F u ll-s p e c tru m b ulb s, e s p e c ia lly th e V e rd -A -R a y c ritiC o lo r b u lb , p ro v id e d th e best s o u rc e of lig h t in th is stu d y fo r m a tc h in g to o th c o lo r s a m p le s in a d e n ta l o p e ra to ry .
Dental operatory lighting and tooth color discrimination
Stephen F. Bergen, DDS, W est O ra n g e , NJ John M cCasland, DD S, W a s h in g to n , DC
Evaluation and matching of tooth color are im portant aspects of restorative dentistry and light ing is one o f the most critical influencing factors. If the spectrum of a light source in a dental oper atory does not contain the desired colors, not all colors will be seen. Four light sources, G E Cool White,* GE Chroma 75,* Verd-A-Ray c r i t i C o l o r , t and Verilu xt were tested to determine which was most effective for tooth color discrimination. Only the G E Cool White was not a full-spectrum bulb. Four rooms in off-white color schemes were each equipped with one of the light sources. Characteristics of the light sources are given in Table 1. The test consisted of two parts; the first was a comparison o f the lighting condition of the rooms to that of outdoor light. Outdoor light, estab lished as the standard, was defined as a clear, sunny day at noon. The second part of the test was to determine the most effective light source
for tooth color discrimination. Other factors not covered in this study should be considered when choosing the proper light source for an operatory. For example, the GE Chroma 75 bulb casts a distinct blue tone to a room. Another consideration is fatigue under different light sources. Studies by investigators from Cornell University (D. A. Kleiber, P. L. Musick, and J. K. Jayson) have shown that less fatigue is produced by a full-spectrum bulb than a Cool White.
Materials and methods The Davidson and Hemmendinger (D& H) Color Rule,§ 1967 edition, was used for the first part of the test to compare outdoor light with differ ent indoor lighting conditions. Perceptions of two observers using the same light source, one observer using different light sources (or any
T a b le 1 ■ C h a ra cte ristics o f th e fo u r lig h t sources. Room no. 1 2 3 4
Bulb
Correlated color temperature— Kelvin Scale
Verilux Verd-A-Ray critiColor Cool White GE Chroma 75
6,000 degrees
Color Rendering Index Apparent tone 93
5,700 degrees
91
7,500 degrees
94
White Green-gray 4,200 degrees65Yellow Blue
*To provide a com parison of color rendition, light sources can be rated by the C olor Rendering Index (CRI) method developed by C om m ission Internationale De L’Eclairage (CIE). A scale of 100 is used to indicate the relative ability of the light source to match the rendition of a standard reference illum inant (equal energy or pure white light).
130 ■ JADA, Vol. 94, January 1977
other light source-observer combination) can be compared with the D&H Color Rule. The Color Rule works on the principle of metamerism. Two objects may seem to have identical colors but different spectrophotometric curves and there fore match under one light source, but not an other. In dentistry, for example, one tooth might match a shade guide tooth under one light source, but not another. This phenomenon occurs be cause the pigments used to color teeth are not identical spectrophotometrically to the pigments found in natural enamel. A spectrophotometric curve is a simple graph which shows the amount of light that a material either reflects or transmits in percentages at each wavelength within the electromagnetic spectrum. How different tooth color samples appear de pends on the spectral energy distribution of the light source and the observer’s perception. The D&H Color Rule has two color scales: the top scale is orange that blends into blue and the bottom scale is a mixture o f violet that blends into green. Most observers generally can find an approximate match between the two scales for most light conditions. A portion of both scales appears through the aperture; the scales are ad justed until the colors match (Fig 1). Both the light source and the observer influence the selec ted match point. A study by Kalmus1 found that manufacturing of the D&H Color Rule has become standard ized. In that study, reliability among partici pants’ answers was demonstrated. The 41 participants in the first part of the study were dental personnel from the Walter Reed Army Medical Center. Each was instructed in the use o f the D&H Color Rule and was required to match the ruler under the five lighting con ditions (outdoors and four room lights). The out door reading, based on a combination of the two scales, was used as a zero baseline for compar ison. Readings in the other rooms were subtract ed from the outdoor reading and the difference was recorded. In each room, only the light source changed. Each of the two recording scales on the D&H Color Rule was further divided in four units so smaller differences could be analyzed. One scale was lettered from A through Z, and one was numbered from 1 to 40. At the end of the study, the lettered scale was translated into numbers for easier analysis. Analysis was done for both scales and the numerical results were plotted on a graph.
