Biomechanical assessment of zygomatic implants in clinical rehabilitation scenarios: A finite element and fatigue analysis

OBJECTIVES

This study utilizes contemporary placement approaches and implant design to investigate zygomatic implants' biomechanical behavior and fatigue lifetime in clinical contexts.

METHODS

A commercially available zygomatic implant assembly and an ex vivo skull were subjected to computed tomography. Three-dimensional models representing intra-sinus, extra-sinus, and extramaxillary configurations were constructed. The finite element analysis (FEA) was executed with vertical, lateral, and masseteric loads applied simultaneously. Von Mises stress served as the failure criterion, with data collection on implant fixtures, abutments, connector screws, and simulated bone structures. The analysis included peak stress locations, contour plots illustrating stress distribution, and fatigue limit assessments for implant components.

RESULTS

Results revealed lower stress concentrations in mesial implant components compared to distal ones. The extra-sinus approach showed lower stresses in most prosthetic components. Peak stress concentrations in the maxillary bone layers (ranging from 25 to 27 MPa) were primarily localized at the alveolar ridge's crest at the zygomatic implant entrance point. On the zygomatic bone, the peak stresses were in the interface with the distal implant and ranged from 12 to 26 MPa. The in silico fatigue testing demonstrated an equally high fatigue lifetime of the implant components in all the approaches analyzed.

SIGNIFICANCE

Because of additional clinical advantages, the extra-sinus approach was considered the optimal reconstruction method when patients' anatomy permits its application. Given the limited long-term clinical data on the latest implant designs and placement techniques, these findings provide valuable insights into the biomechanical performance of zygomatic implants and offer guidance for clinical practice.

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 finite element analysis of stress distribution on different complex macro designs in commercially available implants: An in-vitro study

Objective

This study aimed to investigate the effects of different commercially available complex implant macro designs on stress distributions using Finite element analysis. The experiment is done under varying simulated bone conditions to provide reference for clinical application.

Materials and methods

The study employed the Finite Element Analysis (FEA) method to compare four commercially available complex implant macro designs on a Computer-Aided Design (CAD) model of a maxillary bone segment. The three-dimensional geometrical model of the implants was reconstructed from computed tomography (CT)-slices in Digital Imaging and Communications in Medicine (DICOM) format and contact condition between the implant and the bone was considered as 'Bonded', implying perfect osseointegration. All materials used in the models were assumed to be isotropic, homogeneous, and linearly elastic. The Finite element simulations employed load of 400 N under both axial and non-axial conditions Stresses were analysed under different bone conditions.

Results

Average values of von Mises stresses were used for comparing stress levels between implant designs. There was a definite increase in the equivalent stress values from higher density(D1)to lower density (D4) bone conditions for all implants. The percentage of increase ranged from 23.63 to 49.39 on axial loading and 20.39 to 57.19 when subjected to non-axial loading. The equivalent stress values resulted from non-axial loading were 1.78-2.94 times higher than that of axial loading for all implants under all bone densities. Among the complex designs Equinox Myriad Plus implant exhibited the least stress under axial loading (12.749-19.046 MPa) and (37.462-49.217 MPa) for non-axial loading. The stress on the crestal module was higher (1.49-2.99 times) than the overall stress on the implant regardless of the loading direction or bone conditions.

Conclusions

Data from the present study shows Equinox Myriad Plus implant generating the least equivalent stress and this can be taken as indicator in the biomechanical performance of the design.

