Finite element analysis of peri-implant bone volume affected by stresses around Morse taper implants: effects of implant positioning to the bone crest

Biomechanical Finite Element Analysis of Two Types of Short-Angled Implants Across Various Bone Classifications

The aim of this finite element analysis (FEA) was to investigate the distribution of von Mises stress within dental implant components, as well as trabecular and cortical bone. The study considered various bone qualities that influence cortical thickness in contact with the implant, specifically examining cortical thicknesses of 0.5, 1.5, and 3 mm, corresponding to Bergkvist's classifications IV, III, and II, respectively. A simplified 3D model of the bone was developed for the analysis. Two short implants were inserted into the model: one with a 30° inclined abutment (IA) and another positioned at a 30° angle featuring a straight abutment (II). A vertical force (120 N) was applied to the upper surface of the abutments. FEA software was employed to assess the stresses on the peri-implant tissues and the implants. The findings indicated that a reduction in cortical bone thickness results in an increase in stress within the cortical bone. For IA, the stresses recorded 32.56, 56.12, and 96.14 MPa for cortical thicknesses of 3, 1.5, and 0.5 mm, respectively. Conversely, II exhibited increased stresses across all bone qualities (52.32, 76.15, and 126.32 MPa for the same cortical thicknesses). It is advisable to avoid II in cases of poor bone quality and thin cortical due to the heightened risk of overload-induced bone resorption; however, it may be preferable to use IA in scenarios involving good bone quality and thicker cortical.

Impact of bone levels on stress distribution around all-on-four concept: A 3-D finite element analysis

This study aimed to investigate the impact of implant placement levels within the bone on stress distribution in the context of the All-on-Four concept. In this Finite Element Analysis(FEA), two 4.1 mm x 10 mm implants were axially placed in the anterior region of the jawbone, while two 4.1 mm x 14 mm implants were tilted at 30 ° in the posterior region following the all-on-four concept. In the EC scenario, all implants were inserted at the equicrestal level. In other scenarios, implants were positioned at 1 mm and 2 mm subcrestal levels (SC1, SC2). In all groups, the prosthesis was designed to replicate a group-function occlusion. A total load of 450 N was applied to the prosthesis. Upon deeper implant placement below the crest level, a trend of decreasing Von Mises stresses was observed in both implants and implant fragments. The highest Pmax value in the bone was recorded in SC-2, characterized by the absence of cortical bone support, with values of 3.16 N/mm2 in the anterior region and 1.55 N/mm2 in the posterior region. Conversely, the lowest Pmax values were noted in SC-1 for the anterior implant (2.67 N/mm2) and the EC for the posterior implant (0.87 N/mm2). Implant placements devoid of cortical bone support result in stress transmission from the implant and its components to the peri-implant bone. Optimal stress minimization is achieved by placing anterior axial angle implants deeper than the crest level while retaining cortical bone support and positioning posterior tilted implants at the crest level.

Evaluation of 3D Printing Orientation on Volume Parameters and Mechanical Properties of As-Build TI64ELI

The discovery of the utility of various titanium alloys as implant biomaterials has resulted in these materials becoming far more popular than other metals in the medical world. However, the production of these materials using additive manufacturing has its own challenges some of those being the surface finish that can be used as an implantology material. As such, the purpose of this study is to evaluate the influence of 3D-printed Ti64ELI on the as-built samples printed at 60°, 90°, and 180° orientations. Such studies are very limited, specifically in the development of the laser shock peening surface modification of dental implants. The study showed that each mechanical test that was performed contributes differently to the printing orientation, e.g., some tests yielded better properties when 180° printing orientation was used, and others had poorer properties when a 180° printing orientation was used. It was observed that 60° testing yielded a micro-hardness value of 349.6, and this value was increased by 0.37% when 90° orientation was measured. The lowest HV value was observed under a 180° orientation with 342.2 HV. The core material volume (Vmc) was 0.05266 mm3/mm2 at a 60° orientation, which increased by 11.48% for the 90° orientation. Furthermore, it was observed that the surface roughness (Sa) at 60° orientation was 43.68 μm. This was further increased by 6% when using the 90° orientation.

