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Determination of biomechanical characteristics of dentine and dental enamel in vitro
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Utyuzh Anatolij Sergeevich, Ph. D., Assistant Professor, Head of the department of Prosthetic Dentistry, I. M. Sechenov First Moscow State Medical University
Yumashev Aleksej Valerievich, Ph. D., Professor, Department of Prosthetic Dentistry, I. M. Sechenov First Moscow State Medical University
Zagorsky Vladislav Valerievich, Teaching Assistant of the department of Prosthetic Dentistry, I. M. Sechenov First Moscow State Medical University
Zakharov Aleksej Nikolaevich, assistant, Department of Prosthetic Dentistry, I. M. Sechenov First Moscow State Medical University
Nefedova Irina Valerievna, doctor-intern in the department of Prosthetic Dentistry, I. M. Sechenov First Moscow State Medical University E-mail: [email protected]
Determination of biomechanical characteristics of dentine and dental enamel in vitro
Abstract: Hardness characteristics of the hard tissues of a tooth are widely used in dentistry practice, both in diagnostics and in therapy, they are also very important for individual selection of restoration and other specialized materials. During examination of enamel and dentine hardness, it is very important to handle information that beside its theoretical value also has high practical value. For this purpose, we suggest to calculate hardness of tooth tissue on the basis of quantitative indicator of Vickers microhardness. This method allows to get precise values of hardness characteristics separately for enamels and dentine areas of different localization making a complete picture regarding their biochemical characteristics.
Keywords: change, hardness, microhardness, Vickers method, hard tooth tissues, dentine, enamel.
Studying of physical and chemical characteristics of hard velopment [1, 92-95]. Of no less value is taking into account tooth tissues has invaluable applied significance for dentistry biochemical characteristics of hard tooth tissues during treatment practice. Specialists examine these characteristics directly dur- process itself in order to choose an adequate therapeutic tactic, ing diagnostic testing in order to determine defect or violation tools and special materials required for reconstruction, correc-of integrity of tooth tissues, identify form of affection, type of tion and other types of dentist treatment. The indicator that is clinical progression of a disease and prognosis of its further de- used most frequently for qualitative estimation of biochemical
Section 6. Medical science
characteristics of hard tooth tissues and restoration materials is hardness [5, 143-146].
Examination of samples with special devices providing measurement of force and deformation is a common method for determination of hardness characteristics of materials. Sizes of a sample required for performance of these calculations as a rule exceed sizes of a tooth by a factor of 5-10 and more [2, 1198-1201]. In theory it is possible to make testing models from substance and tissues that form tooth, but results obtained will only characterize the hardness of the tooth in whole and not the hardness for each of these substances separately, and first of all the separate harness of dentine and enamel. Theoretical hardness of biomaterials thus calculated considerably differs from actual hardness due to nonuniform distribution of occlusal force in the areas of irregular geometric shape. Besides, in this case there is no possibility to determine biochemical characteristics in areas of transition from enamel to dentine.
Hardness and its ability to resist plastic deformation is one of the indicators characterizing durability of a substance. This quantitative indicator is widely used in dentistry for examination of characteristics of biomaterials [4, 19-26; 6, 383-386].
In view of the abovementioned facts, we suggest to determine hardness characteristics of tooth tissues by measuring their micro-hardness with following recalculation of obtained values into hardness indicators. Extrinsic value of this method is that it can be carried out without breaking of the test model.
Determination of the principle mechanical characteristics of hard tooth tissues in vitro was the objective of this study.
Materials and methods
After performing of preliminary studies it was determined that sufficiently complete information about hardness characteristics of a tooth may be obtained by determination of hardness of substances it consists of in points located on lines parallel to long axis of the tooth and line perpendicular to them and nearest located to the occlusal surface of tooth crown. In some cases determination of hardness was carried out in different parallel trajectories [3, 70-72].
Vickers hardness test involves calculating of indicator on the basis of the size of print obtained after pressing of pyramid load with a certain angle into testing material. For fine and miniature details it is possible to measure microhardness.
