Finite Element Analysis of a New Dental Implant Design Optimized for the Desirable Stress Distribution in the Surrounding Bone Region

Tribocorrosion of 3D printed dental implants: An overview

With the advancements in dental science and the growing need for improved dental health, it has become imperative to develop new implant materials which possess better geometrical, mechanical, and physical properties. The oral environment is a corrosive environment and the relative motion between the teeth also makes the environment more hostile. Therefore, the combined corrosion and tribology commonly known as tribocorrosion of implants needs to be studied. The complex shapes of the dental implants and the high-performance requirements of these implants make manufacturing difficult by conventional manufacturing processes. With the advent of additive manufacturing or 3D-printing, the development of implants has become easy. However, the various requirements such as surface roughness, mechanical strength, and corrosion resistance further make the manufacturing of implants difficult. The current paper reviews the various studies related to3D-printed implants. Also, the paper tries to highlight the role of 3D-Printing can play in the area of dental implants. Further studies both experimental and numerical are needed to devise optimized conditions for 3D-printing implants to develop implants with improved mechanical, corrosion, and biological properties.

Optimizing functionally graded tibial components for total knee replacements: a finite element analysis and multi-objective optimization study

The optimal design of complex engineering systems requires tracing precise mathematical modeling of the system's behavior as a function of a set of design variables to achieve the desired design. Despite the success of current tibial components of knee implants, the limited lifespan remains the main concern of these complex systems. The mismatch between the properties of engineered biomaterials and those of biological materials leads to inadequate bonding with bone and the stress-shielding effect. Exploiting a functionally graded material for the stem of the tibial component of knee implants is attractive because the properties can be designed to vary in a certain pattern, meeting the desired requirements at different regions of the knee joint system. Therefore, in this study, a Ti6Al4V/Hydroxyapatite functionally graded stem with a laminated structure underwent simulation-based multi-objective design optimization for a tibial component of the knee implant. Employing finite element analysis and response surface methodology, three material design variables (stem's central diameter, gradient factor, and number of layers) were optimized for seven objective functions related to stress-shielding and micro-motion (including Maximum stress on the cancellous bone, maximum and mean stresses on predefined paths, the standard deviation of mean stress on paths, maximum and mean micro-motions at the bone-implant interface and the standard deviation of mean micro-motion). Then, the optimized functionally graded stem with 6 layers, a central diameter of 5.59 mm, and a gradient factor of 1.31, was compared with a Ti6Al4V stem for various responses. In stress analysis, the optimal stem demonstrated a 1.92% improvement in cancellous bone stress while it had no considerable influence on the maximum, mean, and standard deviation of stresses on paths. In micro-motion analysis, the maximum, mean, and standard deviation of mean micro-motion at the interface were enhanced by 24.31%, 39.53%, and 19.77%, respectively.

Toward Digital Twin Development for Implant Placement Planning Using a Parametric Reduced-Order Model

Real-time stress distribution data for implants and cortical bones can aid in determining appropriate implant placement plans and improving the post-placement success rate. This study aims to achieve these goals via a parametric reduced-order model (ROM) method based on stress distribution data obtained using finite element analysis. For the first time, the finite element analysis cases for six design variables related to implant placement were determined simultaneously via the design of experiments and a sensitivity analysis. The differences between the minimum and maximum stresses obtained for the six design variables confirm that the order of their influence is: Young's modulus of the cancellous bone > implant thickness > front-rear angle > left-right angle > implant length. Subsequently, a one-dimensional (1-D) CAE solver was created using the ROM with the highest coefficient of determination and prognosis accuracy. The proposed 1-D CAE solver was loaded into the Ondemand3D program and used to implement a digital twin that can aid with dentists' decision making by combining various tooth image data to evaluate and visualize the adequacy of the placement plan in real time. Because the proposed ROM method does not rely entirely on the doctor's judgment, it ensures objectivity.

Investigating the impact of diameters and thread designs on the Biomechanics of short implants placed in D4 bone: a 3D finite element analysis

BACKGROUND

Dental implants emerge as a dependable and efficacious alternative for patients experiencing partial or complete tooth loss. The stability of these implants is influenced by surface topography and macro-level design. In cases where the height of the maxillary posterior region is diminished, employing short implants can prove advantageous. With the aim of examining the distribution of von Mises stress, strain, and micromovement in D4 bone quality surrounding platform-switched short implants, measuring 6 mm in length and featuring diameters ranging from 4 to 6 mm, as well as different thread designs, an in-depth finite element analysis was conducted under immediate loading conditions.

