Effects of assessing the bone remodeling process in biomechanical finite element stability evaluations of dental implants

Topology Optimization Driven Bone-Remodeling Simulation for Lumbar Interbody Fusion

This study proposes a numerical approach for simulating bone remodeling in lumbar interbody fusion (LIF). It employs a topology optimization method to drive the remodeling process and uses a pixel function to describe the structural topology and bone density distribution. Unlike traditional approaches based on strain energy density or compliance, this study adopts von Mises stress to guide the remodeling of LIF. A novel pixel interpolation scheme associated with stress criteria is applied to the physical properties of the bone, directly addressing the stress shielding effect caused by the implanted cage, which significantly influences the bone remodeling outcome in LIF. Additionally, a boundary inverse approach is utilized to reconstruct a simplified analysis model. To reduce computational cost while maintaining high structural resolution and accuracy, the scaled boundary finite element method (SBFEM) is introduced. The proposed numerical approach successfully generates results that closely resemble human lumbar interbody fusion.

A novel micromorphic approach captures non-locality in continuum bone remodelling

In continuum bone remodelling, bone is considered as continuous matter on the macroscale. Motivated by i) the underlying trabecular microstructure of bone resulting in size-dependence and ii) the non-local characteristics of osteocyte mechanosensing, a novel phenomenological approach based on a micromorphic formulation is proposed. Via illustrative benchmark examples, i.e. elementary unit cube, rod-shaped bone samples, and a 3D-femur sample, the novel approach is compared to the established local formulation, and the influence of the characteristic size of the microcontinuum and the coupling between macro- and microscale deformation is analysed. Taken together, the interaction between continuum points at the macroscale and their neighbourhood is effectively captured by the micromorphic formulation thus influencing the resulting distribution of nominal bone density at the macroscale.

The biomechanical effects of bimaxillary osteotomies to the patients with mandibular retraction under incisal clenching

The purpose of this study is to investigate the biomechanical effect of bimaxillary osteotomies on patients with mandibular retraction. Mandibular retraction, as a typical maxillofacial deformity, and has great adverse effects on TMJ. Bimaxillary osteotomies are widely used to correct symptoms of mandibular retraction. It is necessary to understand the effect of surgery on temporomandibular disc (TMJ). Five patients with mandibular retraction and 10 asymptomatic subjects were involved in this study. Finite element models of preoperative, postoperative and control group were constructed based on the CT data. Nine sets of concentrated forces were used to simulate the muscle effect and contact method was used to simulate the interaction within the TMJs and dentitions. The results showed that bimaxillary osteotomies could effectively improve the maxillofacial morphology and alleviate the overload in TMJ. The facial asymmetry and right chewing side preference could cause imbalanced stress distributions in the TMJs and interfere the surgical treatment.

Biomechanical analysis of alveolar bones with compromised quality supporting a 4-unit implant bridge; a possible association with implant-related sequestration (IRS)

OBJECTIVES

This study aimed to investigate the strain in the bone surrounding dental implants supporting a 4-unit bridge and assess the role of excessive strain as a possible risk factor for implant related sequestration (IRS) or peri-implant medication-related osteonecrosis of the jaw (PI-MRONJ).

MATERIALS AND METHODS

A 3D-mandibular model was constructed using computed tomography and segmented it into cortical and cancellous bones. The 4-unit implant-supported bridges replacing the mandibular posteriors were constructed, and each featuring two, three, and four implants, respectively. The Young's modulus was assigned based on the quality of the bone. A maximum occlusal force of 200 N was applied to each implant in the axial and in a 30-degree oblique direction.

RESULTS

The maximum principal strain of the fatigue failure range (> 3000 µε) in the bone was analyzed. The volume fraction of fatigue failure was higher in poor-quality bone compared to normal bone and oblique load than in axial load. An increasing number of implants may dissipate excessive strain in poor-quality bones.

CONCLUSIONS

Occlusal force applied to poor-quality bone can result in microdamage. Given that unrepaired microdamage may initiate medication-related osteonecrosis of the jaw, long-term occlusal force on fragile bones might be a risk factor.

CLINICAL RELEVANCE

When planning implant treatment for patients with compromised bone status, clinical modifications such as strategic placement of implants and optimization of restoration morphology should be considered to reduce excessive strain which might be associated with IRS or PI-MRONJ.

