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Color Selection—Its Distribution and Interpretation
C O LO R SELECTION— ITS DISTRIBUTION AN D INTERPRETATION
J. Raymond Gill, D.D.S., San Francisco
r e s to r a tio n that will meet the re quirements of esthetics and harmony in the mouth and will defy observa tion is a work of art as all members of the dental profession know. T o be suc cessful in its interpretation, we must have ability and experience in modeling and sculpturing and also some knowledge of the phenomena of light and mixing and blending of colors. Light is our source of color1’2 and wc must understand its absorption and re flection and also the way the light waves are transmitted through an object and reflected. Refraction also plays a very im portant part in color selection. Because of its importance, we must be extremely observing and have extensive experience. Galileo says that observation and ex perience are the best teachers. W ith obser vation and experience we should be able to put our knowledge to more practical use. Therefore, it is necessary to increase our knowledge by studying each indi vidual case. We should observe the ana tomic form of the teeth and their arrange ment3 in a definite pattern and notice how these harmonize with the facial contour and environment. W e should also visualize how grotesque this pattern would appear in a different environment. W e must study the effect of this source of light on the teeth and also on the various architectural designs of the teeth. We must observe the effect of artificial restor ations, of the reflection of light and its effect on the human eye. W e should constantly be on the alert to increase our knowledge of the factors
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that influence anatomy and color of the teeth. There are other factors which require a thorough understanding of the selection of color and its distribution. These courses are in the basic sciences and are: his tology, histopathology, anatomy, dental materials and the phenomena of light and color. Histology
M any of us after completion of our course in histology4 think of the subject only in reference to cavity preparations as related to the dentin, enamel and pulp of the tooth. V ery few use the subject material as a source of information in the way it influences the color of the tooth; depending only on the manu factured shade guide which has no re semblance in character or in distribution of color of the various types or forms of the teeth. It is important that we understand what part of the tooth reflects certain lights and how other parts of the tooth absorb or dilute reflected light waves.5’6
1. Abney, Sir W. de W., Colour Vision. London: Sampson Low, Marston & Company, 1895. 2. Chevreul, M . E ., The Laws of Contrast of Colour. London: Geo. Routledge and Sons, 1868. 3. Vehe, W. D ., Problem of Esthetics in Restorative Procedures. J.A .D .A . 21:969 (June) 1934. 4. Noyes, F .; Schour, Isaac, and Noyes, H. J., A Text-Book of Dental Histology and Embryology, ed 5. Philadelphia: Lea & Febiger, 1938. 5. Beust, Theodore, Physiologic Changes in Enamel After Tooth Eruption. J .A .D .A . 11:396 (M ay) 1924. 6. McBeath. E. C ., N ew Concept of Development and Calcification of Teeth. J .A .D .A . 23:675 (April)
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Therefore, it is essential that we study the various parts of the tooth that will influence our color selection and distri bution. T h e dentin may be considered opaque. It receives its color pigmentation from the blood supply of the pulp. Its colors range from a light yellow, through the orange, grayish orange or brown, varying according to the age of the patient.7 The dentin varies in thickness, density (which affects the color) and luminosity. The surface of the dentin in the dentoenamel junction is not perfectly smooth but ir regular and this varies considerably. M any times we find dentin spindles pro jecting4 into the enamel. This alters the dispersion of light through the enamel which is termed “ diffused reflection.” The light waves that hit the dentin reflect the color of the dentin and because of the irregularity of the surface, diffused re flection also occurs. Enamel
T h e enamel, which is the outer surface of the tooth, gives strength, form and contour. Enamel is considered translucent and is devoid of pigmentation and color. T h e shade of enamel varies from a light gray to a bluish gray. T he mineral de position of enamel varies in different in dividuals and will also vary in density and hardness from the incisal or occlusal to the gingival. T h e enamel on the incisal and prox imal surfaces transmits light from the dark oral cavity, which gives the effect of a bluish tint.8,9 T he transmission of light from the dark oral cavity varies ac cording to the thickness of enamel and the anatomic form of the tooth. The square type tooth which is thin labiolingually transmits a greater amount of light from the oral cavity than either the ovoid or tapering type; therefore, the square type of tooth appears more trans lucent than the tapering or the ovoid. Also, different teeth will vary in thick
ness labiolingually, such as the lateral incisors, and they appear more translu cent than the central incisors or cuspids. T h e enamel varies in thickness from the gingival to the incisal or occlusal. The hue which predominates at the m iddle and gingival third is not as pronounced at the incisal or occlusal portion. T h is is because the reflected color of the dentin is not transmitted through as thick enamel as that of the middle third or incisal third. T h e mineral deposition of the enamel affects its translucency. Those teeth that are highly mineralized appear more trans lucent than those that are not. The amount of attrition and abrasion also will affect the translucency. The surface character of the enamel will either in crease or decrease the luminosity. In youth, where the enamel surface is irregular, high lights are produced, giv ing the effect of brilliancy or luster. When these irregularities‘are reduced by either attrition or abrasion the surface of the enamel becomes more opaque or dull and the tooth appears darker in color. It is extremely important that w e study the surface anatomy and chart the ir regularities and the abnormal character istics so that they may be reproduced ac curately in restorations. Light waves are transmitted through the enamel and into the dentin, some of the colors are ab sorbed and it is reflected as the color of the dentin. T h e light waves entering into and through the enamel are not only transmitted but there is a certain amount of refraction. Also the color from the dentin through the enamel partially is re fracted light; therefore, there is a break ing up of light waves entering on and through the enamel1 which dilutes the color from the dentin. T h e color, there7. Clark, E. Bruce, An Analysis of Tooth Color. J .A .D .A . 18:2093 (Nov.) 1931; The Color Problem in Dentistry. D . Digest 37:499 (Aug.) I931* 8. Clark, E. Bruce, Tooth Color Selection. J .A .D .A . 20:1065 (June) 1933. 9. Loop, Jack LeRoy, Complicating the C olor Prob lem. Pacific P en . Gaz. < 2? Jnt. 4 1 :9 8 8 (April) 1933.
