Finite element analysis in implant dentistry: State of the art and future directions

Finite element analysis of mandibular fracture fixation authenticated by 3D printed mandible mechanical testing

Finite element analysis (FEA) for mandibular fracture fixation in craniomaxillofacial surgery remains promising but has been restricted due to the absence of an authenticated FEA model. This study aims to create an authenticated FEA model. This model was verified through a series of 3D printed mandible mechanical testing (3D-MMT) in a universal tensile machine using an indistinguishable set-up. Non-comminuted mandibular symphysis, parasymphysis, and angle fracture fixation stability were evaluated using a 2.0 mm 4-hole miniplate in three different plate configurations. Both FEA and 3D-MMT outcomes were reproducible and in agreement with the present understanding of stable mandibular fracture treatment. The results show favourable fracture stability with the dual plating, followed by the superior border, with the least stability observed in the inferior border plating. Furthermore, the FEA and the 3D-MMT outcomes were consistently similar, with a systematic 0.56 ± 0.12 mm total displacement difference (standard deviation). An excellent interclass relation coefficient (0.93, 95% confidence interval: 0.80-0.96) was found between the FEA model and the 3D-MMT mechanical test, indicating that both results were consistent with each other. The authenticated FEA can accurately study the recognised biomechanical behaviour of non-comminuted mandibular fractures and shows a potential application for complex fracture fixation analysis.

Biomechanics-based Gradient Nano-surface Implants Screening and Its Adoption in Dental Implant Repair

BACKGROUND

this study aimed to screen the micro/nano surface of pure titanium implant gradient for performance analysis, and to explore its role in dental implant repair.

METHODS

after treatment with different concentrations of hydrofluoric acid and varying etching times, titanium plates with micro/nano gradient surfaces were selected and divided into four groups: polished, b, c, and d. The microscopic morphology of the titanium surfaces was observed, and the contact angle was measured. One implant was inserted into the femoral metaphysis on both sides of 28 SD rats. Histological sections were analyzed, and the maximum pull-out force was measured.

RESULTS

the new bone trabeculae on the surfaces of groups b, c, and d were wider as against polished group. The surface morphology of the titanium disks etched with 1.2 % hydrofluoric acid for 15 min (group d) was more uniform, the diameter of micropores was the largest, and the contact angle was the smallest (12.1 ± 1.17°). The new bone structure on the surface of implant screws in group d was slightly higher as against groups b and c. The bone-to-implant contact (BIC) and the maximum pullout force in groups b (33.25±2.57 %, 58.52±4.03 N), c (35.16±2.35 %, 59.43±3.97 N), d (40.93±2.71 %, 68.22±4.36 N) were higher as against polished group (22.41±2.86 %, 30.12±4.71 N) (P < 0.05). Three months after implantation, the bone fusion rate in the other three groups was significantly higher than that in the polishing group, with group d showing higher rates compared to groups b and c (P < 0.05).

CONCLUSION

the gradient micro/nano surface was constructed by hydrofluoric acid. The osseointegration of hydrofluoric acid etching implant surface and implant was clearly better as against polished group.

Effect of solid abutment diameter and implant placement depth on stress distribution in the posterior mandible: A finite element analysis study

STATEMENT OF PROBLEM

Narrow diameter implants have been considered effective for implant placement in anterior region of maxilla and mandible. However, in regions with heavy masticatory loads, narrow implants may be excessively stressed.

PURPOSE

The purpose of this finite element analysis study was to evaluate the stress generated by narrow implants placed level with and below the bone margin in the posterior mandible and the biomechanical effects of different solid abutment diameters.

MATERIAL AND METHODS

Four 3-dimensional models of an implant-supported prosthesis were simulated in the mandibular bone section of the first molar region. The implants were placed level with and below the bone margin, differing in the gingival height of the prosthetic abutments and testing different abutment diameters. The occlusal force of 365 N was simulated both axially and obliquely to represent medium-intensity physiological loads. Equivalent von Mises stresses were evaluated in the implant-to-abutment connection, and maximum and minimum principal stresses were evaluated in the surrounding bone.

RESULTS

For the implant-abutment interface, under axial loading, stress values decreased by approximately 19 % with increasing abutment diameter. For the surrounding bone under axial loads, tensile stress values increased with subcrestal implant placement, averaging 32.8 MPa for cortical bone and 18.5 MPa for trabecular bone. Conversely, compressive stress in cortical bone decreased by an average of 76.2 MPa with subcrestal implant placement. Regarding the change in abutment diameter, there were no major variations in the stress values of the surrounding bone. With oblique loading, all stresses were considerably higher than with axial loading.

CONCLUSIONS

Although subcrestal implants showed higher stress values, stresses in the bone crest area decreased. Larger diameter abutments tended to generate better stress distribution for posterior prostheses.

From model validation to biomechanical analysis: In silico study of multirooted root analogue implants using 3D finite element analysis

OBJECTIVES

To create a validated 3D finite element model and employ it to examine the biomechanical behaviour of multirooted root analogue implants (RAIs).

METHODS

A validated finite element model comprising either an RAI or a threaded implant (TI) and an idealised bone block was developed based on a previously conducted in vitro study. All the experimental boundary conditions and material properties were reproduced. Force/displacement curves were plotted to ensure complete alignment with the in vitro findings. Following the validation of the FE model, the material properties were adjusted to align with those reported in the literature. Two contact scenarios were then examined: immediate placement with touching contact and osseointegration with glued contact. The bone block was constrained in all directions, and a 300 N point load was applied along the long axis of the implant, and with an angulation of 30°. The resulting values for equivalent stress, maximum principal stress, microstrain, and displacement were evaluated.

