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Chai H, Russ J, Vardhaman S, Lim CH, Zhang Y. A Bilayer Method for Measuring Toughness and Strength of Dental Ceramics. J Dent Res 2024; 103:419-426. [PMID: 38410925 DOI: 10.1177/00220345231225445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2024] Open
Abstract
The ever-increasing usage of ceramic materials in restorative dentistry necessitates a simple and effective method to evaluate flexural strength σF and fracture toughness KC. We propose a novel method to determine these quantities using a bilayer specimen composed of a brittle plate adhesively bonded onto a transparent polycarbonate substrate. When this bilayer structure is placed under spherical indentation, tunneling radial cracks initiate and propagate in the lower surface of the brittle layer. The failure analysis is based on previous theoretical relationships, which correlate σF with the indentation force P and layer thickness d, and KC with P and mean length of radial cracks. This work examines the accuracy and limitations of this approach using a wide range of contemporary dental ceramic materials. The effect of layer thickness, indenter radius, load level, and length and number of radial cracks are carefully examined. The accuracy of the predicted σF and KC is similar to those obtained with other concurrent test methods, such as biaxial flexure and 3-point bending (σF), and bending specimens with crack-initiation flaws (KC). The benefits of the present approach include treatment for small and thin plates, elimination of the need to introduce a precrack, and avoidance of dealing with local material nonlinearity effects for the KC measurements. Finally, the bilayer configuration resembles occlusal loading of a ceramic restoration (brittle layer) bonded to a posterior tooth (compliant substrate).
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Affiliation(s)
- H Chai
- School of Mechanical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv, Israel
| | - J Russ
- School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - S Vardhaman
- Department of Preventive and Restorative Sciences, University of Pennsylvania, School of Dental Medicine, Philadelphia, PA, USA
- College of Dental Medicine, Columbia University, New York, NY, USA
| | - C H Lim
- Department of Preventive and Restorative Sciences, University of Pennsylvania, School of Dental Medicine, Philadelphia, PA, USA
| | - Y Zhang
- Department of Preventive and Restorative Sciences, University of Pennsylvania, School of Dental Medicine, Philadelphia, PA, USA
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2
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Cho DH, Aguayo S, Cartagena-Rivera AX. Atomic force microscopy-mediated mechanobiological profiling of complex human tissues. Biomaterials 2023; 303:122389. [PMID: 37988897 PMCID: PMC10842832 DOI: 10.1016/j.biomaterials.2023.122389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 10/30/2023] [Accepted: 11/04/2023] [Indexed: 11/23/2023]
Abstract
Tissue mechanobiology is an emerging field with the overarching goal of understanding the interplay between biophysical and biochemical responses affecting development, physiology, and disease. Changes in mechanical properties including stiffness and viscosity have been shown to describe how cells and tissues respond to mechanical cues and modify critical biological functions. To quantitatively characterize the mechanical properties of tissues at physiologically relevant conditions, atomic force microscopy (AFM) has emerged as a highly versatile biomechanical technology. In this review, we describe the fundamental principles of AFM, typical AFM modalities used for tissue mechanics, and commonly used elastic and viscoelastic contact mechanics models to characterize complex human tissues. Furthermore, we discuss the application of AFM-based mechanobiology to characterize the mechanical responses within complex human tissues to track their developmental, physiological/functional, and diseased states, including oral, hearing, and cancer-related tissues. Finally, we discuss the current outlook and challenges to further advance the field of tissue mechanobiology. Altogether, AFM-based tissue mechanobiology provides a mechanistic understanding of biological processes governing the unique functions of tissues.
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Affiliation(s)
- David H Cho
- Section on Mechanobiology, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, USA
| | - Sebastian Aguayo
- Dentistry School, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile; Schools of Engineering, Medicine, and Biological Sciences, Institute for Biological and Medical Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Alexander X Cartagena-Rivera
- Section on Mechanobiology, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, USA.
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3
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Chai H. On edge chipping in molar teeth from blunt occlusal contact. J Mech Behav Biomed Mater 2023; 148:106206. [PMID: 37944225 DOI: 10.1016/j.jmbbm.2023.106206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 10/17/2023] [Accepted: 10/20/2023] [Indexed: 11/12/2023]
Abstract
Edge chipping is a leading failure mode in dental teeth. Virtually all chipping studies are limited to Vickers indentation on polished cusps of molar teeth. Such works are here extended to spherical contact. Occlusal loads are applied on the tooth's central fossa or a polished cusp using ball radii ranging from 0.4 to 5.16 mm. The chip dimensions are characterized by h/Dm and D/Dm, where h, D and Dm denote indent distance, chip size and tooth crown diameter. For the fossa loading, h/Dm, D/Dm and the least chipping force Pch are virtually independent of ball radius r for r < ≈ 4 mm. In this range, h/Dm and D/Dm lie between ≈0.30 to 0.36 and 0.51 to 0.69, respectively, while Pch equals ≈1330 N. For r > ≈ 4 mm, the failure occurs by debonding of enamel sectors from the dentin core. In the case of cusp loading, h/Dm < ≈ 0.3 while D/Dm and Pch vary with r. For relatively small h or large r, the failure occurs as soon as radial cracks initiate under the loading point. For a load applied near a cusp tip, the failure occurs by enamel debonding. Finally, the present work is easily extendable to fossil teeth of hominins and apes as well as prosthetic teeth. The morphological features obtained in such studies should provide quantitative means to assess the relationships between chip dimensions, chipping force and diet characteristics.
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Affiliation(s)
- Herzl Chai
- School of Mechanical Engineering, Tel-Aviv University, Tel-Aviv, Israel.