The second part of the test was a color test2 to determine color matching ability within the den tal color spectrum. When testing color matching ability in an industry, only the colors that pre dominate in that industry should be used, be cause the eye is not equally sensitive to all col ors.3 The color spectrum range for natural teeth has been determined.4 A yellow-red to yellow range should be used when testing dentists. Seventy-five color samples of the same mater ial (paint lacquer on paper) were originally pro duced; 25 of these were used in this study. The Munsell Color Notation system of hue, value, and chroma was used.5 Hue refers to the differ ent color families (red, green, and so forth), value refers to a lightness-darkness scale, and chroma refers to a purity or saturation scale. The differ ence between the 25 samples was 0.5 step in hue and 0.2 step in chroma. All had a value o f 8.0. These differences are barely perceptible. Hue ranged from 0.7 yellow to 2.7 yellow; chroma ranged from 2.8 to 3.6. These were well within the range of the dental color spectrum as iden tified by Sproull4 (hue ranges from 7.5 yellowred to 2.7 yellow; value from 5.8 to 8.5; and chro ma from 1.5 to 5.6). From these 25 sample colors, 5 were chosen at random to be test colors. The 25 samples were arranged on a 5 x 5 grid. Each o f the five chosen samples had to be matched to one of the color samples on the grid (the five color samples were taken from a second identical set o f samples). The five test samples were labeled one through five and a numbering code was designed for re cording the answers. Two of the 19 were dropped because o f improper recording of answers. All participants took the same test in each o f the four rooms; however, none of the participants or ad ministrators knew it was the same. The 25-sam ple matching grid was rotated 90° in each room, so it would seem as if different tests were being given. The rooms were the same color; the light source was the only variable. Tests were taken in the following order: participant 1 started in room 1 and proceeded to room 4; participant 2 went in the reverse order, and so on. B ergen— McCasland: LIGHTING, COLOR DISCRIMINATION ■ 131
T a b le 2 ■ R esults o f D&H C o lo r Rule m easurem ents. Outdoors
Room 1
Room 2
Top Bottom Top Bottom Top ________ rule______ rule______ rule______ rule______ rule
_________________■ Average reading (D&H original scale) Average reading transcribed scale (Original trans cribed into numbers for analysis) Difference between room readings and outdoor readings* Order of straight difference (interpretation of difference between room readings and outdoor readings)
8.8
Difference from outdoors without directionf (differences between the right and the left readings on the ruler) Order of difference without direction (interpretation of differences between the right and the left readings on the ruler)
H.5
8.2
G.5
Bottom rule
9.1
H.6
Room 3
Room 4
Top rule
Bottom rule
Top rule
Bottom rule
7.8
G.8
8.2
G.1
16.73
16.48
13.51
12.81
18.09
16.56
12.13
14.93
13.78
11.06
—
—
-3 .2 2
-3 .6 7
+1.36
+0.08
- 4 .6
-1 .5 5
-2 .9 5
-5 .4 2
Top rule Bottom rule
Third
—
First Third
—
5.68
Top rule Bottom rule
Third
6.01
Fourth First
3.56
3.51
First Third
Second Second
5.85
3.98
Fourth First
Fourth
3.80
6.47
Second Second
Fourth
*lf the direction of difference from outdoors was to the right on the rule, the numbers increased and a + value was given. If it was to the left, a - value was given. The signs were considered when the average was computed. fT he signs were dropped for this calculation and the numbers were just added together and considered as different from outdoors, no matter which direction or toward what color on the ruler the change went.
