A Study of the Mechanical Role of Enamel and Dentin in Human Teeth

2012 ◽  
Author(s):  
Keyoung Jin Chun ◽  
Hyun Ho Choi ◽  
Jong Yeop Lee
Keyword(s):  
Surface Hardness ◽  
Mechanical Tests ◽  
Indentation Load ◽  
Bite Force ◽  
Compression Tests ◽  
Healthy Human ◽  
Human Teeth ◽  
Diamond Indenter ◽  
Dental Hard Tissues ◽  
Measured Hardness

The dental hard tissues of a tooth are combined of enamel and dentin together. The enamel protects the dentin and comes in direct contact with food during mastication. Bite force is expressed as compression force. The purpose of this study is to identify the primary roles of enamel and dentin during mastication by analyzing their mechanical properties and hardness. Healthy human teeth (age: 19.3 ± 4.1) were used as specimens for mechanical tests. The teeth, which underwent epoxy resin molding, were machine cut to make 10 enamel specimens, 10 dentin specimens and 10 enamel–dentin composite (ED) specimens of 1.2 mm × 1.2 mm × 3.0 mm (Width × Height × Length) in size. Compression tests were conducted using a micro-load system at 0.1 mm/min test speed. Teeth surface hardness (HV) was measured by a Vickers diamond indenter with a 300g indentation load. Data were obtained from 4 points on each enamel specimen and 4 points on each dentin specimen. The strain (%), stress (MPa) and modulus of elasticity (E, MPa) of the specimens were obtained from compression tests. The MAX. strain of the enamel, dentin and ED specimens were 4.5 ± 0.8 %, 11.9 ± 0.1 % and 8.7 ± 2.7 %, respectively. The MAX. stress of the enamel, dentin and ED specimens were 62.2 ± 23.8 MPa, 193.7 ± 30.6 MPa and 126.1 ± 54.6 MPa, respectively. The E values of the enamel, dentin and ED specimens were 1338.2 ± 307.9 MPa, 1653.7 ± 277.9 MPa and 1628.6 ± 482.7 MPa, respectively. The E of the dentin specimens was the highest and the E of the enamel specimens was the lowest, but the E values of all specimens was not significantly different in the T-test (P > 0.1). The measured hardness value of the enamel specimens (HV = 274.8 ± 18.1) was about 4.2 times higher than that of the dentin specimens (HV = 65.6 ± 3.9). Because of the values of MAX. stress and MAX. strain of the enamel specimens, the enamel specimens tended to fracture earlier than the dentin and ED specimens; therefore, enamel was considered to be more brittle than dentin and ED. Enamel is a harder tissue than dentin based on their measured hardness values. Therefore, enamel has a higher wear resistance, making it suitable for grinding and crushing, whereas dentin has a higher force function, making it suitable for abutment against bite force.

Micro & Nano-Scale Structure of Enamel and Dentin-Enamel Junction of Human Teeth

1999 ◽  
Vol 5 (S2) ◽  
pp. 1010-1011
Author(s):  
Hanson Fong ◽  
Mehmet Sarikaya ◽  
Shane White ◽  
Malcolm Snead
Keyword(s):  
Critical Role ◽  
Dissimilar Materials ◽  
Mechanical Tests ◽  
Microscopical Study ◽  
Dental Restoration ◽  
Human Teeth ◽  
Mechanical Coupling ◽  
Dental Hard Tissues ◽  
Bulk Scale

Enamel, which covers the anatomical crown of the tooth, is the hardest tissue in human body. Supported by a soft but tough dentin structure, the tooth is an advanced nanocomposite that can endure mastication stresses throughout a lifetime. A detail understanding the structure of the tooth, and sepecifically detin-enamel junction (DEJ), not only provides a sound basis for a model for synthetic dental restoration, but also provides lessons from nature on biomimetic regeneration with mechanical integrity. Enamel is a non-growing mineralized tissue and is subjected to most mechanical abuse. Dentin-enamel junction plays a critical role of distributing load between two very dissimilar materials - enamel and dentin. Bulk scale mechanical tests have shown that induced cracks on enamel tend to be arrested DEJ. Furthermore, nanoindentation measurements have also shown that there is a gradual decrease in hardness from enamel to dentin in the DEJ zone suggests a strong mechanical coupling in both deciduous and adult incisors. The objective of this investigation, through microscopical study, is to understand how these two dental hard tissues structurally couple through their junction zone.