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4
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Zu H, Zhang K, Zhang H, Qian X. An Inverse Method to Determine Mechanical Parameters of Porcine Vitreous Bodies Based on the Indentation Test. Bioengineering (Basel) 2023; 10:646. [PMID: 37370577 DOI: 10.3390/bioengineering10060646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 05/16/2023] [Accepted: 05/23/2023] [Indexed: 06/29/2023] Open
Abstract
The vitreous body keeps the lens and retina in place and protects these tissues from physical insults. Existing studies have reported that the mechanical properties of vitreous body varied after liquefaction, suggesting mechanical properties could be effective parameters to identify vitreous liquefaction process. Thus, in this work, we aimed to propose a method to determine the mechanical properties of vitreous bodies. Fresh porcine eyes were divided into three groups, including the untreated group, the 24 h liquefaction group and the 48 h liquefaction group, which was injected collagenase and then kept for 24 h or 48 h. The indentation tests were carried out on the vitreous body in its natural location while the posterior segment of the eye was fixed in the container. A finite element model of a specimen undertaking indentation was constructed to simulate the indentation test with surface tension of vitreous body considered. Using the inverse method, the mechanical parameters of the vitreous body and the surface tension coefficient were determined. For the same parameter, values were highest in the untreated group, followed by the 24 h liquefaction group and the lowest in the 48 h liquefaction group. For C10 in the neo-Hookean model, the significant differences were found between the untreated group and liquefaction groups. This work quantified vitreous body mechanical properties successfully using inverse method, which provides a new method for identifying vitreous liquefactions related studies.
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Affiliation(s)
- Haicheng Zu
- School of Biomedical Engineering, Capital Medical University, Beijing 100069, China
| | - Kunya Zhang
- School of Biomedical Engineering, Capital Medical University, Beijing 100069, China
- Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing 100069, China
| | - Haixia Zhang
- School of Biomedical Engineering, Capital Medical University, Beijing 100069, China
- Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing 100069, China
| | - Xiuqing Qian
- School of Biomedical Engineering, Capital Medical University, Beijing 100069, China
- Beijing Key Laboratory of Fundamental Research on Biomechanics in Clinical Application, Capital Medical University, Beijing 100069, China
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5
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Kruzic JJ, Hoffman M, Arsecularatne JA. Fatigue and wear of human tooth enamel: A review. J Mech Behav Biomed Mater 2023; 138:105574. [PMID: 36473402 DOI: 10.1016/j.jmbbm.2022.105574] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 09/14/2022] [Accepted: 11/15/2022] [Indexed: 11/21/2022]
Abstract
Human tooth enamel must withstand the cyclic contact forces, wear, and corrosion processes involved with typical oral functions. Furthermore, unlike other human tissues, dental enamel does not have a significant capacity for healing or self-repair and thus the longevity of natural teeth in the oral environment depends to a large degree on the fatigue and wear properties of enamel. The purpose of this review is to provide an overview of our understanding of the fatigue and wear mechanisms of human enamel and how they relate to in vivo observations of tooth damage in the complex oral environment. A key finding of this review is that fatigue and wear processes are closely related. For example, the presence of abrasive wear particles significantly lowers the forces needed to initiate contact fatigue cracking while subsurface fatigue crack propagation drives key delamination wear mechanisms during attrition or attrition-corrosion of enamel. Furthermore, this review seeks to bring a materials science and mechanical engineering perspective to fatigue and wear phenomena. In this regard, we see developing a mechanistic description of fatigue and wear, and understanding the interconnectivity of the processes, as essential for successfully modelling enamel fatigue and wear damage and developing strategies and treatments to improve the longevity of our natural teeth. Furthermore, we anticipate that this review will stimulate ideas for extending the lifetime of the natural tooth structure and will help highlight where our understanding is too limited and where additional research into fatigue and wear of human tooth enamel is warranted.
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Affiliation(s)
- Jamie J Kruzic
- School of Mechanical and Manufacturing Engineering, University of New South Wales (UNSW Sydney), Sydney NSW 2052, Australia.
| | - Mark Hoffman
- School of Engineering, University of Newcastle, Callaghan NSW 2308, Australia; School of Materials Science and Engineering, University of New South Wales (UNSW Sydney), Sydney NSW 2052, Australia
| | - Joseph A Arsecularatne
- School of Mechanical and Manufacturing Engineering, University of New South Wales (UNSW Sydney), Sydney NSW 2052, Australia
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Estimates of absolute crown strength and bite force in the lower postcanine dentition of Gigantopithecus blacki. J Hum Evol 2023; 175:103313. [PMID: 36709569 DOI: 10.1016/j.jhevol.2022.103313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 12/18/2022] [Accepted: 12/18/2022] [Indexed: 01/30/2023]
Abstract
Gigantopithecus blacki is hypothesized to have been capable of processing mechanically challenging foods, which likely required this species to have high dental resistance to fracture and/or large bite force. To test this hypothesis, we used two recently developed approaches to estimate absolute crown strength and bite force of the lower postcanine dentition. Sixteen Gigantopithecus mandibular permanent cheek teeth were scanned by micro-computed tomography. From virtual mesial cross-sections, we measured average enamel thickness and bi-cervical diameter to estimate absolute crown strength, and cuspal enamel thickness and dentine horn angle to estimate bite force. We compared G. blacki with a sample of extant great apes (Pan, Pongo, and Gorilla) and australopiths (Australopithecus anamensis, Australopithecus afarensis, Australopithecus africanus, Paranthropus robustus, and Paranthropus boisei). We also evaluated statistical differences in absolute crown strength and bite force between the premolars and molars for G. blacki. Results reveal that molar crown strength is absolutely greater, and molar bite force absolutely higher, in G. blacki than all other taxa except P. boisei, suggesting that G. blacki molars have exceptionally high resistance to fracture and the ability to generate exceptionally high bite force. In addition, G. blacki premolars have comparable absolute crown strength and larger bite force capabilities compared with its molars, implying possible functional specializations in premolars. The dental specialization of G. blacki could thus represent an adaptation to further facilitate the processing of mechanically challenging foods. While it is currently not possible to determine which types of foods were actually consumed by G. blacki through this study, direct evidence (e.g. dental chipping and microwear) left by the foods eaten by G. blacki could potentially lead to greater insights into its dietary ecology.