RESULTS

The numerical model demonstrated a high degree of agreement with the experimental results, particularly regarding displacement in the loading direction (Z). The findings of the applied FEA indicated that RAIs generally outperformed TIs. The RAI exhibited lower equivalent stress, with values of 3.3 MPa for axial loading and 13.1 MPa for oblique loading, compared to 5.4 MPa and 29.5 MPa for the TI, respectively. Furthermore, microstrain was observed to be lower in the RAI, with a value of 4,000 με compared to 13,000 με in the TI under oblique loading. Additionally, the RAI exhibited superior primary and secondary stability, with lower micromotion values compared to the TI.

CONCLUSIONS

The root analogue implant showed superior biomechanical performance, with more uniform stress distribution and greater stability compared to the conventional threaded implant, positioning it as a promising alternative.

Biomechanical analysis of axial-radial integrated functional gradient material implants in healthy and osteoporotic bones

People with osteoporosis, common among middle-aged and elderly individuals, often need dental implants. Titanium implants, though generally safe, can cause problems due to their stiffness, especially in osteoporotic bone, leading to fractures. This study aims to identify gradient types that offer improved biological adaptation. This was achieved by comparing the mechanical properties of four new two-dimensional functional gradient materials (FGMs) implants to those of conventional and one-dimensional FGM implants in healthy and osteoporotic bone models. The new FGM implants, with reduced stiffness at the bottom and outer parts, kept strain on cancellous bone within safe limits, reducing fracture risk. Notably, the FGM RA L-H implant maintained strain levels within the optimal range (1,500-3,000 µɛ), promoting bone healing and remodeling. By evaluating the stresses and strains, it was concluded that the FGM RA L-H implant is well adapted to significantly reduce stresses and improve bone recovery in healthy and osteoporotic bones.

Finite element analysis in the Dental Sciences: A Bibliometric and a Visual Study

INTRODUCTION AND AIMS

Finite element analysis (FEA) is an incrementally practical and precise tool for the prediction of stress effects on different tissue structures and has therefore interested dental researchers for decades. This bibliometric and visualized study was aimed to assess the research progress related to FEA in the dental sciences in terms of research trends and frontiers.

METHODS

The articles about FEA studies in this field during 1999 to 2024 were obtained from Web of Science Core Collection. Then, these results were analysed and plotted using Microsoft Excel, VOSviewer, and CiteSpace in order to find out the historical evolution, current hotspots, and future directions.

RESULTS

Total 2838 literature records related to the topic were retrieved from Web of Science Core Collection. The most active country and institution were USA (538 documents) and Universidade Estadual Paulista (140 documents), respectively. Baggi et al from University of Naples Federico II was the author with the most highly cited article (352 citations), which was published on the Journal of Prosthetic Dentistry in 2008. Dental Materials ranked first (231 documents) among the 10 journals with the greatest numbers of relevant publications. The top three trending keywords were 'dental implant', 'stress distribution', and 'fracture'. The endocrown, clear aligner, and posterior edentulism were scientific frontiers in this field.

CONCLUSION

The present study provides a comprehensive bibliometric analysis of research in the dental science by FEA approaches, which will identify active hotspots of scientific interest to guide further research endeavours.

Structural response of mandibular first molars in the presence of proximal contacts: finite element analysis with antagonist teeth and alternative loading applications

OBJECTIVES

To compare the mechanical responses of a mandibular molar under functional loads using antagonist teeth and different loading applications and configurations.

METHODS

A cone-beam computed tomography of a human mandible and maxilla was used to build 16 different three-dimensional models, including four mandibular configurations [single-tooth model (first mandibular molar-M), and inclusion of mesial (mM), distal (Md) or both proximal contacts (mMd)] and occlusal load applications either with antagonist teeth or alternative Finite Element (FE) models [point load (PL), distributed surface load (SL) and rigid metal sphere (MS)]. FE analysis was performed. Equivalent von Mises (VM) stress was calculated along the entire dentin and periodontal ligament of the first mandibular molar. Maximum VM stresses were compared among the different mandibular configurations and loading applications.

RESULTS

The highest and lowest VM stress at 50 and 100 N corresponded respectively to the single-tooth SL model (5.78 and 11.5 MPa) and to occlusal load application with antagonist teeth and proximal contacts (2.08 and 3.58 MPa). Maximum VM stresses were consistently located at the cervical area of the mesial root and decreased when adjacent teeth were present.

CONCLUSIONS

Highest stresses are located in the cervical area of the mesial root of mandibular molars, but the biomechanical behavior depends on the presence of proximal contacts and the loading methodologies used. Single-tooth models represent the worst structural scenario.

CLINICAL RELEVANCE

Incorporating antagonist teeth and proximal contacts into FE models enhances the biofidelity of dental biomechanics simulations, enabling more accurate extrapolation to clinical conditions.

Prognosis of Crestally Placed Short Plateau Implants in Posterior Maxilla

Crestal placement of short plateau implants in compromised jaws may cause implant failure due to bone overstress. The aim was to evaluate the impact of different sized implants on adjacent bone overload and the implant load-bearing ability in terms of the proposed index-ultimate functional load (UFL). Three-dimensional models of osseointegrated implants placed in types III and IV bone were analysed by the FEM for the case of patient-specific variations in cortical bone elasticity modulus. Maximum von Mises stresses in surrounding bone were calculated and compared with the cortical and cancellous bone ultimate strength characteristics to determine the UFL index for the studied implants. The implant UFL magnitudes were influenced by their dimensions, bone elasticity, and quality. The implant load-bearing ability was predetermined by cancellous bone strength. The maxilla with moderate elasticity modulus allows for the placement of wide short screwless implants in the compromised maxilla molar site with good clinical perspective.

