MOUNTING NATURAL TEETH
material can be trimmed with a laboratory knife. The tooth and the retaining screw are held in place until the acrylic resin hardens completely. After the acrylic resin has polymerized, the retaining screw is loosened about 2 mm (Fig. 3, A). Pressing gently in an occlusal direction on the screw will loosen the tooth from the socket. For complete removal of the tooth from the socket, the retaining screw is removed (Fig. 3, B through D). The soft utility wax is removed and the tooth is thoroughly cleaned under hot running water (Fig. 4, A). The tooth is reinserted into its socket and evaluated for stability, contours, and contact. Any necessary adjustments should be made at this time. Next, a thin layer of impression tray adhesive is painted onto the tooth apical to the cementoenamei junction and on the acrylic resin immediately adjacent to it. A heavyviscosity polyether impression material (Permadyne, ESPE-Premier Dental Products, Norristown, Pa.) is mixed and injected around the tooth (Fig. 4, B). This step fills in the region that had been blocked out with wax, and creates soft artificial gingival tissue. After the impression material polymerizes, the excess is trimmed off with a sharp laboratory knife (Fig. 4, C and D). A proper relationship with the opposing plastic teeth is
achieved by occlusal adjustment with diamond rotary instruments. The natural tooth is now mounted in the dentoform and can be used to help students gain realistic clinical experience. The socket can still be used for plastic teeth when needed. The natural toOth should be removed from the dentoform when it is not in use, and stored in a sealed container of water to prevent dehydration and increased brittleness. SUMMARY Plastic teeth are often poor substitutes for natural teeth when used in prectinical courses in restorative technique. As an alternative to plastic teeth, a method for mounting natural teeth in dentoforms has been developed to help students gain realistic clinical experience. REFERENCE 1. Gregory WA. A method for mounting natural teeth in a typodont. J Dent Educ 1988;52:309.
Reprint requests to: DR. EDWARD J. SWIFT, JR. COLLEGE OF DENTISTRY THE UNIVERSITYOF IOWA IOWA CITY, IA 52242
Shade selection by color v i s i o n - d e f e c t i v e dental personnel S. P. D a v i s o n , B.D.S.,* a n d N. R. M y s l i n s k i , Ph.D.**
University of Maryland, Baltimore College of Dental Surgery, Baltimore, Md. This investigation studied the impairment of Hue, Value, and Chroma matching by color v i s i o n - d e f e c t i v e dental personnel. Color,defective dental personnel w e r e found to m a k e significantly g r e a t e r errors in Hue and Chroma selection than normal-vision dental personnel. Value, the component of shade selection considered the m o s t important, w a s uneffected. Color-normal dental a s s i s t a n t s w e r e significantly m o r e accurate in Hue and Chroma selection than color-defective dental personnel and could a s s i s t affected dentists in clinical situations. (J PROSTHET DENT
1990;63:97-101.)
C o r r e c t shade selection is an important component of prosthetic dentistry. To ensure a successful esthetic prosthesis, development of acceptable morphology of the restoration must be achieved first, followed by careful consideration to correct shade reproduction.1 The shade match
Presented at the Capital Section of the American College of Prosthodontists, Baltimore, Md. Winner of the Victoria Gunning Dental Research Prize, University of Edinburgh, Edinburgh, Scotland. *Resident, Combined Prosthodontics. **Director of Physiology Graduate Studies. 10/1/12547 97
of a restoration or prosthesis to surrounding teeth may be the only parameter of treatment with which the patient is concerned. As early as 1931 Clark 2 realized the inherent problems associated with shade selection and attempted to establish and record the definitive specification of tooth color for further application and research in dentistry. Sproull 3 described color-matching in dentistry by using the Munsell color system as the standard. He elaborated on the shade guide 4 and color-matching problems in dentistry. 5 Factors such as lighting, 6, 7 color-vision deficiencies, 5-8 and experience may modify shade selection. Conflicting results on the influence of experience on correct shade selection have been reported. 7, s JANUARY 1990 VOLUME 83 NUMBER 1
DAV1SON AND MYSLINSKI
Table I. Frequency of shade selection errors in color-defective group (N = 20) Group
Hue Chroma Value
Mean
SD
2.50 0.85 0.05
1.7 0.81 0.22
F Ratio
25.976
F Prob
0.00001
