Digital image correlation in dental materials and related research: A review

OBJECTIVE: Digital image correlation (DIC) is a non-contact image processing technique for full-field strain measurement. Although DIC has been widely used in engineering and biomechanical fields, it is in the spotlight only recently in dental materials. Therefore, the purpose of this review paper is introducing the working principle of the DIC technique with some modifications and providing further potential applications in various dental materials and related fields. METHODS: The accuracy of the algorithm depending on the environmental characteristics of the DIC technique, as well as the advantages and disadvantages of strain measurement using optical measurements, have been elaborated in dental materials and related fields. Applications to those researches have been classified into the following categories: shrinkage behavior of light-cured resin composite, resin-tooth interface, mechanical properties of tooth structure, crack extension and elastic properties of dental materials, and deformation of dental restoration and prosthesis. This classification and discussion were performed using literature survey and review based on numerous papers in the international journals published over the past 20 years. The future directions for predicting the precise deformation of dental materials under various environments, as well as limitations of the DIC technique, was presented in this review. RESULTS: The DIC technique was demonstrated as a more effective tool to measure full-field polymerization shrinkage of composite resin, even in a simulated clinical condition over the existing methods. Moreover, the DIC combined with other technologies can be useful to evaluate the mechanical behavior of material-tooth interface, dentine structure and restorative and prosthetic materials with high accuracy. Three-dimensional DIC using two cameras extended the measurement range in-plane to out-of-plane, enabling measure of the strain directly on the surface of dental restorations or prosthesis. SIGNIFICANCE: DIC technique is a potential tool for measuring and predicting the full-field deformation/strain of dental materials and actual prostheses in diverse clinical conditions. The versatility of DIC can replace the existing complex sensor devices in those studies

Advances in test and measurement of the interface adhesion and bond strengths in coating-substrate systems, emphasising blister and bulk techniques

In this paper, recent advances in the minimum-destructive testing of the adhesion of coating-substrate systems are reviewed, focusing on key techniques such as micro- and nano-scale levels of indentation, scratching, laser-induced wave shock, as well as the blister and buckle approach. Along with adhesion failure tests, the latest and most extensive applications of the adhesion test methods in nano-, micro- and bulk-coating technology and the associated techniques to determine the minimum damage defects left on the coatings are discussed and their use reviewed

Optical Coherence Tomography guided Laser-Cochleostomy

Despite the high precision of laser, it remains challenging to control the laser-bone ablation without injuring the underlying critical structures. Providing an axial resolution on micrometre scale, OCT is a promising candidate for imaging microstructures beneath the bone surface and monitoring the ablation process. In this work, a bridge connecting these two technologies is established. A closed-loop control of laser-bone ablation under the monitoring with OCT has been successfully realised

【研究分野別】シーズ集 [英語版]

[英語版

Overview of biofluids and flow sensing techniques applied in clinical practice

This review summarizes the current knowledge on biofluids and the main flow sensing techniques applied in healthcare today. Since the very beginning of the history of medicine, one of the most important assets for evaluating various human diseases has been the analysis of the conditions of the biofluids within the human body. Hence, extensive research on sensors intended to evaluate the flow of many of these fluids in different tissues and organs has been published and, indeed, continues to be published very frequently. The purpose of this review is to provide researchers interested in venturing into biofluid flow sensing with a concise description of the physiological characteristics of the most important body fluids that are likely to be altered by diverse medical conditions. Similarly, a reported compilation of well-established sensors and techniques currently applied in healthcare regarding flow sensing is aimed at serving as a starting point for understanding the theoretical principles involved in the existing methodologies, allowing researchers to determine the most suitable approach to adopt according to their own objectives in this broad field.This research was supported by the Consejo Nacional de Ciencia y Tecnología (CONACYT) of México through Ph.D. grant 472102 and by the Ministerio de Economía y Competitividad through grant FIS2017-89850R.Peer ReviewedPostprint (author's final draft

NASA Tech Briefs, September 1990

Topics covered include: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences