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fore, is not the true color of the dentin but a diluted color. By this study and observation, we will have a knowledge of the effect of the dentin and enamel in the problem of color selection of a normal tooth. I f there are abnormalities in the enamel or dentin this w ill alter and complicate the prob lems of color selection. These will be con sidered under the study of histopathology. Histopathology
T h e histology of the tooth may be af fected from early youth through adult hood. A ny changes that occur in the tooth or ariy abnormal changes that take place in the development in the dentin or enamel that will affect the color of the tooth in later life may be classified as pathologic conditions. Some of the changes that take place in the dentin and enamel affect the or ganic and mineral composition of both. D uring the development of the tooth if the child has an illness which is accom panied by a high fever there will be a retardation of mineral deposition in the tooth. T h e lines of demarcation that are ob served in the tooth may be caused by im paired mineral deposition during the time of illness. Either a whitish or intense gray ish character in the enamel will be the result. T he dentin will have darker areas of greater opacity due to the lack of density. Some chemical reactions that take place during the development of the tooth will show up as brownish or whitish areas after the tooth has erupted and is exposed to light. T h e action of caries alters the shade and hue of the dentin and the enamel. W hen caries pen etrates into the dentin, owing to the action of acid, it discolors and becomes darker. This is transmitted and reflected through the enamel altering the color in the affected area. In faulty enamel composition we may have effects in the enamel, which in time,
having been exposed to the various ac tions of saliva and light, form brownish or grayish lines. These effects may be regular or irregular. T h e effect of erosion and attrition will also alter the illusion of the color of the tooth.10 Where the dentin is exposed through attrition or abrasion, the action of saliva on the den tin w ill darken it. This darkened area, observed through the enamel, also will affect its shade. There are so many changes which may affect the color and color distribution of the tooth that it will not be possible to enumerate them. W ith observation and experience we can detect these changes and compensate for them in color selection. We must also consider the effect of m etallic fillings in the teeth. A metal fill ing in a tooth will appear to affect the color of the tooth. T w o different colors in juxtaposition produce an illusion of false color. For example, if we place a white strip between two black strips, the white appears gray; the further we move the black strips away from the white one, the more true the white appears on the strip.11 This is the same effect that m etal lic fillings have on the color of the teeth ; therefore, it is necessary to cover these metallic fillings with a natural gray paper to eliminate false color illusion. Anatom y
Anatomy m ay be considered the most important subject in color selection and its distribution in obtaining esthetic re sults that will harmonize within its en vironment.3 W e see so many grotesque results that are obvious to the careful observer. T h e dentist should plan his treatment carefully and study the case so that he will visualize the correct anatomic form of the tooth previous to making the 10. Pilkington, £. L., Esthetics and Optical Illusions in Dentistry J .A .D .A . 23:641 (April) 1936. 11. Luckiesh, M ., Light and Shade and Their Appli cations. New York: D. Van Nostrand Co., Inc., 1916.
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preparation. This is definitely necessary if the alignment of the teeth is to be changed the slightest degree. In these cases it is advisable to prepare the teeth on the study models and reshape them in wax to determine if they will harmonize within their environment. T here are times when the relation of the teeth can be changed without obtaining dishar mony, but if the teeth are rotated or in labial version it is impossible to correct this alignment and expect an esthetic result. We must not make too great an attempt to correct relations because it will invariably alter the expression and personality of the individual. W e should always conform as closely as possible to existing conditions in order to maintain harmonious relation. W e must adhere to the architectural design that has been created in the in dividual mouth without interfering with the personality. Age
U nder histopathology and anatomy, mention was made of changing conditions that may occur from youth through adulthood. Since most of the restorations, whether single, multiple, or in crown and bridge prosthesis, occur in middle age we must have a complete knowledge of various changes that have taken place and how these changes affect the color and the color distribution of the teeth. First, the change in the surface of the anatomy of the tooth should be consid ered. In middle age some of the charac teristics that are found in youth are lost. T h is is caused by attrition, erosion and faulty dentin and enamel composition. These changes are more obvious and recognizable at middle age. Second, there is a reduction of thickness of enamel and an elimination of high lights and contour of the enamel surfaces. T h e tooth be comes dull or opaque compared to that of youth and loses its luminosity. This opacity of the labial surface decreases
the transmission of the light from the oral cavity through the enamel, decreasing its translucency. When the incisal enamel has been worn partially or entirely away exposing the dentin, and the gingival color is decreased by surface wear, the results of the two make the tooth appear darker. T h e pulp recession increases the thickness of the dentin and changes the color of the dentin from a light orange to a dark orange or brown. Caries and fillings at this age have altered the color of the teeth. Therefore, it is obvious that to use a shade guide for the selection of a tooth for young, adult or a middle aged person cannot be successful, especially if the shade guide does not reproduce the various characteristic changes. Materials Used in Restorative Procedures
T h e materials used in restorations of esthetics fall into two groups; ceramics and hydrocarbons (plastics). Neither one of these absorb, refract, transmit or reflect light the same as the tooth.12 T h e enamel rods absorb and reflect some of the colors; the dentin reflects its color. T h e enamel rods vary in their relation to the surface and anatomic form of the tooth. Ceramic material and plastics are homogeneous substances but tooth structure is hetero geneous.13 Porcelain or plastics are void of crystalline structure and are not cap able of presenting the same color phe nomena as the different substances in the tooth; therefore, it is necessary for us to exert our artistic ingenuity in developing and sculpturing these materials to sim ulate as closely as possible the same light and color of the tooth.14 This is more easily accomplished with ceramic material than with plastics. Plas-
12. Brickman, Bernard M ., The Light and Color Phenomena in Teeth and Dental Porcelains. D . Cos (July) 1932. 13. Tylman, Stanley, and Peyton, Floyd A ., Acry
mos 74:666 lics
and
O th e r
Synthetic
Resins
U sed
in
Philadelphia: J. B. Lippincott Company, 14. Felcher, Fred R ., Modern Dental J .A .D .A . 2 3 :1009 (June) 1936.
