3. OPTICAL PROPERTIES OF RESTORATIVE MATERIALS AND SHADE SELECTION.pptx

. OPTICAL PROPERTIES OF RESTORATIVE MATERIALS AND SHADE SELECTION.pptx

1. OPTICAL PROPERTIES OF DENTAL MATERIALS AND SHADE SELECTION Dr Sushmita Rane MDS- Part 1 Seminar 3 12/04/2022

2. COLOuR Colour is the result of the physical modification of light by colourants as observed by the human eye and interpreted by the brain- Billmeyer and Saltzman Colour is the sensation resulting from stimulation of the retina of the eye by light waves of certain lengths- Webster

3. Light Light is a form of visible energy that is a part of the electromagnetic spectrum and possesses specific wavelengths Wavelengths are measured in nanometers or billionth of a meter The wavelength of visible light that can be perceived by the human eye is 380-750nm

4. Physics of colour

5. In order for colour to exist there needs to be interaction between 3 elements LIGHT OBJECT VIEWER COLOUR

6. The wavelengths of visible spectrum are perceived by the three types of color receptors (called cones) in the human eye- Photopic Vision Only perceived as variations of red, green, and blue light Newton’s observation was white light contains all colors. If an object appears to be a particular color, this means that the light reaching our eyes when viewing that object has somehow been changed by the object.

7. EMISSION Emission is defined as production of light from a source through a chemical or physical process To create perfectly white light, a light source would have to emit exactly the same amount of each wavelength This affects color perception since there are only certain wavelengths, produced by the light source to interact with an object

8. Interaction of emitted light with an object Reflection Refraction Absorption Transmission Diffraction Scattering

9. reflection Reflected light rays are those rays which bounce back from the surface of the object being hit instead of being transmitted or absorbed. 2 types: Specular reflection Diffuse reflection

10. TYPES OF REFLECTION

11. Refraction The splitting of white light by a prism into different colours is due to refraction

12. ABSORPTION Absorption is the process by which a matter takes up the energy of a electromagnetic radiation Object Absorb energy of light Excite electrons to higher energy arrangement Then electrons come back to stable energy position giving out heat

13. A material will absorb only a particular wavelength of light, which corresponds exactly to the amount of energy required to excite its electrons The rest of the wavelengths are not absorbed are the wavelengths that form the colour perceived

14. TRANSMISSION Transmission occurs when light passes through a transparent or translucent material If the material is completely transparent, all light is transmitted, and the color white is perceived. If the material is completely opaque, all light is absorbed, and the color black is perceived

15. Diffraction Diffraction is a type of interaction between all types of waves with the objects

16. scattering Scattering occurs when any object changes the direction of the light beam

17. TRANSLUCENT TRANSLUCENT OPAQUE A medium is said to be transparent when it allows maximum transmission of light without any distortion A medium is said to be translucent when it allows transmission of light in a diffuse manner A medium is said to be opaque when it transmits no light , whatsoever None of the transmitted light is scattered 10% of the transmitted light is scattered No light is transmitted through the material A clear window glass A frosted glass A brick wall

18. Light is emitted from a light source This light may reach the eye directly, or it may either strike or pass through an object If the light interacts with an object, some of the light is absorbed by the object The wavelengths that are not absorbed are either reflected or transmitted directly to the eye and are perceived by the rods and cones in the eye Processed and recognized by the brain as a specific color

19. R G B COLOUR MODEL Colour creation by emitting wavelengths that are mixes of RED , GREEN , BLUE light to stimulate the cones in eyes If R G B wavelengths combine, white light would result For this reason , RGB are referred to as ADDITIVE PRIMARY COLOURS The secondary colours are CYAN , Y ELLOW and MAGENTA Seen in electronic media

20. C M Y COLOUR MODEL The primary colors in these color systems are those created by the absorption of one of the RGB wavelengths and the reflection/transmission of the others. They are referred to as cyan, magenta, and yellow (CMY). The absence (or subtraction) of these three colors would mean that no wavelengths could be absorbed and therefore all wavelengths would be reflected/transmitted, resulting in the color white . Therefore, referred as SUBTRACTIVE PRIMARY COLOURS Because dentists work with pigments when dealing with porcelain, the easiest system for clinicians to use is the subtractive system ( Freedman, 2012 )

21. Colour in dentistry PIGMENT COLOURS DIMENSION OF COLOUR Hue Value Chroma Translucency Primary Colours Secondary Colours Complimentary Colours