Surgical probe and implant development for nucleus pulposus replacements

Intervertebral disc degeneration is a major reason why we experience low back pain. Intervertebral discs are located in-between the vertebrae of the spine. They act, among other, as shock absorbers by distributing the mechanical load applied to the spine while giving it its range of motion. An intervertebral disc is composed of a center - a soft core, called nucleus pulposus which is surrounded by a strong ring called the annulus fibrosus. By disc degeneration, we mean a physical deterioration of either the nucleus and/or the annulus. It has been posited that low back pain could be alleviated by replacing the degenerated nucleus pulposus by a synthetic implant. However, such nucleus pulposus replacements have been subjected to highly controversial discussions over the last 50 years and their use has not yet resulted in a positive outcome to treat degenerated disc disease. In this thesis, we report on the development of an implant material consisting of poly(ethylene glycol)dimetacrylate - a hydrogel - loaded with nano-fibrillated cellulose. Photopolymerization was selected as a polymerization method to "harden" the implant in situ. Thus, the implant can be injected in a liquid state through the annulus fiborsus with a small diameter cannula. Furthermore, an in situ photopolymerization method was developed along with an implanting device which was used to insert the composite hydrogel into an intervertebral disc ex vivo. The volume of a human nucleus pulposus is several 100 cubic millimeters, which is a substantial volume to photopolymerize. In order to ensure a homogeneous photopolymerization of this volume, a Monte Carlo model was developed. The model is able to predict accurately the volume of the photopolymerized implant in tissue cavities. This simulation tool was used to tailor the light scattering properties of the hydrogel by loading it with lipid particles. Thus, spherical implant shapes could be photopolymerized. An implanting device was developed to inject and photopolymerize the liquid implant while monitoring the cross-linking reaction of the implant during photopolymerization using fluorescence spectroscopy in situ and in real-time. Using this device, synthetic nucleus pulposus implants were successfully inserted through a 1 mm incision in the annulus fiborsus of an ex vivo bovine intervertebral disc model and the long-term performance of the proposed nucleus pulposus replacement was evaluated. The changes of the fluorescence signal throughout the photopolymerization reaction could be shown to correlate with the photopolymerization volume. It was thus possible to insert the synthetic implant in a controlled manner into the bovine disc model. The implant was able to significantly re-establish intervertebral disc height after surgery (p < 0.0025) and maintain it over 0.5 million loading cycles (p < 0.025). Disc height is one of the essential parameters to restore and maintain in an intervertebral disc. The excellent results achieved in these ex vivo experiments validated the implantation method and the device. More importantly, they showed that the novel implant material might resist mechanical loads similar to the loads that would be experienced in everyday life. However, longer tests (~ 10 million cycles) are required to determine whether this material would truly resists during a clinical study

Image-Based Fracture Mechanics with Digital Image Correlation and Digital Volume Correlation

Analysis that requires human judgement can add bias which may, as a result, increase uncertainty. Accurate detection of a crack and segmentation of the crack geometry is beneficial to any fracture experiment. Studies of crack behaviour, such as the effect of closure, residual stress in fatigue or elastic-plastic fracture mechanics, require data on crack opening displacement. Furthermore, the crack path can give critical information of how the crack interacts with the microstructure and stress fields. Digital Image Correlation (DIC) and Digital Volume Correlation (DVC) have been widely accepted and routinely used to measure full-field displacements in many areas of solid mechanics, including fracture mechanics. However, current practise for the extraction of crack parameters from displacement fields usually requires manual methods and are quite onerous, particularly for large amounts of data. This thesis introduces the novel application of Phase Congruency-based Crack Detection (PC-CD) to automatically detect and characterise cracks from displacement fields. Phase congruency is a powerful mathematical tool that highlights a discontinuity more efficiently than gradient based methods. Phase congruency’s invariance to the magnitude of the discontinuity and its state-of-the-art de-noising method, make it ideal for the application to crack tip displacement fields. PC-CD’s accuracy is quantified and benchmarked using both theoretical and virtual displacement fields. The accuracy of PC-CD is evaluated and compared with conventional, manual computation methods such as Heaviside function fitting and gradient based methods. It is demonstrated how PC-CD can be coupled with a new method that is based on the conjoint use of displacement fields and finite element analysis to extract the strain energy release rate of cracks automatically. The PC-CD method is extended to volume displacement fields (VPC-CD) and semi-autonomously extracts crack surface, crack front and opening displacement through the thickness. As a proof of concept, PC-CD and VPC-CD are applied to a range of fracture experiments varying in material and fracture behaviour: two ductile and one quasi-brittle for surface displacement measurements; and two quasi-brittle and one ductile for volume measurements. Using the novel PC-CD and VPC-CD analyses, the crack geometry is obtained fully automatically and without any user judgement or intervention. The geometrical parameters extracted by PC-CD and VPC-CD are validated experimentally through other tools such as: optical microscope measurements, high resolution fractography and visual inspection

Microelectromechanical Systems and Devices

The advances of microelectromechanical systems (MEMS) and devices have been instrumental in the demonstration of new devices and applications, and even in the creation of new fields of research and development: bioMEMS, actuators, microfluidic devices, RF and optical MEMS. Experience indicates a need for MEMS book covering these materials as well as the most important process steps in bulk micro-machining and modeling. We are very pleased to present this book that contains 18 chapters, written by the experts in the field of MEMS. These chapters are groups into four broad sections of BioMEMS Devices, MEMS characterization and micromachining, RF and Optical MEMS, and MEMS based Actuators. The book starts with the emerging field of bioMEMS, including MEMS coil for retinal prostheses, DNA extraction by micro/bio-fluidics devices and acoustic biosensors. MEMS characterization, micromachining, macromodels, RF and Optical MEMS switches are discussed in next sections. The book concludes with the emphasis on MEMS based actuators