Liudmila A. Denisova

A study of the adhesion between dental cement and dentin using a nondestructive acoustic microscopy approach.

OBJECTIVES The goal of the present study was to investigate the potential for acoustic microscopy techniques to characterize the cement-dentin interface in restored teeth. METHODS Special flat-parallel specimens and whole extracted teeth with restorations were scanned using a high-frequency (50 MHz) focused ultrasonic transducer. Visual acoustic images (B- and C-scans) of the cement-dentin interface were obtained nondestructively, analyzed and compared with optical images taken after the samples were cut along the scanning axis. The shear bonding strength of a subsection of specimens was tested in a Lloyd material testing machine. RESULTS An essential distinction between the acoustical properties associated with good and failed bonding has been shown. In the case of failed adhesion, the ultrasound signal reflection from the cement-dentin interface is up to four to seven times higher in magnitude than in the case of good bonding. The comparison of the ultrasound imaging data with the data obtained using an optical microscope revealed a strong correspondence with the acoustical and optical results with respect to the presence, position and dimensions of the defects. The specimens showing higher ultrasound reflection from cement/dentin interface have also shown lower shear bonding strength. SIGNIFICANCE The results demonstrate that acoustic scanning with a high-frequency focused ultrasonic probe is a valuable method for nondestructive morpho-mechanical analysis of cement/dentin interface for either experimental models or whole restored teeth. An appropriately expanded approach can be widely used for the pre-clinical evaluation of dental materials. Further, this method may prove beneficial in the design of new diagnostic ultrasound devices and techniques for use within clinical dentistry.

Investigation of Human Nail Microstructure with Ultrasound

Investigation of a human fingernail and the extraction of the data on its microstructure and elastic properties is important in three main aspects. First of all, various diseases of the nail can be differentiated more precisely; second of all, it is possible to non-invasively track during time the effects of a cosmetic product upon the nail; third of all, because various processes in the organism have a strong influence upon the nail plate growth, the monitoring of the nail morphology and its mechanical properties may be used as additional information for the diagnosis of a number of medical disorders, such as systemic sclerosis, psoriasis, chronic hand eczema, anemia etc. The aim of the present study was to carry out a detailed ultrasound investigation in the high-frequency range (25–50 MHz) of a human nail including micro-anatomical structure imaging and ultrasound velocity evaluation, using B-scans obtained with a scanning acoustic microscope. On the images, exact topology of the nail, nail matrix and the underlying bone have been revealed. Additionally, a certain type of inclined internal layering along the nails of some individuals has been found, which was not reported in previous ultrasonic studies of the nail.

Ultrasonic Characterization of the Biological Objects of Spherical or Cylindrical Shape Using an Acoustic Microscope

The ability of an acoustic microscope in the investigation of biological objects with irregular surface, layered structure, different physical and acoustical properties has been estimated. Acoustic images and the results of tissue layers thickness measurements have been analyzed with 3 objects: extracted human tooth, cats’ knee joint in vitro and human nail in vivo. It has been demonstrated, that unlike metal or polymeric samples the biological objects of a ball or cylindrical shape due to the fine surface irregularities can produce acoustic images of their internal structures, which are in a good correspondence with the real microanatomical parameters. Morphological resemblance of the biological objects shape in acoustical and optical images provides precise measuring of separate tissue layers in a noninvasive mode that can not be performed with any other method

Fundamental Potential for Acoustic Microscopy Evaluation of Dental Tissues

Comprehensive analysis of the present-day acoustic microscopy experimental approaches from the standpoint of their potential application in dental research and diagnostics has been performed. Whole extracted human teeth and specially prepared dental tissue samples have been investigated. The results of the study demonstrate that there are several experimental techniques that can be used for precise quantitative evaluation of the tissues local mechanical properties in flat-parallel teeth slices, for the pathomorphological investigation of the tissues strength spatial distribution in flat cuts. In the whole tooth, the acoustic microscopy techniques allow us to precisely measure the enamel and dentine layers thickness, the distance between the external surface and pulp, to reveal hidden caries and restoration disbonding. These opportunities form a real ground for the further design of the special acousto-microscopical methods and new equipment for the clinical diagnostics