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Yu S, Sun Z, Ren X, Zhang J, Yu J, Zhang W. An improved Smoothed Particle Hydrodynamics (SPH) method for modelling the cracking processes of teeth and its applications. J Mech Behav Biomed Mater 2022; 136:105518. [PMID: 36265277 DOI: 10.1016/j.jmbbm.2022.105518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 10/03/2022] [Accepted: 10/06/2022] [Indexed: 11/06/2022]
Abstract
The present work aims to propose a meshless method to establish the tooth meso-structures and model the tooth fracturing processes as well as investigate the influencing factors that affect the dental mechanical properties. To this end, the traditional kernel function in the SPH method has been improved by introducing a fracture mark ξ to realize the progressive failure processes of teeth; The "Particle Searching Method" has been proposed, which can realize the establishments of microstructures of teeth such as enamel, dentine, pulp, PDL and alvedar bones. The Weibull function is introduced to represent the heterogeneity of teeth, which can realize the random distribution characteristics of dental mechanical parameters. The simulation results of homogeneous and heterogeneous teeth show that the failure mode changes from tensile splitting (homogeneous) to shear failure (heterogeneous). Meanwhile, the fracture networks become more complex, and the failure stress decreases sharply. The cuspal angles also have a great impact on the teeth fracture characteristics. The failure modes changes from tensile splitting of the enamel tip to the cracking from the contact points between the enamel and the rigid ball; Different fssural morphologies have little influences on the teeth failure characteristics. The research results can provide some references for the applications of SPH method into biomechanical simulations such as teeth failure. Meanwhile, it can also provide some guidance for the understandings of the internal mechanisms of teeth fracture processes, the diagnosis and treatments of clinical diseased teeth as well as the design of bionic teeth materials.
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Affiliation(s)
- Shuyang Yu
- School of Transportation and Civil Engineering, Nantong University, Nantong, 226019, China
| | - Zhaohua Sun
- School of Transportation and Civil Engineering, Nantong University, Nantong, 226019, China.
| | - Xuhua Ren
- College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, 210098, China
| | - Jixun Zhang
- College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, 210098, China
| | - Jun Yu
- School of Transportation and Civil Engineering, Nantong University, Nantong, 226019, China
| | - Wenbing Zhang
- College of Ocean Science and Engineering, Shanghai Maritime University, Shanghai, 201306, China
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8
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Dorado S, Arias A, Jimenez-Octavio JR. Biomechanical Modelling for Tooth Survival Studies: Mechanical Properties, Loads and Boundary Conditions-A Narrative Review. MATERIALS (BASEL, SWITZERLAND) 2022; 15:7852. [PMID: 36363451 PMCID: PMC9657341 DOI: 10.3390/ma15217852] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 11/02/2022] [Accepted: 11/04/2022] [Indexed: 06/16/2023]
Abstract
Recent biomechanical studies have focused on studying the response of teeth before and after different treatments under functional and parafunctional loads. These studies often involve experimental and/or finite element analysis (FEA). Current loading and boundary conditions may not entirely represent the real condition of the tooth in clinical situations. The importance of homogenizing both sample characterization and boundary conditions definition for future dental biomechanical studies is highlighted. The mechanical properties of dental structural tissues are presented, along with the effect of functional and parafunctional loads and other environmental and biological parameters that may influence tooth survival. A range of values for Young's modulus, Poisson ratio, compressive strength, threshold stress intensity factor and fracture toughness are provided for enamel and dentin; as well as Young's modulus and Poisson ratio for the PDL, trabecular and cortical bone. Angles, loading magnitude and frequency are provided for functional and parafunctional loads. The environmental and physiological conditions (age, gender, tooth, humidity, etc.), that may influence tooth survival are also discussed. Oversimplifications of biomechanical models could end up in results that divert from the natural behavior of teeth. Experimental validation models with close-to-reality boundary conditions should be developed to compare the validity of simplified models.