7 6 8
S
5 Ld 3 rr O
4
OUTDOOR READING = 5 ,3 Room 1,2,3 or 4 = 7 ,6
3 °
(7 -5 )2 + (6 -3 )2 - c2
2
-
\[Ï3 = c 3.61 = c
_L
0
1
2
3
_L
4
5
6
7
BOTTOM RULE Fig 3 ■ Graph of average differences between outdoor point Fig 2 ■ Top rule versus bottom rule of D&H Color Rule for one
readings and room point readings on D&H Color Rule for 41 par
participant. Formula a2+ b 2= c 2 was used to calculate difference
ticipants (part one) and number of participants (of the total 19)
between the two points.
who scored their best in each room (part two).
Results Verd-A-Ray critiColor lighting in room 2 pro duced the best results in both parts of the study. In the first part, readings with this bulb in room 2 most closely matched outdoor readings on both the top and bottom scales of the rule (Table 2). Numerical readings were determined by sub 132 ■ JADA, Vol. 94, January 1977
tracting outdoor readings from room readings. Readings for all o f the outdoor and indoor meas urements, as shown on the top and bottom scales o f the D&H Color Rule, also were plotted on a graph. The formula a2+ b2= c 2 was used to cal culate the difference between the two points (c). This is illustrated for one participant in Figure 2. The average differences (Fig 3) between outdoor and room readings were room 1, Verilux, 8.74;
— GE C o o l W h i t ■ ■ Verd-A-Ray critiColor Natural daylight ™
I 90
tL*
80 !
✓
•V i,'
'
■s \-
““
/ /
1
>H
\ i*.
V.
/
.
\
6
? /
/ /
/
V V
\
/
t:
x\
A\
\
30 '
I
il
\ \
V /
RELATIVE
ENERG
V«
/
G E C h r o m a 75 Ve ri ux
/
/
V,
?
3 )0
3 0
.\
\ s,
/•
4 )0
ul tr avioli 5t_ v i o l et
I
I
4 50
5 DO
blue
gre e r
11
I
I
I
I
I
5 0
i
i
I
I
6C 0
6 50
yel lo\ __o r anc e.
I
'
' i
I
I
70 0 ree
7 >0 i n f r a re
1 ' I
I
Fig 4 ■ Relative energy versus spectrum curves for the various light sources.
room 2, Verd-A-Ray critiColor, 5.49; room 3, G E Cool White, 7.74; and room 4, G E Chroma 75, 8.07. (Relative energy versus spectrum curves for the various light sources are given in Figure 4.) The difference between room 2 with Verd-ARay critiColor lighting and the other three rooms was statistically significant, but the differences among the other rooms were not. We can’t ex plain why the other two full-spectrum bulbs (Verilux, room 1 and G E Chroma 75, room 4) did not produce better scores in this part of the test. When the results o f this part of the study were plotted on a graph of computed match points on the D&H Color Rule, they were consistent with what might be expected with outdoor and indoor lighting conditions. Our results also correlated with Hemmendinger’s results.6 (The entire range of computed match points is much greater than in our study. Our results fell within that range; however, Verd-A-Ray came closer to an expect ed result.) In the second part of the test, a score of 0 indi cated a correct answer. A score of 1 was given for each chroma error and a score of 3 for each hue error. These values were used because at these hue, value, and chroma levels, it is three times easier to perceive differences in hue than differences in chroma. The number and score of the participants in each room are given in Table 3. For example,
Table 3 ■ Number o f participants in each room in the second part of the test and their score. No. of participants Score* 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Total
Room 1
Room 2
Room 3
Room 4
0 0 0 1 3 2 2 1 1 1 2 0 1 1 0 3 1 0 19
0 0 1 3 1 6 2 3 0 0 1 1 1 0 0 0 0 0 19
0 1 1 0 0 1 0 3 3 0 2 2 2 0 1 1 1 1 19
0 1 2 1 2 1 1 1 2 0 5 1 1 0 0 0 0 1 19
*A score of 0 was given for each correct answer, 1 for each chroma error, and 3 for each hue error.