METHODOLOGY

A 3D finite element model was constructed to simulate maxillary molar crowns, incorporating an implant with a length of 6 mm and varying diameters and thread designs. The diameters utilized were 4/3.6 mm, 5/4 mm, and 6/4.8 mm, while the thread designs included buttress, square, and triangle patterns. Each model underwent analysis with a 100 N force applied in two directions: vertical and oblique, relative to the long axis of the implant. Stress, strain, and micromovement in the peri-implant region were recorded, employing the Ansys Workbench R v.18.1 software for modelling and analysis.

RESULTS

When comparing all three diameters, the wide diameter (6 mm threads) exhibited the lowest values of peri-implant von Mises stresses (3.3 MPa and 35.1 MPa), strains (194 Ɛ and 484 Ɛ), and micromovements (0.7 μm and 1.3 Ɛ) subjected to axial and non-axial loading of a 100 N force. Notably, square microthreads yielded the most favorable stress parameters among the different thread shapes, manifesting the minimum values of stress, strains, and micromovements in their vicinity.

CONCLUSION

For the treatment of atrophic ridges or in scenarios necessitating extensive surgical preparation of the implant site, a combination of short implants, wide diameters, and platform switching can be employed. In situations with reduced bone height and the requirement for an implant-supported prosthesis to replace a missing permanent maxillary molar, the utilization of wide-diameter platform-switched short implants measuring 6 mm in length, featuring a square thread design, should be taken into consideration.

Influence of rough micro-threaded and laser micro-textured implant-neck on peri-implant tissues: A systematic review

Background and objective

This systematic review aimed to explore clinical outcomes of marginal or crestal bone level (MBL) and soft tissue status around implants, following the placement of rough micro-threaded/laser-microtextured surface (LMS) implants. These outcomes are compared with those following the placement of smooth machined-neck implants.

Materials and methods

Using EBSCO Information Services, we conducted a web-based search of databases such as the PubMed, Scopus, and EMBASE, for relevant English-language scientific papers published between January 2013 and August 2022. Prospective or retrospective controlled cohort studies and randomized controlled trials (RCTs) investigating the role of rough micro-threaded/LMS implant necks on MBL, sulcular probing depth (PD), and/or clinical attachment loss, were included in this review.

Results

From a comprehensive literature search of 247 articles, 6 RCTs, 5 prospective studies, and 4 retrospective studies (n = 15) fulfilled the eligibility criteria. MBL with rough micro-threaded implant necks ranged from 0.12 ± 0.17 mm to 3.25 ± 0.4 mm after loading. The smooth machined-neck implants without a micro-threaded neck had a loading MBL of 0.38 ± 0.51 mm to 3.75 ± 0.4 mm. Micro-threaded implant necks showed much lower MBL than machined-neck implants. LMS implant necks had a lower peri-implant PD than machined-neck implants after 3 years of early loading (2.3 ± 0.7 mm vs. 3.8 ± 0.8 mm). The experimental and control groups showed similar gingival recessions (1.08 ± 0.4 mm vs. 2.46 ± 0.3 mm). Meta-analysis was not feasible owing to heterogeneity of the studies.

Conclusion

Under functional loading, a roughened micro-threaded design for the implant neck could significantly lower MBL. Furthermore, PD and MBL were much lower around LMS neck implants than those around machined-neck or micro-threaded implants.

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

OBJECTIVE

To discuss the state of the art of Finite Element (FE) modeling in implant dentistry, to highlight the principal features and the current limitations, and giving recommendations to pave the way for future studies.

METHODS

The articles' search was performed through PubMed, Web of Science, Scopus, Science Direct, and Google Scholar using specific keywords. The articles were selected based on the inclusion and exclusion criteria, after title, abstract and full-text evaluation. A total of 147 studies were included in this review.

RESULTS

To date, the FE analysis of the bone-dental implant system has been investigated by analyzing several types of implants; modeling only a portion of bone considered as isotropic material, despite its anisotropic behavior; assuming in most cases complete osseointegration; considering compressive or oblique forces acting on the implant; neglecting muscle forces and the bone remodeling process. Finally, there is no standardized approach for FE modeling in the dentistry field.

