The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Thomas M Kaiser - One of the best experts on this subject based on the ideXlab platform.
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Uneven distribution of enamel in the Tooth Crown of a Plains Zebra (Equus quagga).
PeerJ, 2015Co-Authors: Daniela E Winkler, Thomas M KaiserAbstract:Unworn teeth of herbivorous mammals are not immediately functional. They have to be partially worn to expose enamel ridges which can then act as shear-cutting blades to break the food down. We use the Plains Zebra (Equus quagga) as a hypsodont, herbivorous model organism to investigate how initial wear of the Tooth Crown is controlled by underlying structures. We find that the enamel proportion is smaller at the apical half of the Tooth Crown in all upper Tooth positions and suggest that lower enamel content here could promote early wear. Besides this uneven enamel distribution, we note that the third molar has a higher overall enamel content than any other Tooth position. The M3 is thus likely to have a slightly different functional trait in mastication, resisting highest bite forces along the Tooth row and maintaining functionality when anterior teeth are already worn down.
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Uneven distribution of enamel in the Tooth Crown of the hypsodont Plains Zebra Equus quagga
2014Co-Authors: Daniela E Winkler, Thomas M KaiserAbstract:Unworn teeth of herbivorous mammals are not immediately functional. They have to get in wear to expose enamel ridges which can then act as shear-cutting blades to disintegrate the food. We use the Plains Zebra (Equus quagga) as a hypsodont, herbivorous model organism to investigate how initial wear of the Tooth Crown is controlled by underlying structures. We find that the enamel proportion is smaller at the apical part of the Tooth Crown in all upper Tooth positions. Measurements of enamel thickness on the first molar show that the outer enamel band is widest in the lower half of the Tooth Crown, where enamel content is also highest. We therefore find evidence that the distribution of enamel within the Tooth Crown is uneven and lower enamel content at the apex promotes early wear. This gradient in enamel distribution is less pronounced in the last molar (txM3), which has also a higher overall enamel content. The M3 is thus hypothesised to have a slightly different functional trait in mastication, resisting highest bite forces along the Tooth row and maintaining functionality while anterior teeth are already worn down.
Paulo G. Coelho - One of the best experts on this subject based on the ideXlab platform.
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biomechanical evaluation of an anatomically correct all ceramic Tooth Crown system configuration core layer multivariate analysis incorporating clinically relevant variables
Journal of Biomechanical Engineering-transactions of The Asme, 2010Co-Authors: Brian T. Rafferty, Estevam A. Bonfante, Malvin N. Janal, Nelson R.f.a. Silva, E.d. Rekow, Van P Thompson, Paulo G. CoelhoAbstract:In a Crown system, core fracture requires replacement of the restoration. Understanding maximum principal stress concentration in the veneered core of a Tooth-Crown system as a function of variations in clinically relevant parameters is crucial in the rational design of Crown systems. This study evaluated the main and interacting effects of a set of clinical variables on the maximum principal stress (MPS) in the core of an anatomically correct veneer-core-cement-Tooth model. A 3D CAD model of a mandibular first molar Crown was generated; Tooth preparation was modeled by reducing the proximal walls by 1.5 mm and the occlusal surface by 2.0 mm. A cemented veneered core Crown was modeled on the preparation. This "Crown system" permitted finite element model investigation of the main and interacting effects of proximal wall height reduction, core material, core thickness, cement modulus, cement thickness, and load position on the maximum stress distribution in a factorial design. Analysis of variance was used to identify the main and interacting influences on the level of MPS in the Crown core. Statistical significance was set at p <0.05. MPS levels varied as a function of two-way interactions between the following: core thickness and load position; cement thickness and load position; cement modulus and load position; cement thickness and core thickness; and cement thickness and cement modulus; and also three-way interactions among the load position, core material, and proximal wall height reduction, and among the core thickness, cement thickness, and cement modulus. MPS in the Crown-Tooth system is influenced by the design parameters and also by the interaction among them. Hence, while the geometry of molar Crowns is complex, these analyses identify the factors that influence MPS and suggest levels that will minimize the core MPS in future studies of Crown design.