It is conceivable that a discrepancy in the color vision of the dentist may constitute a problem in correct shade selection. Color-defective individuals in small groups have been compared with normal individuals in shade-selection studies. 6s Barna et al.7 found that color-defective dentists make significantly more errors in Hue selection studies than individuals with normal color perception, yet Jacobs et al.9 found them more sensitive in Value selection. Neither study detected differences in Chroma selection. Color-defective vision is a real problem because the prevalence among male dentists of this X-linked recessive trait ac: cording to McMaugh 8 is 8.2 %, to Moser et al. 1° 9.9 %, and to Barna et al. 7 14 %, all of which are at least as great as the 8% prevalence reported for men. It has been suggested that dentists be made aware of their color-vision deficiencies and consult assistants with normal color vision during shade selection. 5, 7, lo However, thus far, no studies in the field of color in dentistry have looked primarily at the color-defective group. This study investigated whether (1) color-defective vision reduces the ability to match shades; (2) color:vision deficiency has an unequal effect on Hue, Value, and Chroma selection, (3) dental assistants are more accurate at shade selection than color-defective dental students and dentists, and (4) experience improves shade selection in Color-normal individuals. METHODS
AND MATERIAL
The sample population for this study consisted of dental students and faculty and staff members at the University of Maryland Dental SchoOl. F o u r experimental groups (N = 20) were selected. They were: (1) color-defective dental students and dentists, (2) color-normal assistants, (3) Color-normal prosthodontic residents and prosthod0ntists, and (4) a control group randomly selected from the sample population. To differentiate color:defective from color-normal subjects, dental students, dental faculty members, and dental assistants were initially screened by using the American College of Prosthodontists Divorine Pseudoisochromatic slide test.* Those who failed were definitively tested by using the corresPonding plate test (Fig. 1). It was necessary to include most of the available assistants and prosthodon-
• 1777 N. E. Loop 410, Suite 904, San Antonio, Texas 78217.
98
tists from the sample population to make up group sizes of 20 individuals. To compare shade-selection ability, the correct matching of standard shade tabs was used. This study used three Munsell color tab grids similar to that described by Bergen and McCasland 6 and Barna et al.7 Clark's study 2 of 6000 natural teeth provided a guide for Hue, Value, and Chroma ranges. Each of the grid s was constant for a single parameter: (1) Hue, 2.5Y; (2) Value, 7/; and (3) Chroma,/4. The other parameters were variable. The Hue range was 7.5 yellow/red to 7.5 yellow in increments Of 2.5 Hue units. The Value range was 4 / t o 8 / i n increments of 1/Value units. The Chroma selections were from a range of/1 to / 12 with increments of/2 Chroma units. A larger range was used because the Munsell color system does not provide lower Chroma choices at higher Value levels. Some shades outside the range of Clark's study had to be used to give a full spectrum of selection, but these were kept to a minimum. Each axis of the grid had five variables for each of the parameters. Five Shade tabs from each of the grids were selected to represent the availability of shades and to avoid a predominance of shade examples from the extremes of the variables. These selected shade tabs were duplicated to be used for shade-matching against the grid from which they were selected (Fig. 2). The 25 tabs in the grid were mixed and i~resented to each individual to match identically the five duplicated tabs. The five duplicated tabs were supplied loose on the bottom line of the grid so that the testing individual could remove them and visually compare tabs side by side (Fig. 3). The grids were presented to every subject in the same order: Hue constant grid, Value constant grid, and finally Chroma constant grid. Because the time required to make a dental shade selection is an individual matter, no time limit was imposed. Incorrect matchings Were recorded for errors in Hue, Value, and Chromas, or a combination thereof (Table !). All definitive color-deficiency screening and shade-selection testing was done in an office fitted with a full-spectrum light source (Durolite Bulb, Durotest, North Bergen, N.J.) as recommended by Bergen and McCasland 6 and Saleski 11 (Fig. 4). RESULTS Color-blind screening of 343 students and faculty members showed a 5.54% incidence of color-defective vision. Since none of the 101 women tested showed color-defective vision, the color-defective group was 7.8% of the men. This compares favorably with the findings of Preston and Bergen 12(8%) and McMaugh s (8.2 % ). It was, however, less than that of Barna et al. 7 (14%) and Moser et al. 1° (9.9%). Statistical analysis was done by using a one-way analysis of variance followed by Duncan's multiple range test. The probability level was set at p < 0.01. The color-defective group was independently analyzed for differences in Hue, Value, and Chroma errors. Two different groups were
JANUARY 1 9 9 0
VOLUME 63 NUMBER 1
COLOR-DEFECTIVE DENTAL PERSONNEL
i:
!):
2
!
3 Fig. 1° Definitive color-defective testing by using Divorine Pseudoisochromatic plate test determined color perception in selecting subjects. Fig. 2. Color tab grids containing 25 tabs were kept cons.tant for one shade parameter. This grid was constant for Value 7/. Fig. 3. Shade tabs in grids were mixed and presented in this manner. Subjects were requested to match five duplicated shade tabs in bottom line. Fig. 4. Office equipped with full-spectrum light source is essential to shade-selection testing.