six o f the participants scored 5 in room 2 (VerdA-Ray critiColor); but in room 3 (G E Cool White), only one participant scored 5. N ine par ticipants scored their lowest score in room 2; 0 was the best possible score. Two of the parti cipants in room 1, three in room 3, and five in room 4 also scored their best (Fig 3). The best score was again obtained for room 2, where 16 participants scored 7 or less; 0 was the highest possible. The poorest result was obtained for room 3, where only six participants scored 7 or less. Nine of the participants in room 1 and nine in room 4 scored 7 or less. As expected, more errors were found in chroB ergen— McCasland: LIGHTING, COLOR DISCRIMINATION ■ 133
Table 4 ■ Number of errors of each type and total points in each room. Room
Chroma errors only
Hue errors only
1 2 3 4 Total
48 43 46 32 169
15 13 16 10 54
Chroma and hue errors that occurred together 23 8 24 24 79
17 7 21 18 63
No. of points* 167 111 181 140
'One point was given for each chroma error and three points for each hue error. The ratio of chroma to hue errors also was 3 to 1.
ma perception than in hue perception. Room 2 had the least total number of errors of each type (Table 4). The difference in points between room 2 and rooms 1 and 3 was statistically significant; the difference between rooms 2 and 4 was not.
Summary and recommendations Full-spectrum bulbs provided the best source of light for matching tooth color samples in a dental operatory. The best results were obtained with a Verd-A-Ray critiColor bulb. The light from that bulb most closely matched the lighting con dition outdoors, according to this test with the D& H Color Rule. We recommend use of a full-spectrum bulb, both in the dental operatory and laboratory, where tooth color discrimination is required. In this study, the Verd-A-Ray critiColor and G E Chroma 75 bulbs were found to be acceptable; the Verilux bulb was not acceptable. Other full-spectrum bulbs not evaluated in this study could be tested by the same tech niques. The color samples produced for this study also could be used for further tests on color knowledge and color matching ability.
134 ■ JADA, Vol. 94, January 1977
The opinions expressed herein are those of the authors and do not necessarily represent the opinions of the Department of Defense, Department of the Army, the Office of the Surgeon Gen eral, the US Army Health Services Command, Walter Reed Army Medical Center, or the Veterans Administration. We acknowledge Henry Hemmendinger for his help in inter preting the results of this study and Lawrence Garfinkel for his aid in statistical analysis. Dr. Bergen is director of prosthodontics at the Manhattan Vet erans Administration Hospital. His address is 1 Colonial Woods Dr, West Orange, NJ 07052. Dr. McCasland is chief of remov able prosthodontics, department of dentistry, Walter Reed Army Medical Center. Address requests for reprints to Dr. Bergen. ‘ General Electric Co., Cleveland, Ohio 44117. tVerd-A-Ray Lighting Products, Inc., Toledo, Ohio 43605. iVerilux, Inc., Greenwich, Conn 06830. iiDavidson and Hemmendinger, Inc., Munsell Color Corp., Baltimore, 21218. 1. Kalmus, H. Metameric “Color Rule” matches of normal, colour deficient, cataractic, and aphakic observers. Ann Hum Genet 36:109 July 1972. 2. Bergen, S.F. Color education for the dental profession, thesis. New York University, College of Dentistry, New York, 1975. 3. Martin, L.C.; Warburton, F.L.; and Morgan, W.J. Determin ation of the sensitiveness of the eye to differences in the satura tion of colors. London, His Majesty’s Stationary Office, 1933. 4. Sproull, R.C. Color matching in dentistry. J Prosthet Dent 29:557 May 1973. 5. Sproull, R.C. Color matching in dentistry. J Prosthet Dent 29:418 April 1973. 6. Hemmendinger, H. Computed match points, D&H Color Rule, 1967 edition. Belvedere, NJ.
