human activity. This option is most popular in production areas dealing with non-ferrous products. Color measurement is also important in printing and painting shops.
Colorimetry allows you to monitor the compliance of the colors of processed products and supplied raw materials with the assigned standards, organizes the tones and shades used into a single database for all partners involved in the process. In multicolor printing, it ensures the same result of the project implementation on various materials, used as a substrate. Industries that rely on mixed paints in their workflow use colorimetry to test constituent elements and create paint mixing formulas.
Assessing the quality of colors is necessary not only in production or printing enterprises, it is also in demand in smaller-scale processes: for design or artwork, calibrating printers, setting up monitors or TVs.
Depending on the specialization of work and target orientation, various types of measuring instruments and devices are used.
For more complex measurements in laboratory conditions, a stationary device with a spherical measurement method (Color Eye 7000 or Ci7800) is required.
To calibrate the printer, you need a special device model, for example, SpyderPrint. For computer display, projector, digital camera- i1Publish Pro 2 kit. Spyder4TV HD will help you adjust the colors on your high-definition TV.
In printing, in addition to spectrophotometers, densitometers are used to evaluate the density of the paint layer applied to the base.
Properties of materials characterizing the aesthetics of restoration. Factors influencing the aesthetic perception of restorative material. Subjective and objective methods for assessing aesthetic properties.
In the previous sections, the physico-chemical and physico-mechanical properties of dental materials that have great importance to restore the structures of the dental system, capable of absorbing and withstanding functional loads in the oral environment for a long time. Another important task of restorative dentistry is the reproduction appearance natural teeth.
IN last years Aesthetics in dentistry has become a priority. In this regard, scientific research has begun to be actively conducted, studying the influence of the composition and technology of using materials on their aesthetic indicators.
The doctor sees and can compare the colors of the tooth and the color standard, because light from the illumination source falls on these objects (Fig. 4.1).
Indicators that characterize the aesthetic properties of restoration materials include color, translucency, surface gloss And fluorescence.
Own color any object or object, as its inherent property, is the result of the interaction of this object with light from the illumination source. A material acquires color as a result of reflecting one part and absorbing another part of the spectrum of light incident on it.
Recall that light is a form of electromagnetic energy that can be perceived by the human eye. The eye perceives light in length
Rice. 4.1. Scheme for determining the appearance of an artificial crown by an observer
waves from approximately 400 nm (violet) to 700 nm (deep red). Light in this spectral range is often called visible light. The combination of wavelengths contained in a ray of light reflected from the surface of an object determines the property we call color. A surface that is blue reflects only the blue part and absorbs all other colors of the spectrum of light that illuminates it. Surface white reflects all wavelengths of the spectrum of light incident on it. A black object completely absorbs the entire light spectrum and does not reflect anything.
Translucency (degree of transparency) or translucency depends on the amount of light that an object can transmit. Objects with high transparency appear lighter. How clearer material, the more its color and appearance will be influenced by the background or substrate. Transparency decreases as the degree of light scattering in the material increases.
Surface gloss- an optical property that gives the surface a glossy, mirror-like appearance. Non-shiny and glossy surface differ in the ratio of specular and diffuse (scattered) reflection of light. Gloss can be characterized by the amount of light specularly reflected from the surface, which falls on it in the form of a beam of parallel rays. For specular reflection, the following law is observed: angle of incidence of light equal to angle his reflection. When a ray of light, I fall -
falling on the surface of an object, dissipates, the surface is perceived as matte, non-shiny or rough. The surface gloss decreases with increasing degree of scattering of the incident light beam. Bright shine is associated with the perfect smoothness of the surface, which is usually called mirror-like.
Fluorescence is the emission or emission of light from an object at a wavelength that is different from the wavelength of light incident or illuminating the object. Fluorescent emission stops immediately after the cessation of illumination of an object capable of fluorescence. Natural teeth fluoresce in the blue light range when exposed to ultraviolet radiation.
Each of the aesthetic indicators, from the point of view of observers such as the dentist, dental technician and patient, is influenced by:
1) lighting and, therefore, the illuminator (light source);
2) the intrinsic optical properties of the restoration material, which determine the nature of the interaction of light from the illuminator with the material;
3) perception of the result obtained by the observer. The characteristics of the light source are extremely important when assessing
colors because the intensity of light at certain wavelengths has a direct effect on the spectrum of light reflected by the object the observer is viewing. For a clearer description of the color, it is necessary to indicate under what lighting this color was determined. In restorative dentistry, it is better to use light sources that create lighting close to daylight. It is in such conditions that fillings and dentures will look as if they were in natural light.
The human eye is the most sensitive instrument for perceiving color and comparing color differences. The determination of color with its help occurs as a result of the action of the so-called color stimulus, which receives information from the cells of the retina (rods and cones). The perception of color is individual; compare, for example, the perception of color by an artist and a person with color vision impairment. There is such a violation of visual perception as color blindness - the inability to distinguish colors.
For an objective assessment of color, as well as other aesthetic characteristics of restoration materials, it is necessary to use standard observation conditions and instrumental measurement methods
using spectrophotometers and colorimeters. These devices must provide the results of observations or color measurements in an understandable, universal form, independent of the type and design of the device. Several color measurement systems have been proposed for this purpose. Let's consider some of them, the most interesting for use in restorative dentistry.
The Munsell color system includes three coordinates:
Color is the main characteristic that determines the observed color of an object, associated with the spectrum of light reflected by the object;
Lightness - characterizes the color as light or dark; if this indicator is low, the restored tooth appears gray and lifeless;
Saturation is a measure of the intensity (richness) of a color. For example, if you prepare an aqueous solution of methylene blue with a concentration of 0.1%, then the color saturation of the solution will be less than that of a solution of the same dye with a concentration of 1%.
The X, Y, Z color system is based on spectral characteristics that express the magnitude of the reflectance at a certain wavelength. It is based on the physical, optical characteristics of color, but it is not very convenient for practical use in assessing the color of dental materials.
The CIE I*a*b* color system also includes the determination of the spectrum of light reflected from an object and the value of the reflectance coefficient in the X, Y, Z system. From the obtained physical parameters X, Y, Z, more convenient values L*, a*, b* are calculated . The advantage of this system is that it can be represented as a three-dimensional color space that matches well visual perception colors, and the units of measurement for each color are easy to understand (Figure 4.2).