Dentistry.
1946. Porcelains.
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tics can be assimilated into the arts in dentistry provided we follow out the same procedure in the technic as that of ceramics. It is necessary, if we are re producing the same characteristics of the tooth, to use various fusing points, porce lain, opaque stains and any means of altering the surface texture to harmonize with that of the natural tooth. The Color Selection
Previous to the selection of color, it is necessary to observe all the facts that have been discussed and their influence on the color of the individual tooth. A chart of the tooth, drawing its exact an atomic form, should be made. Also the dentist should inquire and observe the habits of the mouth hygiene of the patient. These characteristics of the tooth should be noted on the chart or prescrip tion. T h e teeth should be observed at various angles, profile, front view, and in various lights. Photographs will help in determining the reproduction of the high lights. Before selecting the color with the use of a shade guide lipstick should be re moved. If it is not removed, visual fatigue of the eye will be affected and what is termed “ simultaneous contrast” will re sult. In other words, we will observe a certain degree of its complimentary color green in thè teeth. A neutral gray back ground with the form of the tooth out in it is the ideal procedure while selecting the color of the tooth.15 T h e shade guide should be one that is made of the material that is being used. T h e colors in porcelain and plastics will vary in some degree with each supply that is manufactured. Therefore, a shade guide from the manufacturer will not be the true color of the material that is be ing used. Furthermore, the gingival color and incisal shade of the tooth will in fluence the color. When using the shade guide in select ing the gingival hue, the lips of the patient
should be raised and the incisal color covered. T h e ideal procedure would be to select the gingival hue after the enamel has been removed and the dentin exposed ; this would give the true color of the foundation body of the tooth. But the fact that we have no material that trans mits and reflects light like that of the enamel, which is superimposed over the dentin, it would be impossible to make a restoration duplicating the effect of the enamel. It might be possible to select the dentin color after the enamel is removed, then choose one that is slightly diluted to obtain a similar effect. This is very dif ficult for those who have not had a great deal of experience in color selection and its interpretation. Therefore, the pro cedure of selecting the gingival hue and the incisal shade can be made preceding the making of the preparation. After the gingival hue has been selected then the number or combination of numbers, of the porcelain, should be noted on the chart or prescription. In selecting the incisal shade the patient’s lips should be in a speaking position. This gives us a truer concept of the incisal shade and eliminates the influence of the gingival hue. This should be the average position of the lips and the exposed portion of the tooth in average conversation. T h e shade selected is noted on the color chart or prescription. Just to select the color of the tooth does not give us a true interpretation for the construction of the crown; therefore, it is essential that we chart the distribution of the incisal and gingival shades on the tooth. This to some extent m ay be con sidered an arbitrary procedure, but it does give us some indication as to the extent of the overlapping of the incisal shade over the gingival hue, the degree of the thickness of the incisal shade on the latéral surfaces of the tooth and the ex-
15. Tylman, Stanley, Crown and Bridge Prosthesis, ed. 2. St. Louis: C . V . Mosby Company, 1947, pp.
¿71-279-
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Fig. i . — L e ft: T he square type of tooth, showing the high lights, anatomic form and all the markings that are im portant to re produce in the restoration
R ight: T he outline of the color distribution drawn on the tooth and which will be trans ferred to the color chart or prescription
L e ft: O void type of tooth showing its arcnitectural design and alignment
R ig h t: Outline o f color distribution of ovoid type o f tooth which will be transferred to the color chart
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F ig . 2 .— L e f t : T h e ta p erin g type o f to o th w ith its a r ch ite ctu r a l design
R ig h t:
C o lo r
d istr ib u tio n ch a r ted ta p erin g to o th
on
the
tent that the enamel projects incisally from the dentin. It also determines the amount of incisal wear that has taken place and the influence on the gingival hue at the incisal. (See Figures i and 2.) W e chart the outline of the gingival hue which reflects through the dentin on the mesial and distal surfaces, then the outline of the incisal termination of the gingival hue. Then, we follow out the outline approximately to the gingival termination on the lateral surfaces, fol lowing its termination on the labial sur faces from mesial to distal. T h e color selection and its distribution should be made in various positions, frontal, profile and in a standing position and in differ ent sources or angles of light. This will give a true picture of the existing condi tions and environment for notation on the color chart or prescription.16 (See Figure 3A 0
W ith this color distribution chart we
have the accurate guide in helping to in terpret color and its distribution into the construction of the crown. W e should have on this guide, when completed, everything that we have seen on the tooth, which we desire to place in the restoration to obtain an esthetic harmon ious result (Fig. 3B and C ) . Few dentists follow a definite pro cedure in the color selection and its in terpretation or lack sufficient experience in this fine art to obtain accurate results; therefore, they become discouraged and delegate this to a laboratory technician expecting better results. T h e laboratory technician, without an accurate prescrip tion, cannot reproduce any more than that with which he is given to work. W hether one delegates the work to a technician or does it himself, it is ab16. Gill, J. Raymond, Construction of the Porcelain Veneer Crown. J.A.D .A. 27 :1884 (Dec.) 1940.