Dental operatory lighting and tooth color discrimination
Stephen F. Bergen, DDS, W est O ra n g e , NJ John M cCasland, DD S, W a s h in g to n , DC
Evaluation and matching of tooth color are im portant aspects of restorative dentistry and light ing is one o f the most critical influencing factors. If the spectrum of a light source in a dental oper atory does not contain the desired colors, not all colors will be seen. Four light sources, G E Cool White,* GE Chroma 75,* Verd-A-Ray c r i t i C o l o r , t and Verilu xt were tested to determine which was most effective for tooth color discrimination. Only the G E Cool White was not a full-spectrum bulb. Four rooms in off-white color schemes were each equipped with one of the light sources. Characteristics of the light sources are given in Table 1. The test consisted of two parts; the first was a comparison o f the lighting condition of the rooms to that of outdoor light. Outdoor light, estab lished as the standard, was defined as a clear, sunny day at noon. The second part of the test was to determine the most effective light source
for tooth color discrimination. Other factors not covered in this study should be considered when choosing the proper light source for an operatory. For example, the GE Chroma 75 bulb casts a distinct blue tone to a room. Another consideration is fatigue under different light sources. Studies by investigators from Cornell University (D. A. Kleiber, P. L. Musick, and J. K. Jayson) have shown that less fatigue is produced by a full-spectrum bulb than a Cool White.
Materials and methods The Davidson and Hemmendinger (D& H) Color Rule,§ 1967 edition, was used for the first part of the test to compare outdoor light with differ ent indoor lighting conditions. Perceptions of two observers using the same light source, one observer using different light sources (or any
T a b le 1 ■ C h a ra cte ristics o f th e fo u r lig h t sources. Room no. 1 2 3 4
Bulb
Correlated color temperature— Kelvin Scale
Verilux Verd-A-Ray critiColor Cool White GE Chroma 75
6,000 degrees
Color Rendering Index Apparent tone 93
5,700 degrees
91
7,500 degrees
94
White Green-gray 4,200 degrees65Yellow Blue
*To provide a com parison of color rendition, light sources can be rated by the C olor Rendering Index (CRI) method developed by C om m ission Internationale De L’Eclairage (CIE). A scale of 100 is used to indicate the relative ability of the light source to match the rendition of a standard reference illum inant (equal energy or pure white light).
130 ■ JADA, Vol. 94, January 1977
other light source-observer combination) can be compared with the D&H Color Rule. The Color Rule works on the principle of metamerism. Two objects may seem to have identical colors but different spectrophotometric curves and there fore match under one light source, but not an other. In dentistry, for example, one tooth might match a shade guide tooth under one light source, but not another. This phenomenon occurs be cause the pigments used to color teeth are not identical spectrophotometrically to the pigments found in natural enamel. A spectrophotometric curve is a simple graph which shows the amount of light that a material either reflects or transmits in percentages at each wavelength within the electromagnetic spectrum. How different tooth color samples appear de pends on the spectral energy distribution of the light source and the observer’s perception. The D&H Color Rule has two color scales: the top scale is orange that blends into blue and the bottom scale is a mixture o f violet that blends into green. Most observers generally can find an approximate match between the two scales for most light conditions. A portion of both scales appears through the aperture; the scales are ad justed until the colors match (Fig 1). Both the light source and the observer influence the selec ted match point. A study by Kalmus1 found that manufacturing of the D&H Color Rule has become standard ized. In that study, reliability among partici pants’ answers was demonstrated. The 41 participants in the first part of the study were dental personnel from the Walter Reed Army Medical Center. Each was instructed in the use o f the D&H Color Rule and was required to match the ruler under the five lighting con ditions (outdoors and four room lights). The out door reading, based on a combination of the two scales, was used as a zero baseline for compar ison. Readings in the other rooms were subtract ed from the outdoor reading and the difference was recorded. In each room, only the light source changed. Each of the two recording scales on the D&H Color Rule was further divided in four units so smaller differences could be analyzed. One scale was lettered from A through Z, and one was numbered from 1 to 40. At the end of the study, the lettered scale was translated into numbers for easier analysis. Analysis was done for both scales and the numerical results were plotted on a graph.