Crestal and Subcrestal Placement of Morse Cone Implant-Abutment Connection Implants: An In Vitro Finite Element Analysis (FEA) Study

The issue of dental implant placement relative to the alveolar crest, whether in supracrestal, equicrestal, or subcrestal positions, remains highly controversial, leading to conflicting data in various studies. Three-dimensional (3D) Finite Element Analysis (FEA) can offer insights into the biomechanical aspects of dental implants and the surrounding bone. A 3D model of the jaw was generated using computed tomography (CT) scans, considering a cortical thickness of 1.5 mm. Subsequently, Morse cone implant-abutment connection implants were virtually positioned at the model's center, at equicrestal (0 mm) and subcrestal levels (-1 mm and -2 mm). The findings indicated the highest stress within the cortical bone around the equicrestally placed implant, the lowest stress in the -2 mm subcrestally placed implant, and intermediate stresses in the -1 mm subcrestally placed implant. In terms of clinical relevance, this study suggested that subcrestal placement of a Morse cone implant-abutment connection (ranging between -1 and -2 mm) could be recommended to reduce peri-implant bone resorption and achieve longer-term implant success.

Biomechanical Evaluation of Stress Distribution in Equicrestal and Sub-crestally Placed, Platform-Switched Morse Taper Dental Implants in D3 Bone: Finite Element Analysis

Aim The aim of the study was to assess the effect of implant placement depth on stress distribution in bone around a platform-switched and Morse taper dental implants placed at the equi-crestal and 1 mm and 2 mm sub-crestal levels in a D3 bone using the 3D finite element analysis. Methodology A mechanical model of a partially edentulous maxilla was generated from a computerized tomography (CT) scan of an edentulous patient, as it can give exact bony contours of cortical bone. Also, from accurate geometric measurements obtained from the manufacturer, 3D models of Morse taper and platform-switched implants were manually drawn. The implant and bone models were then superimposed to simulate implant insertion in bone. Three implant positioning levels such as the equi-crestal, 1 mm sub-crestal, and 2 mm sub-crestal models were created, and meshing was done to create the number of elements for distribution of applying loads. The elastic properties of cortical bone and implant, such as Young's modulus and Poisson's ratio (µ), were determined. A load (axial and oblique) of 200N that simulated masticatory force was applied. Results On comparing stresses within the bone around the equi-crestal and 1 mm and 2 mm sub-crestal implants, it was observed that the maximum stresses were seen within cortical bone around the equi-crestally placed implant (21.694), the least in the 2 mm sub-crestally placed implant (18.85), and intermediate stresses were seen within the 1 mm sub-crestally placed implant (18.876). Conclusion Sub-crestal (1-2mm) placement of a Morse taper and a platform-switched implant is recommended for long-term success, as maximum von Mises stresses were found within cortical bone around the equi-crestal implant followed by the 1 mm sub-crestal implant and then the 2 mm sub-crestal implant.

The role of cortical zone level and prosthetic platform angle in dental implant mechanical response: A 3D finite element analysis

OBJECTIVE

The aim of this study was to evaluate the influence of three different dental implant neck geometries, under a combined compressive/shear load using finite element analysis (FEA). The implant neck was positioned in D2 quality bone at the crestal level or 2 mm below.

METHODS

One dental implant (4.2 × 9 mm) was digitized by reverse engineering techniques using micro CT and imported into Computer Aided Design (CAD) software. Non-uniform rational B-spline surfaces were reconstructed, generating a 3D volumetric model similar to the digitized implant. Three different models were generated with different implant neck configurations, namely 0°, 10° and 20°. D2 quality bone, composed of cortical and trabecular structure, was modeled using data from CT scans. The implants were included in the bone model using a Boolean operation. Two different fixture insertion depths were simulated for each implant: 2 mm below the crestal bone and exactly at the level of the crestal bone. The obtained models were imported to FEA software in STEP format. Von Mises equivalent strains were analyzed for the peri-implant D2 bone type, considering the magnitude and volume of the affected surrounding cortical and trabecular bone. The highest strain values in both cortical and trabecular tissue at the peri-implant bone interface were extracted and compared.

RESULTS

All implant models were able to distribute the load at the bone-implant contact (BIC) with a similar strain pattern between the models. At the cervical region, however, differences were observed: the models with 10° and 20° implant neck configurations (Model B and C), showed a lower strain magnitude when compared to the straight neck (Model A). These values were significantly lower when the implants were situated at crestal bone levels. In the apical area, no differences in strain values were observed.

SIGNIFICANCE

The implant neck configuration influenced the strain distribution and magnitude in the cortical bone and cancellous bone tissues. To reduce the strain values and improve the load dissipation in the bone tissue, implants with 10° and 20 neck configuration should be preferred instead of straight implant platforms.