To determine the colors of natural teeth and select a restorative material that is similar in color and general aesthetic characteristics, standard color scales are used in dental clinical practice. They are called standard or reference tooth shades. These colors should cover color space, corresponding to all possible shades of natural teeth
Rice. 4.2. CIE L*a*b* color measurement system as a three-dimensional color space
bov. Although the area of tooth shades (see Figure 4.2) corresponding to tooth colors is very small in the CIE L*a*b* color space, dental shades should logically divide this space into a range of colors. Color samples should be made taking into account the nature of the restoration material for which they are intended.
LESSON No. 2
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Subject: |
The main groups of properties of dental materials: adhesion and adhesive properties, aesthetic properties, biocompatibility of dental materials. Quality control of dental materials. |
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Target: |
- study the classification of adhesive compounds, mechanisms of formation and conditions of destruction; To study the factors influencing the aesthetic perception of restorative material and methods for assessing aesthetic properties; Study the concept of biomaterial, bioinertness, biocompatibility and types of effects of biomaterial on the body. Categories of dental materials as biomaterials. Biocompatibility testing program; Study the quality criteria of dental materials and the system of international and national standards. |
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Method: |
Group lesson. | ||||
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Location: |
Classroom, clinical room, dental laboratory, manual skills room, dental materials science laboratory. | ||||
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Security: |
Technical equipment: multimedia equipment, dental units, dental instruments, dental materials. Tutorials: phantoms of the head and jaws, stands, multimedia presentations, educational videos. Controls: control questions, situational tasks, questions for test control, homework. | ||||
Lesson plan
1. Checking homework completion.
2. Theoretical part. Definition of the concept of adhesion. Classification of adhesive compounds in dentistry. Mechanisms of formation of adhesive compounds. Conditions for the formation and nature of destruction of adhesive bonds. Properties of materials characterizing the aesthetics of restoration. Factors influencing the aesthetic perception of restored material and methods for assessing aesthetic properties.
Biocompatibility of dental materials and methods for its assessment.
3. Clinical part. Demonstration by the teacher of types of adhesive bonds: between gels, varnishes and enamel (ceramics); between composites and hard dental tissues (adhesives with pre-etched type “ZM Single Bond” and without it, type “Pro Bond”).
Demonstration of a model of a carious cavity with mechanical adhesion in the form of jamming of material in irregularities to hold amalgam, special grips and irregularities on the surface of a metal frame when a plastic lining is applied to its surface; fixation of fixed dentures with inorganic cement (zinc phosphate cement), etc.
Demonstration by the teacher of materials and products with various aesthetic properties (amalgam, ceramics, polymers) and tooth colors, such as “VITA”, as well as materials biocompatible with dental tissues.
4. Independent work. Introducing students to the main types of adhesive materials: gels, varnishes, sealants, bondings with etching, primers with adhesives (without etching), cements for fixing fixed prosthetics, mechanical adhesives such as hooks, grooves, jamming of filling and veneering materials.
Introducing students to materials with various aesthetic properties with VITA tooth shades, as well as biocompatible dental materials.
5. Analysis of results independent work and theoretical knowledge on control questions and situational tasks.
6. Test control of knowledge.
7. Assignment for the next lesson.
annotation
Adhesion- this is a phenomenon that occurs when dissimilar materials are brought into close contact, and force must be applied to separate them. Adhesion occurs in many applications of restorative materials in dentistry. For example, when combining filling material with tooth tissue, sealant and varnish with tooth enamel, when fixing fixed dentures with cements. In orthodontics, braces are attached to the surface of the tooth using the principles of adhesion. Adhesion is also present in combined dentures: in metal-ceramic dentures - between porcelain and metal; in metal-plastic - between plastic and metal, etc.
The material or layer that is applied to form an adhesive bond is called adhesive. The material on which the adhesive is applied is called substrate.
Fig.1. Classification of types of adhesive joints in dentistry.
There are significant differences between the adhesives of restorative materials to living tissue and the connections of dissimilar materials used in dentures.
There are several mechanisms for the formation of an adhesive joint due to different types of adhesive bonds.
Fig.2. Classification of types of adhesive bonds.
Chemical adhesion is stronger and more reliable. It is based on the chemical interaction of two materials, which is inherent in aqueous cements based on polyacrylic acid, which contains functional groups that can form chemical compounds with hard dental tissues - with calcium hydroxyapatite.
Diffuse the compound is formed as a result of the penetration of components of one material into the surface of another, forming a “hybrid” layer that contains both materials.
In practice in pure form Adhesive joints are difficult to find. In most cases, when using different chemical natures to restore teeth, adhesive interaction of a mechanical, diffuse and chemical nature takes place.
Conditions for creating a strong adhesive connection.
1. Cleanliness of the surface on which the adhesive is applied.
2. Penetration of the liquid adhesive into the surface of the substrate, which depends on the ability of the adhesive to wet the surface of the substrate.
Wettability is characterized by the ability of a drop of liquid to spread over the surface of a substrate. A measure of wetting is the contact angle (θ - ( Greek.) theta), which is formed between the surface of liquid and solid bodies at their interface (Fig. 3).
Fig. 3 Contact wetting angle - adhesion criterion.
3. Minimal shrinkage and minimal stress when the adhesive hardens on the surface of the substrate.
4. Minimum thermal stress. If the adhesive and substrate have different coefficients of thermal expansion, then when heated, the adhesive seam will experience stress (application of porcelain lining to the metal frame, firing of the product at high temperatures, then cooling until room temperature). If the material coefficients are close, the stress will be minimal.
5. Influence of a corrosive environment. The presence of moisture in the oral cavity significantly impairs adhesive bonds, promoting the formation of corrosive fluids.
Adhesive strength.
Adhesion is judged by the value of adhesive strength, i.e. on resistance to destruction of adhesive joints. As follows from the definition of adhesion, it is sufficient to measure the applied forces to separate the adhesive joint. Many methods have been proposed for measuring various adhesive bonds, but all methods have only three failure mechanisms: tension, shear and uneven separation. The fracture surface during testing passes along the weakest link of the connection.
Another important task of restorative dentistry is to reproduce the appearance of natural teeth and their aesthetic characteristics.
Indicators characterizing the aesthetic properties of dental materials include: color, translucency, surface gloss, fluorescence .
Own color of any object (tooth) is the result of the interaction of this object (tooth) with light from a lighting source. The material of the object (tooth) acquires color as a result reflections one part and takeovers another part of the spectrum of light incident on it.
Fig.4. Scheme for determining the appearance of an artificial crown by an observer.
Light is a form of electromagnetic energy that the human eye can perceive with wavelengths ranging from 400 nm (violet) to 700 nm (dark red) - it is called "visible light". The combination of wavelengths contained in a beam of light reflected from the surface of an object determines a property that we call color . The blue surface reflects only the blue part and absorbs all other colors of the illuminating light spectrum; a white surface reflects all wavelengths of the spectrum of light incident on it; The black surface completely absorbs the entire light spectrum and does not reflect anything.
