Why Do X-Rays Still Give Us Amazing Insights into Dental Materials Research

Abstract: Due to the short wavelength of x-rays, they can potentially resolve microstructures of materials including dental materials and teeth. The construction of the X-ray tomography machine (CT scanner) with the help of mathematics including radon transform, converted the 2D data obtained from multiple X-ray projections into 3D data, created a revolution in the field of medical diagnosis. Changes such as the source and detector being stationary (to reduce noises), the use of smaller X-ray focus and higher optical magnification, make it possible to obtain images with a much higher resolution in the construction micro-CT scanners. However, the higher radiation dose, the limitation of the sample dimensions and … have made the use of this attractive technique limited to laboratory studies. The huge volume of obtained data, thanks to the advanced algorithms that have made it possible to perform very complex reconstructions with today's modern computers, provides researchers with accurate 3D volumetric images. Due to the non-destructive nature of this technique, there is a growing range of applications associated with it. From archeological studies (study of rare and valuable objects) and inspection of parts whose safe operation is critical (e.g., aircraft engine turbine blade) to volume fraction or particle distribution analysis of different phases of composites. In the field of medicine, some studies have focused on the histological validation of findings obtained from micro-CT or cooperation of micro-CT with histological analyzes to increase the accuracy of histological sections results. Studying the internal structure of teeth and dental materials, without the need for preparation or slicing, has made micro-CT scanning to be as a standard tool in various dental researches (e.g., in endodontics, restorative dentistry…). Also, in recent years, a type of limited angle tomography known as sIOT® (stationary Intraoral Tomosynthesis) is designed for intraoral imaging of patients. It has attracted the attention of researchers due to its low x-ray dose and high resolution. The emerging technology of photon counting detectors (PCD) in combination with the capabilities of spectral CT scanners (They can reconstruct various images e.g., mapping of known attenuation characteristics) has attracted attention in the medical field due to the potential of displaying finer details of tissues with less radiation. Finally, considering the promising results of the use of artificial intelligence during the Covid-19 pandemic, the increasing use of its capabilities in the future, both for image reconstruction and image interpretation, is highly anticipated.