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solutely essential that he write a prescrip tion with accurately detailed information. Interpretation
The art of constructing a crown or bridge so well that it will not be recog nized as an artificial restoration requires a great deal of experience. T h e inform a tion discussed requires experience to bring it into the form of reality. There is no greater happiness in den tistry than reproducing an artifical restor ation which cannot be detected by an observer. T h at happiness which is re
flected to the patient is one of the health services that should be rendered. Mental complexes acquired through faulty es thetic restorations may alter the hap piness and personality of the individual. W ith this in mind we should use all our ingenuity and artistic ability in reproduc tions. T h e dentin is relatively opaque and is the basic color of the tooth. T h e enamel is translucent and transmits, reflects and refracts the light waves that are inter preted into color; therefore, if we are to reproduce a restoration to attain these effects we should vary the material to
Pig. 3,— A : Color distribution charted on the tooth and transferred to the prescription. B : A square ovoid type tooth with subsurface stains showing the need for a porcelain inlay. C : C om pleted inlay reproducing subsurface stains and giving the natural effect
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Fig. 4 -—L e ft: T he gingival porcelain condensed to full contour. R ight: Trimming o f the condensed porcelain for the distribution of the incisal shade
obtain the desired results. In the con struction of the crown or facing we should, therefore, use as the gingival color a material that is opaque or one that will be fired to vitrification, m ain taining its opacity. The enamel body should be of either lower fusing or one that is translucent and one that will not affect the opacity of the original body application. Therefore, in the construc tion of a porcelain crown or facing a high fusing body should be used (Fig. 4, left). This first application is condensed and contoured to the outline of the gin gival color of the tooth described on the prescription. It is advisable to carvc it to full contour before trimming for color distribution. This gives a more accurate idea of the amount to reduce on the mesial, distal and labial portions for the overlapping of the incisal color. All the irregularities should be placed in the built up crown after condensation and previous to vitrification. T h e condensed porcelain is trimmed on the mesial, distal and labial portions for the color distribu tion of the incisal shade (Fig. 4, right).
This is then vitrified to a temperature ap proximately 150 degrees below its glazing point. If stains are to be employed to re produce life-like appearances, they should be placed on the dentin or gingival body after vitrification. These are then fired to a setting temperature. T h e enamel body should be of sufficiently low fusing so that it will not affect the opacity of the dentin body. T h e enamel will give a sufficient glaze so that light will be transmitted and reflected as similarly as possible to that of the natural tooth. T h e enamel body is placed over the dentin body with both the gingival hue and incisal shade following the distribution as described on the prescription. T h e labial surface is contoured to fol low the irregularities that appear on,the natural tooth. This will reproduce the high lights and will obtain the defused reflection that is desired.17 A more natural appearance can be obtained by carving these irregularities in the prefired porce17 . Iw an sson , R o b e rt, T h e P o rc e la in Jack et C ro w n a n d th e C o lo r P ro b lem . D . H em s In terest 7 0 : 2i 8 (M a rc h ) 1948.
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at this time we compare its surface luster with that of the adjacent teeth (Fig. 5 ). If the surface luster is too great it is corrected by holding the labial surface of the restoration over the fumes of hydro fluoric acid. It is again tried in the mouth and if further correction is necessary the same procedure is followed until the luster of the restoration is equal to that of the adjacent teeth. Conclusion
Fig. 5 . — Finished crown reproducing the ana tom ic form , surface markings and high lights
lain than by grinding them in with a stone after glazing. A fter these irregular ities are placed on the labial surface of the condensed porcelain it is placed in a furnace and glazed. M y experience has been that the medium or surface porcelain should be carried to a temperature of a high glaze. This is corrected after it is tried in the mouth and the matrix removed. A fter glazing the porcelain is permitted to an neal in a furnace at a low temperature. T h e crown is tried in the mouth and any necessary corrections are made. This is refired to a temperature 50 degrees below that of glazing. A fter the matrix has been removed the crown or facing is tried in the mouth and
This discussion may appear to be rather academic but it is necessary from time to time to review the courses and literature of some of the basic sciences that have a definite influence in the practical application of dentistry. Not only is it necessary to review the courses and literature but it is relevant that we make up some technic work on the un usual cases that are observed. This prac tice increases our experience and en hances the knowledge of the problems that confront us. In this way we can visualize some of the intricacies and de termine how to reproduce them with a minimum of effort. T o master the science of dental art we must have experience and be observant in every detail of our work. W e cannot expect to master the art of ceramics or artistic restorations without understanding color and master ing the art of sculpturing. This requires years of experience and the dentist should not be disillusioned if his first efforts are not masterpieces in esthetics and harmony.— 450 Sutter Street.
A O n T h e F u n ction o f R e c o rd s in D e n tistry — R ecord s a t th eir best are only tools. T h e y Can assist but th ey can n ot create. N o carp en ter ever m ade a piece of oak or w a ln u t w ith a saw and ham m er. H is tools w ill enable him to perform a jo b m ore skillfu lly bu t th ey do not produ ce the wood. Sim ilarly, records, be th ey ever so fine, can n ot overcom e in accurate observation, inertia, or lack of faith .— “ T h e Adm inistrative Im portance o f G ood R ecord s,” Bulletin of the Am erican Asso ciation of Public Health Dentists, August 1949, p. 6.
