Biomechanical reinforcement by CAD-CAM materials affects stress distributions of posterior composite bridges: 3D finite element analysis.

OBJECTIVES: This 3D finite element analysis study aimed to investigate the effect of reinforcing CAD-CAM bars on stress distribution in various components of a posterior composite bridge. METHODS: A virtual model mimicking the absence of an upper second premolar was created, featuring class II cavity preparations on the proximal surfaces of the adjacent abutment teeth surrounding the edentulous space. Five distinct finite element analysis (FEA) models were generated, each representing a CAD-CAM reinforcing bar material: 3-YTZP (IPS. emax ZirCAD MO; Zr), lithium disilicate (IPS e.max CAD; EX), nano-hybrid resin composite (Grandio Blocs; GB), Fibre-reinforced composite (Trilor; Tri), and polyetheretherketone (PEEK). A veneering resin composite was employed to simulate the replacement of the missing premolar (pontic). In the FEA, an axial force of 600 N and a transverse load of 20 N were applied at the center of the pontic. Subsequently, maximum von Mises (mvM) and maximum principal stresses (σmax) were computed across various components of the generated models. Additionally, shear stresses at the interface between the CAD-CAM bars and the veneering resin composite were determined. RESULTS: CAD-CAM materials with high modulus of elasticity, such as Zr and EX, exhibited the highest mvM stresses and shear stresses while transferring the lowest stress to the veneering resin composite in comparison to other materials. Conversely, PEEK demonstrated the lowest mvM stresses but produced the highest stresses within the veneering resin composite. There was a uniform distribution of mvM stresses in the remaining tooth structure among all groups, except for a noticeable elevation in the molar region of Zr and EX groups. SIGNIFICANCE: Reinforcing CAD-CAM bar materials with a high modulus of elasticity, such as Zr and EX, may result in debonding failures at the connector sites of posterior composite bridges. Conversely, GB, PEEK, and Tri have the potential to cause fracture failures at the connectors rather than debonding.

Design of customized coated dental implants using finite element analysis.

BACKGROUND: Dental implants are used as a traditional technique to replace missing teeth. In the longterm evaluation of dental implants, the stability and durability of the implant-bone interface are crucial. Furthermore, the success of dental implants depends on several factors, such as osseointegration, implant geometry and surface topography. OBJECTIVES: The aim of the study was to investigate the effects of coating materials on dental implants by altering several parameters, including the material used, the coating thickness, and different combinations of the cortical and cancellous bones. MATERIAL AND METHODS: The coating materials used were hydroxyapatite (HAP), monticellite (MTC) and titanium nitride (TiN). The coating thickness was varied as 50 µm, 100 µm, 150 µm, and 200 µm. Five different bone combinations were used for the proposed finite element model. An axial compressive load of 150 N was applied. RESULTS: The FEA showed that the HAP coating material had a significant effect on minimizing the induced stress concentration for all 5 bone combinations. However, the MTC coating material had a significant effect only on 2 bone combinations (combination 2 and combination 3). Meanwhile, the TiN coating material induced higher stress values. CONCLUSIONS: Based on finite element analysis (FEA), it was observed that the coating thickness greatly influenced the concentration of the mechanical stress. Indeed, when the coating thickness was relatively high, the stress concentration value significantly decreased.

Design and Development of Tantalum and Strontium Ion Doped Hydroxyapatite Composite Coating on Titanium Substrate: Structural and Human Osteoblast-like Cell Viability Studies.

In order to reduce the loosening of dental implants, surface modification with hydroxyapatite (HA) coating has shown promising results. Therefore, in this present study, the sol-gel technique has been employed to form a tantalum and strontium ion-doped hybrid HA layer coating onto the titanium (Ti)-alloy substrate. In this study, the surface modification was completed by using 3% tantalum pent oxide (Ta2O5), 3% strontium (Sr), and a combination of 1.5% Ta2O5 and 1.5% Sr as additives, along with HA gel by spin coating technique. These additives played a prominent role in producing a porous structure layer coating and further cell growth. The MG63 cell culture assay results indicated that due to the incorporation of strontium ions along with tantalum embedded in HA, cell proliferation increased significantly after a 48 h study. Therefore, the present results, including microstructure, crystal structure, binding energy, and cell proliferation, showed that the additives 1.5% Ta2O5 and 1.5% Sr embedded in HA on the Ti-substrate had an optimized porous coating structure, which will enhance bone in-growth in surface-modified Ti-implants. This material had a proper porous morphology with a roughness profile, which may be suitable for tissue in-growth between a surface-modified textured implant and bone interface and could be applicable for dental implants.

Effect of polyethylene glycol on surface coating of Ta2O5 onto titanium substrate in sol-gel technique.