Carbon fiber-reinforced PEEK in implant dentistry: A scoping review on the finite element method

Objective: The aim of the present study was to perform an integrative systematic review on the stress distribution assessed by finite element analysis on dental implants or abutments composed of carbon fiber-reinforced PEEK composites.Method: An electronic search was performed on PUBMED and ScienceDirect using a combination of the following search terms: PEEK, Polyetheretherketone, FEA, FEM, Finite element, Stress, Dental implant and Dental abutment.Results: The findings reported mechanical properties and the stress distribution through implant and abutment composed of PEEK and its fiber-reinforced composites. Unfilled PEEK revealed low values of elastic modulus and strength that negatively affected the stress distribution through the abutment and implant towards to the bone tisues. The incorporation of 30% carbon fibers increased the elastic modulus and strength of the PEEK-matrix composites although some studies reported no statistic differences in stress magnitude when compared to unfilled PEEK. However, an increase in short carbon fibers up to 60% revealed an enhancement on the stress distribution through abutment and implants towards to the bone tissues. PEEK veneering onto titanium core structures can also be a strategy to control the stress distribution at the implant-to-bone interface.Conclusions: The stiffness and strength of PEEK-matrix composites can be increased by the improvement of the carbon fibers' network. Thus, the content, shape, dimensions, and chemical composition of fibers are key factors to improve the stress distribution through abutment and implants composed of PEEK-matrix composites.

Biomechanical analyses of one-piece dental implants composed of titanium, zirconia, PEEK, CFR-PEEK, or GFR-PEEK: Stresses, strains, and bone remodeling prediction by the finite element method

This work aimed to assess the biomechanics, using the finite element method (FEM), of traditional titanium Morse taper (MT) dental implants compared to one-piece implants composed of zirconia, polyetheretherketone (PEEK), carbon fiber-reinforced PEEK (CFR-PEEK), or glass fiber-reinforced PEEK (GFR-PEEK). MT and one-piece dental implants were modeled within a mandibular bone section and loaded on an oblique force using FEM. A MT implant system involving a Ti6Al4V abutment and a cp-Ti grade IV implant was compared to one-piece implants composed of cp-Ti grade IV, zirconia (3Y-TZP), PEEK, CFR-PEEK, or GFR-PEEK. Stress on bone and implants was computed and analyzed while bone remodeling prediction was evaluated considering equivalent strain. In comparison to one-piece implants, the traditional MT implant revealed higher stress peak (112 MPa). The maximum stresses on the one-piece implants reached ~80 MPa, regardless their chemical composition. MT implant induced lower bone stimulus, although excessive bone strain was recorded for PEEK implants. Balanced strain levels were noticed for reinforced PEEK implants of which CFR-PEEK one-piece implants showed proper biomechanical behavior. Balanced strain levels might induce bone remodeling at the peri-implant region while maintaining low risks of mechanical failures. However, the strength of the PEEK-based composite materials is still low for long-term clinical performance.

Biomechanical behavior of functionally graded S53P4 bioglass-zirconia dental implants: Experimental and finite element analyses

OBJECTIVES

The aim of this work was to evaluate the biomechanical behavior of one-piece zirconia implants with a functionally graded bioglass (BG) layer as compared to monolithic zirconia and BG-coated implants, using the finite element method (FEM).

METHODS

Zirconia disks were infiltrated with bioglass S53P4 and then morphologically inspected by scanning electron microscopy (SEM) followed by mechanical analyses on micro-indentation tests for further biomechanical validation using the finite element method (FEM). On modeling, zirconia dental implants anchored into mandibular bone were simulated on occlusal loading as recorded under mastication. Three types of implants were simulated: i) free of BG coating, ii) with 100 μm or 150 μm thick conventional BG coatings; and iii) with graded BG coatings involving 3 different chemical composition distributions. The stress state at both implant and bone were evaluated using the FEM. The mechanically-induced bone remodelling was analyzed through the bone strain results.

RESULTS

Infiltration of BG into a zirconia structure resulted in a ∼100 μm thick layer with an exponential-like gradation of chemical composition and properties. Regarding the FEM calculations, the BG coating induced up to 30% decrease on stress in the implant body when compared to the monolithic zirconia implant. The gradient of chemical composition also improved the stresses' distribution. The stresses distribution towards the BG-coatings were significantly high and could lead to failure. Stresses on the bone were recorded down to its strength threshold, with insignificant influence of the coating layer. The bone strain values on all models indicates further bone remodelling although BG-coated and BG-graded zirconia implants showed the highest strain magnitude that may enhance the mechanical stimulation for bone maintenance.

SIGNIFICANCE

Graded BG-zirconia dental implants showed enhanced overall biomechanical behaviour as compared to the BG-coated or monolithic zirconia dental implants. Also, such biomechanical improvements noticed for the BG-graded system should be considered in combination with the well-known osseointegration benefits of bioactive glasses.

Comparison of CAD-CAM and traditional chairside processing of 4-unit interim prostheses with and without cantilevers: Mechanics, fracture behavior, and finite element analysis

STATEMENT OF PROBLEM

How processing by computer-aided design and computer-aided manufacturing (CAD-CAM) or traditional chairside fabrication techniques affects the presence of defects and the mechanical properties of interim dental prostheses is unclear.