J. Raymond Gill, D.D.S., San Francisco
r e s to r a tio n that will meet the re quirements of esthetics and harmony in the mouth and will defy observa tion is a work of art as all members of the dental profession know. T o be suc cessful in its interpretation, we must have ability and experience in modeling and sculpturing and also some knowledge of the phenomena of light and mixing and blending of colors. Light is our source of color1’2 and wc must understand its absorption and re flection and also the way the light waves are transmitted through an object and reflected. Refraction also plays a very im portant part in color selection. Because of its importance, we must be extremely observing and have extensive experience. Galileo says that observation and ex perience are the best teachers. W ith obser vation and experience we should be able to put our knowledge to more practical use. Therefore, it is necessary to increase our knowledge by studying each indi vidual case. We should observe the ana tomic form of the teeth and their arrange ment3 in a definite pattern and notice how these harmonize with the facial contour and environment. W e should also visualize how grotesque this pattern would appear in a different environment. W e must study the effect of this source of light on the teeth and also on the various architectural designs of the teeth. We must observe the effect of artificial restor ations, of the reflection of light and its effect on the human eye. W e should constantly be on the alert to increase our knowledge of the factors
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that influence anatomy and color of the teeth. There are other factors which require a thorough understanding of the selection of color and its distribution. These courses are in the basic sciences and are: his tology, histopathology, anatomy, dental materials and the phenomena of light and color. Histology
M any of us after completion of our course in histology4 think of the subject only in reference to cavity preparations as related to the dentin, enamel and pulp of the tooth. V ery few use the subject material as a source of information in the way it influences the color of the tooth; depending only on the manu factured shade guide which has no re semblance in character or in distribution of color of the various types or forms of the teeth. It is important that we understand what part of the tooth reflects certain lights and how other parts of the tooth absorb or dilute reflected light waves.5’6
1. Abney, Sir W. de W., Colour Vision. London: Sampson Low, Marston & Company, 1895. 2. Chevreul, M . E ., The Laws of Contrast of Colour. London: Geo. Routledge and Sons, 1868. 3. Vehe, W. D ., Problem of Esthetics in Restorative Procedures. J.A .D .A . 21:969 (June) 1934. 4. Noyes, F .; Schour, Isaac, and Noyes, H. J., A Text-Book of Dental Histology and Embryology, ed 5. Philadelphia: Lea & Febiger, 1938. 5. Beust, Theodore, Physiologic Changes in Enamel After Tooth Eruption. J .A .D .A . 11:396 (M ay) 1924. 6. McBeath. E. C ., N ew Concept of Development and Calcification of Teeth. J .A .D .A . 23:675 (April)
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Therefore, it is essential that we study the various parts of the tooth that will influence our color selection and distri bution. T h e dentin may be considered opaque. It receives its color pigmentation from the blood supply of the pulp. Its colors range from a light yellow, through the orange, grayish orange or brown, varying according to the age of the patient.7 The dentin varies in thickness, density (which affects the color) and luminosity. The surface of the dentin in the dentoenamel junction is not perfectly smooth but ir regular and this varies considerably. M any times we find dentin spindles pro jecting4 into the enamel. This alters the dispersion of light through the enamel which is termed “ diffused reflection.” The light waves that hit the dentin reflect the color of the dentin and because of the irregularity of the surface, diffused re flection also occurs. Enamel
T h e enamel, which is the outer surface of the tooth, gives strength, form and contour. Enamel is considered translucent and is devoid of pigmentation and color. T h e shade of enamel varies from a light gray to a bluish gray. T he mineral de position of enamel varies in different in dividuals and will also vary in density and hardness from the incisal or occlusal to the gingival. T h e enamel on the incisal and prox imal surfaces transmits light from the dark oral cavity, which gives the effect of a bluish tint.8,9 T he transmission of light from the dark oral cavity varies ac cording to the thickness of enamel and the anatomic form of the tooth. The square type tooth which is thin labiolingually transmits a greater amount of light from the oral cavity than either the ovoid or tapering type; therefore, the square type of tooth appears more trans lucent than the tapering or the ovoid. Also, different teeth will vary in thick
ness labiolingually, such as the lateral incisors, and they appear more translu cent than the central incisors or cuspids. T h e enamel varies in thickness from the gingival to the incisal or occlusal. The hue which predominates at the m iddle and gingival third is not as pronounced at the incisal or occlusal portion. T h is is because the reflected color of the dentin is not transmitted through as thick enamel as that of the middle third or incisal third. T h e mineral deposition of the enamel affects its translucency. Those teeth that are highly mineralized appear more trans lucent than those that are not. The amount of attrition and abrasion also will affect the translucency. The surface character of the enamel will either in crease or decrease the luminosity. In youth, where the enamel surface is irregular, high lights are produced, giv ing the effect of brilliancy or luster. When these irregularities‘are reduced by either attrition or abrasion the surface of the enamel becomes more opaque or dull and the tooth appears darker in color. It is extremely important that w e study the surface anatomy and chart the ir regularities and the abnormal character istics so that they may be reproduced ac curately in restorations. Light waves are transmitted through the enamel and into the dentin, some of the colors are ab sorbed and it is reflected as the color of the dentin. T h e light waves entering into and through the enamel are not only transmitted but there is a certain amount of refraction. Also the color from the dentin through the enamel partially is re fracted light; therefore, there is a break ing up of light waves entering on and through the enamel1 which dilutes the color from the dentin. T h e color, there7. Clark, E. Bruce, An Analysis of Tooth Color. J .A .D .A . 18:2093 (Nov.) 1931; The Color Problem in Dentistry. D . Digest 37:499 (Aug.) I931* 8. Clark, E. Bruce, Tooth Color Selection. J .A .D .A . 20:1065 (June) 1933. 9. Loop, Jack LeRoy, Complicating the C olor Prob lem. Pacific P en . Gaz. < 2? Jnt. 4 1 :9 8 8 (April) 1933.