Translucency or translucency depends on the amount of light that an object can transmit. Objects with high transparency appear lighter, but the more transparent the material, the more its color is affected by the background or underlying material.
Shine surfaces - an optical property that gives the surface a glossy, mirror-like appearance. Non-shiny and glossy surfaces differ in the ratio of specular and diffuse reflection of light. Shine is characterized by mirror quantity reflected light, which falls on it in the form of a beam of parallel rays. For specular reflection, the following law is observed: the angle of incidence of light is equal to the angle of its reflection. When the incident beam of light is scattered, the surface of the object is perceived as matte, dull or rough. The surface gloss decreases with increasing scattering of the incident light. Bright shine is associated with the perfect smoothness of the surface, which is called mirror-like.
Fluorescence is the emission or emission of light by an object with a wavelength different from the wavelength of light incident or illuminating the object. Fluorescent emission ends immediately after the cessation of illumination capable of fluorescence of the object. Natural teeth fluoresce in the blue light range when exposed to ultraviolet radiation.
Each of the aesthetic indicators from the point of view of the dentist, dental technician and patient is influenced by:
1. light source;
2. own optical properties of the restoration material;
3. perception of the result obtained by the observer.
Characteristic light source extremely important. In restorative dentistry, it is better to use a light source that is daylight or close to daylight. It is under such conditions that fillings and dentures will look natural.
The human eye is the most sensitive instrument for perception of light and comparison of color differences, but it is individual (the perception of color by an artist and a person with impaired color vision or a complete lack of color perception - color blindness). The determination of color by the eye occurs as a result of a color stimulus receiving information from the cells of the retina.
To objectively assess light, as well as other aesthetic characteristics of restoration materials, standard conditions are used using spectrophotometers and colorimeters. Several measurement systems have been proposed for use in restorative dentistry, for example, the Munsell color system, which includes 3 coordinates:
Color, the main characteristic that determines the observed color of an object, associated with the spectrum of light, the reflected object;
Lightness - characterizes the light as light or dark; if the indicator is low, the color of the tooth being restored appears gray and lifeless;
Saturation is a measure of color intensity (more than bright hues or darker ones of the same color).
The color system X, Y, Z and CIE L*a*b* are based on the spectral characteristics of the reflectance value at a certain wavelength, but they are cumbersome and not convenient for practical use in assessing the light of dental materials.
International system CIE L*a*b* for instrumental color measurement, where L* - determines the degree of whiteness from black (0) to white (100); a* - defines green and red colors; b* - defines blue and yellow colors. Color samples should be made taking into account the nature of the restoration material for which they are intended.
In practice, standard color scales are used to determine the color of teeth and select restorative materials. This shade scale should cover all possible shades of natural teeth. The most popular is the VITA color scale, in which the letter A denotes red-orange shades, the letter B - yellowish, C - grayish - green, D - brownish. The numbers indicate the degree of lightness and saturation of a given color (for example, color A1 is less saturated and lighter than A3.5).
No matter how durable and aesthetically pleasing a material is, if its use can cause negative reactions in the body, the use of this material should be abandoned. Until now, we have simply talked about materials of various chemical natures and their properties without taking into account its interaction with the tissues of the patient’s body at the local and systemic level. Consequently, dental material is not just a material of a certain chemical nature, but the concept of “biological” material (biomaterial) is applicable to it.
Biomaterial - any foreign material that is placed into the tissues of the body for any period of time in order to eliminate deformities or defects or to replace natural tissues of the body that are damaged or lost due to injury or disease.
The biomaterial must have properties biocompatibility . This term appeared in 1960. Before this it was customary to talk about bioinert material in relation to the surrounding tissues: does not have any effect harmful effects on them and does not interact with them in any way. Currently, from a material, for example, to restore a tooth crown, one expects not only the formation of a strong bond with the dental tissues, but also their healing and regeneration. It is incorrect to call such a material inert. Therefore the term is used bioacceptable, biocompatible.
Basic requirements for biocompatible and bioinert materials:
Bioinert material:
Does not damage the pulp and soft fabrics oral cavity;
Does not contain harmful substances;
Does not contain sensitizing substances that cause allergic reactions;
Non-carcinogenic;
Forms an adhesive connection with the hard tissues of the tooth.
Biocompatible material:
It has the same properties as bioinert, and also has a healing, regenerating effect.
When assessing biocompatibility, materials are distinguished according to the type of effect on the body:
General: toxic, allergic, psychological;
Local: mechanical, toxic local, temperature.
To determine the biocompatibility of a material before its clinical use, tests are carried out to determine whether the material complies with the standards and requirements in accordance with GOST R ISO 10993 standards for biocompatibility and toxicity. The program is compiled based on the specific purpose of the material.
For a standardized approach, all dental biomaterials are divided into categories depending on the body tissues with which the material must come into contact and the time of contact.
With the mucous membranes of the oral cavity;
With bone tissue, hard tooth tissues;
With periodontal tissues, blood;
With skin;
With tooth pulp.
Once or repeatedly, but not less than 24 hours;
Single or multiple times for more than 24 hours, but not less than 30 days;
Constant contact for more than 30 days.
Having determined these parameters, we begin to draw up a test program, which includes a number of methods or tests, which are divided into 3 levels:
Level 1: initial rapid tests;
Level 2: experimental tests on animals;
Level 3 - preclinical tests of purpose (on animals).
Toxicological tests on experimental animals are lengthy and expensive. Therefore, “0” level is often used for preliminary assessment - these are sanitary and chemical tests that are widely used in our country. This level is relevant for content in dental materials chemical substances, for which maximum permissible concentrations upon contact with the body are known.
Quality control of dental materials
The main groups of material properties for preclinical assessment of their quality:
Biological:
- biocompatibility indicators,
- hygienic properties,
- organoleptic.
Important for the safety of using the material in the clinic are toxicological tests that determine a set of material properties and evaluate it biocompatibility.
Hygienic properties - the ability of dental materials to be cleaned with conventional means of hygienic teeth cleaning and not to change their properties under the influence of various means hygiene.
Biological requirements are related to organoleptic- the restoration material should not have an unpleasant taste or odor.
Technical :
- physical-chemical and physical-mechanical properties;
- aesthetic: color and color fastness, translucency, surface smoothness, fluorescence.
- technological: mixing time of components, hardening time, consistency and fluidity.