Agglomeration effect on biomechanical performance of CNT-reinforced dental implant using micromechanics-based approach

Dental implants have long played an important role in restoring lost teeth, but there are still concerns about their durability and long-term success. Commercial dental implants have traditionally been made of metallic and ceramic materials like titanium and zirconia; however, each kind of material has restrictions regarding osseointegration and mechanical characteristics that differ between native bone and the implant material, limiting the implant's longevity and reliability. To address these concerns, this research explores the use of carbon nanotubes (CNTs) in restorative dentistry, their excellent properties make them an ideal candidate for promoting bone growth around implanted device and ensuring long-lasting success. The objective of this study was to understand how CNT properties when incorporated into the titanium matrix may be able to better adapt to the oral environment taking into consideration the CNT agglomeration effects when designing reinforced nanocomposite materials for dental implant. A mathematical formulation of the micromechanics model was developed and improved to extend its application for the case of CNT-based composite materials for dental implants. A three dimensional (3D) model of bone structure around the osseointegrated dental implant was established considering different compositions of implant material. Finite Element Analysis (FEA) were conducted to assess the aggregation effect of implant incorporating CNTs into the titanium matrix, considering CNTs with both spherical inclusions (CNT clusters), and randomly dispersive ones (CNTs) in the titanium matrix, on osseointegration and bone remodeling around the dental implant and supporting bone system over a period of 48 months. Firstly, the effects of CNT-Ti implantation on time-dependent performance are evaluated in a computational remodeling framework. Then, Von Mises equivalent stresses are investigated to evaluate the stress distributions and micromotions in jaw bones of loaded implant with different composition of prosthetic material. Three agglomeration patterns are considered, particularly without agglomeration (ζ = ξ), partial and complete agglomeration (ζ < ξ, ξ = 1). Further, the influence of CNTs volume fraction variation is taken into account to predict the mechanical response of the bony system after CNT-reinforced dental implantation. It can be inferred that the agglomeration of CNTs reduces the elastic stiffness of the matrix. This is due to the fact that when CNTs are agglomerated, the inter-tube contacts are reduced and the effective stiffness of the matrix is decreased.

Using Finite Element Modeling in Bone Mechanoadaptation

PURPOSE OF THE REVIEW

Bone adapts structure and material properties in response to its mechanical environment, a process called mechanoadpatation. For the past 50 years, finite element modeling has been used to investigate the relationships between bone geometry, material properties, and mechanical loading conditions. This review examines how we use finite element modeling in the context of bone mechanoadpatation.

RECENT FINDINGS

Finite element models estimate complex mechanical stimuli at the tissue and cellular levels, help explain experimental results, and inform the design of loading protocols and prosthetics. FE modeling is a powerful tool to study bone adaptation as it complements experimental approaches. Before using FE models, researchers should determine whether simulation results will provide complementary information to experimental or clinical observations and should establish the level of complexity required. As imaging technics and computational capacity continue increasing, we expect FE models to help in designing treatments of bone pathologies that take advantage of mechanoadaptation of bone.

Peri-implant bone resorption risk of anterior maxilla narrow single implants: a finite-element analysis

Statement of the problem: Narrow implants have been recommended in high esthetic demand regions to ensure greater buccal bone thickness (BBT) and minimize soft-tissue recession due to insufficient bone support. However, a limited area of bone-implant interface can increase the risk of peri-implant bone resorption due to occlusal forces. Purpose: This article encourages the use of evidence-based finite element analysis to optimize the aesthetic outcomes in maxillary lateral incisor single-supported implant crown by accurate biomechanical planning. This study aimed to analyze the best implant dimensions that would preserve the maximum BBT and avoid peri-implant bone resorption due to occlusal forces. Materials and methods: A maxilla segment was constructed based on anthropological measurements. Four implant diameters (Ø = 3.25; 3.50; 3.75 or 4.00 mm) and two lengths (L = 10 or 13 mm) were simulated. The occlusal force parameters were defined to simulate clinical conditions. The bone resorption risk analysis was based on Frost's mechanostat theory altering the strain output to strain energy density (SED). The peri-implant bone resorption risk indexes (PIBR_ri) were calculated by dividing the average of the top ten SED elements of the cortical and trabecular buccal wall by the pathologic resorption limit for each bone. Results: For trabecular bone, only the model Ø4.00_L13 exhibited a low PIBR_ri. For cortical bone, all models presented a low PIBR_ri, except for models Ø3.25. Conclusion: The selection of a 3.25 mm dental implant to preserve a 2 mm BBT should be avoided since it generates a high peri-implant bone resorption risk induced by occlusal overload.