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fore, is not the true color of the dentin but a diluted color. By this study and observation, we will have a knowledge of the effect of the dentin and enamel in the problem of color selection of a normal tooth. I f there are abnormalities in the enamel or dentin this w ill alter and complicate the prob lems of color selection. These will be con sidered under the study of histopathology. Histopathology
T h e histology of the tooth may be af fected from early youth through adult hood. A ny changes that occur in the tooth or ariy abnormal changes that take place in the development in the dentin or enamel that will affect the color of the tooth in later life may be classified as pathologic conditions. Some of the changes that take place in the dentin and enamel affect the or ganic and mineral composition of both. D uring the development of the tooth if the child has an illness which is accom panied by a high fever there will be a retardation of mineral deposition in the tooth. T h e lines of demarcation that are ob served in the tooth may be caused by im paired mineral deposition during the time of illness. Either a whitish or intense gray ish character in the enamel will be the result. T he dentin will have darker areas of greater opacity due to the lack of density. Some chemical reactions that take place during the development of the tooth will show up as brownish or whitish areas after the tooth has erupted and is exposed to light. T h e action of caries alters the shade and hue of the dentin and the enamel. W hen caries pen etrates into the dentin, owing to the action of acid, it discolors and becomes darker. This is transmitted and reflected through the enamel altering the color in the affected area. In faulty enamel composition we may have effects in the enamel, which in time,
having been exposed to the various ac tions of saliva and light, form brownish or grayish lines. These effects may be regular or irregular. T h e effect of erosion and attrition will also alter the illusion of the color of the tooth.10 Where the dentin is exposed through attrition or abrasion, the action of saliva on the den tin w ill darken it. This darkened area, observed through the enamel, also will affect its shade. There are so many changes which may affect the color and color distribution of the tooth that it will not be possible to enumerate them. W ith observation and experience we can detect these changes and compensate for them in color selection. We must also consider the effect of m etallic fillings in the teeth. A metal fill ing in a tooth will appear to affect the color of the tooth. T w o different colors in juxtaposition produce an illusion of false color. For example, if we place a white strip between two black strips, the white appears gray; the further we move the black strips away from the white one, the more true the white appears on the strip.11 This is the same effect that m etal lic fillings have on the color of the teeth ; therefore, it is necessary to cover these metallic fillings with a natural gray paper to eliminate false color illusion. Anatom y
Anatomy m ay be considered the most important subject in color selection and its distribution in obtaining esthetic re sults that will harmonize within its en vironment.3 W e see so many grotesque results that are obvious to the careful observer. T h e dentist should plan his treatment carefully and study the case so that he will visualize the correct anatomic form of the tooth previous to making the 10. Pilkington, £. L., Esthetics and Optical Illusions in Dentistry J .A .D .A . 23:641 (April) 1936. 11. Luckiesh, M ., Light and Shade and Their Appli cations. New York: D. Van Nostrand Co., Inc., 1916.
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preparation. This is definitely necessary if the alignment of the teeth is to be changed the slightest degree. In these cases it is advisable to prepare the teeth on the study models and reshape them in wax to determine if they will harmonize within their environment. T here are times when the relation of the teeth can be changed without obtaining dishar mony, but if the teeth are rotated or in labial version it is impossible to correct this alignment and expect an esthetic result. We must not make too great an attempt to correct relations because it will invariably alter the expression and personality of the individual. W e should always conform as closely as possible to existing conditions in order to maintain harmonious relation. W e must adhere to the architectural design that has been created in the in dividual mouth without interfering with the personality. Age
U nder histopathology and anatomy, mention was made of changing conditions that may occur from youth through adulthood. Since most of the restorations, whether single, multiple, or in crown and bridge prosthesis, occur in middle age we must have a complete knowledge of various changes that have taken place and how these changes affect the color and the color distribution of the teeth. First, the change in the surface of the anatomy of the tooth should be consid ered. In middle age some of the charac teristics that are found in youth are lost. T h is is caused by attrition, erosion and faulty dentin and enamel composition. These changes are more obvious and recognizable at middle age. Second, there is a reduction of thickness of enamel and an elimination of high lights and contour of the enamel surfaces. T h e tooth be comes dull or opaque compared to that of youth and loses its luminosity. This opacity of the labial surface decreases
the transmission of the light from the oral cavity through the enamel, decreasing its translucency. When the incisal enamel has been worn partially or entirely away exposing the dentin, and the gingival color is decreased by surface wear, the results of the two make the tooth appear darker. T h e pulp recession increases the thickness of the dentin and changes the color of the dentin from a light orange to a dark orange or brown. Caries and fillings at this age have altered the color of the teeth. Therefore, it is obvious that to use a shade guide for the selection of a tooth for young, adult or a middle aged person cannot be successful, especially if the shade guide does not reproduce the various characteristic changes. Materials Used in Restorative Procedures
T h e materials used in restorations of esthetics fall into two groups; ceramics and hydrocarbons (plastics). Neither one of these absorb, refract, transmit or reflect light the same as the tooth.12 T h e enamel rods absorb and reflect some of the colors; the dentin reflects its color. T h e enamel rods vary in their relation to the surface and anatomic form of the tooth. Ceramic material and plastics are homogeneous substances but tooth structure is hetero geneous.13 Porcelain or plastics are void of crystalline structure and are not cap able of presenting the same color phe nomena as the different substances in the tooth; therefore, it is necessary for us to exert our artistic ingenuity in developing and sculpturing these materials to sim ulate as closely as possible the same light and color of the tooth.14 This is more easily accomplished with ceramic material than with plastics. Plas-
12. Brickman, Bernard M ., The Light and Color Phenomena in Teeth and Dental Porcelains. D . Cos (July) 1932. 13. Tylman, Stanley, and Peyton, Floyd A ., Acry
mos 74:666 lics
and
O th e r
Synthetic
Resins
U sed
in
Philadelphia: J. B. Lippincott Company, 14. Felcher, Fred R ., Modern Dental J .A .D .A . 2 3 :1009 (June) 1936.