PURPOSE: Recently, titanium (Ti) and its alloys have been widely used in dental and surgical implants in the last few decades. However, there is a loosening effect over a long period usage. Therefore, the present study aimed to increase life of an implant by its surface modification. METHODS: In present study, sol-gel process has been applied to create tantalum pentoxide (Ta2O5) layer coating on Ti-substrate. In this technique, polyethylene glycol (PEG) plays an important role to form uniform porous coating, which can have potential application in formation of strong bonding to the natural bone. RESULTS: Microstructural, elemental, structural and binding energy results showed that the material with 100% PEG-enhanced sol-gel Ta2O5 with spin coating onto Ti substrate followed by an optimized sintering temperature (500 °C) has better porous structure than that of 5% PEG-enhanced sol-gel Ta2O5 coating, and would be suitable for tissue in-growth properties. CONCLUSIONS: Therefore, it was concluded that the present spin coated 100% PEG-enhanced Ta2O5 coating onto Ti, having the most suitable morphology with enhanced roughness, could be noteworthy for potential tissue in-growth and it could provide desired bonding at the interface of Ti-implant coating and host tissues in biomedical applications.

Mechanical response of different types of surface texture for medical application using finite element study.

Titanium implants are commonly used in dental and other joint replacements and its several modifications have been taken place to improve the adhesion between bone and implant. Different chemical and physical modifications are generally applied to the titanium surface for improving interlocking between bone and implant materials. The present work has been investigated the shear strength stiffness and stress concentration between Representative Volume Element (RVE) model and coating material while the surface of the RVE model modified with different types of surface textures. The surface topology parameters resulted a significant increase in shear strength by 55% and 45% for straight texture and U-shape texture, respectively compared with plain surface. The stiffness reduced significantly by 18% for U-shape and but to 36% only for X-shape, when compared with plain surface. The stress concentration factor in biaxial case both dome shape and X-shape has 45%and 25% in U-shape lower than that of the plain surface. Therefore, this investigation predicted the interfacial shear strength properties generated for different surface topologies to determine the bonding behavior of the implant materials.

Design of dental implant using design of experiment and topology optimization: A finite element analysis study.

Ever since the introduction of topology optimization into the industrial and manufacturing fields, it has been a top priority to maximize the performance of any system by optimizing its geometrical parameters to save material while keeping its functionality unaltered. The purpose of this study is to design a dental implant macro-geometry by removing expendable material using topology optimization and to evaluate its biomechanical function. Three-dimensional finite element models were created of an implant embedded in cortical and cancellous bone. Parameters like the length and diameter of the implant and the bone quality (±20% variation in Young's modulus, Poisson's ratio and density for both cortical and cancellous bone) were varied to evaluate their effect on the principal stresses induced on the peri-implant bone tissues and the micromotion of the implant at 150 N applied load. Design optimization is used to select one suitable implant for each material property combination with optimum parameters that experiences the least von Mises stress and axial deformation, out of twenty implants with different length and diameter for each material property combination. Topology optimization was then used on the selected implants to remove the redundant material. The biomechanical functions of the implants with optimized parameter and volume were then evaluated. The finite element analyses estimated that a reduction of 32% to 45% in the implant volume is possible with the implant still retaining all of its functionality.

Human Skin Expansion Using Circular Implants: A Finite Element Study.

The aim of using circular implants is to produce additional skin in healthy parts of the body, so that new skin that is produced may be used to aid in healing injured areas that occur with plastic surgery. This study shows the amount of additional skin that is produced over time from implants, corresponding to the amount of liquid that is inside the implant membrane. The authors perform the study first on implants alone and then we place implants under the skin. Results of the first step are in agreement with previously conducted research. Second-step results are the first of their kind, because to the best of our knowledge, no similar studies have been conducted, either experimentally or numerically. Our study is motivated by wavering and inconsistent results that are obtained during real-time surgical procedures.

Stress distribution of overdenture using odd number implants - A Finite Element Study.

The objective of this study is to look at stress patterns actuated by locator connections when used to hold mandibular overdentures retained by odd number implants. Two 3D models were prepared to simulate mandibular Implant overdentures retained by three and five Implants. The geometric solid models were modelled in solid modelling software, the models were then assembled and analysed. Three different vertical loads 50N, 100N and 150N were applied on the overdenture. Stresses were assessed at the areas of implant and connection parts, Mucosa hidden overdentures, and cortical and cancellous bone adjoining the implants. The results of this examination demonstrated that the Von Mises stresses produced by applying vertical load differed by the number of Implants used to retain the overdenture. It has been observed that maximum von misses stress induced in the implant complex and the stress induced in the mucosa layer was very low. The adaptability of the overdenture material assumed a noteworthy job in circulating the load stress and twisting of all basic structure. Stress induced in overdenture is higher in three-implant when compared to five-implant retained overdenture. The stresses induced in overdenture in two models were investigated under different loading conditions, five different combinations of the bone quality and it was found that in all the cases the maximum stress has been concentrated in the implant complex, and stress induced in overdenture is low in the case of five implant retained overdenture.

Influences of Stresses on Dental Implant Threads Using Finite-Element Analysis.

The objective of this finite-element analysis (FEA) study is to check the effect of stress on different types of threaded implants. To perform the FEA study of 81 models, the geometry of cancellous bone is imported and corresponding materials are set using FEA software. A common biting force is applied on the implant. After applying the load, each model is compared on the basis of equivalent von Mises stress. From the analysis, we observe that a trapezoidal type of thread profile is most suitable for dental implants.