The technical properties of materials are determined in laboratories using standard samples. The choice of quality indicators depends on its purpose and chemical nature (it is pointless to determine the aesthetic qualities of amalgam, etc.). In Russia, there is a procedure for the development of dental materials before obtaining permission for their use in clinical practice (GOST R 15013-94).
Structure of the standard (GOST R):
I. Scope of the standard.
II. Terms and Definitions.
III. Classification.
IV. Requirements (standards) for property indicators.
V. Test methods.
VI. Packaging requirements and instructions.
These standards (as well as the methods for determining them) are the main content of the standards for dental materials. Any newly developed material must be tested for the appropriate requirements according to the classification of dental materials.
The Federation Dentaire Internationale (FDI) and the International Organization for Standardization ISO are working on new and improved standards.
SYSTEM
Dental Materials Standards
International Dental Federation, FDI
International Organization for Standardization, ISO
TK 106 (founded 1963)
Russia - TK 279, 1980
USA - ADA, 1966
Australia - 1973
Scandinavian countries - 1973
European Normalization Committee, 1995
Fig.5. International and national organizations for the standardization of dental materials.
The ISO standards for dental materials are managed by technical committee TC 106, which includes national committees from more than 80 countries.
Russia is also a member of ISO, represented by the Technical Committee for Standardization of Dental Apparatuses, Instruments and Materials TK 279 (Dental Medicine). Standardization work within the framework of the International Organization ISO includes the determination of requirements and standards for the properties of each class of dental materials, standardization of terminology and test methods. A dentist who works with materials that meet the requirements of the standards can be confident that the material used will not give significant negative results during its clinical use.
The final criterion for the quality of a dental material is its behavior in the patient’s oral cavity. This can only be assessed by a clinician based on his observations, analysis of successful results and failures.
Scheme of the indicative basis of action
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Stages of work |
Facilities and working conditions |
Criteria for self-control |
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1 |
2 |
3 |
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I Adhesion |
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The main attention is paid to the teacher’s information about various types adhesive connections |
Gels, varnishes, sealants, bonding agents with etching, primers with adhesives without etching, cements for fixing fixed dentures. Mechanical adhesives for fixing amalgam, plastic veneers, porcelain facets on models artificial teeth. |
Background knowledge guidelines, diagrams, stands, notebooks. Models of artificial teeth with mechanical types of adhesion. |
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II Aesthetics in dentistry |
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1. Compare in general materials of different chemical orientations according to their aesthetic properties: color, translucency, shine and fluorescence. |
Metals - amalgam, metal frames for removable dentures, metal crowns, ceramics, polymers. |
Background knowledge, lectures, methodological developments, homework. |
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2. Compare the translucency of enamel and dentin of a natural tooth. |
Natural teeth, cuts of groups of teeth. |
Basic knowledge about factors influencing aesthetic indicators: lighting, own tooth color, observer perception. |
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3. Determine the color of natural teeth and select a restorative material. |
Standard VITA color scale, natural teeth, materials: ceramics, polymers. |
Knowledge of the VITA color scale: designations of letters A, B, C, D and numbers - 1, 2, 3, 4...... |
Control questions
Adhesion and its importance in restorative dentistry
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1. What is adhesion and its importance in dentistry?
2. What is adhesive and substrate? Give examples in the field of dentistry.
3. List and characterize the types of adhesive bonds, give examples of adhesive bonds: mechanical, chemical, diffuse.
4. What is contact angle? What is the significance of this characteristic for an adhesive connection?
5. What effect does the shrinkage of the adhesive during curing have on the strength of the adhesive joint?
6. What conditions and properties of materials affect the quality of the adhesive connection?
7. What methods exist for determining the strength of an adhesive joint used in dentistry?
Aesthetic properties of restoration materials
8. What indicators characterize the aesthetic properties of dental materials?
9. Compare in general dental materials of different chemical natures: metals, ceramics, polymers according to their aesthetic properties.
10. What factors influence the perception of the color of a restoration material?
11. What optical properties are associated with surface gloss, degree of transparency and fluorescence of the restoration material?
12. What systems and devices for objective color measurement can you name?
13. What are the reference colors for dental restorative materials?
Biocompatibility of dental materials
14. What is biocompatibility and bioinertness?
15. List the basic requirements for biocompatible and bioinert material. Give examples.
17. What levels should a dental materials toxicology testing program include?
18. What are the hygiene tests of dental materials?
Quality criteria for dental materials
19. List the groups of requirements that materials for dental use must meet.
20. What are the technical tests dental materials?
21. Structure of the national standard of Russia - GOST R?
22. International and national organizations for organizing the standardization of dental materials?
Situational tasks
1. Mark the type of adhesive biological compound with a “+” sign:
2. Match the types of adhesive bonds:
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Adhesive bonds |
mechanical |
chemical |
diffuse |
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1. Macro-mechanical | |||
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2. Ionic | |||
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3. Metal | |||
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4. Covalent | |||
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5. Micromechanical | |||
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6. Penetration of one material into the surface of another with the formation of a “hybrid” layer |
3. Relate the necessary conditions creating a strong adhesive connection:
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The necessary conditions |
Adhesive strength |
Minor Conditions |
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1. Surface cleanliness | ||
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2. Generation of liquid adhesive into the surface of the substrate | ||
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3. Minimal shrinkage of the adhesive during hardening | ||
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4. Minimum possible thermal stress: a) with different coefficients of thermal expansion of the adhesive and substrate; b) with similar expansion coefficients of the adhesive and substrate | ||
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5. No influence of corrosive environment |
4. At what angle of wetting with the adhesive will there be a strong mutual attraction between the molecules of the adhesive and the substrate?
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Contact angle |
No wetting |
Satisfactory wetting |
Good wetting |
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θ 1 > 90 0 | |||
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θ 2 | |||
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θ 3 |
5. Correlate the indicators characterizing the aesthetic properties of materials:
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Properties of materials |
Yes |
No |
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1. Color | ||
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2. Elasticity | ||
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3. Translucency | ||
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4. Durability | ||
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5. Surface gloss | ||
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6. Fluorescence | ||
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7.Hardness | ||
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8. Plasticity |
6. Correlate the methods for assessing aesthetic characteristics:
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Methods for measuring and determining tooth color |
Hardware |
Standard color scales |
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1. Munsell color system | ||
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2. Color system X, Y, Z | ||
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3. CIEL*a*b* color system, three-dimensional image | ||
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4. VITA colors |
7. Compare the requirements for biocompatible and bioinert dental materials:
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Requirements |
Towards biocompatible materials |
To bioinert materials |
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1. Do not damage the pulp and soft tissues of the oral cavity | ||
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2. Provide a healing and regenerating effect | ||
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3. Do not contain harmful substances | ||
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4. Do not contain sensitizing substances that cause allergies | ||
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5. Form an adhesive connection with hard tooth tissues | ||