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Affiliation(s)
- Saúl Dorado
- Department of Mechanical Engineering, Escuela Técnica Superior de Ingeniería ICAI, Universidad Pontificia Comillas, 28015 Madrid, Spain
| | - Ana Arias
- Department of Conservative and Prosthetic Dentistry, School of Dentistry, Complutense University, 28040 Madrid, Spain
| | - Jesus R. Jimenez-Octavio
- Instituto de Investigación Tecnológica, Escuela Técnica Superior de Ingeniería ICAI, Universidad Pontificia Comillas, 28015 Madrid, Spain
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9
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Chai H. On the evolution of the morphology and resilience of molar cusps in fossil hominid teeth. J Mech Behav Biomed Mater 2022; 133:105357. [PMID: 35841750 DOI: 10.1016/j.jmbbm.2022.105357] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Revised: 06/29/2022] [Accepted: 07/02/2022] [Indexed: 10/17/2022]
Abstract
Teeth play an important role in evolutionary studies due to their good preservation and direct link to diet. The present work makes use of a previously generated database on molar teeth of fossil hominids which consists of cuspal enamel thickness dc, dentin horn angle φ and section width D, all measured on a given histological tooth section. These data are here interpreted with the aid of "fracture stress" QF = PF/D2 and geological age t, where PF is the occlusal force needed to cause cusp failure as determined from dc and φ. QF is virtually a constant in non-hominins ("apes") while monotonically increasing toward present time in hominins. These two trends intersect at t = ts = 4.5 (0.11) mya, a value similar to other divergence estimates. QF was fitted with a function f(t) which is proportional to (dc/D)2. The monotonic variation of QF and in turn dc/D with t contrasts the more complex behavior generally characterizing other physical entities of fossil hominids. The increase in dc/D in hominins promotes tooth resilience and in turn life span. Finally, it is suggested that PF provides an upper bound to the maximum bite force produced by the jaw structure.
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Affiliation(s)
- Herzl Chai
- School of Mechanical Engineering, Tel-Aviv University, Israel.
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10
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Chi J, Yang L, Liu Y, Yang J, Deng J. Biomechanical Characteristics of Maxillary Molar Distalization Using Different Attachments with Clear Aligners: A 3-Dimensional Finite Element Analysis. J BIOMATER TISS ENG 2022. [DOI: 10.1166/jbt.2022.3094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
This study aimed to compare the biomechanical characteristics of maxillary teeth in molar distalization with different orthodontic attachments. A 3-dimensional finite model of maxillary molar distalization with clear aligners was generated by computed tomography and contained different
components. Four models—non-attachment (model A), horizontal rectangular attachment (model B), vertical rectangular attachment (model C), and combined attachment (model D)—were set up. The modalities of molar distalization were simulated using a finite element analysis. The results
showed that the minimum displacement (rotation center) of the second molar in models A and B was located at the root furcation. In model C, the minimum displacement was located in the middle third of the palatal root. In model D, the minimum displacement was located at the apical third of
the root. The anchorage teeth in all the four groups tended to have mesial tipping movement. Models B and D had more uniform stress distribution of the periodontal ligament than models A and C. Models with attachment had a larger tooth displacement pattern than that without attachment. Collectively,
if molar distalization is planned before treatment, the appropriate application of attachments can help achieve the desired tooth movements more efficiently.
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Affiliation(s)
- Jingwen Chi
- School of Stomatology, Qingdao University, Qingdao, 266003, China
| | - Lixia Yang
- School of Stomatology, Qingdao University, Qingdao, 266003, China
| | - Yicong Liu
- School of Stomatology, Qingdao University, Qingdao, 266003, China
| | - Jianjun Yang
- Department of Oral and Maxillofacial Surgery, Affiliated Hospital, Qingdao University, Qingdao, 266001, China
| | - Jing Deng
- School of Stomatology, Qingdao University, Qingdao, 266003, China
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11
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Liu S, Xu Y, An B, Zhang D. Interaction of rod decussation and crack growth in enamel. Comput Methods Biomech Biomed Engin 2022; 26:700-709. [PMID: 35815376 DOI: 10.1080/10255842.2022.2084333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Enamel possesses ingenious hierarchical structure that gives rise to superior fracture resistance. Despite considerable efforts devoted to characterization of fracture behavior of enamel, the role of rod decussation in fracture of enamel is largely unknown. In this study, the features of rod decussation in the inner enamel are experimentally identified, and analyses of crack growth in enamel are carried out using a micromechanical model of enamel, in which the structural features of the outer enamel and rod decussation of the inner enamel are incorporated. We carry out calculations within a framework based on the extended finite element method, and the crack growth and crack path selection are natural outcomes of imposed loading. We show that crack deflection in enamel is controlled by rod decussation. For crack growth in the parazone, the crack path is oriented along the axis of enamel rods, leading to gross crack deflection. The microstructure of inner enamel with intermediate inclination angle enables multiple crack deflections, giving rise to enhanced toughness. For crack growth in the diazone, the transition in orientation of crack deflection occurs as inclination angle increases. The relatively straight crack path emerges in the case of the microstructure of enamel with intermediate inclination angle, leading to weak fracture resistance. It is further found that compared with the diazone, the gross crack deflection in the parazone provides greater contribution to fracture resistance of enamel. The findings of this study provide a good mechanistic understanding of the role of rod decussation in enamel.
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Affiliation(s)
- Siyong Liu
- School of Mechanics and Engineering Science, Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai, China.,Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai, China
| | - Yuanzhi Xu
- Department of Stomatology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, 200072, P R China
| | - Bingbing An
- School of Mechanics and Engineering Science, Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai, China.,Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai, China
| | - Dongsheng Zhang
- School of Mechanics and Engineering Science, Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai, China.,Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai, China
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12
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Chai H. On the morphology and failure of worn human molar cusps. J Mech Behav Biomed Mater 2022; 130:105212. [DOI: 10.1016/j.jmbbm.2022.105212] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 03/19/2022] [Accepted: 03/26/2022] [Indexed: 11/26/2022]
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13
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Samartzi TK, Papalexopoulos D, Sarafianou A, Kourtis S. Immediate Dentin Sealing: A Literature Review. Clin Cosmet Investig Dent 2021; 13:233-256. [PMID: 34188553 PMCID: PMC8232880 DOI: 10.2147/ccide.s307939] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Accepted: 05/20/2021] [Indexed: 02/04/2023] Open
Abstract
Purpose The immediate application of a dentin-bonding agent after tooth preparation and before impression-taking (immediate dentin sealing [IDS]) has been suggested to provide several advantages concerning bacterial microleakage, hypersensitivity, and bonding quality. We reviewed the literature and clarified certain aspects related to each step of IDS application. Materials and Methods The search strategy comprised an electronic research in MEDLINE, Cochrane, Ovid and Scopus for studies published from January 1990 to December 2020 regarding the IDS technique and including both in vitro and clinical studies. Results After exclusion of irrelevant or duplicate articles, 88 articles focusing on aspects of the IDS technique were assessed. IDS seems to be advantageous with regard to bond strength, gap formation, bacterial microleakage, and dentin hypersensitivity. However, issues arising from interaction with impression materials, the provisional phase, and conditioning methods before cementation require further investigation. Conclusion There are no documented reasons preventing clinicians applying IDS in their everyday practice. On the contrary, the presented technique seems to be beneficial in certain aspects regarding indirect restorations.