Dentistry.
1946. Porcelains.
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tics can be assimilated into the arts in dentistry provided we follow out the same procedure in the technic as that of ceramics. It is necessary, if we are re producing the same characteristics of the tooth, to use various fusing points, porce lain, opaque stains and any means of altering the surface texture to harmonize with that of the natural tooth. The Color Selection
Previous to the selection of color, it is necessary to observe all the facts that have been discussed and their influence on the color of the individual tooth. A chart of the tooth, drawing its exact an atomic form, should be made. Also the dentist should inquire and observe the habits of the mouth hygiene of the patient. These characteristics of the tooth should be noted on the chart or prescrip tion. T h e teeth should be observed at various angles, profile, front view, and in various lights. Photographs will help in determining the reproduction of the high lights. Before selecting the color with the use of a shade guide lipstick should be re moved. If it is not removed, visual fatigue of the eye will be affected and what is termed “ simultaneous contrast” will re sult. In other words, we will observe a certain degree of its complimentary color green in thè teeth. A neutral gray back ground with the form of the tooth out in it is the ideal procedure while selecting the color of the tooth.15 T h e shade guide should be one that is made of the material that is being used. T h e colors in porcelain and plastics will vary in some degree with each supply that is manufactured. Therefore, a shade guide from the manufacturer will not be the true color of the material that is be ing used. Furthermore, the gingival color and incisal shade of the tooth will in fluence the color. When using the shade guide in select ing the gingival hue, the lips of the patient
should be raised and the incisal color covered. T h e ideal procedure would be to select the gingival hue after the enamel has been removed and the dentin exposed ; this would give the true color of the foundation body of the tooth. But the fact that we have no material that trans mits and reflects light like that of the enamel, which is superimposed over the dentin, it would be impossible to make a restoration duplicating the effect of the enamel. It might be possible to select the dentin color after the enamel is removed, then choose one that is slightly diluted to obtain a similar effect. This is very dif ficult for those who have not had a great deal of experience in color selection and its interpretation. Therefore, the pro cedure of selecting the gingival hue and the incisal shade can be made preceding the making of the preparation. After the gingival hue has been selected then the number or combination of numbers, of the porcelain, should be noted on the chart or prescription. In selecting the incisal shade the patient’s lips should be in a speaking position. This gives us a truer concept of the incisal shade and eliminates the influence of the gingival hue. This should be the average position of the lips and the exposed portion of the tooth in average conversation. T h e shade selected is noted on the color chart or prescription. Just to select the color of the tooth does not give us a true interpretation for the construction of the crown; therefore, it is essential that we chart the distribution of the incisal and gingival shades on the tooth. This to some extent m ay be con sidered an arbitrary procedure, but it does give us some indication as to the extent of the overlapping of the incisal shade over the gingival hue, the degree of the thickness of the incisal shade on the latéral surfaces of the tooth and the ex-
15. Tylman, Stanley, Crown and Bridge Prosthesis, ed. 2. St. Louis: C . V . Mosby Company, 1947, pp.
¿71-279-
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Fig. i . — L e ft: T he square type of tooth, showing the high lights, anatomic form and all the markings that are im portant to re produce in the restoration
R ight: T he outline of the color distribution drawn on the tooth and which will be trans ferred to the color chart or prescription
L e ft: O void type of tooth showing its arcnitectural design and alignment
R ig h t: Outline o f color distribution of ovoid type o f tooth which will be transferred to the color chart
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J.A.D.A.. Vol. 40. M a y 1950 . . . 545
F ig . 2 .— L e f t : T h e ta p erin g type o f to o th w ith its a r ch ite ctu r a l design
R ig h t:
C o lo r
d istr ib u tio n ch a r ted ta p erin g to o th
on
the
tent that the enamel projects incisally from the dentin. It also determines the amount of incisal wear that has taken place and the influence on the gingival hue at the incisal. (See Figures i and 2.) W e chart the outline of the gingival hue which reflects through the dentin on the mesial and distal surfaces, then the outline of the incisal termination of the gingival hue. Then, we follow out the outline approximately to the gingival termination on the lateral surfaces, fol lowing its termination on the labial sur faces from mesial to distal. T h e color selection and its distribution should be made in various positions, frontal, profile and in a standing position and in differ ent sources or angles of light. This will give a true picture of the existing condi tions and environment for notation on the color chart or prescription.16 (See Figure 3A 0
W ith this color distribution chart we
have the accurate guide in helping to in terpret color and its distribution into the construction of the crown. W e should have on this guide, when completed, everything that we have seen on the tooth, which we desire to place in the restoration to obtain an esthetic harmon ious result (Fig. 3B and C ) . Few dentists follow a definite pro cedure in the color selection and its in terpretation or lack sufficient experience in this fine art to obtain accurate results; therefore, they become discouraged and delegate this to a laboratory technician expecting better results. T h e laboratory technician, without an accurate prescrip tion, cannot reproduce any more than that with which he is given to work. W hether one delegates the work to a technician or does it himself, it is ab16. Gill, J. Raymond, Construction of the Porcelain Veneer Crown. J.A.D .A. 27 :1884 (Dec.) 1940.
