are investigated with FEA and confirmed by the microleakage tests^[49], most of FEA models do not take long-term biomechanical effects into account on bioceramic root canal filling and repair materials and mostly investigate stress distributions.^[14]

• Recommendation: Time-dependent material models should be established to examine the aging process of bioceramic root canal sealers and repair materials. Leakage failures at the microscopic level (microleakage) should be predicted using FEA, and these predictions should also be supported by clinical validation studies.^[50]

Addressing the limitations outlined above is essential to advance the clinical relevance and predictive power of FEA in dentistry and particularly in the field of endodontics. It is essential to overcome current modeling limitations that often rely on oversimplified material properties and anatomical designs, geometric assumptions, and loading conditions that fail to capture the complex behavior of dental tissues, materials, and clinical procedures.

Special focus should be placed on the following topics in future research:

• Population-specific anatomy-based modeling using high-resolution CBCT or micro-CT data to reconstruct realistic advanced root canal geometries.

• Incorporation of anisotropic and heterogeneous material properties, derived from nanoindentation and micromechanical tests, to better reflect the biomechanical behavior of dentin, enamel, and periodontal ligament (PDL) and deformation analyses of rotary files within the canal.

• Crack initiation and propagation simulations using the Extended Finite Element Method (XFEM) to evaluate vertical root fractures, microcracks, and failure risks over time.

• Integration of dynamic, cyclic, and multi-axial loading scenarios into FEA models for improved occlusal stress distribution analysis.

• Modeling of time-dependent aging and leakage models capturing degradation due to thermal changes, moisture, enzymatic activity, and cyclic mechanical loads. Future research should be directed towards ensuring that FEA more accurately reflects biomechanical and biological parameters.

Clinical validation of FEA findings through in vitro and long-term in vivo studies is critical to bridge the gap between theoretical simulations and real-world outcomes. By integrating these advanced approaches, FEA will evolve into a more robust and clinically reliable tool, supporting evidence-based treatment strategies and personalized care in dentistry.

Not applicable. Not required as this study did not involve human participants.

The authors declared that no clinical trials were used in the present study.

The authors declared that no experiments on humans or human tissues were performed for the present study.

The authors declared that no informed consent was obtained from the humans, donors or donors’ representatives participating in the study.

The authors declared that no experiments on animals were performed for the present study.

The authors declared that no commercially available immortalized human and animal cell lines were used in the present study.

The authors have declared that no competing interests exist.

No funding was reported.

No use of AI was reported.

All data used are referenced or included in the article.

AÖK designed the study, analyzed the data, prepared the manuscript, and approved the final manuscript; EY designed the study and approved the final manuscript.

The authors have no support to report.