Evaluating the effect of functionally graded materials on bone remodeling around dental implants

OBJECTIVES

This study evaluates the potential for osseointegration and remodeling of customized dental implants made from Titanium-Hydroxyapatite Functionally Graded Material (Ti-HAP FGM) with optimized geometry, using the finite element method (FEM).

METHODS

The study utilized CT scan images to model and assemble various geometrical designs of dental implants in a mandibular slice. The mechanical properties of Ti-HAP FGMs were computed by varying volume fractions (VF) of hydroxyapatite (0-20%), and a bone remodeling algorithm was used to evaluate the biomechanical characteristics of the ultimate bone configuration in the peri-implant tissue.

RESULTS

The findings of the FEA reveal that osseointegration improves with changes in the density and mechanical properties of the bone surrounding Ti-HAP implants, which are influenced by the varying VF of hydroxyapatite in the FGM.

SIGNIFICANCE

Increasing the hydroxyapatite fraction improves osseointegration, and appropriate length and diameter selection of Ti-HAP dental implants contribute to their stability and longevity.

Expression of VEGF and BMP-2 in Osteoblast cells exposed to a combination of polymethylmethacrylate (PMMA) and hydroxyapatite (HAp)

Objectives

Polymethylmethacrylate (PMMA) has been widely used, but it has several fallback properties in its interaction with bone tissue, so the addition of hydroxyapatite (HAp) material aims to improve the biocompatibility, regeneration process, and osteointegration of bone implants. The HAp material can be sourced from bovine bone and processed through Good Manufacturing Practice from Tissue Bank (HApGMP), and from limestone (CaCO3) processed by Balai Besar Keramik (HApBBK).This study was to observe the expression of vascular endothelial growth factor (VEGF) and Bone morphogenetic protein-2 (BMP2) in cultured osteoblasts exposed to PMMA-HApGMP and PMMA-HApBBK as implant candidate materials.

Methods

Sample of PMMA and HAp materials with a mixture of PMMA and HApBBK in the first group and a mixture of PMMA and HApGMP in the second group. Twenty-four fetal rat calvarie osteoblast cell cultures were randomly divided into 6 groups: 7- and 14-day control group, 7 and 14 days PMMA-HApGMP group, 7 and 14 days PMMA-HApBBK group. The expression of VEGF and BMP-2 was seen by immunocytochemical examination.

Results

The one-way ANOVA with a significance value of 0.000 (p < 0.05). BMP-2 and VEGF expression was increased in the 7- and 14-days groups after exposure to PMMA-HApGMP and PMMA-HApBBK.

Conclusion

The application of PMMA-HApGMP and PMMA-HApBBK showed an increase in the expression of VEGF and BMP-2 in osteoblast cell cultures which indicates a potential increase in the accelerated angiogenesis and osteogenesis in the bone regeneration process of bone implants.

Development of Ultrafine–Grained and Nanostructured Bioinert Alloys Based on Titanium, Zirconium and Niobium and Their Microstructure, Mechanical and Biological Properties

For this paper, studies of the microstructure as well as the mechanical and biological properties of bioinert titanium, zirconium, and niobium alloys in their nanostructured (NS) and ultrafine-grained (UFG) states have been completed. The NS and UFG states were formed by a combined two-step method of severe plastic deformation (SPD), first with multidirectional forging (MDF) or pressing into a symmetrical channel (PSC) at a given temperature regime, and then subsequent multi-pass groove rolling (MPGR) at room temperature, with pre-recrystallization annealing. Annealing increased the plasticity of the alloys in the NS and UFG states without changing the grain size. The UFG structure, with an average size of structural elements of no more than 0.3 μm, was formed as a result of applying two-step SPD and annealing. This structure presented significant improvement in the mechanical characteristics of the alloys, in comparison with the alloys in the coarse-grained (CG) or small-grained (SG) states. At the same time, although the formation of the UFG structure leads to a significant increase in the yield strength and tensile strength of the alloys, their elastic modulus did not change. In terms of biocompatibility, the cultivation of MG-63 osteosarcoma cells on the polished and sandblasted substrates demonstrated high cell viability after 10 days and good cell adhesion to the surface.