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6. Not carcinogenic |
8. What level of testing for the biological assessment of dental materials is most often used in Russia?
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Nature of contact |
Categories |
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by duration of contact |
by the nature of contact with the body |
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1. With the mucous membranes of the oral cavity | ||
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2. Once or repeatedly, but less than 24 hours | ||
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3. With bone tissue, hard tooth tissues | ||
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4. Single or multiple times, more than 24 hours, but less than 30 days | ||
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5. With blood | ||
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6. With periodontal tissues | ||
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7. With leather | ||
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8. With tooth pulp | ||
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9. Constant contact, more than 30 days | ||
10. Determine the content of the GOST R (Russia) standard for dental materials:
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Contents of the standard |
GOST R standard |
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Yes |
No |
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1. Scope of the standard | ||
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2. Terms and definitions | ||
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3. Classification | ||
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4. Requirements (standards) for indicators of material properties | ||
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5. Test methods | ||
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6. Packaging requirements and instructions | ||
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7. Physico-chemical properties | ||
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8. Adhesive properties | ||
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9. Biocompatibility of the material | ||
11. Correlate international and national organizations for the standardization of dental materials:
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Organizations |
international |
national |
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1.FDI | ||
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2. ISO | ||
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3. TK 106 | ||
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4. TK 279 | ||
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5. ADA |
Test knowledge control
1. What failure mechanisms are present when testing adhesive strength?
a) when stretched;
b) shift;
c) with uneven separation;
d) during compression;
d) during torsion.
2. What contact angle is optimal for creating a strong adhesive joint?
a) θ 1 > 90 0;
3. What kind of light is called “visible”?
a) from 200 to 300 nm;
b) from 400 to 700 nm;
c) from 800 to 1000 nm;
d) from 1100 to 1500 nm.
4. How does the blue color surface of the illuminating light spectrum reflect and absorb?
a) a blue surface reflects only the blue part and absorbs
all other colors;
b) a blue surface absorbs only white color and reflects
other;
c) a blue surface absorbs only black color and reflects
other;
5. How does a white color surface reflect and absorb the spectrum of illuminating light?
a) a white surface reflects all wavelengths of the spectrum
the light falling on it and does not absorb anything;
b) a white surface absorbs all wavelengths of incident light
and does not reflect anything;
c) a white surface absorbs black wavelengths and
reflects all the others.
6. What determines the translucency of a material or object?
a) on the amount of light that an object can transmit;
b) on the degree of scattered light;
c) from the background (substrate);
d) from the smoothness of the material;
e) on the roughness of the material.
7. How do natural teeth fluoresce when exposed to ultraviolet radiation?
a) in the pink color range;
b) in the white color range;
c) in the blue range;
d) in the greenish color range.
8. Under what conditions will fillings and prostheses made from restored materials look natural?
a) in natural light at night;
b) in natural daylight;
c) in the light of a normal electric lamp;
d) in the light of fluorescent lamps.
9. What does the biocompatibility testing program for dental materials include, according to GOST R ISO 10993 standards?
Test methods :
c) level 1 - initial rapid tests;
d) Level 2 - experimental tests on animals;
e) 3rd level - preclinical tests of purpose (on animals);
f) Level 0 - sanitary and chemical tests.
10. What is the procedure for developing dental materials before obtaining permission for their use in the clinic in accordance with GOST R 15013-94 in Russia?
a) standards for property indicators:
Flexural Strength of Composite Restoration Material
must be at least 50 MPa;
The compressive strength of silicate cement is not less than 190 MPa;
Adhesive strength of the connection between the composite and hard dental tissues
Not less than 7 MPa;
Water absorption of polymer material for removable denture bases
should not be more than 32 μg/mm 3, etc.
b) these standards are laid down in material standards only for
dental materials used in clinics;
c) these standards are laid down in the standards of materials for laboratory
clinical work;
d) these standards are laid down for each class of materials, according to
classifying them.
Homework
1. Draw a diagram of adhesive connections in dentistry.
2. Draw a diagram of the types of adhesive bonds.
3. Describe the conditions for creating a strong adhesive joint.
Literature
Main:
1. Bazikyan E.A. Propaedeutic dentistry. Tutorial for medical universities. - M.: Publishing house "GEOTAR-Media", 2008. - P. 482-489, 518-527.
2. Popkov V.A., Nesterova O.V., Reshetnyak V.Yu., Avertseva I.N. Dental materials science. - M.: Publishing house "Mediapress-inform", 2006, - P.5-19.
3. Methodological developments Department of Propaedeutics of Dental Diseases of St. State Medical Academy.
Additional:
1. Poyurovskaya I.Ya. Dental materials science. Tutorial. - M.: Publishing group "GEOTAR-Media", 2007. - P.5-10.
2. Vyazmitina A.V., Usevich T.L. Materials science in dentistry. Tutorial. - Rostov-on-Don, 2002. - pp. 11-15.
3. Craig R., Powers J., Vataga J. Dental materials: properties and applications. Translation from English by Shulgi O.A. - M.: Publishing house "MEDI", 2005. - P.9-38.
4. Trezubov V.N., Mishnev L.M., Zhulev E.N. Orthopedic dentistry. Applied materials science. Textbook for medical schools. - M.: MEDIpress-inform", 2008. - P.9-11.
5. Dmitrieva L.A. Modern filling materials and medications in therapeutic dentistry. - M.: Medical Information Agency, 2011. - P.6-13.
Although the human eye is a perfect data transmission system, it is not capable of providing exact description colors. This requires additional physical tools that accurately quantify the key parameters of color samples. In this case, colorimetry helps - the science of measuring and quantifying color. Visual and photoelectric colorimeters, color comparators, spectrophotometers - instruments for studying color. They are used in various fields human activity. For example, light industry, geology, heterogeneous design, etc.
The eye can distinguish up to 13 thousand shades with the help of devices and about 200 tones without them. Since progress is growing exponentially, a clear system for grouping colors was needed. This is exactly what colorimetry does.
Colorimetry is the science of measuring color.
