Automated digital odontometric study of manual and computer-aided methods of tooth crown modelling in dentistry

One of the most widely used methods of prosthetic treatment in dentistry is restoration of damaged teeth by artificially fabricated crowns, which, regardless of technological variations, always pass through modelling stage. The main two methods of restoration modelling are traditionally used manual and becoming more advanced and widespread computer-aided, or digital. A similar situation is observed in odontometry – tooth measurements – where manual and digital approaches meet, fuse and new methods, as automated digital odontometry, appear. In this study the measurement method is applied to crowns modelled by different dental technicians on trial basis for teeth, prepared on stone cast model of complete dental arches. The same plaster models, before and after tooth preparations, as well as after modelling tooth crowns manually, were scanned for comparative and modelling (this time using computer-aided techniques) reasons. The obtained 3D images were used for measurements by digital automated odontometry to estimate differences of modelled crowns with initial shape of intact, subjected to experimental preparation and restoration, tooth. Comparisons were made within each, manual and digital, crown modelling groups as well; thus comparisons of proposed on default by professional dental software crown shapes were made, and in line with it the influence of different technicians adjustments on modelling precision was estimated. At the same time the measurement method was tested as well by determining the most characteristic differentiating odontometric parameters for the study, which is held largely due to and on the basis of photogrammetric techniques. © Authors 2019. CC BY 4.0 License

New approach to dental morphometric research based on 3D imaging techniques

Recent progress in imaging and image processing techniques has provided for improvements in odontological research in a variety of aspects. Thus, the presented method has been developed precisely in order to assess metrically 3D reconstructions of teeth. Rapidly and accurately obtained data of a wide range and appropriate density are sufficient enough for morphometric studies rather than tooth size assessments which are inherent to conventional techniques. The main contributions providing for holistic and objective morphometric analysis of teeth are the following: (1) interpretation of basic dental morphological features; (2) automated of orientational coordinate system setup based on tooth surface analysis; (3) new tooth morphometric parameters which could not be obtained through application of conventional odontometric techniques; (4) methodological novelty for automated odontomorphometric analysis pipeline. Application of tomographic imaging, which has been used for obtaining 3D models, expands the proposed method potential further through providing detailed and comprehensive reconstructions of teeth. The current study was conducted on unique material from the archaeological site of Sunghir related to the Upper Palaeolithic period. Metric assessments of external and internal morphological layers of teeth were performed in common orientation and sectioning. The proposed technique allowed more profound analysis of Sunghirian teeth which date back to the times of modern human morphology formation. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Enamel thickness measurements on 3d reconstructions of teeth for paleontological applications

Findings of teeth play a significant role in palaeoanthropology. And excavations in Vietnamese LangTrank cave serve as a vivid example and evidence of this statement. Teeth constitute the majority of the paleontological material dated to Middle and Late Pleistocene periods. This is to some extent the result of dietary preferences of porcupines as these rodents include in their diets bones of animals however avoiding extremely hard coronal parts of teeth. Under such circumstances teeth serve a key to taxonomic differentiation of findings as genetic analysis is often hindered by a lack of preserved DNA at such dating of material. However morphological analysis is difficult in some cases either, as teeth can be worn out or broken. In that case enamel thickness measurements become an effective study instrument as this feature varies between species. In the current study two teeth with clear signs of expressed dental wear, presumably upper fourth premolars of wild boar required more detailed analysis. Thus they were reconstructed after micro-computed tomography scanning similarly to other upper teeth picked for comparison: orang-utan tooth from the same location and two teeth from the Upper Palaeolithic Sunghir (they have been scanned earlier). This study required new approaches to image processing and measurement methodology due to marked attrition of the samples. The workflow and results of enamel thickness assessments which facilitated taxonomical differentiation of the findings are presented in the article. © Authors 2021. CC BY 4.0 License