SIGNIFICANCE

FE modeling is an effective computational tool to investigate the long-term stability of implants. The ultimate aim is to transfer such technology into clinical practice to help dentists in the diagnostic and therapeutic phases. To do this, future research should deeply investigate the loading influence on the bone-implant complex at a microscale level. This is a key factor still not adequately studied. Thus, a multiscale model could be useful, allowing to account for this information through multiple length scales. It could help to obtain information about the relationship among implant design, distribution of bone stress, and bone growth. Finally, the adoption of a standardized approach will be necessary, in order to make FE modeling highly predictive of the implant's long-term stability.

Strain based in vitro analysis of dental implant using artificial bone model and validation by numerical technique

BACKGROUND/PURPOSE

Dental implant fails due to mechanical failure of the implant contribute to about 10-15 % of implant failures. It is necessary to prevent the design failure of the implant since it leads to bone loss which further leads to complications in reimplantation. This makes it important to test the design of a dental implant using FEM and in vitro testing before its application. The purpose of this article is to test the design of a dental implant using in vitro testing by using an artificial bone model and validation of the data using Finite Element Method (FEM).

METHODS

A dental implant was selected for in vitro testing and 3D FE analysis was conducted to observe the stress values. The in vitro study was done on a custom designed testing rig where the implant was drilled into a ABS and sawbone (polyurethane) bone model. Vertical and lateral loads of 100 N and 40 N respectively, were applied to evaluate the micro-strains using strain gauge technique. 3D FEA technique was used to evaluate stress concentrations and micro-strains in the bone-implant interface.

RESULTS

The strain values were found to be higher in the case of lateral loading than vertical loading with in vitro testing. The von-mises stresses on the cortical bone were greater at the bone-implant interface near the neck region of the implant.

CONCLUSIONS

The results obtained from the in vitro analysis and FEA were found to have a good agreement with an error percentage of 2-5 %.

Biomechanical evaluations of the long-term stability of dental implant using finite element modeling method: a systematic review

PURPOSE

The aim of this study is to summarize various biomechanical aspects in evaluating the long-term stability of dental implants based on finite element method (FEM).

MATERIALS AND METHODS

A comprehensive search was performed among published studies over the last 20 years in three databases; PubMed, Scopus, and Google Scholar. The studies are arranged in a comparative table based on their publication date. Also, the variety of modeling is shown in the form of graphs and tables. Various aspects of the studies conducted were discussed here.

RESULTS

By reviewing the titles and abstracts, 9 main categories were extracted and discussed as follows: implant materials, the focus of the study on bone or implant as well as the interface area, type of loading, element shape, parts of the model, boundary conditions, failure criteria, statistical analysis, and experimental tests performed to validate the results. It was found that most of the studied articles contain a model of the jaw bone (cortical and cancellous bone). The material properties were generally derived from the literature. Approximately 43% of the studies attempted to examine the implant and surrounding bone simultaneously. Almost 42% of the studies performed experimental tests to validate the modeling.

CONCLUSION

Based on the results of the studies reviewed, there is no "optimal" design guideline, but more reliable design of implant is possible. This review study can be a starting point for more detailed investigations of dental implant longevity.

Evaluation of Stress Distribution during Insertion of Tapered Dental Implants in Various Osteotomy Techniques: Three-Dimensional Finite Element Study

Conventional osteotomy techniques can, in some cases, induce higher stress on bone during implant insertion as a result of higher torque. The aim of the present study was to evaluate and compare the stress exerted on the underlying osseous tissues during the insertion of a tapered implant using different osteotomy techniques through a dynamic finite element analysis which has been widely applied to study biomedical problems through computer-aided software. In three different types of osteotomy techniques, namely conventional (B1), bone tap (B2), and countersink (B3), five models and implants designed per technique were prepared, implant insertion was simulated, and stress exerted by the implant during each was evaluated. Comparison of stress scores on the cortical and cancellous bone at different time points and time intervals from initiation of insertion to the final placement of the implant was made. There was a highly statistically significant difference between B1 and B2 (p = 0.0001) and B2 and B3 (p = 0.0001) groups. In contrast, there was no statistically significant difference in the stress scores between B1 and B3 (p = 0.3080) groups at all time points of implant placement. Overall, a highly significant difference was observed between the stresses exerted in each technique. Within the limitations of our study, bone tap significantly exerted lesser stresses on the entire bone than conventional and countersink type of osteotomy procedures. Considering the stress distribution at the crestal region, the countersink showed lower values in comparison to others.