Distance between separate points where the hardness was measured was taken as 0.22 mm. This pitch size was determined as a minimal one where the results of neighboring measurements, performed via introduction of measuring prism in the material do not mutually affect each other. The selected interval was also chosen due to the resolving power of the method. In our studies it meant that it is impossible to register the hardness changes within this pitch [1, 92-95]. When processing the results the hardness values, deviating abnormally from similar parameters in neighboring points, were excluded and were replaced by mean value for the site. Such deviations were caused by increased calcium content in some zones, size of which was 0.2-0.3 mm. Within the study the described inclusions were considered not significantly affecting the hardness of tooth as a whole.
Results
Study of mircoslices of teeth in a number of samples showed the presence of altered dentin in form of ball-like inclusions of irregular shape with diameter to 0.5-0.8 mm of significant density. Also, in the apex part of dental root we noted the increase of dentin hardness. Statistical processing of the data and analysis of diagrams showed that all the samples are characterized by presence of at least two sites, where the harness values differ significantly from each other and conform to enamel and dentin hardness. At the same time the hardness values differ approximately 7-10 times. Some samples are characterized by the presence of sites with significantly increased hardness in the root apex. Length of those local areas was about 1 mm, and established hardness was comparable to enamel hardness. The presence of such sites was typical for the teeth of people older than 50 years. In our opinion, it can be caused by them developing the initial stage of dentin calcification, which, as known, starts from the area maximally close to the blood vessels near the root apex.
Thus, the most typical diagram of changes in hardness, and thus changes in durability of hard tissues of tooth is a stepped line. The largest section with low height of "step" conforms to dentin 500 to 1 000 Vickers hardness units with average value in longitudinal direction 467 ± 18.2, in transverse direction 565.8 ± 32.8, which explosively changes to the step of high hardness, conforming to enamel 500 to 4 700, with average value in longitudinal direction 2, 150.8 ± 24.8 and in transverse 3, 470.2 ± 17.4 Vickers hardness units. Results of microhardness measurements were confirmed by the data from microscopic studies [4, 19-26]. This showed clear border of transfer from dentin to enamel without transitional structures. If you compare mechanical properties of substances forming the tooth to the ones of steels used in engineering, you can say, that dentin conforms to the low-grade steel, and enamel — to special wear-resistant coatings of steel details, manufactured as the result of thermal diffusion saturation of surface layer with carbon, nitrogen or cyan salts. The resulting longitudinal and transverse hardness values differ due to specific orientation of enamel and dentin frames in longitudinal direction, caused by specific distribution of chewing load.
Statistical processing showed that the substances forming hard tissues of tooth have expressed individual properties (variability index in our studies was 28.7 %). Results of studies of hardness properties of substances forming the tooth, subsequently were used for analysis of distribution of internal forces, which presumes the mandatory knowledge of the values [3, 70-72]. When studying hardness of enamel and dentin on different levels of intact teeth using microradiography we did not detect the significant differences in density values separately for enamel and dentin. However the comparison of the density values for enamel and dentin showed that they differ significantly and this difference is 1.7 times. At the same time analysis of mechanic properties of the materials showed values differing 7-10 times. The resulting data signify that out of those two materials dentin is the main structure, where the stresses from enamel are actively redistributed and neutered in crown and root parts of tooth dentin regardless of its mechanical properties.
References:
1. Gaidarova T.A, Eremina N. A., Inshakov D. V. Method of lifetime measurement of dental tissue hardness//Journal of East Siberian Research Center of Siberian Division of Russian Academy of Medical Science. - 2007. - № 6(58). - P. 92-95.
2. ZaitsevD. V., Buzova E. V., Panfilov P. E. Hardness properties of dentin and enamel//TSU Journal. - 2010. - № 15(3). - P. 1198-1201.
3. Melikyan M. L., Gavryushin S. S., Melikyan K. M., Melikyan G. M. Analysis of strains in reinforced and non-reinforced composite restoration after removal of oblique defects (M. L. Melikyan class Ill) (PART I)//Dentistry Institute. - 2010. - № 4(49). - P. 70-72.