Comparison of stress distribution in fully porous and dense-core porous scaffolds in dental implantation

The aim of this study is to compare the stress distribution in porous scaffolds with different structures with similar geometric parameters to study a new approach in dental implantation. Three-dimensional finite element models of the fully porous and dense-core porous scaffolds with defined porosity parameters including space diameter and thickness with two porosity patterns were embedded in the jaw bone model with cortical and cancellous bone. The cylindrical shape was considered as the main shape of the scaffolds. To evaluate the mechanical performance, the Von Mises stress was compared in the models under static and dynamic masticatory loading. Incidentally, to validate the modeling results, experimental strain gauge tests were performed on four specimens fabricated from Ti6Al4V. Finally, the stress distribution in the models was compared with the results of previous studies on commercial implants. The results of the finite element analysis show that there are considerable differences in the magnitude of the equivalent stress in the models in static and dynamic phases. Also, changes in the defined geometric parameters have significant effects on the stress distribution in terms of Von Mises stress in the overall models. The experimental results indicated good agreement with those of the modeling. It can be concluded that some porous structures with optimal geometries can be proposed as a new structure for dental implants. However, considering the physiology of bone when confronted with porous structures, further studies such as in vivo experiments are needed in this field.

On the fatigue life of dental implants: Numerical and experimental investigation on configuration effect

Dental implants have seen widespread and successful use in recent years. Given their long-term application and the critical role of geometry in determining fracture and fatigue characteristics, fatigue assessments are of utmost importance for implant systems. In this study, nine dental implant system samples were subjected to testing in accordance with ISO 14801 standards. The tests included static evaluations to assess ultimate loads and fatigue tests conducted under loads of 270 N and 230 N at a frequency of 15 Hz, aimed at identifying fatigue failure locations and fatigue life. Fatigue life predictions and related calculations were carried out using Fe-safe software. The initial model featured a 22° angle for both the fixture and abutment. Subsequently, variations in abutment angles at 21° and 23° were considered while keeping the fixture angle at 22°. In the next phase, the fixture and abutment angles were set as identical, at 21° and 23°. The results unveiled that when the angles of the abutment and fixture matched, stress values decreased, and fatigue life increased. Conversely, models featuring abutment angles of 21° and 23°, with a 22° angle for the fixture, led to a 49.1 % increase in stress and a 36.9 % decrease in fatigue life compared to the primary model. Notably, in the case of the implant with a 23° angle for both abutment and fixture, the fatigue life reached its highest value at 10 million cycles. Conversely, the worst-case scenario was observed in the implant with a 21° abutment angle and a 23° fixture angle, with a fatigue life of 5.49 million cycles.

Three-Dimensional Finite Element Investigation into Effects of Implant Thread Design and Loading Rate on Stress Distribution in Dental Implants and Anisotropic Bone

Variations in the implant thread shape and occlusal load behavior may result in significant changes in the biological and mechanical properties of dental implants and surrounding bone tissue. Most previous studies consider a single implant thread design, an isotropic bone structure, and a static occlusal load. However, the effects of different thread designs, bone material properties, and loading conditions are important concerns in clinical practice. Accordingly, the present study performs Finite Element Analysis (FEA) simulations to investigate the static, quasi-static and dynamic response of the implant and implanted bone material under various thread designs and occlusal loading directions (buccal-lingual, mesiodistal and apical). The simulations focus specifically on the von Mises stress, displacement, shear stress, compressive stress, and tensile stress within the implant and the surrounding bone. The results show that the thread design and occlusal loading rate have a significant effect on the stress distribution and deformation of the implant and bone structure during clinical applications. Overall, the results provide a useful insight into the design of enhanced dental implants for an improved load transfer efficiency and success rate.

Effect of macrogeometry and bone type on insertion torque, primary stability, surface topography damage and titanium release of dental implants during surgical insertion into artificial bone