The second part of the test was a color test2 to determine color matching ability within the den tal color spectrum. When testing color matching ability in an industry, only the colors that pre dominate in that industry should be used, be cause the eye is not equally sensitive to all col ors.3 The color spectrum range for natural teeth has been determined.4 A yellow-red to yellow range should be used when testing dentists. Seventy-five color samples of the same mater ial (paint lacquer on paper) were originally pro duced; 25 of these were used in this study. The Munsell Color Notation system of hue, value, and chroma was used.5 Hue refers to the differ ent color families (red, green, and so forth), value refers to a lightness-darkness scale, and chroma refers to a purity or saturation scale. The differ ence between the 25 samples was 0.5 step in hue and 0.2 step in chroma. All had a value o f 8.0. These differences are barely perceptible. Hue ranged from 0.7 yellow to 2.7 yellow; chroma ranged from 2.8 to 3.6. These were well within the range of the dental color spectrum as iden tified by Sproull4 (hue ranges from 7.5 yellowred to 2.7 yellow; value from 5.8 to 8.5; and chro ma from 1.5 to 5.6). From these 25 sample colors, 5 were chosen at random to be test colors. The 25 samples were arranged on a 5 x 5 grid. Each o f the five chosen samples had to be matched to one of the color samples on the grid (the five color samples were taken from a second identical set o f samples). The five test samples were labeled one through five and a numbering code was designed for re cording the answers. Two of the 19 were dropped because o f improper recording of answers. All participants took the same test in each o f the four rooms; however, none of the participants or ad ministrators knew it was the same. The 25-sam ple matching grid was rotated 90° in each room, so it would seem as if different tests were being given. The rooms were the same color; the light source was the only variable. Tests were taken in the following order: participant 1 started in room 1 and proceeded to room 4; participant 2 went in the reverse order, and so on. B ergen— McCasland: LIGHTING, COLOR DISCRIMINATION ■ 131
T a b le 2 ■ R esults o f D&H C o lo r Rule m easurem ents. Outdoors
Room 1
Room 2
Top Bottom Top Bottom Top ________ rule______ rule______ rule______ rule______ rule
_________________■ Average reading (D&H original scale) Average reading transcribed scale (Original trans cribed into numbers for analysis) Difference between room readings and outdoor readings* Order of straight difference (interpretation of difference between room readings and outdoor readings)
8.8
Difference from outdoors without directionf (differences between the right and the left readings on the ruler) Order of difference without direction (interpretation of differences between the right and the left readings on the ruler)
H.5
8.2
G.5
Bottom rule
9.1
H.6
Room 3
Room 4
Top rule
Bottom rule
Top rule
Bottom rule
7.8
G.8
8.2
G.1
16.73
16.48
13.51
12.81
18.09
16.56
12.13
14.93
13.78
11.06
—
—
-3 .2 2
-3 .6 7
+1.36
+0.08
- 4 .6
-1 .5 5
-2 .9 5
-5 .4 2
Top rule Bottom rule
Third
—
First Third
—
5.68
Top rule Bottom rule
Third
6.01
Fourth First
3.56
3.51
First Third
Second Second
5.85
3.98
Fourth First
Fourth
3.80
6.47
Second Second
Fourth
*lf the direction of difference from outdoors was to the right on the rule, the numbers increased and a + value was given. If it was to the left, a - value was given. The signs were considered when the average was computed. fT he signs were dropped for this calculation and the numbers were just added together and considered as different from outdoors, no matter which direction or toward what color on the ruler the change went.