PURPOSE

The purpose of this in vitro study was to compare the effects of CAD-CAM versus traditional chairside material processing on the fracture and biomechanical behavior of 4-unit interim prostheses with and without a cantilever.

MATERIAL AND METHODS

Two types of 4-unit interim prostheses were fabricated with abutments on the first premolar and first mandibular molar, one from a prefabricated CAD-CAM block and one with a traditional chairside polymer-monomer autopolymerizing acrylic resin (n=10). Both groups were assessed by compressive strength testing and additionally with or without a cantilevered second molar by using a universal testing machine with a 5-kN load cell. A finite element model (FEM) was built by scanning both prosthesis designs. Finite element analysis (FEA) replicated the experimental conditions to evaluate the stress distribution through the prostheses.

RESULTS

Interim fixed prostheses manufactured by CAD-CAM showed significantly higher mean fracture loading values (3126 N to 3136 N) than for conventionally made interim fixed prostheses (1287 N to 1390 N) (P=.001). The presence of a cantilever decreased the fracture loading mean values for CAD-CAM (1954 N to 2649 N), although the cantilever did not influence the traditional prostheses (1268 N to 1634 N). The highest von Mises stresses were recorded by FEA on the occlusal surface, with the cantilever design, and at the transition region (connector) between the prosthetic teeth.

CONCLUSIONS

Interim partial prostheses produced by CAD-CAM had a higher strength than those manufactured traditionally. The presence of a cantilever negatively affected the strength of the prostheses, although the structures manufactured by CAD-CAM still revealed high strength and homogenous stress distribution on occlusal loading.

Radiological implications of crestal and subcrestal implant placement in posterior areas. A cone-beam computed tomography study

Background

Subcrestal implant placement has been suggested as a method that could contribute to maintain the periimplant soft and hard tissues in comparison with crestal placement. The objective of this study was to investigate the relationship between implant placement at different depths in the alveolar bone and (a) the thickness of the buccal bone plate (BBP); and (b) crestal cortical bone thickness, based on the use of cone-beam computed tomography (CBCT).

Material and Methods

A cross-sectional study was performed, analyzing CBCT scans from the database of the Oral Surgery Unit of the University of Valencia. Individuals with single missing teeth in posterior sectors were included. Two trained dentists used a software application to plan implant placement at four different depths from the bone crest (from 0-2 mm subcrestal). The thickness of the BBP was measured at each established depth, tracing a line from the implant platform to the outermost part of the facial alveolar bone, and the ratio between the implant platform and cortical bone thickness was calculated.

Results

The study sample consisted of 64 patients. In the case of implants placed in a crestal position, the distance from the platform to the BBP was 1.99±1.10 mm. This distance increased significantly (p<0.001) with the planned implant placement depth, reaching an average of 2.90±1.22 mm when placement was 2 mm subcrestal. Subcrestal implant placement at this depth implied surpassing the cortical bone in 91% of the cases.

Conclusions

Radiological planning of implant placement in a subcrestal position results in a greater distance from the implant platform to the BBP. In general terms, planning implant placement at a depth of 2 mm subcrestal surpassed the cortical bone in 91% of the cases.

Key words:Subcrestal implant, cortical bone thickness, buccal bone plate, cone-beam computed tomography.

New Dental Implant with 3D Shock Absorbers and Tooth-Like Mobility-Prototype Development, Finite Element Analysis (FEA), and Mechanical Testing

Background: Once inserted and osseointegrated, dental implants become ankylosed, which makes them immobile with respect to the alveolar bone. The present paper describes the development of a new and original implant design which replicates the 3D physiological mobility of natural teeth. The first phase of the test followed the resistance of the implant to mechanical stress as well as the behavior of the surrounding bone. Modifications to the design were made after the first set of results. In the second stage, mechanical tests in conjunction with finite element analysis were performed to test the improved implant design. Methods: In order to test the new concept, 6 titanium alloy (Ti6Al4V) implants were produced (milling). The implants were fitted into the dynamic testing device. The initial mobility was measured for each implant as well as their mobility after several test cycles. In the second stage, 10 implants with the modified design were produced. The testing protocol included mechanical testing and finite element analysis. Results: The initial testing protocol was applied almost entirely successfully. Premature fracturing of some implants and fitting blocks occurred and the testing protocol was readjusted. The issues in the initial test helped design the final testing protocol and the new implants with improved mechanical performance. Conclusion: The new prototype proved the efficiency of the concept. The initial tests pointed out the need for design improvement and the following tests validated the concept.