This study investigated the influence of implant macrogeometry and bone type on insertion torque (IT), primary stability (ISQ), surface topography damage, and the amount of titanium (Ti) released during insertion. Forty implants with different macrogeometries (Facility - Cylindrical with spiral-shaped threads; Alvim - Tapered with buttress-shaped threads) were inserted into artificial bone types I-II and III-IV. Surface morphology was evaluated by Scanning Electron Microscope (SEM) and roughness parameters with Laser Scanning Confocal Microscopy (LSCM) before and after insertion (AI). Implant macrogeometry was characterized by LSCM. The chemical composition of bone beds was determined by SEM associated with Energy Dispersive X-Ray Spectroscopy. The amount of Ti released was analyzed with Energy Dispersive X-Ray Fluorescence. Alvim had greater IT and ISQ than Facility. Bone types I-II require higher IT of implants. Alvim also had greater internal threads angle, higher initial roughness, and significant reduction of roughness AI, compared to Facility. The functional surface height reduced AI, especially in flank and valley of threads. Height of surface roughness of Alvim and Facility implants was similar AI. Implants surface morphology changes and metallic particles on bone beds were observed after implant insertion, mainly into bone types III-IV. Implants inserted into bone types I-II showed less surface damage. Alvim implants released more Ti (37.52 ± 25.03 ppm) than Facility (11.66 ± 28.55 ppm) on bone types III-IV. The implant macrogeometry and bone types affect IT, ISQ, surface damage, and Ti amount released during insertion. Alvim implants were more wear susceptible, releasing higher Ti concentration during insertion into bone types III-IV.

Bone and Cartilage Interfaces With Orthopedic Implants: A Literature Review

The interface between a surgical implant and tissue consists of a complex and dynamic environment characterized by mechanical and biological interactions between the implant and surrounding tissue. The implantation process leads to injury which needs to heal over time and the rapidity of this process as well as the property of restored tissue impact directly the strength of the interface. Bleeding is the first and most relevant step of the healing process because blood provides growth factors and cellular material necessary for tissue repair. Integration of the implants placed in poorly vascularized tissue such as articular cartilage is, therefore, more challenging than compared with the implants placed in well-vascularized tissues such as bone. Bleeding is followed by the establishment of a provisional matrix that is gradually transformed into the native tissue. The ultimate goal of implantation is to obtain a complete integration between the implant and tissue resulting in long-term stability. The stability of the implant has been defined as primary (mechanical) and secondary (biological integration) stability. Successful integration of an implant within the tissue depends on both stabilities and is vital for short- and long-term surgical outcomes. Advances in research aim to improve implant integration resulting in enhanced implant and tissue interface. Numerous methods have been employed to improve the process of modifying both stability types. This review provides a comprehensive discussion of current knowledge regarding implant-tissue interfaces within bone and cartilage as well as novel approaches to strengthen the implant-tissue interface. Furthermore, it gives an insight into the current state-of-art biomechanical testing of the stability of the implants. Current knowledge reveals that the design of the implants closely mimicking the native structure is more likely to become well integrated. The literature provides however several other techniques such as coating with a bioactive compound that will stimulate the integration and successful outcome for the patient.

Orthopaedic osseointegration: Implantology and future directions

Osseointegration (OI) is the direct anchorage of a metal implant into bone, allowing for the connection of an external prosthesis to the skeleton. Osseointegration was first discovered in the 1960s based on the microscopic analysis of titanium implant placed into host bone. New bone was observed to attach directly to the metal surface. Following clinical investigations into dentistry applications, OI was adapted to treat extremity amputations. These bone anchored implants, which penetrate the skin and soft tissues, eliminate many of the challenges of conventional prosthetic sockets, such as poor fit and suspension, skin breakdown, and pain. Osseointegrated implants show promise to improve prosthesis use, pain, and function for amputees. The successful process of transcutaneous metal integration into host bone requires three synergistic systems: the host bone, the metal implant, and the skin-implant interface. All three systems must be optimized for successful incorporation and longevity of the implant. Osseointegration begins during surgical implantation of the metal components through a complex interplay of cellular mechanisms. While implants can vary in design-including the original screw, press fit implants, and compressive osseointegration-they face common challenges to successful integration and maintenance of fixation within the host bone. Overcoming these challenges requires the understanding of the complex interactions between each element of OI. This review outlines (a) the basic components of OI, (b) the science behind both the bone-implant and the skin-implant interfaces, (c) the current challenges of OI, and (d) future opportunities within the field.