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Affiliation(s)
| | | | - Aspasia Sarafianou
- Department of Prosthodontics, National and Kapodistrian University of Athens, Athens, Greece
| | - Stefanos Kourtis
- Department of Prosthodontics, National and Kapodistrian University of Athens, Athens, Greece
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14
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Schlenz MA, Skroch M, Schmidt A, Rehmann P, Wöstmann B. Monitoring fatigue damage in different CAD/CAM materials: A new approach with optical coherence tomography. J Prosthodont Res 2020; 65:31-38. [PMID: 32938871 DOI: 10.2186/jpr.jpor_2019_466] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
PURPOSE To investigate fatigue damage over time, monolithic posterior computer-aided-designed/computer-aided-manufactured (CAD/CAM) crowns were artificially aged in a mouth-motion-simulator, and damage was monitored with optical coherence tomography (OCT). METHODS Forty-eight crowns were milled of six different CAD/CAM-materials (n=8), including 3Y-TZP (Lava Plus,'3Y'), 4Y-PSZ (Pritidentamultidisc,'4Y'), 5Y-PSZ (Prettauanterior,'5Y'), zirconia-reinforced lithium silicate (CeltraDuo,'ZLS'), hybrid ceramic (Vita Enamic,'VE'),and resin composite (BrilliantCrios,'COM'), and were adhesively luted on CAD/CAM-milled human molars. Specimens were artificially aged in a mouth-motion-simulator (50-500N, 2Hz, 37°C) for a period of 1 million cycles. Before loading and every 250,000 cycles, the specimens were investigated with spectral domain (SD)-OCT (RS-3000). The maximum vertical and horizontal damage were measured with imaging-processing-software (ImageJ). After testing, the specimens were sliced and analysed via light microscope (Zeiss) to compare the new OCT method with the established light microscope method. Data were subjected to ANCOVA and 2x4-ANOVA. RESULTS No failure occurred during mouth-motion-simulation. However, all specimens (except for 3Y and 4Y) showed fatigue damage. There was a significant difference in the maximum damage between the CAD/CAM-materials (p<.05). ZLS exhibited the highest damage, followed by VE, COM and 5Y. While damage associated with 5Y was initially noticed after 750,000 cycles, all other materials already showed crack formation after 250,000 cycles. Furthermore, a linear increase in damage over time was noticed in all materials. Due to the shallow light penetration of OCT, damage in the outer area could only be visualized with light microscope. CONCLUSIONS OCT is feasible for monitoring fatigue damage over time within different CAD/CAM-materials, particularly for subsurface damages.
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Affiliation(s)
- Maximiliane Amelie Schlenz
- Justus Liebig University, Dental Clinic, Department of Prosthodontics, Schlangenzahl 14, 35392 Giessen, Germany
| | - Marianne Skroch
- Justus Liebig University, Dental Clinic, Department of Prosthodontics, Schlangenzahl 14, 35392 Giessen, Germany
| | - Alexander Schmidt
- Justus Liebig University, Dental Clinic, Department of Prosthodontics, Schlangenzahl 14, 35392 Giessen, Germany
| | - Peter Rehmann
- Justus Liebig University, Dental Clinic, Department of Prosthodontics, Schlangenzahl 14, 35392 Giessen, Germany
| | - Bernd Wöstmann
- Justus Liebig University, Dental Clinic, Department of Prosthodontics, Schlangenzahl 14, 35392 Giessen, Germany
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Li P, Oh C, Kim H, Chen-Glasser M, Park G, Jetybayeva A, Yeom J, Kim H, Ryu J, Hong S. Nanoscale effects of beverages on enamel surface of human teeth: An atomic force microscopy study. J Mech Behav Biomed Mater 2020; 110:103930. [PMID: 32957225 DOI: 10.1016/j.jmbbm.2020.103930] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 05/17/2020] [Accepted: 06/10/2020] [Indexed: 11/17/2022]
Abstract
Dental erosion has become a prevalence disease and attracted increasing attention worldwide. In this research, we quantitatively evaluate the mechanical and morphological changes in the very early stages of softening and weakening of human enamel surfaces induced by soft drinks using atomic force microscopy (AFM). With an increase of the immersion time in soft drinks, we found a significant increase of surface roughness (Rq) of the enamel surface. The prismatic structure of enamel was clearly observed after a 1-h immersion in Coca-Cola®, which shows its strong erosion effect. According to the elastic modulus mapping images obtained by AFM, a considerable decrease of elastic modulus (E) of enamel surface has been found as the enamel surface structures are etched away by soft drinks. A high surface roughness of enamel will result in a high chance of cavities due to easier bacterial adhesion on rougher surface, while a drastic deterioration of the mechanical properties of the enamel will weaken its protection property. Our findings show the serious influence of acidic drinks on enamel surface at the very beginning stage of etching process, which is quite meaningful for people to prevent dental erosion and keep dental health.