Effect of silver nitrate on some mechanical properties of heat polymerizing acrylic resins

2019 ◽  
Vol 14 (1) ◽  
pp. 110
Author(s):  
Assiss. Prof. Dr. Sabiha Mahdi Mahdi ◽  
Dr. Firas Abd K. Abd K.
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Silver Nitrate ◽  
Surface Hardness ◽  
Mechanical Tests ◽  
Hardness Tester ◽  
Acrylic Resins ◽  
The Difference

Aim: The aimed study was to evaluate the influence of silver nitrate on surfacehardness and tensile strength of acrylic resins.Materials and methods: A total of 60 specimens were made from heat polymerizingresins. Two mechanical tests were utilized (surface hardness and tensile strength)and 4 experimental groups according to the concentration of silver nitrate used.The specimens without the use of silver nitrate were considered as control. Fortensile strength, all specimens were subjected to force till fracture. For surfacehardness, the specimens were tested via a durometer hardness tester. Allspecimens data were analyzed via ANOVA and Tukey tests.Results: The addition of silver nitrate to acrylic resins reduced significantly thetensile strength. Statistically, highly significant differences were found among allgroups (P≤0.001). Also, the difference between control and experimental groupswas highly significant (P≤0.001). For surface hardness, the silver nitrate improvedthe surface hardness of acrylics. Highly significant differences were statisticallyobserved between control and 900 ppm group (P≤0.001); and among all groups(P≤0.001)with exception that no significant differences between control and150ppm; and between 150ppm and 900ppm groups(P>0.05).Conclusion: The addition of silver nitrate to acrylics reduced significantly the tensilestrength and improved slightly the surface hardness.

Computerized infrared thermographic imaging and pulpal blood flow: Part 2. Rewarming of healthy human teeth following a controlled cold stimulus

2000 ◽  
Vol 33 (5) ◽  
pp. 448-462 ◽  
Author(s):  
B. E. Kells ◽  
J. G. Kennedy ◽  
P. A. Biagioni ◽  
P. J. Lamey
Keyword(s):  
Blood Flow ◽  
Healthy Human ◽  
Human Teeth ◽  
Cold Stimulus ◽  
Pulpal Blood Flow ◽  
Thermographic Imaging ◽  
Flow Part

The Effect of Substituting Metakaolin for Sand on the Thermomechanical Behaviour of Reactive Powder Concrete (RPC)

2019 ◽  
Vol 41 ◽  
pp. 115-130
Author(s):  
Nawal Siham Adamou Doumi ◽  
Hadjila Bournine Amrane ◽  
Ali Ahmed Benyahia
Keyword(s):  
Mechanical Strength ◽  
Microscopic Analysis ◽  
Mechanical Tests ◽  
Reactive Powder Concrete ◽  
Compression Tests ◽  
Electron Microscopic ◽  
Major Drawback ◽  
Thermomechanical Behaviour ◽  
Substitution Ratio ◽  
Reactive Powder