Impact of physiological and non-physiological loading scenarios and crown material on periimplant bone stress distribution: A 3D finite element study

This study numerically investigates the impact of different loading modes on the biomechanical response of an osseointegrated dental implant. While finite element modeling is commonly employed to investigate the mechanical behavior of dental implants, several models lack physiological accuracy in their loading conditions, omitting occlusal contact points that influence stress distribution in periimplant bone. Using 3D finite element modeling and analysis, stress distributions at the bone-implant interface are evaluated under both physiological loading, incorporating natural occlusal contact points, and non-physiological loading conditions, with a focus on load transmission mechanisms and the potential risk of bone overloading. Two crown materials, zirconia and lithium disilicate, are analyzed under load values of 150 N and 300 N. The physiological loading mode leads to significantly higher Von Mises stress concentrations in both cortical and trabecular periimplant regions compared to non-physiological loading. This results in different load transfer mechanisms underlining the importance of accurately modeling load application points. Crown material seems to have a minimal impact, whereas increasing the load intensity markedly increases stress levels. Notably, physiological loading reveals stress distribution at the implant apex, unlike non-physiological models. Additionally, peak values of tensile and compressive stresses at the periimplant interfaces increase under physiological conditions, with cortical bone stress rising by up to 210%. This highlights that relying on non-physiological loading modes may inadequately capture the risk of implant failure. Overall, these results emphasize the need to consider physiological loading scenarios, particularly for assessing failure risk to better guide implant design modifications, enhancing clinical outcomes and implant longevity.

Three-dimensional in vivo and finite element analyses of peri-implant bone remodeling after superstructure placement

STATEMENT OF PROBLEM

Understanding the factors affecting loading-induced longitudinal peri-implant bone changes is crucial for successful implant-supported prosthetic treatment.

PURPOSE

The purpose of the study was to assess the biomechanical factors influencing 3-dimensional changes in the peri-implant bone volume and buccal bone thickness (BBT) with follow-up cone beam computed tomography (CBCT) images and finite element analysis (FEA).

MATERIAL AND METHODS

Twelve study participants received dental implants without bone augmentation, resulting in the evaluation of 22 posterior dental implants. Each participant underwent 3 separate CBCT scans: the first at 3 months after loading, followed by scans at 15 months and 27 months after loading. CBCT images were superimposed at each interval with an image-processing software program. The peri-implant buccal bone area was determined as the volume of interest (VOI), and volumetric change in VOI and changes in BBT at 2, 4, and 6 mm below the implant platform were measured. FEA was performed to examine the mechanical stimulation in the VOI with occlusal force data obtained from the Dental Prescale. Interobserver reliability was evaluated by 3 experienced prosthodontists and dentists experienced with dental implants. Linear regression analyses were performed to evaluate the relationship between variables.

RESULTS

Occlusal force and mechanical stimulation (strain energy density [SED]) in the VOI demonstrated a positive correlation; moreover, a positive correlation was observed between SED and bone volume loss in the VOI at 3 and 27months after loading. Similar correlations were observed with BBT, except at a depth of 6 mm under the implant platform. The interclass correlation coefficient values were 0.995 for volume and 0.982 for BBT, thereby indicating a high level of agreement among the observers' measurements.

CONCLUSIONS

This combined FEA and clinical study suggested that force-induced bone remodeling depends on the occlusal force in the early phases after superstructure placement.

Comparison of biomechanical characteristics of the Schneiderian membrane with different transcrestal sinus floor elevation techniques using three-dimensional finite element analysis

OBJECTIVE

The aim of this study was to establish a three-dimensional finite element (FE) hydraulic pressure technique model and compare the biomechanical characteristics of the osteotome technique and the hydraulic pressure technique using three-dimensional finite element analysis (FEA).

METHODS

Three FE models were created: the hydraulic pressure technique (M1), the osteotome technique with a Ø 1.6-mm osteotome (M2), and the osteotome technique with a Ø 3.0-mm osteotome (M3) models. Three models were simulated via computer-aided design software, with the sinus membrane elevated to 1, 3 and 5 mm, after which the required loading force was recorded. Stress distribution, including the equivalent von Mises stress, tensile stress, compressive stress, shear stress, as well as strain (i.e., sinus membrane displacement in horizontal dimensions) of the three models were subsequently examined and statistically compared.

RESULTS

Overall, the required loading force, stress and strain increased as the elevation height increased. The loading force required to elevate the sinus membrane to 1,3 and 5 mm in M1 was 24.9 kPa, 77.1 kPa and 130 kPa, comparing 32.5 kPa, 112. 9 kPa and 200.8 kPa in M2 as well as 54.5 kPa, 160.6 kPa and 273.2 kPa in M3. Under the same elevation height, M1 exhibited the least von Mises stress (P<0.001), as well as the largest horizontal sinus membrane displacement (P<0.001).

CONCLUSIONS

It can be seen from the FEA results that the hydraulic pressure technique enables a greater portion of the sinus membrane to detach from the sinus floor while exerting less stress on the mucosa when the sinus membrane is elevated up to 5 mm. Based on this study, the hydraulic pressure technique was found to be safer and more effective than the osteotome technique under the same elevation height.

Summed Tissue Resistance of Periodontal Ligaments and Alveolar Bone in Orthodontic Distal Retraction of Maxillary Canines: Mathematical Simulation of Clinical Data and Interpretation of Results

Background: The mechanical properties of either alveolar bone or periodontal ligaments under orthodontic loading, as well as orthodontic tooth movement, have been studied in recent years using computational approaches. In previous studies, we developed a theoretical mathematical approach that uses a weighting coefficient of the summed resistance of periodontal structures, namely the bone and periodontal ligaments, in relation to apex movement, the center of rotation, orthodontic force loading, and time in order to quantify the biological response to orthodontic biomechanics. Methods: We analyzed the distal retraction of three maxillary canines and integrated the clinical data obtained in the previously developed mathematical programs. Results: The values of the (σ) weighting coefficient of the tissue resistance were interpreted in the context of the clinical data obtained: the smaller the value of (σ), the higher the actual tissue resistance, with a greater difference between the crown and root movement; also, the higher the value of (σ), the lower the actual tissue resistance, with a small difference between the crown and apex movement. Conclusions: The clinical interpretation of the results allows us to set a premise for the refinement of the mathematical programs so that we can use them in assessing the orthodontic biomechanics of larger patient groups over longer periods of time and create premises of treatment protocol simplification and adjustment.