7 6 8
S
5 Ld 3 rr O
4
OUTDOOR READING = 5 ,3 Room 1,2,3 or 4 = 7 ,6
3 °
(7 -5 )2 + (6 -3 )2 - c2
2
-
\[Ï3 = c 3.61 = c
_L
0
1
2
3
_L
4
5
6
7
BOTTOM RULE Fig 3 ■ Graph of average differences between outdoor point Fig 2 ■ Top rule versus bottom rule of D&H Color Rule for one
readings and room point readings on D&H Color Rule for 41 par
participant. Formula a2+ b 2= c 2 was used to calculate difference
ticipants (part one) and number of participants (of the total 19)
between the two points.
who scored their best in each room (part two).
Results Verd-A-Ray critiColor lighting in room 2 pro duced the best results in both parts of the study. In the first part, readings with this bulb in room 2 most closely matched outdoor readings on both the top and bottom scales of the rule (Table 2). Numerical readings were determined by sub 132 ■ JADA, Vol. 94, January 1977
tracting outdoor readings from room readings. Readings for all o f the outdoor and indoor meas urements, as shown on the top and bottom scales o f the D&H Color Rule, also were plotted on a graph. The formula a2+ b2= c 2 was used to cal culate the difference between the two points (c). This is illustrated for one participant in Figure 2. The average differences (Fig 3) between outdoor and room readings were room 1, Verilux, 8.74;
— GE C o o l W h i t ■ ■ Verd-A-Ray critiColor Natural daylight ™
I 90
tL*
80 !
✓
•V i,'
'
■s \-
““
/ /
1
>H
\ i*.
V.
/
.
\
6
? /
/ /
/
V V
\
/
t:
x\
A\
\
30 '
I
il
\ \
V /
RELATIVE
ENERG
V«
/
G E C h r o m a 75 Ve ri ux
/
/
V,
?
3 )0
3 0
.\
\ s,
/•
4 )0
ul tr avioli 5t_ v i o l et
I
I
4 50
5 DO
blue
gre e r
11
I
I
I
I
I
5 0
i
i
I
I
6C 0
6 50
yel lo\ __o r anc e.
I
'
' i
I
I
70 0 ree
7 >0 i n f r a re
1 ' I
I
Fig 4 ■ Relative energy versus spectrum curves for the various light sources.
room 2, Verd-A-Ray critiColor, 5.49; room 3, G E Cool White, 7.74; and room 4, G E Chroma 75, 8.07. (Relative energy versus spectrum curves for the various light sources are given in Figure 4.) The difference between room 2 with Verd-ARay critiColor lighting and the other three rooms was statistically significant, but the differences among the other rooms were not. We can’t ex plain why the other two full-spectrum bulbs (Verilux, room 1 and G E Chroma 75, room 4) did not produce better scores in this part of the test. When the results o f this part of the study were plotted on a graph of computed match points on the D&H Color Rule, they were consistent with what might be expected with outdoor and indoor lighting conditions. Our results also correlated with Hemmendinger’s results.6 (The entire range of computed match points is much greater than in our study. Our results fell within that range; however, Verd-A-Ray came closer to an expect ed result.) In the second part of the test, a score of 0 indi cated a correct answer. A score of 1 was given for each chroma error and a score of 3 for each hue error. These values were used because at these hue, value, and chroma levels, it is three times easier to perceive differences in hue than differences in chroma. The number and score of the participants in each room are given in Table 3. For example,
Table 3 ■ Number o f participants in each room in the second part of the test and their score. No. of participants Score* 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 Total
Room 1
Room 2
Room 3
Room 4
0 0 0 1 3 2 2 1 1 1 2 0 1 1 0 3 1 0 19
0 0 1 3 1 6 2 3 0 0 1 1 1 0 0 0 0 0 19
0 1 1 0 0 1 0 3 3 0 2 2 2 0 1 1 1 1 19
0 1 2 1 2 1 1 1 2 0 5 1 1 0 0 0 0 1 19
*A score of 0 was given for each correct answer, 1 for each chroma error, and 3 for each hue error.