Orientation VS. orientation: Image processing for studies of dental morphology

Many odontological studies held through application of traditional and modern techniques, especially when related to measurements and morphology, very much depend on methodological aspects referred to orientation of teeth. And this is particularly relevant to new imaging and 3d reconstruction implemented in dental research and practice in a wide range of disciplines from anthropology to dentistry. The current paper deals with studies of palaeoanthropological findings dating back to the Upper Palaeolithic period in Central Russia - well-known archaeological site of Sunghir. Micro-computed tomography has been used for digital reconstructions of teeth - molars and premolars representing well-preserved dental morphology of an adolescent individual. This is due to new opportunities introduced by 3d reconstruction techniques in general and high-resolution x-ray imaging in particular that this study has become relevant. Thus digital techniques do not only provide for operating convenience but, which is even more important, allow application of image processing algorithms. In the suggested methodology these are automated, based on morphological interpretations and serve for orientation of studied teeth for further measurements. At the same time micro-computed tomographic imaging allows accurate reconstruction of other morphologically important structures which are used for an alternative orientation algorithm. Comparisons of dental measurements' results obtained through automated digital odontometry (aDo) after both orientations applied are presented in the current paper. © 2021 International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives. All rights reserved

Shade and texture mapping on teeth for palaeoanthropological reconstructions

Over the past few years closer cooperation can be observed in various aspects of digital techniques in such disciplines as dentistry and anthropology. And in most cases that consists in imaging and image processing which results in obtaining 3D reconstructions. And indeed, they can significantly improve research and practice. Thus, depending on imaging technique and application, they can support CAD/CAM technology or precisely reconstruct morphology of invisible structures. However the currently presented study refers to technical aspects of shade and texture mapping, which is more aimed to obtain more realistic 3D reconstructions of palaeoanthropological material. Colour or shade matching has become an integral part of dental practice. It can be carried in a traditional manner though matching the tooth with conventional shade-guides, or, which is in line with the subjects of our study, by means of spectrophotometry. And the main procedures of shade detection have been performed by SpectroShade (MHT). Necessary attention has been paid to conditions influencing shade detection process with respect to the studied material teeth taken from the Bronze Age findings. Reconstructive techniques have traditionally been a scientific and practical part of palaeoanthropological research which is directed at appearance reconstruction. Though the leading part of this branch has been always aimed at analysis of skull morphology. In our time of rapidly developing digital techniques reconstructions have become to a large extent a matter of improvements of imaging and image processing techniques. Even though this doesnt directly refer to soft tissue reconstruction, it undoubtedly applies to dental reconstructions. And the current study presents improvements in reconstruction through combining imaging with shade and texture mapping on 3D models of teeth. © Authors 2021. CC BY 4.0 License

Optical system calibration for 3D measurements in a hydrodynamic tunnel

Для проведения бесконтактных трёхмерных измерений в гидродинамических трубах фотограмметрическими методами требуется уточнение стандартной модели формирования изображения в съёмочной камере, учитывающее эффект преломления лучей на границах оптических сред, а именно, на границе воздух–стекло и стекло–рабочая жидкость. В статье представлены модель формирования изображения для случая съёмки в рабочем пространстве, включающем различные оптические среды, и методика калибровки оптической системы для проведения трёхмерных измерений координат объектов сцены с учётом имеющихся границ оптических сред. Приведены результаты экспериментальных исследований по калибровке системы трёхмерных измерений для случая съёмки объекта через две границы оптических сред. For non-contact 3D measurements in hydrodynamic tunnels by photogrammetry methods, it is necessary to refine the standard model of image formation in the camera by taking into account an effect of refraction of rays at the boundaries of optical media, namely, at an air-glass boundary and glass-working fluid boundary. The article presents a model of image formation for shooting in a working environment that includes various optical media and methods for calibrating an optical system for 3D measurements of the coordinates of scene objects, while taking into account the real boundaries of the optical media. Experimental results on calibrating the system of three-dimensional measurements when an object image is formed by rays passing through two optical boundaries are discussed.Исследования были выполнены при поддержке Российского фонда фундаментальных исследований (РФФИ) в соответствии с проектом № 19-29-13040

Comparative morphological analysis of enamel and dentin surfaces' reconstructions by means of automated digital odontometry