Unlocking Osseointegration: Surface Engineering Strategies for Enhanced Dental Implant Integration

Tooth loss is a prevalent problem faced by individuals of all ages across the globe. Various biomaterials, such as metals, bioceramics, polymers, composites of ceramics and polymers, etc., have been used for the manufacturing of dental implants. The success of a dental implant primarily depends on its osseointegration rate. The current surface modification techniques fail to imbibe the basics of tooth development, which can impart better mineralization and osseointegration. This can be improved by developing an understanding of the developmental pathways of dental tissue. Stimulating the correct signaling pathways through inductive material systems can bring about a paradigm shift in dental implant materials. The current review focuses on the developmental pathway and mineralization process that happen during tooth formation and how surface modifications can help in biomimetic mineralization, thereby enhancing osseointegration. We further describe the effect of dental implant surface modifications on mineralization, osteoinduction, and osseointegration; both in vitro and in vivo. The review will help us to understand the natural process of teeth development and mineralization and how the surface properties of dental implants can be further improved to mimic teeth development, in turn increasing osseointegration.

Application of Ultrashort Implants in Posterior Maxilla With Insufficient Bone Height: A Finite Element Analysis

INTRODUCTION AND AIMS

Implantation of the posterior maxilla with insufficient bone height faces challenges. Studies have shown that the use of ultrashort implants can avoid additional damage. This finite element analysis study aimed to evaluate the impacts of different lengths of ultrashort implants and three surgical approaches on stress, strain, and displacement in the posterior maxilla with varying bone heights.

METHODS

Twelve models of different lengths (3.0, 4.0, 5.0, and 6.0 mm) of ultrashort implants combined with unicortical fixation, bicortical fixation, and transalveolar sinus elevation were established, and conventional implants and short implants were considered as control models. Von Mises stresses within the implants and the sinus floor cortical bone, maximum and minimum principal stresses within the alveolar ridge cortical bone, and the maximum principal strain of the cancellous bone were determined using these models. Additionally, the displacement of the implants was analysed.

RESULTS

Stress distribution range and peak values increased as implant length decreased. In the ultrashort implant group, H5L6 exhibited the smallest maximum and minimum principal stresses, 35.77 and 10.66 MPa, respectively. Among groups with different bone heights, 6 mm long implants presented the lowest maximum von Mises stress, whereas 3 mm long implants presented the highest.

CONCLUSION

In the posterior maxilla with bone heights of 3, 4, and 5 mm, the stresses in different lengths of ultrashort implants and surrounding bone tissue were lower than the yield strengths in these areas, and the use of 6 mm-long ultrashort implants combined with osteotome sinus floor elevation can achieve lower stress distribution.

CLINICAL RELEVANCE

This study provides important insights into the biomechanical properties of ultrashort implants combined with three different surgical procedures in severely atrophic maxilla. The 6-mm long implant combined with osteotome sinus floor elevation is most suitable for this area.

Finite element analysis on implant-supported bar with different geometric shapes

BACKGROUND

The selection guideline for the implant-supported bar connectors (ISBC) of hybrid denture is lacking. This study investigated the maximum von Mises stress (vMS), stress distribution, and displacement of various geometric ISBC in mandibular hybrid dentures, as well as the maximum principal stress (σmax) in the acrylic resin part, through finite element analysis.

METHODS

Four different geometric cross-sectional patterns for mandibular ISBC-L, Y, I, and Square-of equal volume, based on the "All-on-4" concept, were created. Titanium alloy was used for ISBC with an acrylic resin wraparound. Models were integrated into the software and loading simulations mimicking mastication forces on posterior teeth in centric and eccentric loadings were performed. vMS was used for ISBC assessment, and σmax was assessed in acrylic resin.

RESULTS

In centric loading, vMS was mainly at the distal screw channel across most ISBCs. Y ISBC showed the least vMS, while I and Square ISBC demonstrated uniform stress distribution on both sides; load and non-load-bearing sides. The others showed concentrated vMS only on the load-bearing side. Square ISBC exhibited the most displacement. In the acrylic resin region of each, σmax was found concentrated around the contact point between two adjacent denture teeth at different locations, with Square showing the highest σmax. Under eccentric loading, the maximum vMS of each model was found at the interface between the distal screw channel and the lingual aspect of the abutment, with comparable vMS. Square ISBC experienced the most significant displacement and showed the highest σmax within the acrylic resin juxtaposed with the screw channel.

CONCLUSION

The Y model of titanium-alloy in mandibular ISBC demonstrated the lowest vMS and displacement.

Heterogeneous material models for finite element analysis of the human mandible bone - A systematic review

Subject-specific finite element (FE) modeling of the mandible bone has recently gained attention for its higher accuracy. A critical modeling factor is including personalized material properties from medical images especially when bone quality has to be respected. However, there is no consensus on the material model for the mandible that realistically estimates the Young's modulus of the bone. Therefore, the present study aims to review FE studies employing heterogeneous material modeling of the human mandible bone, synthesizing these models, investigating their origins, and assessing their risk of bias. A systematic review using PRISMA guidelines was conducted on publications before 1st July 2024, involving PubMed, Scopus, and Web of Science. The search string considered (a) anatomical site (b) modeling strategy, and (c) metrics of interest. Two inclusion and five exclusion criteria were defined. A review of 77 FE studies identified 12 distinct heterogeneous material models, built based on different in vitro or computational methodologies leading to varied performance and highly deviated range of estimated Young's modulus. They are proposed for bones from five different anatomical sites than mandible and for both trabecular and cortical bone domains. The original studies were characterized with a low to medium risk of bias. This review assessed the current state of material modeling for subject-specific FE models in the craniomaxillofacial field. Recommendations are provided to support researchers in selecting density-modulus relationships. Future research should focus on standardizing experimental protocols, validating models through combined simulation and experimental approaches, and investigating the anisotropic behaviour of the mandible bone.