Nowadays, there are several color systems - CIE, RGB, CMYK, TGL, NCS, HLS, YIQ, etc. The basis of each is an atlas. Some reproduce more than 20,000 shades. He serves the most important tool, which brings order to the production of coloring compositions. Each of them is obtained by mixing together the main purest chromatic pigments. In addition, black or white pigments. Thus, each new shade gets its own personal number. Moreover, its other characteristics are also used. As a result, manufacturers achieve precise recipes for preparing coloring compositions. Subsequently, the manufacturer can accurately reproduce the shade desired by the customer. In colorimetry, the following tone “coordinates” are used:
The first process includes the following subtypes:
The second color mixing process is subtractive or subtractive mixing. Its essence is the partial absorption of colored rays from the light stream. It is present in almost every material body. Its basic law is that any chromatic body reflects or transmits rays of its own color and absorbs a color that is complementary to its own.
Color theory through the eyes of a child
For convenience, catalogs, reference scales, color books, color fans, color libraries are created, which help to select and create harmonious combinations of colors in all possible areas of human activity. For example, you can collect a color library yourself. Magazine clippings and photographs are suitable for her.
methods for measuring and quantifying color. Together with different ways mathematical description of color color and. constitute the subject of colorimetry. As a result, C. and. 3 numbers are determined, the so-called. color coordinates (CC), which completely determine the color (under certain strictly standardized conditions for viewing it).
The basis of the mathematical description of color in colorimetry is the experimentally established fact that any color, subject to the above conditions, can be represented as a mixture (sum) of certain quantities of 3 linearly independent colors, i.e., such colors, each of which cannot be represented as a sum any quantities of 2 other colors. There are infinitely many groups (systems) of linearly independent colors, but only a few of them are used in colorimetry. Three selected linearly independent colors are called primary colors (See Primary colors) ; they define the color coordinate system (CCS). Then the 3 numbers describing a given color are the quantities of primary colors in a mixture whose color is visually indistinguishable from the given color; this is the Central Committee of this color.
Experimental results, which form the basis for the development of a colorimetric CF, are obtained by averaging observational data (under strictly defined conditions) a large number observers; therefore, they do not accurately reflect the properties of color vision (See Color Vision) of any particular observer, but refer to the so-called. to the average standard colorimetric observer.
Being related to a standard observer under certain unchanging conditions, standard color mixing data and the colorimetric CKS constructed on them actually describe only the physical aspect of color, without taking into account changes in color perception of the eye when observing conditions change and for other reasons (see Color).
When the central center of any color is laid out along 3 mutually perpendicular coordinate axes, this color is geometrically represented by a point in three-dimensional, so-called. color, space or Vector , the beginning of which coincides with the origin of coordinates, and the end with the mentioned color point. Point and vector geometric interpretations of color are equivalent and both are used when describing colors. The points representing all real colors fill some region of color space. But mathematically, all points in space are equal, so we can conditionally assume that points outside the region of real colors represent some colors. This expansion of the interpretation of color as a mathematical object leads to the concept of the so-called. unreal colors that are practically impossible to realize in any way. Nevertheless, mathematical operations can be performed with these colors in the same way as with real colors, which turns out to be extremely convenient in colorimetry. The ratio between the primary colors in the CFB is chosen so that their quantities, which give a certain initial color in the mixture (most often white), are taken equal to 1.
A kind of “quality” of color, which does not depend on the absolute value of the color vector and is called its chromaticity, is geometrically convenient to characterize in two-dimensional space - on a “unit” plane of color space passing through 3 unit points of the coordinate axes (axes of primary colors). The lines of intersection of the unit plane with the coordinate planes form an equilateral triangle on it, at the vertices of which are the unit values of the primary colors. This triangle is often called Maxwell's triangle. The chromaticity of a color is determined not by its 3 CCs, but by the relationship between them, i.e., the position in the color space of a straight line drawn from the origin through a point of a given color. In other words, chromaticity is determined only by the direction, and not the absolute value, of the color vector, and, therefore, it can be characterized by the position of the point of intersection of this vector (or the specified straight line) with the unit plane. Instead of Maxwell's triangle, a color triangle of a more convenient shape is often used - rectangular and isosceles. The position of the chromaticity point in it is determined by two chromaticity coordinates, each of which is equal to the quotient of dividing one of the central centers by the sum of all 3 central centers. Two chromaticity coordinates are sufficient, because by definition, the sum of its 3 coordinates is equal to 1. The chromaticity point of the original (reference) color, for which the 3 color coordinates are equal to each other (each equal to 1/3), is located at the center of gravity of the color triangle.
The representation of color using CKS should reflect the properties of human color vision. Therefore, it is assumed that the basis of all CCS is the so-called. physiological CCS. This system is determined by 3 functions of spectral sensitivity (See Spectral sensitivity) 3 different types of light receivers (See Light receivers) (the so-called cones) that are present in the retina (See Retina) human eyes and, according to the most commonly used three-color theory of color vision, are responsible for human color perception. The reactions of these 3 receivers to radiation are considered to be the central concentration in the physiological central nervous system, but the functions of the spectral sensitivity of the eye cannot be established by direct measurements. They are determined indirectly and are not used directly as a basis for constructing colorimetric systems.
The properties of color vision are taken into account in colorimetry based on the results of experiments with color mixing. In such experiments, a visual comparison is made of pure spectral colors (i.e., colors corresponding to monochromatic light (See Monochromatic light) with different wavelengths) with mixtures of the 3 primary colors. Both colors are observed side by side on 2 halves of the photometric comparison field. Once equalization is achieved, the quantities of the 3 primary colors and their ratios to the quantities of primary colors taken as 1 in the mixture equalizing the selected reference white color are measured. The resulting values will be the central center of the equalized color in the central color coordinate system, determined by the primary colors of the device and the selected reference white color. If unit quantities of red, green and blue primary colors are denoted as (K), (Z), (S), and their quantities in the mixture (CC) - K, Z, S, then the result of the equalization can be written in the form of a color equation: C * = K (K) + Z (Z) + S (S). The described procedure does not allow the majority of pure spectral colors to be equalized with mixtures of the 3 primary colors of the device. In such cases, some amount of one of the main colors (or even two) is added to the equalized color. The color of the resulting mixture is equalized with the mixture of the remaining 2 primary colors of the device (or with one). In the color equation, this is taken into account by moving the corresponding term from the left side to the right. So, if red color was added to the field of the measured color, then C* = - K (K) + Z (Z) + C (S). Assuming negative CC values, all spectral colors can be expressed through the selected three primary colors. By averaging the results of a similar procedure for several observers, values were obtained for the quantities of 3 specific colors required in mixtures that were visually indistinguishable from pure spectral colors that correspond to monochromatic radiation of the same intensity. When plotting graphically the dependences of the quantities of primary colors on the wavelength, functions of the wavelength are obtained, called color addition curves or simply addition curves.