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solutely essential that he write a prescrip tion with accurately detailed information. Interpretation
The art of constructing a crown or bridge so well that it will not be recog nized as an artificial restoration requires a great deal of experience. T h e inform a tion discussed requires experience to bring it into the form of reality. There is no greater happiness in den tistry than reproducing an artifical restor ation which cannot be detected by an observer. T h at happiness which is re
flected to the patient is one of the health services that should be rendered. Mental complexes acquired through faulty es thetic restorations may alter the hap piness and personality of the individual. W ith this in mind we should use all our ingenuity and artistic ability in reproduc tions. T h e dentin is relatively opaque and is the basic color of the tooth. T h e enamel is translucent and transmits, reflects and refracts the light waves that are inter preted into color; therefore, if we are to reproduce a restoration to attain these effects we should vary the material to
Pig. 3,— A : Color distribution charted on the tooth and transferred to the prescription. B : A square ovoid type tooth with subsurface stains showing the need for a porcelain inlay. C : C om pleted inlay reproducing subsurface stains and giving the natural effect
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Fig. 4 -—L e ft: T he gingival porcelain condensed to full contour. R ight: Trimming o f the condensed porcelain for the distribution of the incisal shade
obtain the desired results. In the con struction of the crown or facing we should, therefore, use as the gingival color a material that is opaque or one that will be fired to vitrification, m ain taining its opacity. The enamel body should be of either lower fusing or one that is translucent and one that will not affect the opacity of the original body application. Therefore, in the construc tion of a porcelain crown or facing a high fusing body should be used (Fig. 4, left). This first application is condensed and contoured to the outline of the gin gival color of the tooth described on the prescription. It is advisable to carvc it to full contour before trimming for color distribution. This gives a more accurate idea of the amount to reduce on the mesial, distal and labial portions for the overlapping of the incisal color. All the irregularities should be placed in the built up crown after condensation and previous to vitrification. T h e condensed porcelain is trimmed on the mesial, distal and labial portions for the color distribu tion of the incisal shade (Fig. 4, right).
This is then vitrified to a temperature ap proximately 150 degrees below its glazing point. If stains are to be employed to re produce life-like appearances, they should be placed on the dentin or gingival body after vitrification. These are then fired to a setting temperature. T h e enamel body should be of sufficiently low fusing so that it will not affect the opacity of the dentin body. T h e enamel will give a sufficient glaze so that light will be transmitted and reflected as similarly as possible to that of the natural tooth. T h e enamel body is placed over the dentin body with both the gingival hue and incisal shade following the distribution as described on the prescription. T h e labial surface is contoured to fol low the irregularities that appear on,the natural tooth. This will reproduce the high lights and will obtain the defused reflection that is desired.17 A more natural appearance can be obtained by carving these irregularities in the prefired porce17 . Iw an sson , R o b e rt, T h e P o rc e la in Jack et C ro w n a n d th e C o lo r P ro b lem . D . H em s In terest 7 0 : 2i 8 (M a rc h ) 1948.
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at this time we compare its surface luster with that of the adjacent teeth (Fig. 5 ). If the surface luster is too great it is corrected by holding the labial surface of the restoration over the fumes of hydro fluoric acid. It is again tried in the mouth and if further correction is necessary the same procedure is followed until the luster of the restoration is equal to that of the adjacent teeth. Conclusion
Fig. 5 . — Finished crown reproducing the ana tom ic form , surface markings and high lights
lain than by grinding them in with a stone after glazing. A fter these irregular ities are placed on the labial surface of the condensed porcelain it is placed in a furnace and glazed. M y experience has been that the medium or surface porcelain should be carried to a temperature of a high glaze. This is corrected after it is tried in the mouth and the matrix removed. A fter glazing the porcelain is permitted to an neal in a furnace at a low temperature. T h e crown is tried in the mouth and any necessary corrections are made. This is refired to a temperature 50 degrees below that of glazing. A fter the matrix has been removed the crown or facing is tried in the mouth and
This discussion may appear to be rather academic but it is necessary from time to time to review the courses and literature of some of the basic sciences that have a definite influence in the practical application of dentistry. Not only is it necessary to review the courses and literature but it is relevant that we make up some technic work on the un usual cases that are observed. This prac tice increases our experience and en hances the knowledge of the problems that confront us. In this way we can visualize some of the intricacies and de termine how to reproduce them with a minimum of effort. T o master the science of dental art we must have experience and be observant in every detail of our work. W e cannot expect to master the art of ceramics or artistic restorations without understanding color and master ing the art of sculpturing. This requires years of experience and the dentist should not be disillusioned if his first efforts are not masterpieces in esthetics and harmony.— 450 Sutter Street.
A O n T h e F u n ction o f R e c o rd s in D e n tistry — R ecord s a t th eir best are only tools. T h e y Can assist but th ey can n ot create. N o carp en ter ever m ade a piece of oak or w a ln u t w ith a saw and ham m er. H is tools w ill enable him to perform a jo b m ore skillfu lly bu t th ey do not produ ce the wood. Sim ilarly, records, be th ey ever so fine, can n ot overcom e in accurate observation, inertia, or lack of faith .— “ T h e Adm inistrative Im portance o f G ood R ecord s,” Bulletin of the Am erican Asso ciation of Public Health Dentists, August 1949, p. 6.