Ultrastructure of duodenal ulcers, their micro-collectors at hemorrhages and blood laser irradiation
4. Novak N. V., Baitus N. A. Analysis of physic-mechanical characteristics of hard tissues of tooth and of filling materials//Journal of Vitebsk State Medical University. - 2016. - № 15(1). - P. 19-26.
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Khadjibaev Abdukhakim Muminovich, PhD, ScD, Professor, Director General, Republican Research Centre of Emergency Medicine (RRCEM), Tashkent, Uzbekistan E-mail: [email protected] Baybekov Iskander Mukhamedovich, PhD, ScD, Professor, Republican Specialized Center of Surgery named after acad. V. Vakhidov (RSCS),
Tashkent, Uzbekistan E-mail: [email protected] Pulatov Dilmurod Tuhtabaevich, Senior scientific researcher, Republican Research Centre of Emergency Medicine (RRCEM), Tashkent, Uzbekistan E-mail: [email protected]
Ultrastructure of duodenal ulcers, their micro-collectors at hemorrhages and blood laser irradiation
Abstract: With the help of light and electronic microscopy duodenal ulcers morphology complicated by hemorrhage has been studied. The presence of micro-collectors (MC) and significant quantity of erythrocytes with the prevalence of their pathologic forms (EPF) in ulcers and in periulcerous zones has been shown. Ulcerous hemorrhages promote significant increase of EPF in peripheral blood and decrease of normal erythrocytes — discocytes (D). Intravascular laser irradiation of blood promotes normal ratio of D\EPF. The role of MC in ulcerous hemorrhages development is discussed.
Keywords: Ulcerous hemorrhage, micro-collector, erythrocytes, discocytes, intravascular laser irradiation of blood.
Ulcerous hemorrhages (UH) are the most dangerous compli- 35 microwatt. The use of disposable fiberglass conductor with teflon
cations of ulcerous disease. They are observed in 15-20 % patients coating allowed to increase significantly an efficiency and mainly to
with ulcerous disease [1; 9; 13]. simplify carrying out this not easy procedure and to make it abso-
Conducted morphologic investigations of chronic gastric and lutely safe [7; 8]. duodenal ulcers and peri-ulcerous zones with the use of light, elec- But investigations of duodenal ulcers at bleeding from them
tronic microscopy and special markers have proved an existence of with the presence of micro-collectors and influence on their patho-
so called micro-collectors (MC). They are the ways of aggression morphosis and peripheral blood erythrocytes with the use of IBLI,
factors (AF) penetration into mucous membrane thickness. It is a especially with the help of scanning electronic microscopy (SEM),
basic cause of ulcers occurrence and persisting [11-13]. have not been carried out.
The concept has been accepted as discovery — «Infiltration Object
of gastric juice occurrence through ulcerous defect in stomach and To show ultra-structural changes of bleeding ulcers of their
duodenum wall in patients with ulcerous disease». Priority dated micro-collectors and also erythrocytes after complex treatment
by February, 6, 1991 № OT - 12119. with the use of IBLI.
The role of MC in UH development has not been studied. Materials and methods
US promote significant shifts of discocytes (D) ratio in 62 cases of bleedings from chronic duodenal ulcers in patients
blood — normal erythrocytes and their pathologic forms (EPF) who were treated in RRCEM from 2008 to 2011 have been mor-
which is one of the main causes of micro-circulation abnormality. phologically investigated. All 62 patients with acute duodenal ulcers
Intro-vascular blood laser irradiation (IBLI) is widely used in hemorrhages have been performed operative interventions. Basic
complex treatment of various pathologic diseases [3; 14; 15]. It is type of surgery at duodenal ulcers hemorrhages, complications at
the most effective method of erythrocytes forms correction. IBLI is hospital were different ways of stomach resections. It has been per-
effective at different types of hemorrhages [5-8]. formed in 61 (98.3 %) patients. Only in 1 case laparotomy by exci-
Adoption into practice new generation of apparatus for IBLI sion of duodenal ulcer with pyloroplasty by Judd. allows to impact on blood and other organs by different ranges For hemorrhage severity estimation we have used subjective
of waves from 0.36 to 0.9 micrometers and with power from 1 to data after patien's examination and anamnesis collection, receiv-
