Finite element analysis
Failure of implants is a relatively common problem, and there is a need of analysis of the abutments. FEA is becoming a common method in implant dentistry that allows engineers/scientists to study jawbone and implant properties, and bone-implant interface as well as to understand how to improve implant design in order to function within physiological acceptable limits. FEA consists on a computerized three-dimensional model that has been extensively used to predict the characteristics of stress distribution in bone surrounding implants, which are influenced by both the implant dimensions and the biomechanical bond formed between the bone and the implant.
Computer-aided design and computer-aided manufacturing technology
Implants and abutment fabrication has and continues to undergo significant metamorphosis, and since nowadays, complicated shape implants and abutments are used, CAD/CAM techniques are being implemented. The advantages of the technique are accuracy and less time required for manufacturing the parts.
Using a metal melt which is cast into a micro structured mold, the micro casting technique enables the manufacture of small structures and complex geometrical details in the micrometer range. The advantages are relatively low cost and scalability from single items to large numbers of identical items.
Sometimes, it is important to study the effect of the phase composition of the surface oxide layer. However, since the oxide layer is very thin and many of the techniques are used for flat surfaces, analyzing complex geometry implants with increased surface roughness becomes a difficult task. Microscopy techniques such as high resolution transmission electron microscopy allows accurate measurements of the lattice parameters as well as analysis of the microstructure and grain sizes of the surface layer. In addition, electron diffraction can be used for phase identification on nanoscale features. Electron backscattering diffraction detection using scanning electron microscopy allows electron diffraction analysis of surface films without extensive sample preparation.
Nanotechnology approaches require novel ways of manipulating matter in the atomic scale. Currently, extensive research on techniques to produce nanotechnology-based implants are being investigated. Nanotechnology-based trends for dental implants consist on surface roughness modification at the nanoscale level to promote protein adsorption and cell adhesion, biomimetic calcium phosphate coatings, and the incorporation of growth factors for accelerating the bone healing process.
Most attempts to get nanoroughness have used processing methods like lithography and surface laser-pitting, but only a few studies have reported modifications to the roughness as well as the chemistry at the nanometer scale in a reproducible manner. Other technique is the deposition of nanoparticles like biomimetic calcium phosphate, alumina, titania, zirconia, and other materials to coat Ti surfaces. The surface of Ti dental implants can also be coated with bone-stimulating agents such as growth factors (transforming growth factor-β, bone morphogenetic proteins [BMPs], platelet-derived growth factors and insulin-like growth factor [IGF]-1 and 2) and antiresorptive drugs (biophosphonates) in order to enhance the bone healing process locally. In one study, a Ti machine smooth implant was compared to a Type-1 collagen coated Ti implant and a Type-1 collagen-BMP-2 coated implant. The results of this animal study showed greatest peri-implant bone formation within the grooves of the endosseous screw for the collagen-BMP implant when compared to the collagen-coated implant. In this example, both collagen and BMP-2 serve as bioactive molecules. In addition to adding biomolecules which promote bone growth, molecules such as biophosphonates which prevent bone resorption may also be added.
In terms of surface modification at the grain boundaries level, one approach involves the physical method of compaction of nanoparticles of TiO2 versus the compaction of micron-level particles to yield surfaces with nanoscale grain boundaries. Other interesting approach is the process of molecular self-assembled monolayers which are formed by the spontaneous positioning of molecules on the surface, exposing only the end-chain group(s) at the interface which can have osteoinductive or cell adhesive molecules such as RGD domains.
Functionally graded materials
As described by Mehrali et al. in 2013, the suitable design of porous bone with a porosity gradient from a dense, stiff external structure (the cortical bone) to a porous internal one (the cancellous bone), and with an adequate degree of interconnectivity exhibits that functional gradation is applied by biological adaptation. Therefore, functionally graded materials (FGMs) are gaining attention in dental implant applications. FGM is a heterogeneous composite material including a number of constituents that exhibit a compositional gradient from one surface of the material to the other subsequently, resulting in a material with continuously varying properties in the thickness direction. This design creates an optimized mechanical behavior and improves biocompatibility and osseointegration.