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Biomechanical Evaluation of an Anatomically Correct All-Ceramic Tooth-Crown System Configuration: Core Layer Multivariate Analysis Incorporating Clinically Relevant Variables
Journal of biomechanical engineering, 2010Co-Authors: Brian T. Rafferty, Estevam A. Bonfante, Malvin N. Janal, Nelson R.f.a. Silva, E.d. Rekow, Van P. Thompson, Paulo G. CoelhoAbstract:In a Crown system, core fracture requires replacement of the restoration. Understanding maximum principal stress concentration in the veneered core of a Tooth-Crown system as a function of variations in clinically relevant parameters is crucial in the rational design of Crown systems. This study evaluated the main and interacting effects of a set of clinical variables on the maximum principal stress (MPS) in the core of an anatomically correct veneer-core-cement-Tooth model. A 3D CAD model of a mandibular first molar Crown was generated; Tooth preparation was modeled by reducing the proximal walls by 1.5 mm and the occlusal surface by 2.0 mm. A cemented veneered core Crown was modeled on the preparation. This "Crown system" permitted finite element model investigation of the main and interacting effects of proximal wall height reduction, core material, core thickness, cement modulus, cement thickness, and load position on the maximum stress distribution in a factorial design. Analysis of variance was used to identify the main and interacting influences on the level of MPS in the Crown core. Statistical significance was set at p
Daniela E Winkler - One of the best experts on this subject based on the ideXlab platform.
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Uneven distribution of enamel in the Tooth Crown of a Plains Zebra (Equus quagga).
PeerJ, 2015Co-Authors: Daniela E Winkler, Thomas M KaiserAbstract:Unworn teeth of herbivorous mammals are not immediately functional. They have to be partially worn to expose enamel ridges which can then act as shear-cutting blades to break the food down. We use the Plains Zebra (Equus quagga) as a hypsodont, herbivorous model organism to investigate how initial wear of the Tooth Crown is controlled by underlying structures. We find that the enamel proportion is smaller at the apical half of the Tooth Crown in all upper Tooth positions and suggest that lower enamel content here could promote early wear. Besides this uneven enamel distribution, we note that the third molar has a higher overall enamel content than any other Tooth position. The M3 is thus likely to have a slightly different functional trait in mastication, resisting highest bite forces along the Tooth row and maintaining functionality when anterior teeth are already worn down.
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Uneven distribution of enamel in the Tooth Crown of the hypsodont Plains Zebra Equus quagga
2014Co-Authors: Daniela E Winkler, Thomas M KaiserAbstract:Unworn teeth of herbivorous mammals are not immediately functional. They have to get in wear to expose enamel ridges which can then act as shear-cutting blades to disintegrate the food. We use the Plains Zebra (Equus quagga) as a hypsodont, herbivorous model organism to investigate how initial wear of the Tooth Crown is controlled by underlying structures. We find that the enamel proportion is smaller at the apical part of the Tooth Crown in all upper Tooth positions. Measurements of enamel thickness on the first molar show that the outer enamel band is widest in the lower half of the Tooth Crown, where enamel content is also highest. We therefore find evidence that the distribution of enamel within the Tooth Crown is uneven and lower enamel content at the apex promotes early wear. This gradient in enamel distribution is less pronounced in the last molar (txM3), which has also a higher overall enamel content. The M3 is thus hypothesised to have a slightly different functional trait in mastication, resisting highest bite forces along the Tooth row and maintaining functionality while anterior teeth are already worn down.
Lassi Alvesalo - One of the best experts on this subject based on the ideXlab platform.
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Molar morphology and the expression of Carabelli's trait in 45,X females.
American journal of human biology : the official journal of the Human Biology Council, 2015Co-Authors: Mitsuko Nakayama, Raija Lähdesmäki, Ahti Niinimaa, Lassi AlvesaloAbstract:Objectives The purpose of this study was to observe the expression of Carabelli's trait in maxillary first (M1) and second (M2) permanent molars in relation to Tooth Crown size and cusp number and to consider the role of the shortage of sex chromosome material in these features during Tooth Crown development. Methods The data were derived from dental casts belonging to the KVANTTI Research Project on sex chromosome abnormalities headed by Professor Lassi Alvesalo in Finland. The subjects comprised 86 45,X females, 51 first-degree female relatives, and 150 population control females. Carabelli's trait was divided into three grades and cusp number was classified into two classes in Dahlberg's P12 and P9. The Tooth Crown diameters were measured with a sliding digital caliper. Results M1 in the 45,X females expressed a lower frequency of Carabelli's trait (19.8%) than in the female relatives (37.2%, P < 0.05). There was also a higher frequency of the three-cusp pattern (11.1%) than in the female relatives (2.4%, P = 0.055) or the control females (1.3%, P < 0.001). The expression of Carabelli's trait in M2 was of the same magnitude in the 45,X females and normal controls and was related to Tooth Crown size, whereas its expression in M1 of the 45,X females was associated with the cusp number rather than the Tooth Crown size. Conclusions The shortage of one X chromosome in females has an influence on the morphology of the lingual cingulum region of the maxillary first permanent molar during Tooth Crown development. Am. J. Hum. Biol. 27:486–493, 2015. © 2015 Wiley Periodicals, Inc.