Biomechanics of Osseointegration of a Dental Implant in the Mandible Under Shock Wave Therapy: In Silico Study

The most time-consuming aspect of dental prosthesis installation is the osseointegration of a metal implant with bone tissue. The acceleration of this process may be achieved through the use of extracorporeal shock wave therapy. The objective of this study is to investigate the conditions for osseointegration of the second premolar implant in the mandibular segment through the use of a poroelastic model implemented in the movable cellular automaton method. The mandibular segment under consideration includes a spongy tissue layer, 600 µm in thickness, covered with a cortical layer, 400 µm in thickness, and a gum layer, 400 µm in thickness. Furthermore, the periodontal layers of the roots of the first premolar and first molar were considered, while the implant of the second premolar was situated within a shell of specific tissue that corresponded to the phase of osseointegration. The model was subjected to both physiological loading and shock wave loading across the three main phases of osseointegration. The resulting fields of hydrostatic pressure and interstitial fluid pressure were then subjected to analysis in accordance with the mechanobiological principles. The results obtained have indicated that low-intensity shock wave therapy can accelerate and promote direct osseointegration: 0.05-0.15 mJ/mm2 in the first and second phases and less than 0.05 mJ/mm2 in the third phase. In comparison to physiological loads (when bone tissue regeneration conditions are observed only around the implant distal end), shock waves offer the primary advantage of creating conditions conducive to osseointegration along the entire surface of the implant simultaneously. This can significantly influence the rate of implant integration during the initial osteoinduction phase and, most crucially, during the longest final phase of bone remodeling.

Prosthesis repair of oral implants based on artificial intelligenc`e finite element analysis

Dentists often suggest dental implants to replace missing teeth; nevertheless, mechanical issues can develop with these implants, which could lead to prosthesis replacement or repairs. When investigating implant systems' mechanical characteristics and stress distribution, finite element analysis (FEA) is a popular computational tool. In biomechanical investigations, this strategy is widely used. However, traditional FEA methods can be tedious and require expert expertise for accurate simulation and translation of results. To automate and simplify the process of mending oral implant prostheses, the article suggests a new framework called AI-FEA. The three primary parts that make up the suggested AI-FEA framework are 1. An AI-powered model creation module that utilizes data from medical imaging to autonomously construct 3D finite element designs that are unique to each patient. Utilizing deep learning approaches, this module segments and reconstructs three-dimensional geometries from computed tomography (CT) or cone-beam CT data using material properties and boundary conditions. 2. A FEA solver that runs simulations to test the way the implant system handles different loads. This component uses state-of-the-art numerical methods to model the implant and bone interface and determine stress distributions. 3. An AI-based decision support system that takes all that data and recommends the best way to fix the prosthesis. Combining FEA findings with patient-specific variables, this decision support system uses machine learning algorithms educated on an extensive dataset of implant failure instances and repair results to provide the optimal repair strategy. For patients experiencing issues with oral implants, the suggested AI-FEA framework might mean huge time and skill savings in prosthesis repair planning, leading to better, more individualized care.

Residual Stress Homogenization of Hybrid Implants

OBJECTIVES

Hybrid implants commonly exhibit decreased corrosion resistance and fatigue due to differences in compressive residual stresses between the smooth and rough surfaces. The main objective of this study was to investigate the influence of an annealing heat treatment to reduce the residual stresses in hybrid implants.

METHODOLOGY

Commercially pure titanium (CpTi) bars were heat-treated at 800 °C and different annealing times. Optical microscopy was used to analyze the resulting grain growth kinetics. Diffractometry was used to measure residual stress after heat treatment, corrosion resistance by open circuit potential (EOCP), corrosion potentials (ECORR), and corrosion currents (ICORR) of heat-treated samples, as well as fatigue behavior by creep testing. The von Mises distribution and the resulting microstrains in heat-treated hybrid implants and in cortical and trabecular bone were assessed by finite element analysis. The results of treated hybrid implants were compared to those of untreated hybrid implants and hybrid implants with a rough surface (shot-blasted).

RESULTS

The proposed heat treatment (800 °C for 30 min, followed by quenching in water at 20 °C) could successfully homogenize the residual stress difference between the two surfaces of the hybrid implant (-20.2 MPa). It provides better fatigue behavior and corrosion resistance (p ˂ 0.05, ANOVA). Stress distribution was significantly improved in the trabecular bone. Heat-treated hybrid implants performed worse than implants with a rough surface.

CLINICAL SIGNIFICANCE

Annealing heat treatment can be used to improve the mechanical properties and corrosion resistance of hybrid surface implants by homogenizing residual stresses.

Finite Element Combined Design and Material Optimization Addressing the Wear in Removable Implant Prosthodontics

Wear at the male-female interface of retentive elements in implant-supported removable prostheses is the most frequent complication in such applications. The lack of an ideal/optimal insertion path, as well as the fabrication inaccuracies, are the primary contributors to this issue. A male attachment with a common ball anchor enhanced by lateral flexibility was investigated as a solution, compared to the widely used rigid ball anchor design. A parametric finite element analysis was performed to compare the wear-inducing maximum strain at the female polymer counterpart by various attachment designs made from titanium and Nitinol. The evolution of mechanical strains causing wear in the female part, as well as the contribution of stresses and martensitic transformation in the implant's flexible shaft, were evaluated under several insertion misfit scenarios. Results indicate that introducing a long flexible shaft in the titanium implant reduced maximum strains in the female attachment part by up to 61% as compared to the solid ball anchor. Further improvement was observed by using the shape memory alloy Nitinol as shaft material, leading to a minor reduction in stress and strain at the contact surface but allowing for a shorter abutment. Finally, the optimized Nitinol implant design with a short, necked flexible shaft promoting martensitic transformation at low plateau stress resulted in an approximate 90% reduction in maximum strains at the inner surface of the female part during manual insertion, which indicates a significantly reduced wear phenomenon at the contact.