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Affiliation(s)
- Panpan Li
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Daejeon, 34141, Republic of Korea
| | - Chungik Oh
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Daejeon, 34141, Republic of Korea
| | - Hongjun Kim
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Daejeon, 34141, Republic of Korea
| | - Melodie Chen-Glasser
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Daejeon, 34141, Republic of Korea
| | - Gun Park
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Daejeon, 34141, Republic of Korea
| | - Albina Jetybayeva
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Daejeon, 34141, Republic of Korea
| | - Jiwon Yeom
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Daejeon, 34141, Republic of Korea
| | - Hoon Kim
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Daejeon, 34141, Republic of Korea
| | - Jeongjae Ryu
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Daejeon, 34141, Republic of Korea
| | - Seungbum Hong
- Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Daejeon, 34141, Republic of Korea; KAIST Institute for NanoCentury (KINC), Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Daejeon, 34141, Republic of Korea.
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Ortiz A, Schander-Triplett K, Bailey SE, Skinner MM, Hublin JJ, Schwartz GT. Enamel thickness variation in the deciduous dentition of extant large-bodied hominoids. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2020; 173:500-513. [PMID: 32767577 DOI: 10.1002/ajpa.24106] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 05/16/2020] [Accepted: 06/11/2020] [Indexed: 11/09/2022]
Abstract
OBJECTIVES Enamel thickness features prominently in hominoid evolutionary studies. To date, however, studies of enamel thickness in humans, great apes, and their fossil relatives have focused on the permanent molar row. Comparatively little research effort has been devoted to tissue proportions within deciduous teeth. Here we attempt to fill this gap by documenting enamel thickness variation in the deciduous dentition of extant large-bodied hominoids. MATERIALS AND METHODS We used microcomputed tomography to image dental tissues in 80 maxillary and 78 mandibular deciduous premolars of Homo sapiens, Pan troglodytes, Gorilla, and Pongo. Two-dimensional virtual sections were created from the image volumes to quantify average (AET) and relative (RET) enamel thickness, as well as its distribution across the crown. RESULTS Our results reveal no significant differences in enamel thickness among the great apes. Unlike the pattern present in permanent molars, Pongo does not stand out as having relatively thicker-enameled deciduous premolars than P. troglodytes and Gorilla. Humans, on the other hand, possess significantly thicker deciduous premolar enamel in comparison to great apes. Following expectations from masticatory biomechanics, we also find that the "functional" side (protocone, protoconid) of deciduous premolars generally possesses thicker enamel than the "nonfunctional" side. DISCUSSION Our study lends empirical support to anecdotal observations that patterns of AET and RET observed for permanent molars of large-bodied apes do not apply to deciduous premolars. By documenting enamel thickness variation in hominoid deciduous teeth, this study provides the comparative context to interpret rates and patterns of wear of deciduous teeth and their utility in life history reconstructions.
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Affiliation(s)
- Alejandra Ortiz
- Institute of Human Origins, School of Human Evolution and Social Change, Arizona State University, Tempe, Arizona, USA.,Center for the Study of Human Origins, Department of Anthropology, New York University, New York, New York, USA
| | - Katherine Schander-Triplett
- Barrett, The Honors College, College of Liberal Arts and Sciences, Arizona State University, Tempe, Arizona, USA
| | - Shara E Bailey
- Center for the Study of Human Origins, Department of Anthropology, New York University, New York, New York, USA.,Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Matthew M Skinner
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.,School of Anthropology and Conservation, University of Kent, Canterbury, UK
| | - Jean-Jacques Hublin
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.,Collège de France, Paris, France
| | - Gary T Schwartz
- Institute of Human Origins, School of Human Evolution and Social Change, Arizona State University, Tempe, Arizona, USA
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17
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Angermair J, Nolte D, Linsenmann R, Kunzelmann KH. The influence of storage temperature on fracture behavior of cryopreserved teeth-An in vitro study. Clin Exp Dent Res 2020; 6:373-380. [PMID: 32222040 PMCID: PMC7301388 DOI: 10.1002/cre2.283] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 02/17/2020] [Accepted: 02/23/2020] [Indexed: 11/20/2022] Open
Abstract
Objectives Cryopreservation is discussed as a viable method of preserving teeth for determined autogenous tooth transplantation. Unchanged physical properties of hard tooth tissues are crucial for functional healing. Due to different thermal expansion coefficients of enamel and dentin or the crystallization process, the freezing process may lead to crack formation, which could adversely impact the long‐term prognosis of the teeth. Material and methods Twenty third molars (n = 20) were frozen slowly using a conservative cryopreservation protocol and stored at −80°C (group 1) and −196°C (group 2). After a storage time of 2 weeks, the samples were thawed to a temperature of +36°C and embedded in polymethyl methacrylate blocks. Cyclic loading was carried out using a spherical steel test specimen with 50,000 mechanical load cycles, followed by load to failure testing for determination of critical load. Results No significant difference in the first load drop could be detected during the load to failure test under different storage conditions. The values until fracture correlated very closely in contralateral tooth pairs, which emphasizes the importance of crown geometry in load to failure tests. Conclusions Conclusions: Cryopreservation, specifically the storage temperature, does not appear to have a significant effect on the physical properties of tooth transplants.