22. HUE Dominant colour of the object Represents the dominant wavelength present In the younger permanent dentition, hue tends to be similar throughout the mouth. With aging, variations in hue often occur because of intrinsic and extrinsic staining from restorative materials, foods, beverages, smoking, and other influences ( Aschheim , 2015 )

23. Chroma It is the degree of saturation or intensity of hue It is only present with hue For example, to increase the chroma of a porcelain restoration, more of that hue is added

24. Value Value is the relative lightness or darkness of a colour It is not the quantity of the colour “ gray ”, but rather the quality of brightness on a gray scale- Gray scale value Value is the most important factor in shade matching. If the value blends, small variations in hue and chroma will not be noticeable ( Preston JD, 1980 )

25. Primary cOLOURS RED , YELLOW , BLUE These colours are perceived when one of the R G B wavelength is absorbed Red is perceived when green is absorbed; yellow is perceived when blue is absorbed; and blue is perceived when red is absorbed

26. SECONDARY COLOURS Orange , Green , Violet The secondary colors are formed by combining two of the primary colors Red + yellow = orange ; yellow + blue = green ; blue + red = violet

27. COMPLIMENTARY COLOURS Complementary colors are those that, when combined in equal proportions , will form gray that absorbs and reflects all wavelengths in equal amounts They neutralize each other and form gray This is clinically significant because complementary colors can be combined to lower the value of excessively bright restorations

28. COLOUR OF HUMAN TEETH Dr. E. B. Clark indicated the Hue ranged from 6 YR (yellow-red) to 9.3 Y (yellow) the Value ranged from 4 to 8, the Chroma ranged from 0 to 7 Lemire and Burk found a Hue range from 8.9 YR to 3.3 Y a Value range of 5.8 to 8, a Chroma range from 0.8 to 3.4 Goodkind and Schwabacher identified the Hue range as 4.5 YR to 2.6 Y, the Value range as 5.7 to 8.5, and the Chroma range from 1.1 to 5 Studies indicate that human teeth are in the yellow-red to yellow portion of the spectrum, they are relatively high in Value (light or bright), and they have a relatively low Chroma (not too much colour intensity)

29. OPTICAL TRIAD Fluorescence Opalescence Translucency

30. Fluorescence Fluorescence by definition is the absorption of light by a material and the spontaneous emission of light in a longer wavelength ( McLaren, 1997 ) Natural tooth has fluorescing qualities and is believed to have because of the organic content. It absorbs Shorter wavelengths between 300 to 400nm i.e ultraviolet radiations. This energy is then released as radiations of longer wavelengths 400-500nm (yellow white fluorescence) and the tooth appears to be a light source With the characteristic of fluorescence, restorations look brighter and more alive.

31. Opalescence Translucent materials have the property of opalescence, which give them a milky white appearance : opal stone This is the ability of Translucent material to appear Blue in Reflected light and Red orange in Transmitted light Enamel: highly mineralised tissue

32. Opalescence Under DIRECT ILLUMINATION Under TRANS-ILLUMINATION Shorter wavelengths(blue) are reflected from Natural enamel and Porcelain Longer wavelengths(Red –Orange) are absorbed Results in Bluish appearance of the tooth Longer wavelengths(Orange) are reflected at the surface Shorter wavelengths(Blue) are absorbed White tooth appears Orange

33. 4 th dimension of colour Not addressed by Munsell But one of the most important factors for esthetics The degree to which light is transmitted rather than absorbed or reflected The incisal edges of natural teeth are translucent Translucency TRANSLUCENCY Highest (Transparent)- all light is transmitted than absorbed/reflected Lowest (Opacity) i.e all light is reflected /absorbed

34. Measurement of colour Colour systems Munsell System CIE L*a*b system

35. Munsell system Created by AH Munsell in 1915 Still considered the standard today Cylindrical Coordinate system In this system colour is divided into three parameters—Hue, Value and Chroma Munsell notationis given as H V/C eg. Purple colour of medium value and high chroma “ 5P 5/10” Used in Matching denture base acrylics, gingival porcelains

36. CIE L*a*b System Adams Coordinate system 3 coordinates: L* = Vertical axis and represents the value a = Horizontal axis and it is the measurement along the red green line b = Rectangular axis and it is the measurement along the yellow blue line Numerical representation Any colour in this system is represented by a unique point in space determined by the amount of coordinates relative to different axes used in the system

37. Factors affecting colour perception There are many variables that affect how a colour is perceived The Factors that play vital roles in colour perception and evaluation in the clinic are Lighting Conditions The Environment The Viewer