Finite element models: A road to in-silico modeling in the age of personalized dentistry

OBJECTIVE

This article reviews the applications of Finite Element Models (FEMs) in personalized dentistry, focusing on treatment planning, material selection, and CAD-CAM processes. It also discusses the challenges and future directions of using finite element analysis (FEA) in dental care.

DATA

This study synthesizes current literature and case studies on FEMs in personalized dentistry, analyzing research articles, clinical reports, and technical papers on the application of FEA in dental biomechanics.

SOURCES

Sources for this review include peer-reviewed journals, academic publications, clinical case studies, and technical papers on dental biomechanics and finite element analysis. Key databases such as PubMed, Scopus, Embase, and ArXiv were used to identify relevant studies.

STUDY SELECTION

Studies were selected based on their relevance to the application of FEMs in personalized dentistry. Inclusion criteria were studies that discussed the use of FEA in treatment planning, material selection, and CAD-CAM processes in dentistry. Exclusion criteria included studies that did not focus on personalized dental treatments or did not utilize FEMs as a primary tool.

CONCLUSIONS

FEMs are essential for personalized dentistry, offering a versatile platform for in-silico dental biomechanics modeling. They can help predict biomechanical behavior, optimize treatment outcomes, and minimize clinical complications. Despite needing further advancements, FEMs could help significantly enhance treatment precision and efficacy in personalized dental care.

CLINICAL SIGNIFICANCE

FEMs in personalized dentistry hold the potential to significantly improve treatment precision and efficacy, optimizing outcomes and reducing complications. Their integration underscores the need for interdisciplinary collaboration and advancements in computational techniques to enhance personalized dental care.

Homogenized finite element simulations can predict the primary stability of dental implants in human jawbone

Adequate primary stability is a pre-requisite for the osseointegration and long-term success of dental implants. Primary stability depends essentially on the bone mechanical integrity at the implantation site. Clinically, a qualitative evaluation can be made on medical images, but finite element (FE) simulations can assess the primary stability of a bone-implant construct quantitatively based on high-resolution CT images. However, FE models lack experimental validation on clinically relevant bone anatomy. The aim of this study is to validate such an FE model on human jawbones. Forty-seven bone biopsies were extracted from human cadaveric jawbones. Dental implants of two sizes (Ø3.5 mm and Ø4.0 mm) were inserted and the constructs were subjected to a quasi-static bending-compression loading protocol. Those mechanical tests were replicated with sample-specific non-linear homogenized FE models. Bone was modeled with an elastoplastic constitutive law that included damage. Density-based material properties were mapped based on μCT images of the bone samples. The experimental ultimate load was better predicted by FE (R2 = 0.83) than by peri-implant bone density (R2 = 0.54). Unlike bone density, the simulations were also able to capture the effect of implant diameter. The primary stability of a dental implant in human jawbones can be predicted quantitatively with FE simulations. This method may be used for improving the design and insertion protocols of dental implants.

Biomechanical behaviour of tilted abutment after fixed partial denture restoration of CAD/CAM materials

BACKGROUND

Failure to restore missing teeth in time can easily lead to the mesial tilting of the distal abutment teeth. However, a fixed partial denture (FPD) can improve stress conduction and distribution and prevent periodontal injuries. In these more complex cases, it is necessary to consider various factors comprehensively to improve conventional treatment planning and achieve better results.

METHODS

We selected a patient with a missing first molar and a mesial inclination of the second molar, leaving inadequate space or bone mass for implant denture restoration, necessitating an FPD for restoration. Three-dimensional finite element analysis (3D-FEA) combined with photoelastic analysis were used to explore how the inclination angle (0 ‒ 30°) and different dental restoration materials (zirconia, lithium disilicate, polymer-infiltrated ceramic network, and resin composite) affect the biomechanical behaviour of FPD‒abutments‒periodontal tissue complex.

RESULTS

The stress was easily concentrated in the FPD connectors, enamel shoulder collar, periapical area, and root bifurcation. The stress on FPD and the periodontal ligament (PDL) of the second premolar increased with an increase in the elastic modulus of FPD, with an opposite trend in the abutments, the alveolar bone, and the PDL of the second molar. The stress on the FPD and alveolar bone increased with increased inclination angle of the distal abutment. The stress on two abutments and their PDL were positively correlated with the inclination angle in two stages; however, when the inclination angle > 12°, the second premolar and its PDL showed a negative correlation.

CONCLUSIONS

FPDs can be used for restoration within 24° of distal abutment inclination, but protecting the abutments (< 12° especially) and the periodontal tissue (> 12° especially) must be taken seriously. For this purpose, an FPD material with higher strength is recommended.

Impact Testing in Implant-Supported Prostheses and Natural Teeth: A Systematic Review of Properties and Performance

Dental implants offer an effective solution for partial and total edentulism, but mechanical and biological complications exist. Furthermore, high occlusal loads challenge implants and lead to potential failures. This review focuses on impact testing in contrast to incremental and static tests, an underexplored aspect of assessing daily loads on implants, bringing to light potential complications. The review examines studies employing impact forces to assess implant-supported prostheses and natural teeth properties, highlighting their significance in dental research. A systematic search following PRISMA guidelines identified 21 relevant articles out of 224, emphasizing studies employing impact forces to evaluate various aspects of dental implant treatments. The diverse applications of impact forces in dental research were categorized into tooth structure, restorative materials, interface evaluation, implant properties, and finite element models. Some studies showed the significance of impact forces in assessing stress distribution, shock absorption, and biomechanical response. Impact testing is a critical tool for understanding the daily forces on implants. Despite diverse experimental approaches, a lack of standardized protocols complicates the systematization of the results and, therefore, the conclusions. This review highlights the need for consistent methodologies in impact testing studies for future research on implant-supported prostheses.