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Affiliation(s)
- Johannes Angermair
- Clinic of Oral- and Maxillofacial Surgery, Translational Implantology, Medical Center Freiburg - Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Dirk Nolte
- Private Practice for Oral and Maxillofacial Surgery, Munich, Germany
| | - Robert Linsenmann
- Private Practice for Oral and Maxillofacial Surgery, Munich, Germany
| | - Karl-Heinz Kunzelmann
- Department of Conservative Dentistry and Parodontology, University Medical Center Munich, Munich, Germany
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18
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Chai H. Determining primates bite force from histological tooth sections. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2020; 171:683-703. [PMID: 31912901 DOI: 10.1002/ajpa.24003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 10/06/2019] [Accepted: 12/16/2019] [Indexed: 11/09/2022]
Abstract
OBJECTIVES The ability to accurately estimate bite force (BF) in extant and fossil primates is valuable to biological anthropologists. BF is generally evaluated using complex jaw musculature and lever arm analyses employing numerous assumptions and requiring complete cranial morphology. Here, a simple method to determine BF from data measured on histological sections of fossil teeth is proposed. METHODS Published sections of molar teeth encompassing 27 different extinct and extant primates dating back to as early as 17 million years ago were examined. Focusing on the cusp region, the extracted data include characteristic enamel thickness dc and dentin horn angle φ. The occlusal force needed to fracture a cusp, PF , was determined from these variables with the aid of a finite element stress analysis similarly to a previous study on postcanine human teeth. The bite force was obtained by linking BF to PF using a universal constant. RESULTS The measured variables dc and φ are conclusively linked. This link produces a virtually constant fracture force PF and in turn bite force BF for all cusps in the molar row. An explicit formula tying BF to dc and φ was derived. For nonhominin taxa the bite force, molar crown area, and body mass are found to be intimately related. The case of hominins is more involved. The so determined BF is gender-averaged, with the bite force of males estimated to be ≈12% greater than that of females. CONCLUSIONS The use of "fracture mechanics" concepts from mechanics of materials facilitates determination of critical bite force in primates based on characteristic enamel thickness dc and dentin horn angle φ as extracted from histological sections of molar teeth. This novel approach enables quantitative insight into the role played by crown area, body mass and bite force on evolutionary trends. The conclusive link between cuspal enamel thickness and dentin horn angle facilitates optimal food processing without hindering cusp resilience. The proposed approach may be extended to mammals having asymmetric cusp structures.
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Affiliation(s)
- Herzl Chai
- School of Mechanical Engineering, Tel-Aviv University, Tel-Aviv, Israel
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19
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Dentin horn angle and enamel thickness interactively control tooth resilience and bite force. Acta Biomater 2018; 75:279-286. [PMID: 29874598 DOI: 10.1016/j.actbio.2018.06.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2018] [Revised: 05/30/2018] [Accepted: 06/02/2018] [Indexed: 11/21/2022]
Abstract
Fossil teeth are a primary source for inferring species development via evolutionary adaptation due to their linkage to feeding ecology and well perseverance. The main working tools in such studies are bite force analysis derived from jaw musculature and lever arms and morphogenetic based on enamel thickness and occlusal surface area. Despite progress made, quantitative correlation between predictions and behavior is still lacking. We studied histological sections in varieties of extracted premolar and molar human teeth. Sections corresponding to planes intersecting tips of primary cusps as well as more random planes were considered. The results revealed a unique, conclusive link between cuspal enamel thickness dc and dentin horn angle φ, a developmental parameter which contribution to tooth functioning has been overlooked. Naturally led by design principles of corbel arches, we examined the bending stress at the horn apex due to axial cuspal loading. The results show that this dc vs. φ relationship produces a constant force causing cusp fracture PF, making the latter a viable measure of tooth resilience. A preliminary study on published sections of extinct hominin teeth showed that their dc vs. φ behavior is consistent with modern humans albeit with varying PF. Scaling BF with PF enables direct estimate of bite force from measures of dc and φ in fossil teeth, achievable nondestructively from micro-computed tomography scans. STATEMENT OF SIGNIFICANCE The correspondence between cuspal enamel thickness and dentin horn angle in the postcanine row is a natural design here revealed for the first time. This correspondence yields constant force causing fracture at the horn apex, PF, making the latter a viable measure of tooth resilience. Scaling bite force (BF) with PF enables direct estimate of BF. The proposed mechanistic link between bite force and anatomical parameters dc and φ, expressed in a simple analytic form, offers direct, development-based expectation for examining evolutionary processes in hominins.
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Abstract
This article provides a brief review of recent investigations concerning the structure and properties of the tooth. The last decade has brought a greater emphasis on the durability of the tooth, an improved understanding of the fatigue and fracture behavior of the principal tissues, and their importance to tooth failures. The primary contributions to tooth durability are discussed, including the process of placing a restoration, the impact of aging, and challenges posed by the oral environment. The significance of these findings to the dental community and their importance to the pursuit of lifelong oral health are highlighted.