How to design a more stable dental implant: A topology optimization approach

The body shape design is one of the most influential factors in the success of dental implants. This study presents a strategy to design the geometrical features of a threaded implant. The topology optimization technique is applied to identify appropriate spaces in the implant body to be removed for bone growth. The exact shape, position, and dimensions of the spaces are determined using a finite element model. This model consists of a mandibular segment, implant, abutment, and crown. During the optimization process, some grooves and holes are created in the implant by removing redundant materials. Bone growth into these spaces causes mechanical locking between the implant and surrounding bone. The smoothing process is performed following the optimization to remove stress concentration. The results indicate that this design strategy reduces the maximum displacement of the implant by approximately 20%. Moreover, a reduction in the implant's volume and an increase in the contact area between the implant and bone are obtained. All mentioned issues would increase the stability and reduce the risk of implant loosening. Finally, using conventional production methods, the optimal implant was produced from titanium alloy to demonstrate the possibility of production of the proposed design.

Evaluation of Fatigue Life for Dental Implants Using FEM Analysis

The purpose of this study is to numerically analyze a 3D model of an implant under fatigue loads. A bone and a V shape implant were modeled using SolidWorks2008 software. In order to obtain an exact model, the bone was assumed as a linear orthotropic material. Mechanical loads were applied in terms of fastening torque to the abutment and mastication force applied at the top of the crown. The abutment was tightened into the implant by applying a 35 N.cm torque causing tensile stress within the abutment screw as a preload that is harmful not only for the fatigue life of the abutment, but also for the stability of the implant-abutment interface. A 700 N force at an angle of 30 degrees to the vertical direction was applied to the crown. The mechanical analysis results showed that the abutment is the critical component of the implant system in terms of fatigue failure. This is due to the fact that the tensile preloads originated from the fastening torque. The results were presented in terms of fatigue life in the abutment. Fatigue life of the abutment and implant were calculated based on the Goodman, Soderberg, Smith–Watson–Topper (SWT), and Marrow theories. According to the results of the fatigue life prediction, abutment screws may fail after about 3 × 105 cycles. The predicted results by the Goodman theory are at a very good accordance with the clinical data.

Applications of Finite Element in Implant Dentistry and Oral Rehabilitation

Finite element is widely applied in dentistry to study the stress distributions on adjoining bone, the biomechanics of dental implant and bone; implant and bone interface and study its fatigue behaviors of the implant. This article presents various applications of finite element in implant dentistry. Available articles were searched and reviewed from March 1980 till September 2020 from Pubmed, Scopus, Google Scholar, and Science direct. Relevant studies were included and critically analyzed. Finite element is an important tool in implant dentistry to study the stress distributions on adjoining bone, the biomechanics of dental implant and bone; implant and bone interface, and fatigue behaviors.

Healing Pattern Analysis for Dental Implants Using the Mechano-Regulatory Tissue Differentiation Model

(1) Background: Our aim is to reveal the influence of the geometry designs on biophysical stimuli and healing patterns. The design guidelines for dental implants can then be provided. (2) Methods: A two-dimensional axisymmetric finite element model was developed based on mechano-regulatory algorithm. The history of tissue differentiation around eight selected implants can be predicted. The performance of the implants was evaluated by bone area (BA), bone-implant contact (BIC); (3) Results: The predicted healing patterns have very good agreement with the experimental observation. Many features observed in literature, such as soft tissues covering on the bone-implant interface; crestal bone loss; the location of bone resorption bumps, were reproduced by the model and explained by analyzing the solid and fluid biophysical stimuli and (4) Conclusions: The results suggested the suitable depth, the steeper slope of the upper flanks, and flat roots of healing chambers can improve the bone ingrowth and osseointegration. The mechanism related to solid and fluid biophysical stimuli were revealed. In addition, the model developed here is efficient, accurate and ready to extend to any geometry of dental implants. It has potential to be used as a clinical application for instant prediction/evaluation of the performance of dental implants.