Addition curves play an important role in colorimetry. From them it is possible to calculate the quantities of primary colors required to obtain a mixture that is visually indistinguishable from the color of radiation of a complex spectral composition, i.e., the central center of this color in the central color coordinate system, determined by these addition curves. To do this, the color of complex radiation is represented as a sum of pure spectral colors corresponding to its monochromatic components (taking into account their intensity). The possibility of such a representation is based on one of the experimentally established laws of color mixing, according to which the CCs of the colors of the mixture are equal to the sums of the corresponding coordinates of the colors being mixed. Thus, the addition curves characterize the reactions to radiation of 3 different radiation receivers. It is obvious that the functions of the spectral sensitivity of 3 types of receivers in the human retina represent addition curves in the physiological central nervous system. Each of the infinitely large number of possible CFBs has its own group of 3 addition curves, and all groups of addition curves are interconnected by linear relationships. Consequently, the addition curves of any of all 1 possible CFBs can be considered linear combinations (see. Linear dependence) functions of the spectral sensitivity of 3 types of receivers of the human eye.
In fact, the basis of all CFBs is a system whose addition curves were determined experimentally in the manner described above. Its primary colors are pure spectral colors corresponding to monochromatic radiation with wavelengths of 700.0 (red), 546.1 (green) and 435.8 nm(blue). Initial (reference) chromaticity - the chromaticity of equal-energy white color E(i.e., colors of emission with a uniform distribution of intensity across the entire visible spectrum). The addition curves of this system, adopted by the International Commission on Illumination (CIE) in 1931 and known as the international colorimetric system CIE RGB (from English, German red, rot - red, green, grun - green, blue, blau - blue, blue ), shown in rice. 1 .
Addition curves of the MKO RGB system have negative sections (negative amounts of primary colors) for some spectral colors, which is inconvenient for calculations. Therefore, along with the RGB system MKO in 1931 adopted another CKS, XYZ system , which did not have the disadvantages of the RGB system and which provided a number of other possibilities for simplifying calculations. Primary colors ( X), (Y), (Z) of the XYZ system are unreal colors chosen so that the addition curves of this system ( rice. 2 ) do not have negative sections, and the coordinate Y equal to the brightness (See Brightness) of the observed colored object, because addition curve at coincides with the relative spectral luminous efficiency function (See Spectral luminous efficiency) of the standard CIE observer for daytime vision. On rice. 3 shows a chromaticity graph (color triangle) x, y systems XYZ. It shows the line of spectral chromaticities, the line of magenta chromaticities, the color triangle ( R) (G) (IN) MKO RGB systems , the chromaticity line of the radiation of an absolutely black body and the chromaticity points of standard CIE lighting sources A, B, C And D. Equal-energy white chromaticity E(the reference chromaticity of the XYZ system) is located at the center of gravity of the color triangle of the XYZ system. This system has become widespread and is widely used in colorimetry. But it does not reflect the color-distinguishing properties of the eye, i.e. the same distances on the chromaticity graph x, y in its different parts do not correspond to the same visual difference between the corresponding colors at the same brightness (see Color contrast).
It has still not been possible to create a completely visually homogeneous color space. This is mainly due to the nonlinear nature of the dependence of visual perception on the intensity of excitation of color-sensitive photoreceptors (See Photoreceptors) (light receptors in the retina). Many empirical formulas have been proposed for calculating the number of color differences (color thresholds) between different colors. A more limited task - creating a visually uniform chromaticity graph - has been approximately solved. The ICE recommended this schedule in 1960 u, v, obtained in 1937 by D. L. McAdam by modifying the graph proposed by D. B. Judd (both USA) based on numerous experimental data. To calculate the number of color discrimination thresholds ΔE between different colors at the present time (1970s), according to the temporary recommendation of the CIE, the empirical formula of G. Vyshetsky is used:
The description given above shows that the purpose of the color measurement process is to determine its CC in some CF. Most often this is the standard MKO XYZ colorimetric system.
When a color (in objective color schemes we always mean the color of a colored object or light source (See Light Sources)) is represented by the spectral distribution of radiation (emitted by the source, or reflected or transmitted by the object), then to find its central value it is necessary to use addition curves as weighting functions that evaluate this radiation. This assessment can be carried out in two ways.
The first way (the so-called spectrophotometric method of color correction) consists of measuring the spectral distribution of radiation energy and subsequent calculation of the color concentration by multiplying the found spectral distribution function by 3 addition functions and integrating the products. If E(λ) - source spectral distribution function, ρ(λ) - the function of the spectral reflection or transmission of an object, X, Y, Z are determined as follows:
(integration is carried out in the wavelength range of visible radiation - from 380 to 760 nm). In practice, integration is replaced by summation over the interval Δλ (from 5 to 10 nm), because integrand spectral functions are usually inconvenient for integration:
The spectral distribution of radiation and the spectral characteristic of reflection (transmission) are measured by decomposing light into a spectrum, for example in a Spectrophotometer or Monochromator. Addition curves are specified in the form of tables of specific coordinate values in 5 or 10 nm. There are also tables of values E(λ) etc. for standard light sources MKO A, B, C, D, representing the most typical conditions of natural ( B, C And D) and artificial ( A) lighting.
The second way of C. and. based on addition curves - this is an analysis of radiation using 3 light receivers (See Light receivers) , Spectral sensitivity characteristics (See Spectral sensitivity) which coincide with the addition curves. Each such photoelectric converter performs the actions of multiplying 2 spectral functions and integrating the products, as a result of which the electrical signal at its output is equal (with appropriate calibration of the device) to one of the CCs. Such color measuring instruments are called photoelectric (or objective) colorimeters. They estimate the resulting radiation, taking into account both the selective reflection (or transmission) of non-self-luminous objects and illumination, i.e. the device “sees” what the eye sees. The main difficulty in the manufacture of photoelectric colorimeters is the sufficiently accurate “formation” of addition curves, for which appropriate filters are usually selected. If the instrument is designed to work with x̅ addition curves, , then it is most difficult to form a double-humped curve x̅ ( rice. 2 ). Usually each of its branches is formed separately; then the device contains 4 channels (filters). Sometimes colorimeters use other CKS, all of whose addition curves are single-humped. One of the colorimeter channels can simultaneously serve as a brightness meter. Often such devices provide for the calculation of chromaticity coordinates. Maximum accuracy Ts. and. photoelectric colorimeters for chromaticity in coordinates x, y ranges from 0.002 to 0.005.
Another fundamental possibility of C. and. is the direct definition of the Central Committee.