six o f the participants scored 5 in room 2 (VerdA-Ray critiColor); but in room 3 (G E Cool White), only one participant scored 5. N ine par ticipants scored their lowest score in room 2; 0 was the best possible score. Two of the parti cipants in room 1, three in room 3, and five in room 4 also scored their best (Fig 3). The best score was again obtained for room 2, where 16 participants scored 7 or less; 0 was the highest possible. The poorest result was obtained for room 3, where only six participants scored 7 or less. Nine of the participants in room 1 and nine in room 4 scored 7 or less. As expected, more errors were found in chroB ergen— McCasland: LIGHTING, COLOR DISCRIMINATION ■ 133
Table 4 ■ Number of errors of each type and total points in each room. Room
Chroma errors only
Hue errors only
1 2 3 4 Total
48 43 46 32 169
15 13 16 10 54
Chroma and hue errors that occurred together 23 8 24 24 79
17 7 21 18 63
No. of points* 167 111 181 140
'One point was given for each chroma error and three points for each hue error. The ratio of chroma to hue errors also was 3 to 1.
ma perception than in hue perception. Room 2 had the least total number of errors of each type (Table 4). The difference in points between room 2 and rooms 1 and 3 was statistically significant; the difference between rooms 2 and 4 was not.
Summary and recommendations Full-spectrum bulbs provided the best source of light for matching tooth color samples in a dental operatory. The best results were obtained with a Verd-A-Ray critiColor bulb. The light from that bulb most closely matched the lighting con dition outdoors, according to this test with the D& H Color Rule. We recommend use of a full-spectrum bulb, both in the dental operatory and laboratory, where tooth color discrimination is required. In this study, the Verd-A-Ray critiColor and G E Chroma 75 bulbs were found to be acceptable; the Verilux bulb was not acceptable. Other full-spectrum bulbs not evaluated in this study could be tested by the same tech niques. The color samples produced for this study also could be used for further tests on color knowledge and color matching ability.
134 ■ JADA, Vol. 94, January 1977
The opinions expressed herein are those of the authors and do not necessarily represent the opinions of the Department of Defense, Department of the Army, the Office of the Surgeon Gen eral, the US Army Health Services Command, Walter Reed Army Medical Center, or the Veterans Administration. We acknowledge Henry Hemmendinger for his help in inter preting the results of this study and Lawrence Garfinkel for his aid in statistical analysis. Dr. Bergen is director of prosthodontics at the Manhattan Vet erans Administration Hospital. His address is 1 Colonial Woods Dr, West Orange, NJ 07052. Dr. McCasland is chief of remov able prosthodontics, department of dentistry, Walter Reed Army Medical Center. Address requests for reprints to Dr. Bergen. ‘ General Electric Co., Cleveland, Ohio 44117. tVerd-A-Ray Lighting Products, Inc., Toledo, Ohio 43605. iVerilux, Inc., Greenwich, Conn 06830. iiDavidson and Hemmendinger, Inc., Munsell Color Corp., Baltimore, 21218. 1. Kalmus, H. Metameric “Color Rule” matches of normal, colour deficient, cataractic, and aphakic observers. Ann Hum Genet 36:109 July 1972. 2. Bergen, S.F. Color education for the dental profession, thesis. New York University, College of Dentistry, New York, 1975. 3. Martin, L.C.; Warburton, F.L.; and Morgan, W.J. Determin ation of the sensitiveness of the eye to differences in the satura tion of colors. London, His Majesty’s Stationary Office, 1933. 4. Sproull, R.C. Color matching in dentistry. J Prosthet Dent 29:557 May 1973. 5. Sproull, R.C. Color matching in dentistry. J Prosthet Dent 29:418 April 1973. 6. Hemmendinger, H. Computed match points, D&H Color Rule, 1967 edition. Belvedere, NJ.