Studies of teeth represent a significant part of palaeoanthropological research. Over the past two decades these studies have significantly developed with implementation of high resolution imaging based on x-ray scanning techniques. Highly informative reconstructions based on image processing have provided an opportunity to study morphological layers and structures of teeth which are usually hidden under the outer layer of dental enamel. Thus micro-computed tomography of the studied teeth has been performed in order to obtain reconstructions of enamel and dentin surfaces. The material is represented by well-preserved teeth of an adolescent from Upper Palaeolithic archaeological site of Sunghir world-renowned archaeological site in Vladimir Oblast in the Russian Federation. The characteristic feature of the studied teeth is in their unusual, presumably archaic, morphology, which has been previously studied and described through measurements by application of automated digital odontometry method; however the mentioned study referred to the enamel surface. And in the current study these algorithms are applied to measure the surface of dentin. As this is the first successful attempt of measuring dentin surface morphology, the process has to be improved for complete automation. Nevertheless even currently applied approaches allow to compare enamel and dentin morphology through measurements. © Authors 2021. CC BY 4.0 License

AUTOMATED DIGITAL ODONTOMETRY: MEASUREMENT DATA ANALYSES in CASES of COMPLICATED DENTAL MORPHOLOGY

3D imaging techniques, which started to be exact in regard to the current study with photogrammetry, have brought to development of measurement method - automated digital odontometry (aDo) - with wider opportunities in terms of understanding morphological characteristics of human (or, non-human) teeth and dentition. Revealing them through odontometric parameters, not as visual descriptions, as it has been accepted for decades and is widespread till today, digital measurement methods provide for various previously unattainable detailed objective studies including descriptions or comparisons. These types of studies, carried out for dental and anthropological applications, are of high demand in palaeoanthropology, especially in cases of rare combination of finding uniqueness and preservation degree with considerations of unusual morphology. Thus odontological samples from the Upper Palaeolithic Sunghir' (individual C2) are of particular interest in the current study which is aimed to detect distinctive parameters related to morphological features and to compare the degree of feature expression on antimere teeth and teeth with lower degree of that feature expression. © 2020 International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives

3D RECONSTRUCTION and IMAGE PROCESSING of ANTHROPOLOGICAL ARCHAEOLOGICAL FINDINGS

A wide variety of methods are used in archaeological research today, including 3D imaging techniques (photogrammetry) which are involved at different stages starting from explorations preceding excavation to multiple studies. The archaeologically obtained material includes anthropological findings, among which odontological (related to human teeth) are of interest as they are composed of resistible tissues (hence are preserved well) and can serve for biological as well as historical interpretations. However, among the methods employed in odontological studies some are destructive and bring to unwelcome irreversible changes or even complete loss of the analysed samples. However, the existing and rapidly-developing techniques, especially, referring to 3D imaging and prototyping, suggest different approaches which can facilitate avoiding undesirable consequences of invasive methods of research. Thus they can provide for either preservation of findings through development and application of non-invasive study techniques, or, at least, preserve data referring the findings which have to be destroyed in order to receive valuable, in terms of research, information. It is shown on the example of the studied mandibular fragment from the Early Bronze archaeological site of Shengavit how multidisciplinary cooperation and the described workflow contribute to preservation of information regarding the finding and possible restoration of its original features. An effective communication between different professionals was provided due to implementing non-contact measurements techniques, obtaining and processing 3D images and 3D printing. © 2020 International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives

X-ray based imaging and 3d reconstruction of dental pathologies on the example of palaeoanthropological finding

Findings from Bronze Age burials of Shengavit settlement have become a source of multiple studies referred to anthropological, and especially odontological, research based on 3d imaging and image processing techniques. The currently presented case is an example of palaeopathological analysis of bone tissue resorption caused by complications of dental pathologies. Thus by analogy with diagnostic procedures in clinical dentistry, conventional x-ray based cone-beam tomographic scanning have been applied and have shown its effectiveness as a study method. Through CBCT imaging we managed to reveal a hidden pathological process in the body of the studied semi-mandible fragment, though initially another pathological area located on the same finding was planned to be studied. Application of micro-computed tomography has improved analytical, or diagnostic, part of the current palaepathological study. It has brought to finding unusual morphological features hypothetically causing bone resorption as a complication of dental pathological conditions. However our intention to obtain 3d reconstructions as evidence supporting the most likely version required several attempts to correct image processing in line with the increase of imaging resolution. © Authors 2021. CC BY 4.0 License