38. Illumination & LIGHT INTENSITY Colour can be neither accurately perceived nor correctly evaluated without proper illumination Quantity as well as quality of illumination is important The intensity of light is the most common regulator of pupil diameter, which is a crucial factor in accurate shade matching This is achieved by maintaining a lighting intensity of 150 to 200 foot-candles, as verified by a light meter ( Carsten,2003 )

39. LIGHT TYPE COLOUR TEMPERATURE (Kelvin i.e K) LIGHT SOURCE A 2856 INCANDESCENT BULB B 4860 MIDDAY SUNLIGHT C 6770 AVERAGE NORTHERN SUNLIGHT D 6500 AVERAGE DAYLIGHT E 3000 FLUORESCENT TUBE (WARM WHITE) DIFFERENT TYPES OF LIGHT AND THEIR DESIGNATION AS GIVEN BY CIE

40. Clinical lighting challenges LIGHTING CONFLICT METAMERISM BEZOLD BRUCKE EFFECT

41. LIGHTING CONFLICTS Light coming through the window mixes with fluorescent light coming from the hallway and the colour corrected light in the dental operatory. It is the job of the clinician to determine the accurate shade in these various lighting conflicts

42. If the clinician or the lab technician has access to a natural light source, it is best to perform shade matching at 10 am or 2 pm on a clear, bright day when the ideal colour temperature of 5,000 K is present Colour-corrected lighting tubes that burn at about 5,000 K (D50 illuminants ) should be installed when there is no natural light. A lighting intensity of 175 + or - 25 foot-candles must be maintained (verified by colour temperature meter) A colour temperature meter should be used periodically to verify that a colour temperature of 5,000 K is achieved in the shade-matching area Dust and dirt should be cleaned from lighting tubes and diffusers routinely, since the presence of dust may alter the quantity and quality of emitted light

43. Metamerism The phenomenon when two objects appearing to match in color under one condition but showing apparent differences under another is termed as metamerism. This occurs because a certain light source produces only certain wavelengths to interact with an object and thus the same object will appear to be in different colors when viewed using different light sources

44. Bezold brucke effect At low light levels, the rods of the human eye are more dominant than the cones and colour perception is lost At the same time, when the light is too bright, colour appears to change This phenomenon is known as Bezold Brucke effect

45. PROBLEMS IN COLOUR PERCEPTION Colour Blindness- A person with color blindness has trouble seeing red, green, blue, or mixtures of these colors It is a X linked recessive disorder affects males more commonly than females Aging- Detrimental to colour matching because cornea and lens of eyes become yellow with age, imparting yellow brown bias Fatigue- Tired eyes cannot perceive colour as accurately as alert eyes can Binocular Difference- Perception variance between right and left eye Place tab on the same side of the tooth to be matched

46. Patient position- Patient should be upright with his mouth at the observer’s eye level Selection of distance- clinician’s eyes at tooth level, 25 to 35 cm (10 to 14 inches) away. A 1-foot distance is appropriate for color comparison of the tooth and shade tab, which should be placed in edge-to-edge contact . Time of selection- 10 AM & 2 PM are considered the best time for shade selection in natural light because the temperature of natural light at that time is 5000K Surroundings- Distracting surroundings should be avoided like bright walls, bright clothes and loud cosmetics (such as lipstick) as they interfere with colour perception

47. Shade selection STEPS The patient is in upright position, mouth at dentist eye level Selection should be made when subject tooth and adjacent teeth are clean Should be done before any intraoral procedures are started Hold the shade tab as close to the tooth as possible Selection is done at the start of the appointment

48. Cosmetics should be removed and bright coloured clothes covered View in many light source as possible and from varying distances Do not stare for more than 5 seconds Move your eyes away and look at a neutral colour (light blue or grey)

49. COMMERCIAL SHADE GUIDES Most convenient and common method of making shade selections Guides consist of shade tabs Metal backing Opaque porcelain Neck, body, and incisal color Select tab with the most natural intraoral appearance

50. COMMERCIAL SHADE GUIDES Vita Classic Vitapan 3D Master Chromascop ( Ivoclar Vivadent ) Extended Range Shade Guides

51. VITA CLASSIC SHADE GUIDE A B C D Very popular shade guide Tabs of similar hue are clustered into letter groups A (red-yellow) B (yellow) C (grey) D (red-yellow - gray) Chroma is designated with numerical values A3 = hue of red-yellow , chroma of 3 The chroma and value for each hue are communicated by a system of numbers:1 = Least chromatic, highest value 4 = Most chromatic, lowest value