A STUDY OF THE POTENTIAL TO DETECT CARIES LESIONS AT THE WHITE-SPOT STAGE USING V(Z) TECHNIQUE

Current wide-spread methods of non-destructive methods of caries diagnostics, such as X-ray techniques, do not provide the possibility to efficiently detect enamel caries lesions at the beginning (“white-spot”) stage, when the tooth tissue is only slightly altered and no loss of the tissue occurs. Therefore, it is of paramount importance to develop new, more sensitive methods of caries diagnostics. In this paper, certain aspects of the ultrasonic approach to the problem are discussed - in particular, detection of the enamel’s surface caries at the white-spot stage with a focused ultrasonic sensor positioned in front of the caries lesion (without cross-sectioning the tooth). Theoretical model using V(z) approach for layered media was applied to perform computer simulations resulting in V(z) curves for the different parameters of carious tissue and the degree of degradation. The curves were analyzed and it was shown that, comparing to a short-pulse/echo technique, V(z) approach provides much better distinction between sound and carious enamel and even makes possible to evaluate the degree of demineralization.

Acoustic Microscopy Methods in a Morphological Study of the Articular Cartilage and Subchondral Bone

In the recent years a number of papers have been dedicated to the application of acoustic microscopy to the experimental investigation of articular cartilage. Most of them have been carried out with early stages of the experimentally induced arthritis in young animals [Senzig et al.,. 1992; Cherin et al., 1998, Pellaumail et al., 1998; Toyras, Rieppo, 1999; Saied et al., 1994, 1995, 1997, 2000; and others]. It is known, that even in normal natural conditions, aged mammals develop cartilage involution and degradation, subchondral bone destruction and other syndromes of the arthritis. The aim of the present investigation is to study acoustical properties of mammalian articular cartilage in young and aged animals and clarify what histological elements contribute to the formation of cartilage acoustic properties in normal and pathological condition.

Application of an Acoustic Microscope for the Investigation of Embryonic Development in Quails Coturnix Coturnix

The aim of the present study was to investigate potentials of acoustic microscopy in the evaluation of embryonic development of the quail. The study has been conducted with the quail embryos in the period from the 7th to 11th day of incubation

Morpho-mechanical analysis of the dentin-cement interface strength using a scanning acoustic microscope

An acoustic microscope (50 MHz) has been used for the investigation of the cement-dentin interface, using special samples and extracted teeth with restorations. It has been shown, that in the case of the strong contact between cement and dentin focused ultrasonic beam passes through cement-dentin interface into the tooth tissue and we can register no distinct ultrasound reflection at the interface. When there are some pores, cavities, voids or improper contact between cement and dentin caused by shrinkage or by secondary caries, we can register a strong reflection in the site of the interface defect. The results of nondestructive evaluation in the acoustic microscope were compared with the results of morphological analysis of the same samples in optical microscope after the sectioning the same tooth by the line of scanning. A good correlation between data obtained in acoustic and light microscopy confirms that focused ultrasound can be useful in nondestructive intraoral evaluation of the quality of restorations as well as in the secondary caries diagnostics.

Evaluation of Rubber-PVC Blends Structure and Properties Using Scanning Acoustic Microscope

Ozone-resistant materials can be obtained by mixing butadiene-nitrile rubber (BNR) with polymers or elastomers. It has been established that depending on the rubber polar butadiene-nitrile groups content and BNR/PVC ratio, the blends can display the properties of either homo- or heterogeneous systems. In high-compatible blends the PVC forms a developed spatial framework that provides the highest ozone-resistance. Therefore, the investigation of the BNR-PVC blends morphology concerning various BNR/PVC compatibility and BNR/PVC ratios is of considerable importance both for fundamental polymer research and applied polymer material characterization with regard to a deeper understanding of the mechanisms of the ozone-protecting properties formation.