Biomechanical assessment of mandibular fracture fixation using finite element analysis validated by polymeric mandible mechanical testing

The clinical finite element analysis (FEA) application in maxillofacial surgery for mandibular fracture is limited due to the lack of a validated FEA model. Therefore, this study aims to develop a validated FEA model for mandibular fracture treatment, by assessing non-comminuted mandibular fracture fixation. FEA models were created for mandibles with single simple symphysis, parasymphysis, and angle fractures; fixated with 2.0 mm 4-hole titanium miniplates located at three different configurations with clinically known differences in stability, namely: superior border, inferior border, and two plate combinations. The FEA models were validated with series of Synbone polymeric mandible mechanical testing (PMMT) using a mechanical test bench with an identical test set-up. The first outcome was that the current understanding of stable simple mandibular fracture fixation was reproducible in both the FEA and PMMT. Optimal fracture stability was achieved with the two plate combination, followed by superior border, and then inferior border plating. Second, the FEA and the PMMT findings were consistent and comparable (a total displacement difference of 1.13 mm). In conclusion, the FEA and the PMMT outcomes were similar, and hence suitable for simple mandibular fracture treatment analyses. The FEA model can possibly be applied for non-routine complex mandibular fracture management.

Biomechanical Effects of Ti-Base Abutment Height on the Dental Implant System: A Finite Element Analysis

This study aims to analyse, using a finite element analysis, the effects of Ti-base abutment height on the distribution and magnitude of transferred load and the resulting bone microstrain in the bone-implant system. A three-dimensional bone model of the mandibular premolar section was created with an implant placed in a juxta-osseous position. Three prosthetic models were designed: a 1 mm-high titanium-base (Ti-base) abutment with an 8 mm-high cemented monolithic zirconia crown was designed for model A, a 2 mm-high Ti-base abutment with a 7 mm-high crown for model B, and a 3 mm-high abutment with a 6 mm-high crown for model C. A static load of 150 N was applied to the central fossa at a six-degree angle with respect to the axial axis of the implant to evaluate the magnitude and distribution of load transfer and microstrain. The results showed a trend towards a direct linear association between the increase in the height of the Ti-base abutments and the increase in the transferred stress and the resulting microstrain to both the prosthetic elements and the bone/implant system. An increase in transferred stress and deformation of all elements of the system, within physiological ranges, was observed as the size of the Ti-base abutment increased.

Biomechanical Fatigue Behavior of a Dental Implant Due to Chewing Forces: A Finite Element Analysis

The use of titanium as a biomaterial for the treatment of dental implants has been successful and has become the most viable and common option. However, in the last three decades, new alternatives have emerged, such as polymers that could replace metallic materials. The aim of this research work is to demonstrate the structural effects caused by the fatigue phenomenon and the comparison with polymeric materials that may be biomechanically viable by reducing the stress shielding effect at the bone-implant interface. A numerical simulation was performed using the finite element method. Variables such as Young's modulus, Poisson's coefficient, density, yield strength, ultimate strength, and the S-N curve were included. Prior to the simulation, a representative digital model of both a dental implant and the bone was developed. A maximum load of 550 N was applied, and the analysis was considered linear, homogeneous, and isotropic. The results obtained allowed us to observe the mechanical behavior of the dental implant by means of displacements and von Mises forces. They also show the critical areas where the implant tends to fail due to fatigue. Finally, this type of non-destructive analysis proves to be versatile, avoids experimentation on people and/or animals, and reduces costs, and the iteration is unlimited in evaluating various structural parameters (geometry, materials, properties, etc.).

Advancing 3D Dental Implant Finite Element Analysis: Incorporating Biomimetic Trabecular Bone with Varied Pore Sizes in Voronoi Lattices

The human mandible's cancellous bone, which is characterized by its unique porosity and directional sensitivity to external forces, is crucial for sustaining biting stress. Traditional computer- aided design (CAD) models fail to fully represent the bone's anisotropic structure and thus depend on simple isotropic assumptions. For our research, we use the latest versions of nTOP 4.17.3 and Creo Parametric 8.0 software to make biomimetic Voronoi lattice models that accurately reflect the complex geometry and mechanical properties of trabecular bone. The porosity of human cancellous bone is accurately modeled in this work using biomimetic Voronoi lattice models. The porosities range from 70% to 95%, which can be achieved by changing the pore sizes to 1.0 mm, 1.5 mm, 2.0 mm, and 2.5 mm. Finite element analysis (FEA) was used to examine the displacements, stresses, and strains acting on dental implants with a buttress thread, abutment, retaining screw, and biting load surface. The results show that the Voronoi model accurately depicts the complex anatomy of the trabecular bone in the human jaw, compared to standard solid block models. The ideal pore size for biomimetic Voronoi lattice trabecular bone models is 2 mm, taking in to account both the von Mises stress distribution over the dental implant, screw retention, cortical bone, cancellous bone, and micromotions. This pore size displayed balanced performance by successfully matching natural bone's mechanical characteristics. Advanced FEA improves the biomechanical understanding of how bones and implants interact by creating more accurate models of biological problems and dynamic loading situations. This makes biomechanical engineering better.

Stress analysis of horizontal mid-root fracture managed with different intraradicular fixation protocols: A 3D-finite element study

The current study evaluated the stress distribution in a maxillary central incisor with mid-root fracture after splinting with different intra-radicular posts using 3D-finite element analysis (FEA). Five 3D-FEA models were constructed. Model 1 was an intact tooth with no fracture, Model 2: A tooth with a horizontal mid-root fracture, with no treatment. Model 3: Same as model 2, and intraradicular splinting using fiber post. Model 4: Same as model 2 and intra-radicular splinting using Protaper Gold file F3. Model 5: Same as model 2, and with intraradicular splinting with Ribbond. The FEA of all models was done to obtain the maximum Von-Mises stress in the root canal space, the dentin, the periodontal ligament, and the bone. The highest Von Mises stresses for the root canal space and the dentin were found in Model 3, followed by models 4, 5, and 2, and least in Model 1. The Von Mises stress of the periodontal ligament was the least in model 1. The Von Mises stress of bone was higher in all experimental models than in the baseline model. The results suggest that in cases where intra-radicular splinting is indicated, fiber posts and Ribbond are better alternatives to endodontic files due to the lower stresses exerted.