52. Red - Yellow Ye l l ow G r a y R ed- Y ellow-Gray

53. HUE SELECTION Four categories representing hue i.e Red-Yellow, Yellow, Gray, Red-Yellow-Gray Operator should select hue closest to that of natural tooth Use area of tooth - highest in chroma i.e Cervical area of tooth

54. CHROMA SELECTION Hue selection done; eg. B Chroma is selected from gradations within the B tabs B1, B2, B3, B4 Several comparisons should be made Avoid retinal fatigue Rest eyes between comparisons ( look at the neutral colour i.e blue-gray)

55. VALUE SELECTION V alue ordered shade guide is recommended Value oriented shade guide B1, A1, B2, D2, A2, C1, C2, D4, A3,D3, B3, A3.5, B4, C3, A4, C4 Value best determined by squinting wit h comparisons made at arms length Decreases light coming in the eye Diminishes cone sensitivity, increases rod sensitivity

56. FINAL CHECK Potential Problem Following value selection, tabs selected for hue and chroma may not coincide with shade tab selected for value Possible Findings / Solutions Value of shade tab < natural teeth Select new shade tab with higher value ( i.e bright) Cannot increase value of restoration with extrinsic staining Will only increase opacity, decrease light transmission Value of shade tab > natural teeth Select new shade tab with lower value Bridge difference with intrinsic or extrinsic staining

57. VITAPAN 3D-MASTER SHADE GUIDE

58. VITA-3D – STEP 1 Determine the lightness level (value) Hold shade guide to patient’s mouth at arms length Start with darkest group moving right to left Select Value group 1, 2, 3, 4, or 5

59. VITA-3D – STEP 2 Select ion of chroma From your selected Value group, remove the middle tab (M) and spread the samples out like a fan Select one of the three shade samples to determine chroma

60. VITA-3D – STEP 3 Determine the hue Check whether the natural tooth is more yellowish or more reddish than the shade sample selected

61. VITA-3D – VALUE MODIFICATION For more precise shade, intermediate levels for value is selected 2.5M2 = value between 2M2 and 3M2

62. VITA-3D – CHROMA MODIFICATION For more precise shade, intermediate levels for chroma can be selected 3M1.5 = chroma between 3M1 and 3M2

63. VITA-3D – HUE MODIFICATION For more precise shade, intermediate levels for hue can be selected 3M2 / 3L2.5 = hue between 3M2 and 3L2.5 2. 5

64. CHROMASCOP T he tabs are initially divided based on hue Chromascop uses a three-digit numbering system consisting of five groups of four tabs, as follow: Group 100 = White Group 200 = Yellow Group 300 = Orange Group 400 = Gray Group 500 = Brown Chroma and value are communicated by a system of numbers: 10 = Least chromatic, highest value 40 = Most chromatic, lowest value

65. EXTENDED RANGE SHADE GUIDES Most shade guides do not cover all the colo u rs in the natural dentition Some porcelain systems extend the typical range Bleached shades Dentin shades Custom shade guides

66. BLEACHED GUIDE The progression of lightening in natural teeth was found to be identical to the order suggested by Bleached guide (Ontiveros, et al., 2009)

67. SHADE MAPPING Recommended even when good custom shade match exists Tooth is divided into Three regions Nine segments Each region is matched independently Further characterizations are sketched on diagram, may includ e Craze lines Hypocalcifications Proximal discolorations Translucency

68. TECHNOLOGY-BASED SHADE MATCHING The SpectroShade System was commercially available system that maps the whole tooth surface

69. 2) X-Rite’s ShadeVision stores hue, value, and chroma to efficiently measure tooth shade. Its optical capture device is small, light, and easily maneuverable

70. 3) The EasyShade compact (a spot-measurement device). The tip of the instrument is positioned on the tooth surface. Single or multiple points can be measured on natural teeth, ceramic restorations, and shade tabs. Correct positioning of the tip is crucial for correct results .

71. 4)Complete-tooth measurement devices measure the entire surface of the tooth and provide a detailed color distribution map .

72. CONCLUSION Although limitations in materials and techniques may make a perfect colo u r match impossible, a harmonious restoration can almost be achieved Shade selection should be approached in a methodical and organized manner This will enable the practitioner to make the best choice and communicate it accurately to the laboratory An understanding of the science of colour and colour perception is crucial to the success in the ever expanding field of a esthetic restorative dentistry

73. References Stephen Chu- Fundamentals of Colour: Shade Matching and Communication Dental Phillips Materials used in dentistry- S. Mahalaxmi

74. Thank You