THE JOURNAL OF PROSTHETIC DENTISTRY
99
DAVISON AND MYSLINSKI
~ tb
T a b l e II. Results of the color-defective group (N = 20) Errors
Age
Experience
Hue
Value
Chroma
Total
23 23 32 25 33 28 24 35 23 34 38 26 37 49 33 38 31 28 46 24 Mean 31.5 +_ 7.5
1 1 1 1 2 2 2 10 1 10 18 2 1 27 6 16 7 2 24 2 6.8 +- 8.19
0 2 2 2 1 1 4 0 5 0 2 6 3 4 3 2 3 3 2 5 2.5 _+ 1.7
0 0 0 0 0 0 ,0 0 0 0 0 1 0 0 0 0 0 0 0 0 0.05 + 0.22
0 2 1 2 0 0 2 0 2 0 1 1 1 0 0 2 0 1 1 1 0.85 + 0.81
0 4 3 4 1 1 6 0 7 0 3 8 4 4 3 4 3 4 3 6 3.4 + 2.25
Table III. Type of shade selectionerror made by color-defectiveand color-normal groups G r o u p (N = 2 0 )
Mean
SD
F Ratio
Color-defective Control Assistant Value Color-defective Control Assistant Chroma Color-defective Assistant Control
2.50 0.10 0.05
1.70 0.30"] 0.22A
38.707
0.05 0.00 0.05
0.22-] J O.OO/ 0.31A
1.036
0.85 0.35 2
0.81 0.58~] 0.4 J
5.922
~-*
~.~ ~~t
4
44~
,~-
¢~
t, ~
T a b l e IV. Total shade-selection errors made by normal
color-vision groups
F Prob
Group (N = 20)
Mean
0.00001
Control Assistants Prosthodontists
0.3 0.5 0.4
Hue
SD
0.65-] / 0.83| 0.753
F Ratio
F Prob
0.356
0.702
~e--,t
t~
0.3613
0.0046
compared in the following order: (1) the color-defective individuals, the control group, and the dental assistants, and (2) the control group, the assistant group, and the prosthodontists group. A comparison was made of age and experience as well as errors in Hue, Value, Chroma, and total shade-selection errors (Table II). Isolated analysis of the color-defective group showed a statistically significant difference in the type of error made (p = 0.00001, Hue > Chroma > Value) (Table I). Compared with the control group and the assistants group, the color-defective group showed significantly more errors in
100
~"
Hue (p = 0.00001) and in Chroma (p = 0.0046) (Table III). The Value-matching was unaffected by color-defective vision. A comparison of the control group, assistants group, and prosthodontists showed a difference in age and n u m ber of years of experience for the prosthodontists, yet no statistically different errors in shade selection were found (Table IV). The mean n u m b e r of years of experience was 4.35 years for the control group, 7.55 years for the assistant group, and 19.2 years (10.75 specialty practice) for the prosthodontists (p = 0.0035). In errors made, the assistant group was statistically identical to the control group.
r.-
~4
DISCUSSION Color-defective dental students and dentists made significantly more errors in shade selection than normalvision controls. These errors are specifically in Hue a n d Chroma. This is important because Clark, la Hayashi, 14 and SproulP considered Value the most important parameter of shade selection. W h e n Clark TM designed a custom shade
JANUARY 1990
VOLUME 63
NUMBER 1
4-
COLOR-DEFECTIVEDENTAL PERSONNEL
guide, it contained 19 Value variations, compared with 10 Chroma and three Hue variations. As advised by previous authors, routine color-vision testing in dental schools is advocated to make students aware of their shade-selection deficiencies.5,10,15 Dental assistants are significantly more accurate than color-defective personnel in shade selection. This gives credence to the opinions of Barna et al., 7 Bentley, 16 Sproull, 5 and Schillingburg 15 that the shade-matching ability of an assistant should be used. The assistant group was all women; yet when compared with the control group of mixed gender and the prosthodontist group, which was 90% men, there was no statistically significant improvement in shade selection. The important factor was their normal color-vision. Even though the prosthodontists had a significantly greater number of years of experience with a mean of 19.2 years, with 10.75 years in specialty practice, they showed no significant improvement in shade selection. McMaugh s compared first-year dental students with prosthodontists and found that experience improves shade selection. However, Barna et al. 7 found no difference between individuals with more or less than 10 years in dental practice. These results agree with Barna et al., 7 that experience does not improve shade selection in color-normal individuals. CONCLUSIONS 1. Color-defective vision reduces the ability to match shades. 2. Color-vision deficiency has an unequal effect on shade selection for Hue, Chroma, and Value. 3. Value selection was not affected by color-defective vision in this study. 4. Dental assistants are more accurate at shade selection than color-defective dental students and dentists.