Clinical challenges of biomechanical performance of narrow-diameter implants in maxillary posterior teeth in aging patients: A finite element analysis

This study evaluated the biomechanical performance of narrow-diameter implant (NDI) treatment in atrophic maxillary posterior teeth in aging patients by finite element analysis. The upper left posterior bone segment with first and second premolar teeth missing obtained from a patient's cone beam computed tomography data was simulated with cortical bone thicknesses of 0.5 and 1.0 mm. Three model groups were analyzed. The Regimen group had NDIs of 3.3 × 10 mm in length with non-splinted crowns. Experimental-1 group had NDIs of 3.0 × 10 mm in length with non-splinted crowns and Experimental-2 group had NDIs of 3.0 × 10 mm in length with splinted crowns. The applied load was 56.9 N in three directions: axial (along the implant axis), oblique at 30° (30° to the bucco-palatal plane compared to the vertical axis of the tooth), and lateral load at 90° (90° in the bucco-palatal plane compared to the vertical axis of the tooth). The results of the von Mises stress on the implant fixture, the elastic strain, and principal value of stress on the crestal marginal bone were analyzed. The axial load direction was comparable in the von Mises stress values in all groups, which indicated it was not necessary to use splinted crowns. The elastic strain values in the axial and oblique directions were within the limits of Frost's mechanostat theory. The principal value of stress in all groups were under the threshold of the compressive stress and tensile strength of cortical bone. In the oblique and lateral directions, the splinted crown showed better results for both the von Mises stress, elastic strain, and principal value of stress than the non-splinted crown. In conclusion, category 2 NDIs can be used in the upper premolar region of aging patients in the case of insufficient bone for category 3 NDI restorations.

Finite element analysis of the angle range in trans-inferior alveolar nerve implantation at the mandibular second molar

BACKGROUND

Trans- inferior alveolar nerve (IAN) implantation technique was wildly used while the potential appropriate angle range in which the residual alveolar bone can bear the stress without absorption are currently unclear. This study aimed to evaluate the stress distribution pattern of the interface between bone and implant by finite element analysis (FEA) to determine the appropriate range of the implant tilt angle.

METHODS

Cone beam computed tomography (CBCT) images of 120 patients with missing mandibular second molars and vertical bone height < 9 mm in the edentulous area were selected. The distances from the mandibular nerve canal to the buccal cortex, the lingual cortex and the alveolar ridge crest were measured by using a combination of software. The angular ranges of the buccal-lingual inclination of simulated trans-IAN implants were measured and three-dimensional finite element models were constructed in the mandibular second molar area according to the differences of the inclination angles. A vertical load (200N) was then applied to analyze the biomechanical conditions of the implant-bone interface during median occlusion.

RESULTS

The distance at the second molar from the nerve canal to the buccal cortex, lingual cortex and alveolar crest were 6.861 ± 1.194 mm, 2.843 ± 0.933 mm and 7.944 ± 0.77 mm. Trans-IAN implantation was feasible in 73.33% of patients. The minimum angle and maximum angles of the buccal-lingual inclination of the simulated implant were 19.135 ± 6.721° and 39.282 ± 6.581°. When a vertical static load of 200N was applied, the tensile stress in cortical bone gradually increased with the increase of the implant tilt angle. When the inclination angle reached 30°, the tensile stress (105.9 MPa) exceeded the yield strength (104 MPa) of cortical bone. Compared with the conventional implants, the stress peak value of the vertical ultra-short implant in cortical bone was greater than the stress peak value of the conventional implants at 10°(79.81 MPa) and 20°(82.83 MPa) and was smaller than the stress of the implant at 30°(105.9 MPa) and 40°(107.8 MPa). Therefore, when the bone mass allows, conventional-length implants should be selected whenever possible, and an operative range of the trans-IAN implantation in the mandibular second molar could be retained with an inclination angle of < 30°.

CONCLUSIONS

The mandibular nerve canal at the mandibular second molar was obviously biased to the lingual side, which ensured sufficient bone mass at the buccal side. In most patients with severe mandibular atrophy, it was possible to maintain a safe distance from the nerve canal with conventional-length implants via the trans-IAN implantation technique.

The All-on-4 Concept Using Polyetheretherketone (PEEK)-Acrylic Resin Prostheses: Follow-Up Results of the Development Group at 5 Years and the Routine Group at One Year

BACKGROUND

It is necessary to investigate the application of polymer materials in implant dentistry. The aim of this study was to examine the outcome of full-arch polyetheretherketone (PEEK)-acrylic resin implant-supported prostheses.

METHODS

Seventy-six patients were rehabilitated consecutively with 100 full-arch implant-supported prostheses of PEEK-acrylic resin (a development group (DG): 37 patients with 5 years of follow-up; a routine group (RG): 39 patients with 1 year of follow-up). The primary outcome measure was prosthetic survival. Secondary outcome measures were implant survival, marginal bone loss, biological complications, prosthetic complications, veneer adhesion, plaque levels, bleeding levels, and a patient subjective evaluation (including the Oral Health Impact Profile for the RG).

RESULTS

In both groups, prosthetic (DG: 93.6%; RG: 100%) and implant survival (DG: 98.9%; RG: 99.5%) were high, and marginal bone loss was low (DG: 0.54 mm; RG: 0.28 mm). The veneer adhesion rate was 28.6% of prostheses in DG (RG = 0%). Mechanical complications occurred in 49% and 11.8% of prostheses in DG and RG, respectively. Biological complications, plaque, and bleeding levels were low in both groups. The subjective patient evaluation was excellent in both groups (8.6 < DG < 8.8; 9.3 < RG < 9.5; OHIP = 1.38).

CONCLUSIONS

Within the limitations of this study, PEEK can be considered a viable prosthetic alternative.