Enhancing the Mechanical Behaviour and Antibacterial Activity of Bioepoxy Using Hybrid Nanoparticles for Dental Applications

The appropriate capability of handling several forces exerted inside the mouth, and preventing the adhesion and proliferation of oral microorganisms are among the most vital factors for achieving effective alternative dental materials to the damaged native. Nevertheless, lack of mechanical and antimicrobial properties of dental resins hinders their use in most clinical applications in dentistry. In the present study, the main aim was to provide bioepoxy composite biomaterials that could meet the required mechanical and antibacterial properties for dental related fields. Herein, highly biocompatible epoxy and hybrid reinforcing materials were utilised to produce a composite material, which could have features resembling those of original dental parts. Various weight fractions of nanosilver/nano-alumina particles at 1, 2, and 3 wt% were incorporated into the bioepoxy for improving the mechanical and antibacterial characteristics of the biocompatible epoxy resin. Three-point bending and Izod impact tests were performed to evaluate the flexure and impact strengths of the obtained nanocomposites. The morphology of pristine bioepoxy and nanoparticle reinforced bioepoxy composites was characterized by scanning electron microscopy. The influence of these fillers on the bioepoxy resin antibacterial sensitivity was assessed using the agar diffusion technique. Nanofiller contents have been revealed to have a remarkable role to play in tuning the mechanical properties of the nanocomposites; the flexure strength and modulus were higher when the total ratio of hybrid reinforcement was 2 wt%. In contrast, the addition of higher percentage of hybrid nanoparticles could cause deterioration in the flexure characteristics of nanocomposites, yet they were better than those of pristine epoxy. Regarding the impact strength, the enhancement in this property was only observed for the composite containing 1 wt% of AgNps-Al₂O₃; the impact strength was dropped gradually beyond this ratio. The antibacterial effectiveness of the nanocomposites was demonstrated to positively depend on the increase in AgNps mass fraction. Among all evaluated unmodified and modified bioepoxy, the nanocomposite containing 2.5 wt% of AgNps had the higher antibacterial activity against Escherichia coli and Staphylococcus aureus. Based on the attainable outcomes, the prepared composites, particularly at moderate levels of Al₂O₃-AgNps, could provide biocomposites having the potential to be utilised in several biomedical fields, particularly in dental technology.

Bioinstructive Micro-Nanotextured Zirconia Ceramic Interfaces for Guiding and Stimulating an Osteogenic Response In Vitro

Osseous implantology’s material requirements include a lack of potential for inducing allergic disorders and providing both functional and esthetic features for the patient’s benefit. Despite being bioinert, Zirconia ceramics have become a candidate of interest to be used as an alternative to titanium dental and cochlear bone-anchored hearing aid (BAHA) implants, implying the need for endowing the surface with biologically instructive properties by changing basic parameters such as surface texture. Within this context, we propose anisotropic and isotropic patterns (linear microgroove arrays, and superimposed crossline microgroove arrays, respectively) textured in zirconia substrates, as bioinstructive interfaces to guide the cytoskeletal organization of human mesenchymal stem cells (hMSCs). The designed textured micro-nano interfaces with either steep ridges and microgratings or curved edges, and nanoroughened walls obtained by direct femtosecond laser texturing are used to evaluate the hMSC response parameters and osteogenic differentiation to each topography. Our results show parallel micro line anisotropic surfaces are able to guide cell growth only for the steep surfaces, while the curved ones reduce the initial response and show the lowest osteogenic response. An improved osteogenic phenotype of hMSCs is obtained when grown onto isotropic grid/pillar-like patterns, showing an improved cell coverage and Ca/P ratio, with direct implications for BAHA prosthetic development, or other future applications in regenerating bone defects.

Implant Material Sciences

In the past, the only way to replace missing teeth was to have a removable appliance. However, these days, dental implants are commonly being used to replace missing teeth. The dental implants are improving as a result of new technological and scientific advances. Different materials have been used in the past for dental implants such as lead, stainless steel, and gold. Currently, the focus is on using Roxolid, surface-modified titanium implants, and zirconia. These materials have superior esthetic and functional characteristics for dental implants.

DOES PEEK DENTAL IMPLANT HAVE THERMAL ADVANTAGE OVER ZIRCONIA OR TITANIUM IMPLANTS?

Purpose: To evaluate the thermal performance of PEEK dental implant and compare it with its conventional counterparts, i.e., titanium (Ti) and zirconia ([Formula: see text]). Materials and Methods: A three-dimensional finite element model of the dental implant and the surrounding bone was developed to simulate thermal analysis of the implant with three different materials, i.e., Ti, ZrO2 and PEEK for two types of heat load. Zirconia artificial crown was utilized in all three different implant materials. Results: In loading type I, the maximum temperature of the mandible bone at the cervical implant/bone interface was almost the same (37.7∘C) in all models, but the time to reach this temperature was 18[Formula: see text]s for Ti, 30[Formula: see text]s for ZrO2 and 65.7[Formula: see text]s for PEEK implant. The maximum temperature in loading type II was 41.8∘C, 41.6∘C and 41.3∘C, respectively, in ZrO2, Ti and PEEK models. Ti implant showed the fastest rising and recovery time. Conclusions: Under the considered heat loads, the maximum temperatures in the bone were below the bone necrosis temperature in all three cases. In addition the temperature change along the implant body in [Formula: see text] and PEEK implants are smaller than that in Ti. Moreover, PEEK was found to be a thermally viable option for dental implants.