The weakening of the behavior of reactive powder concrete (RPC) under high temperature is a major drawback; therefore, it is necessary to find an ingredient that improves their resistance under rising temperatures. The present work involves the use of metakaolin as a substitute for sand in a reactive powder concrete (RPC) in order to assess its effect on the mechanical strength at high temperatures. The test specimens are preheated up to 100°, 300°, 500°, 700° and 900°C, respectively following a well-defined cycle, thereafter subjected to a three-point bending followed by compression tests. Samples of the tested specimens were used for thermal, mineralogical and microstructural analyses using the thermogravimetric and differential thermal analysis (TG / DTA), the X-ray diffraction (XRD) and the scanning electron microscopic Analysis (SEM).The heating tests revealed that all the specimens exploded before reaching 500°C. However, they can withstand 300°C before exploding for different exposure durations depending on the metakaolin substitution ratio. Therefore, the mechanical tests were applied only on unheated specimens and those heated up to 100°C. The results showed that the use of metakaolin improves the mechanical strength of the RPC, both at room temperature (25°C±1°C) and at 100°C. This result is confirmed by the microstructure analysis, which revealed the absence of portlandite. The latter did react with the metakaolin silica to form new calcium silicate hydrates (CSH) enhancing the mechanical strength.

Determination of the Elastic-Plastic Properties of 15Kh2MFA Steel with Austenitic Cladding

2013 ◽  
Vol 586 ◽  
pp. 43-46 ◽  
Author(s):  
Aleš Materna ◽  
Jiri Nohava ◽  
Petr Haušild ◽  
Vladislav Oliva
Keyword(s):  
Tensile Test ◽  
Indentation Test ◽  
Strain Curve ◽  
Indentation Load ◽  
Spherical Indentation ◽  
Compression Tests ◽  
Material Interface ◽  
Plastic Properties ◽  
Longitudinal Orientation ◽  
Sufficient Distance

The spherical indentation response of pressure vessel reactor steel with austenitic cladding is investigated both experimentally and numerically. The instrumented indentation test was performed for both materials at a sufficient distance from the bi-material interface, thus the results can be compared with the bulk data obtained from the standard tensile and compression tests. The stress – plastic strain curve for austenitic cladding estimated by a simplified inverse analysis of the indentation load – penetration curve is shifted to a harder response compared with that determined from the tensile test. One of the possible reasons, anisotropy of the cladding metal, was experimentally observed during the compression tests performed in the longitudinal orientation of the tensile test specimens and in the transverse orientation identical with the direction of the material indentation.

Effects of External Bleaching on Indentation and Abrasion Characteristics of Human Enamel in vitro

1992 ◽  
Vol 71 (6) ◽  
pp. 1340-1344 ◽  
Author(s):  
R.R. Seghi ◽  
I. Denry
Keyword(s):  
Fracture Toughness ◽  
Surface Hardness ◽  
In Vitro Study ◽  
Organic Matrix ◽  
Chemical Action ◽  
Apparent Fracture Toughness ◽  
Human Enamel ◽  
Dental Hard Tissues ◽  
Bleaching Gels

The application of home-bleaching procedures as a means of lightening multiple teeth has become increasingly popular. Very few studies, however, have determined the effect of this treatment upon dental hard tissues. This in vitro study evaluated the effects of a 10% carbamide peroxide gel on the apparent fracture toughness, hardness, and abrasion characteristics of human enamel. The apparent fracture toughness of enamel was reduced by about 30% after bleaching for a period of 12 hours with no significant change in surface hardness. Enamel treated with the bleaching gels also exhibited a small but significant decrease in abrasion resistance. This behavior was most likely due to an alteration of the organic matrix of enamel under the chemical action of hydrogen peroxide. Further investigation of the clinical significance of this process is needed.

Study of the ratcheting by the indentation fatigue method with a flat cylindrical indenter: Part I. Experimental study

2006 ◽  
Vol 21 (7) ◽  
pp. 1793-1797 ◽  
Author(s):  
B.X. Xu ◽  
Z.F. Yue
Keyword(s):  
Steady State ◽  
Fatigue Test ◽  
Indentation Depth ◽  
Fatigue Testing ◽  
Indentation Load ◽  
Compression Tests ◽  
Constant Rate ◽  
Secondary Stage ◽  
Indentation Fatigue ◽  
Analogous Equation