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Crown heights in the permanent teeth of 45,X and 45,X/46,XX females.
Acta Odontologica Scandinavica, 2014Co-Authors: Raija Helena Pentinpuro, Raija Lähdesmäki, Ahti Niinimaa, Paula Pesonen, Lassi AlvesaloAbstract:Abstract Objective. Previous results regarding human sex chromosome aneuploidies have shown that the X and Y chromosomes affect Tooth size and morphology. This study looked for the effect of sex chromosome deficiency on permanent Tooth Crown heights. Materials and methods. The material, from the Finnish KVANTTI Research Project, consisted of 97 45,X females and 15 45,X/46,XX females. The controls were 32 sisters and 28 mothers of the 45,X females, eight sisters and two mothers of the 45,X/46,XX females and 35 female population controls. Crown heights of all the available teeth except third molars on both sides of the jaws were measured from panoramic radiographs with a digital calliper according to the defined procedure. Results. The Tooth Crown heights were significantly smaller in the 45,X females than in the female population controls, except for the incisors and one canine in the maxilla, whereas the Tooth Crown heights of the 45,X/46,XX females were close to those of the normal control females. The d...
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Deciduous Tooth Crown size in prematurely born children
Early Human Development, 2003Co-Authors: Virpi Harila, Tuomo Heikkinen, Lassi AlvesaloAbstract:Abstract Aim: The purpose of our study was to examine deciduous Tooth Crown size in preterm children. Subjects and methods: The subjects consisted of 328 prematurely born (
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Deciduous Tooth Crown size in prematurely born children.
Early human development, 2003Co-Authors: Virpi Harila, Tuomo Heikkinen, Lassi AlvesaloAbstract:The purpose of our study was to examine deciduous Tooth Crown size in preterm children. The subjects consisted of 328 prematurely born (< 37 gestational weeks) white and black children and 1804 controls, who participated in the cross-sectional study of the Collaborative Perinatal Project (USA) in the 1960s and 1970s. Documents of the present research consisted of dental casts of the 6-12 years old children. Tooth Crown measurements on canines and molars were performed on the dental casts with an electronic measuring device according to precise definitions generally quoted in the anthropological and genetic literature. For the results, the preterm and control groups were divided by sex and race. There were both increased and decreased mesiodistal and labiolingual Tooth Crown dimensions in prematurely born children, but no significant differences between the study groups was found. The findings of the present research suggest that short gestation is not associated with reduced deciduous Tooth Crown size as suggested by earlier studies and are parallel with our previous results of permanent Tooth Crown dimensions in prematurely born children. Boys showed clearly larger Tooth Crown sizes than girls within all preterm and control groups. This indicates that sexual dimorphism is apparent in its final form beginning some months after birth.
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Deciduous Tooth Crown size and asymmetry in strabismic children.
Orthodontics & craniofacial research, 2002Co-Authors: Tuomo Heikkinen, Lassi Alvesalo, Juha TienariAbstract:Structured Abstract Authors – Heikkinen T, Alvesalo L, Tienari J Objectives – To explore deciduous Tooth Crown dimensions in strabismic children and the relationship between the type of strabismus and Tooth Crown mesio-distal (M-D) and labio-lingual (L-L) size asymmetries. Material – Dental casts at mixed dentition of 2159 Collaborative Perinatal Study black and white children were measured, 123 of them strabismic at 1 year of age, age ranging from 6 to 12 years. Methods– Directional and fluctuating asymmetries in antimeric teeth were explored in various types of strabismus having unilateral, bilateral or alternating expression. ANOVA and T-square test were used for size comparisons and calculated asymmetries were explored by comparing the variances and Pearson correlations. Results – Strabismus was associated with significant M-D size increase of deciduous maxillary canines in black boys and white girls, black girls had size reduction in their mandibular canine, but white boys were unaffected. Right side size dominance was found in the strabismic children in the lower second deciduous molar M-D dimensions and in the children with alternating strabismus in their upper deciduous canine M-D dimensions. Children with unilateral strabismus had random fluctuating dental asymmetry in their upper deciduous second molar L-L dimensions when compared with healthy normals. Higher left-right correlations were found in lower second deciduous molar dimensions in strabismic girls when compared with that in controls and in strabismic boys, suggesting better developmental canalization in female. Conclusions – Asymmetries in the head area, such as promoted here in strabismic children, may have associations with asymmetries in the dentition, focusing the embryonal origins and timing of developmental processes.
Yuchun Sun - One of the best experts on this subject based on the ideXlab platform.