Effect of crystalline phases of titania nanotube arrays on adipose derived stem cell adhesion and proliferation

The aim of this work was to evaluate the cellular response to titanium nanotube arrays with variable crystalline structure. Cytotoxicity, viability and the ability of the titania nanotube arrays to stimulate adhesion and proliferation of adipose derived stem cells (ADSCs) was evaluated. Titania nanotube arrays were fabricated by electrochemical anodization of titanium in diethyleneglycol/hydrofluoric acid electrolyte at 60 V for 6 h, then annealed at 300, 530 and 630 °C for 5 h. The nanotube arrays were characterized using scanning electron microscopy (SEM), contact angle goniometry, x-ray diffraction (XRD) and protein adsorption. ADSCs were cultured on titania nanotube arrays at a density of 1 × 10⁴ cells/ml. The cells were allowed to adhere and to proliferate for 1, 4 and 7 days. Cell viability was characterized by the CellTiter-Blue® Cell Viability Assay; and cell morphology was characterized by SEM. Cell adhesion, proliferation and morphology were characterized using fluorescence microscopy by staining the cells with DAPI and rhodamine/phalloidin. The results from this study showed that the annealing at 300 and 530 °C formed anatase phase, and annealing at 630 °C formed anatase/rutile phase. The results indicated that the modification of the crystalline structure (i.e. anatase/rutile phase) of titania nanotube arrays influenced the ADSC adhesion and proliferation. Future studies are now directed towards evaluating differentiation of this cellular model in osteoblasts.

A review of nanostructured surfaces and materials for dental implants: surface coating, patterning and functionalization for improved performance

The emerging field of nanostructured implants has enormous scope in the areas of medical science and dental implants. Surface nanofeatures provide significant potential solutions to medical problems by the introduction of better biomaterials, improved implant design, and surface engineering techniques such as coating, patterning, functionalization and molecular grafting at the nanoscale. This review is of an interdisciplinary nature, addressing the history and development of dental implants and the emerging area of nanotechnology in dental implants. After a brief introduction to nanotechnology in dental implants and the main classes of dental implants, an overview of different types of nanomaterials (i.e. metals, metal oxides, ceramics, polymers and hydrides) used in dental implant together with their unique properties, the influence of elemental compositions, and surface morphologies and possible applications are presented from a chemical point of view. In the core of this review, the dental implant materials, physical and chemical fabrication techniques and the role of nanotechnology in achieving ideal dental implants have been discussed. Finally, the critical parameters in dental implant design and available data on the current dental implant surfaces that use nanotopography in clinical dentistry have been discussed.

Human mesenchymal stem cell behavior on femtosecond laser-textured Ti-6Al-4V surfaces

AIM

The aim of the present work was to investigate ultrafast laser surface texturing as a surface treatment of Ti-6Al-4V alloy dental and orthopedic implants to improve osteoblastic commitment of human mesenchymal stem cells (hMSCs).

MATERIALS & METHODS

Surface texturing was carried out by direct writing with an Yb:KYW chirped-pulse regenerative amplification laser system with a central wavelength of 1030 nm and a pulse duration of 500 fs. The surface topography and chemical composition were investigated by scanning electron microscopy and x-ray photoelectron spectroscopy, respectively. Three types of surface textures with potential interest to improve implant osseointegration can be produced by this method: laser-induced periodic surface structures (LIPSSs); nanopillars (NPs); and microcolumns covered with LIPSSs, forming a bimodal roughness distribution. The potential of the laser treatment in improving hMSC differentiation was assessed by in vitro study of hMSCs spreading, adhesion, elongation and differentiation using epifluorescence microscopy at different times after cell seeding, after specific stainings and immunostainings.

RESULTS

Cell area and focal adhesion area were lower on the laser-textured surfaces than on a polished reference surface. Obviously, the laser-textured surfaces have an impact on cell shape. Osteoblastic commitment was observed independently of the surface topography after 2 weeks of cell seeding. When the cells were cultured (after 4 weeks of seeding) in osteogenic medium, LIPSS- and NP- textured surfaces enhanced matrix mineralization and bone-like nodule formation as compared with polished and microcolumn-textured surfaces.

CONCLUSION

The present work shows that surface nanotextures consisting of LIPSSs and NPs can, potentially, improve hMSC differentiation into an osteoblastic lineage.

Implant biomaterials: A comprehensive review

Appropriate selection of the implant biomaterial is a key factor for long term success of implants. The biologic environment does not accept completely any material so to optimize biologic performance, implants should be selected to reduce the negative biologic response while maintaining adequate function. Every clinician should always gain a thorough knowledge about the different biomaterials used for the dental implants. This article makes an effort to summarize various dental bio-materials which were used in the past and as well as the latest material used now.