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Affiliation(s)
- Dwayne D Arola
- Department of Materials Science and Engineering, University of Washington School of Dentistry, Roberts Hall, 333, Box 352120, Seattle, WA 98195-2120, USA; Department of Oral Health Sciences, University of Washington School of Dentistry, Seattle, WA 98195-2120, USA; Department of Restorative Dentistry, Box 357456, University of Washington School of Dentistry, Seattle, WA 98195-7456, USA.
| | - Shanshan Gao
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Renmin South Road, Chengdu, 610041, China
| | - Hai Zhang
- Department of Restorative Dentistry, Box 357456, University of Washington School of Dentistry, Seattle, WA 98195-7456, USA
| | - Radi Masri
- Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland School of Dentistry, 650 West Baltimore Street, 4th Floor, Suite 4228, Baltimore, MD 21201, USA
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21
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Enamel Microcracks Induced by Simulated Occlusal Wear in Mature, Immature, and Deciduous Teeth. BIOMED RESEARCH INTERNATIONAL 2018; 2018:5658393. [PMID: 29850534 PMCID: PMC5926526 DOI: 10.1155/2018/5658393] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Accepted: 02/12/2018] [Indexed: 11/17/2022]
Abstract
Enamel wear, which is inevitable due to the process of mastication, is a process in which the microcracking of enamel occurs due to the surface contacting very small hard particles. When these particles slide on enamel, a combined process of microcutting and microcracking in the surface and subsurface of the enamel takes place. The aim of this study was to detect microscopic differences in the microcrack behavior by subjecting enamel specimens derived from different age groups (immature open-apex premolars, mature closed-apex premolars, and deciduous molars) to cycles of simulated impact and sliding wear testing under controlled conditions. Our findings indicated that the characteristics of the microcracks, including the length, depth, count, orientation, and relation to microstructures differed among the study groups. The differences between the surface and subsurface microcrack characteristics were most notable in the enamel of deciduous molars followed by immature premolars and mature premolars whereby deciduous enamel suffered numerous, extensive, and branched microcracks. Within the limitations of this study, it was concluded that enamel surface and subsurface microcracks characteristics are dependent on the posteruptive age with deciduous enamel being the least resistant to wear based on the microcrack behavior as compared to permanent enamel.
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Zhang A, Zhang S, Bian C. Mechanical properties of bovine cortical bone based on the automated ball indentation technique and graphics processing method. J Mech Behav Biomed Mater 2018; 78:321-328. [DOI: 10.1016/j.jmbbm.2017.11.039] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 10/22/2017] [Accepted: 11/22/2017] [Indexed: 11/26/2022]
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Gao S, An B, Yahyazadehfar M, Zhang D, Arola D. Contact fatigue of human enamel: Experiments, mechanisms and modeling. J Mech Behav Biomed Mater 2016; 60:438-450. [DOI: 10.1016/j.jmbbm.2016.02.030] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 02/04/2016] [Accepted: 02/23/2016] [Indexed: 10/22/2022]
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Scheider I, Xiao T, Yilmaz E, Schneider G, Huber N, Bargmann S. Damage modeling of small-scale experiments on dental enamel with hierarchical microstructure. Acta Biomater 2015; 15:244-53. [PMID: 25484332 DOI: 10.1016/j.actbio.2014.11.036] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 10/27/2014] [Accepted: 11/18/2014] [Indexed: 11/27/2022]
Abstract
Dental enamel is a highly anisotropic and heterogeneous material, which exhibits an optimal reliability with respect to the various loads occurring over years. In this work, enamel's microstructure of parallel aligned rods of mineral fibers is modeled and mechanical properties are evaluated in terms of strength and toughness with the help of a multiscale modeling method. The established model is validated by comparing it with the stress-strain curves identified by microcantilever beam experiments extracted from these rods. Moreover, in order to gain further insight in the damage-tolerant behavior of enamel, the size of crystallites below which the structure becomes insensitive to flaws is studied by a microstructural finite element model. The assumption regarding the fiber strength is verified by a numerical study leading to accordance of fiber size and flaw tolerance size, and the debonding strength is estimated by optimizing the failure behavior of the microstructure on the hierarchical level above the individual fibers. Based on these well-grounded properties, the material behavior is predicted well by homogenization of a representative unit cell including damage, taking imperfections (like microcracks in the present case) into account.
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25
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Chai H. On crack growth in molar teeth from contact on the inclined occlusal surface. J Mech Behav Biomed Mater 2014; 44:76-84. [PMID: 25621848 DOI: 10.1016/j.jmbbm.2014.12.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 12/08/2014] [Accepted: 12/11/2014] [Indexed: 10/24/2022]
Abstract
Extracted human molar teeth are indented by hard balls laid at the central fossa, sectioned, and their interior examined for damage. Contact on the fissured enamel coat generally occurs on three distinct spots. The main forms of damage are radial cracks growing from the DEJ to the occlusal surface and median radial and cylindrical cracks growing from a contact spot to the DEJ. For large balls failure by edge chipping near a cusp apex may occur. The median cracks tend to run unstably to the DEJ upon reaching the middle part of the enamel coat. The corresponding load, PFM, and the load needed to initiate radial cracks at the DEJ, PFR, are taken to signal crown failure. The mean values of PFM and PFR are on the order of 1000N. A conical bilayer model defined by thickness d, inclination angle θ, failure stress σF and toughness KC of the enamel coat is developed to assess crown failure. The analytical predictions for PFR and PFM agree well with the tests. The results indicate that enamel thickness is so designed as to ensure that PFR and PFM just exceed the maximum bite force under normal conditions while the choice of θ seems to reflect a compromise between needs to resist crown failure and break hard food particles. Both PFR and PFM are greatly reduced with reducing d, which points to the danger posed by tooth wear. The analytical expressions for PFR and PFM may also apply to other multi-cusp mammalian or prosthetic molar crowns. Cone cracking, suppressed in the anisotropic tooth enamel, may be an important failure mode in prosthetic crowns.
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Affiliation(s)
- Herzl Chai
- School of Mechanical Engineering, Faculty of Engineering, Tel Aviv University, Israel.
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