Naturally, this is not always possible, because... in the general case, color sensations are excited by light radiation of an arbitrary spectral composition, and the CC does not physically exist. Direct measurement of the color concentration is possible in three-color additive color creation devices, used, for example, to reproduce color images. The primary colors of such a device are determined by the CFB, and their quantities in the mixture that gives a certain color are the CF of this color in the CFB of the device. An example of such a device is a three-color kinescope , in which separate control of the glow of 3 phosphors (See Phosphors) ensures the production of the entire set of colors, the chromaticities of which are contained within the color triangle determined by the primary colors of the kinescope (the chromaticities of the glow of phosphors, see Color television). To directly measure the quantities of the 3 primary colors in the color mixture reproduced on the kinescope screen, i.e., the CC in the CKS of the kinescope, you can use a photoelectric radiation detector with an arbitrary spectral sensitivity, as long as it does not go beyond the visible spectrum. Measuring instrument connected to such a receiver, it is enough to one by one measure the glow intensities of individual phosphors of the kinescope. (When measuring the intensity of the red phosphor, the rays that excite the green and blue colors, etc.) Calibration of such a device consists of taking its readings while alternately measuring the glow intensities of 3 phosphors after installing a reference white color on the screen, i.e. a color with the reference chromaticity of the CMS kinescope and maximum brightness. Later, when measuring different colors The instrument readings are divided into readings for the corresponding primary colors with the reference color being white. The results of such division will be the Central Committee in the CKS of the kinescope. During calibration, the reference white color is set as accurately as possible using other instruments (spectrophotometer, photoelectric colorimeter) or visually using a special white standard. The accuracy of setting the reference white color during calibration determines the accuracy of subsequent colors. You can obtain the values of the central circulation in other central coefficients (for example, international ones) by recalculating the instrument readings using the formulas for converting the central circulation. To derive conversion formulas, you need to know the chromaticity coordinates of the reference white color and the primary colors of a given kinescope, which are measured by some other method. Big advantage such direct measurement of the Central Committee in comparison with the Central Committee. using a photoelectric colorimeter is that there is no need to form certain curves of the spectral sensitivity of the photodetector. Ts. and. using the described method, it is possible to perform the full color glow of the screen, without turning off the rays that excite individual phosphors. In this case, the device must have 3 light filters with arbitrary, but different spectral characteristics. In such a device, each reading is the sum of 3 readings of a single-filter device for all 3 separate color luminescences. To obtain CC values from 3 readings of a three-filter device, a conversion matrix is used, the elements of which are determined during calibration of the device. Calibration consists of sequential measurements by each of the channels of the device of each of the colored glows of the phosphors separately after setting the reference white color on the screen. The specified recalculation, as well as the transition from the Central Committee in the CKS of a kinescope to the international CKS in a device of the described type can be carried out automatically, using a specially built-in electrical diagram. That. You can receive readings directly from the CMS of the kinescope or from the international CMS.
Central circulation is also determined when C. and. visual colorimeters. The observer, by adjusting the quantities of the 3 primary colors of such a device, achieves visual identity of the color of the mixture of these colors and the measured color. Then, instead of the latter, the color of the mixture is measured. And its CC is simply the quantities of the primary colors of the colorimeter, related to the quantities of these same colors included in the mixture, which gives the reference white color of the colorimeter. It is even easier to measure the quantities of primary colors in a visual colorimeter than in a color picture tube. It is enough to read the readings of 3 scales, calibrated according to the opening of the slits, transmitting light fluxes of the corresponding colors to the comparison field. Thus, when using visual colorimeters, it is not the color of the sample that is measured directly, but its metamer - the color of a mixture of the three primary colors of the colorimeter. The process of visual equalization of two colors serves in this case to obtain a metamer of the color of the sample, the CC of which can be easily measured. The advantage of visual colorimetry is the high accuracy of color measurements. The disadvantage is that the results obtained are valid for a specific observer (performing visual equalization of two colors), and not for a standard observer. In addition, this method makes it difficult to measure the colors of objects rather than individual samples.
The principle of visual comparison of the measured color with a color whose color concentrations are known or can be easily measured is also used in color measurement. using color atlases. The latter are sets of color samples in the form of painted papers, which are systematized in a certain order. When comparing with the measured color, a sample from the atlas that is closest to it is selected. The measured color receives the name of this sample in accordance with the notation system adopted in this atlas. To express it in the international CKS, all atlas samples are measured in advance in this system under certain lighting. It is advisable to observe the measured colors under the same lighting. Color atlases allow you to measure the colors of objects, and not just special samples, but the discreteness of the set of colors in the atlas reduces the accuracy of measurements, which is further reduced due to the fact that the conditions for visual comparison here are worse than with visual colorimetry. In the USSR, Rabkin and VNIIM color atlases are used; in the USA, measurements using the Munsell atlas (Menzell) are widely used. Ts. and. using color atlases are approximate and can be successfully carried out where greater accuracy is not needed or where it is inconvenient to use other methods.
The expression of color in a specific central coordinate system, i.e., when specifying its central coordinate (or brightness and chromaticity coordinates), is universal and most commonly used. But they also resort to other methods of quantitatively expressing color. An example is the just described expression of color in the system of a color atlas. Another such method is the expression of color through its brightness, predominant wavelength and colorimetric purity of color. (The last two parameters characterize color.) The advantage of this method lies in the close correspondence of the 3 listed color parameters to its usual subjective characteristics (see Color) - respectively lightness, hue and saturation.
It would be very convenient to characterize color with one number. But its two-dimensionality requires, in the general case, two numbers to express it. Only for some sets of chromaticities (lines on a chromaticity graph) can a one-dimensional expression be used. The first such set is pure spectral colors and pure magenta colors, the chromaticities of which are determined by the values of the predominant wavelength. The second set for which a one-dimensional expression is possible is the chromaticity of the radiation of an absolutely black body (See Absolutely black body) , used to characterize light sources with luminescence chromaticities close to the chromaticity of white. The value that determines the position of a point on the line of chromaticities of black body radiation (and the chromaticities of the mentioned sources) - Color temperature , i.e., the temperature in degrees Kelvin of an absolutely black body at which it has a given color.
Lit.: Gurevich M. M., Color and its measurement, M. - L., 1950; Krivosheev M.I., Kustarev A.K., Light measurements in television, M., 1973; Nyberg N. D., Color measurement and color standards, M., 1933; Wright W. D., The measurement of color, 3 ed., L., 1964; Wyszecky G., Stiles W. S., Color science, N. Y., 1967.
A.K. Kustarev.
They are intended to determine the parameters of the trajectories of an aircraft - coordinates, velocity vector, angular position in space, etc. For V. and. are used...
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