Generally, ratcheting is studied on round specimens under tension–compression tests with a nonzero mean load. This work explored the possibility of studying ratcheting by indentation fatigue with a flat cylindrical indenter. In the experiment, emphasis was concentrated on the influence of maximum indentation load (Pmax.), indentation load variance (ΔP = Pmax − Pmin) and frequency of cycling (f) on the indentation depth–cycle curves. The experimental results showed that the indentation depth–cycle curves are analogous to the conventional strain–cycle curve of uniaxial fatigue testing, which has a primary stage of decaying indentation depth per cycle followed by a secondary stage of nearly constant rate of indentation depth per cycle. It was found that the steady-state indentation depth per cycle is an approximate linear function of maximum indentation load (Pmax) and indentation load variance (ΔP = Pmax − Pmin) in the log–log grid. This relationship can be given with a power-law expression as an analogous equation of steady-state ratcheting rate. Further study showed that the influence of frequency of cycling on the steady state indentation depth per cycle can be ignored when the frequency of cycling exceeds a certain value. Finally, comparison was made between the conventional uniaxial fatigue test and indentation fatigue test for the steady-state stage. It was shown that the conventional uniaxial fatigue parameters can be obtained by the indentation fatigue method.

scholarly journals Thermomechanical Characterization of Monolithic Refractory Castables

2010 ◽  
Vol 70 ◽  
pp. 37-46 ◽  
Author(s):  
Thierry Cutard ◽  
Nicolas Donval ◽  
Aurélien Mazzoni ◽  
Claire Michel ◽  
Fabien Nazaret
Keyword(s):  
Tensile Tests ◽  
Thermomechanical Behavior ◽  
Mechanical Tests ◽  
Image Correlation ◽  
Compression Tests ◽  
Creep Tests ◽  
Refractory Castables ◽  
Complex Shapes ◽  
Damage Processes

This paper deals with the characterization of the thermomechanical behavior of monolithic refractory castables in a wide temperature range, up to 1200°C. Different test types are considered: tensile tests, compression tests, bending tests and tests on more complex shapes and geometries. A particular attention is paid to the detailed characterization and interpretation of the non-linear behaviors of these materials. Monotonic, cyclic and creep tests are considered. In some cases, digital image correlation (DIC) methods can be coupled to mechanical tests to obtain strain fields. Such results are particularly interesting to observe and to understand damage processes. As damage is a major characteristic of the monolithic castable behaviors, links are established between the thermomechanical behavior and damage mechanisms. Two main scales are taken into account for damage characterization: the macroscopic and the microscopic ones. Main mechanisms that are considered deal with microcracking, macrocracking, debonding and cavitation. Two types of materials are considered: non-reinforced and fiber reinforced refractory castables.

scholarly journals Three-Point Bending Tests of Zirconia Core/Veneer Ceramics for Dental Restorations

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
Massimo Marrelli ◽  
Carmine Maletta ◽  
Francesco Inchingolo ◽  
Marco Alfano ◽  
Marco Tatullo
Keyword(s):  
Surface Roughness ◽  
Comparative Study ◽  
Mechanical Strength ◽  
Surface Hardness ◽  
Mechanical Tests ◽  
Bending Tests ◽  
Three Point Bending ◽  
Dental Restorations ◽  
Modes Of Failure ◽  
Cad Cam

Introduction. The mechanical strength and the surface hardness of commercially available yttrium-doped zirconia were investigated. Furthermore, a comparative study of eight different ceramic veneers, to be used for the production of two-layered all-ceramic restorative systems, was carried out.Materials and Methods. Four types of zirconia specimens were analyzed, according to a standard ISO procedure (ISO 6872). Besides, two-layered zirconia-veneer specimens were prepared for three-point bending tests.Results. A strong effect of the surface roughness on the mechanical strength of zirconia specimens was observed. Finally, a comparative study of eight commercially available veneering ceramics shows different modes of failure between the selected veneers.Conclusion. The results indicate that close attention should be paid to the preparation of zirconia-based crowns and bridges by CAD/CAM process, because surface roughness has an important effect on the mechanical strength of the material. Finally, the results of the mechanical tests on two-layered specimens represent an important support to the choice of the veneering ceramic.

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