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research and development of three dimensional reconstruction of Tooth Crown and root with digital models
Chinese journal of stomatology, 2020Co-Authors: Yujia Zhu, Yuchun Sun, Bo Jiang, Yijiao Zhao, Yong WangAbstract:With the wide application of digital technology in the field of stomatology, the acquisition of three-dimensional Tooth and dentition information through three-dimensional (3D) image data and optical scan data has become an indispensable process in clinical diagnosis and analysis. Cone-beam CT images and optical scanning images have their own characteristics in terms of data acquisition range and the accuracy of data. Single data source is not accurate enough or complete in the delivery of Tooth and dental information. At present, two data sources are used to construct a 3D Crown root model with high-precision Crown and complete root information to meet the requirement of clinical orthodontic functional setup and implant surgical guide design. The integration of Tooth Crown and root is one of the focused topics of clinical research. This review will summarize the research progress of 3D Crown root model construction method, introduce the application of various algorithms, and analyze the characteristics of these approaches, in order to provide reference for clinical application and scientific research.
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An automatic robotic system for three-dimensional Tooth Crown preparation using a picosecond laser.
Lasers in surgery and medicine, 2014Co-Authors: Lei Wang, Dangxiao Wang, Yuru Zhang, Yuchun SunAbstract:Background Laser techniques have been introduced into dentistry to overcome the drawbacks of traditional treatment methods. The existing methods in dental clinical operations for Tooth Crown preparation have several drawbacks which affect the long-term success of the dental treatment. Objective To develop an improved robotic system to manipulate the laser beam to achieve safe and accurate three-dimensional (3D) Tooth ablation, and thus to realize automatic Tooth Crown preparation in clinical operations. Method We present an automatic laser ablation system for Tooth Crown preparation in dental restorative operations. The system, combining robotics and laser technology, is developed to control the laser focus in three-dimensional motion aiming for high speed and accuracy Crown preparation. The system consists of an end-effector, a real-time monitor and a Tooth fixture. A layer-by-layer ablation method is developed to control the laser focus during the Crown preparation. Experiments are carried out with picosecond laser on wax resin and teeth. Results The accuracy of the system is satisfying, achieving the average linear errors of 0.06 mm for wax resin and 0.05 mm for dentin. The angle errors are 4.33° for wax resin and 0.5° for dentin. The depth errors for wax resin and dentin are both within 0.1 mm. The ablation time is 1.5 hours for wax resin and 3.5 hours for dentin. Conclusions The ablation experimental results show that the movement range and the resolution of the robotic system can meet the requirements of typical dental operations for Tooth Crown preparation. Also, the errors of Tooth shape and preparation angle are able to satisfy the requirements of clinical Crown preparation. Although the experimental results illustrate the potential of using picosecond lasers for 3D Tooth Crown preparation, many research issues still need to be studied before the system can be applied to clinical operations. Lasers Surg. Med. 46:573–581, 2014. © 2014 Wiley Periodicals, Inc.
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Preliminary study on a miniature laser manipulation robotic device for Tooth Crown preparation
The international journal of medical robotics + computer assisted surgery : MRCAS, 2014Co-Authors: Dangxiao Wang, Lei Wang, Yuru Zhang, Yuchun Sun, Jing XiaoAbstract:Background The existing methods in dental clinical operations for hard tissue removal have several drawbacks which affect the long-term success of the dental treatment. Methods In this paper, we introduce a miniature robotic device called LaserBot, which can manipulate a femtosecond laser beam to drill/burr a decayed Tooth to realize clinical Tooth Crown preparation. In order to control the 3D motion of the laser focal point on the surface of a Tooth, three miniature voice-coil motors with optical grating rulers are utilized to drive the 2D pitch/yaw rotation of a vibration mirror and 1D translation of a protruding optical lens. This method can provide high-resolution control of the laser beam. In order to maintain the small size of the robot, a parallel five linkage mechanism combined with a slider-rocker mechanism is developed to realize 2D pitch/yaw rotation of the vibration mirror. Results Experiment results show that the movement range and resolution of the laser beam point can meet the requirement of typical dental operations. The size of the working end of the device that enters the mouth is 25 × 22 × 57 mm (height × width × length), which is small enough to be mounted on any Tooth. The average repeatability error of the laser focal point is about 40 µm. Ablation experiments on wax-resin material and on Tooth validate that a femtosecond laser can be used for Tooth ablation. Conclusions The developed robotic device achieved precise 3D motion control of a laser focal point and is small enough to be used in the narrow workspace of the oral cavity. Limitations of the prototype have been identified, and quantified specifications are identified for designing the next generation prototype. Copyright © 2014 John Wiley & Sons, Ltd.