THE JOURNAL OF PROSTHETIC DENTISTRY
5. In this study, experience did not improve shade selection in individuals with normal color-vision. REFERENCES 1. Preston JD. Current status of shade selecting and color matching. Quintessence Int 1985;16:47-58. 2. Clark EB. An analysis of tooth color. J Am Dent Assoc 1931;18:20932103. 3. Sproull RC. Color matching in dentistry. Part I. The three-dimensional nature of color. J PROSTHETDENT 1973;29:416-24. 4. Sproull RC. Color matching in dentistry. Part If. Practical applications of the organization of color. J PROSTHETDENT 1973;29:556-66. 5. Sproull RC. Color matching in dentistry. Part II1. Color control. J PROSTHET DENT 1974;31:146-54. 6. Bergen SF, McCasland J. Dental operatory lighting and tooth color discrimination. J Am Dent Assoc 1977;94:130-4. 7. Barna GJ, Taylor JW, King GE, Pelleu GB Jr. The influence of selected light intensities on color perception within the color range of natural teeth. J PROSTHET DENT 1981;46:450-3. 8. McMaugh DR. A comparative analysis of the colour matching ability of dentists, dental students, and ceramic technicians. Aust Dent J 1977;22:165-7. 9. Jacobs SH, Goodacre CJ, Moore BK, Dykema RW. Effect of porcelain thickness and type of metal-ceramic alloy on color. J PROSTHETDENT 1987;57:138-45. 10. Moser JB, Wozniak WT, Naleway CA, et al. Color vision in dentistry: a survey. J Am Dent Assoc 1985;110:509-10. 11. Saleski CG. Color, light, and shade matching. J PROSTHET DENT 1972;27:263-8. 12. Preston JD, Bergen SF. Color science and dental art. 1st ed. St Louis: CV Mosby Co, 1980. 13. Clark EB. Tooth color selection. J Am Dent Assoc 1933;20:1065-73. 14. Hayashi T. Medical color standard V tooth crown. Tokyo: Japan Color Research Institute, 1967. 15. Shillingburg HT, Hobo S, Whitsett LD. Fundamentals of fixed prosthodontics. 2nd ed. Chicago: Quintessence Publ Co, lnc, 1979. 16. Bentley AN. The color and light problems in dentistry. J Ky Dent Assoc 1967;19:13-6.
Reprint requests
to:
DR. NOREERTR. MYSLINSKI BALTIMORECOLLEGEOF DENTALSURGERY 666 W. BALTIMOREST. BALTIMORE, MD 21201
101
material can be trimmed with a laboratory knife. The tooth and the retaining screw are held in place until the acrylic resin hardens completely. After the acrylic resin has polymerized, the retaining screw is loosened about 2 mm (Fig. 3, A). Pressing gently in an occlusal direction on the screw will loosen the tooth from the socket. For complete removal of the tooth from the socket, the retaining screw is removed (Fig. 3, B through D). The soft utility wax is removed and the tooth is thoroughly cleaned under hot running water (Fig. 4, A). The tooth is reinserted into its socket and evaluated for stability, contours, and contact. Any necessary adjustments should be made at this time. Next, a thin layer of impression tray adhesive is painted onto the tooth apical to the cementoenamei junction and on the acrylic resin immediately adjacent to it. A heavyviscosity polyether impression material (Permadyne, ESPE-Premier Dental Products, Norristown, Pa.) is mixed and injected around the tooth (Fig. 4, B). This step fills in the region that had been blocked out with wax, and creates soft artificial gingival tissue. After the impression material polymerizes, the excess is trimmed off with a sharp laboratory knife (Fig. 4, C and D). A proper relationship with the opposing plastic teeth is
achieved by occlusal adjustment with diamond rotary instruments. The natural tooth is now mounted in the dentoform and can be used to help students gain realistic clinical experience. The socket can still be used for plastic teeth when needed. The natural toOth should be removed from the dentoform when it is not in use, and stored in a sealed container of water to prevent dehydration and increased brittleness. SUMMARY Plastic teeth are often poor substitutes for natural teeth when used in prectinical courses in restorative technique. As an alternative to plastic teeth, a method for mounting natural teeth in dentoforms has been developed to help students gain realistic clinical experience. REFERENCE 1. Gregory WA. A method for mounting natural teeth in a typodont. J Dent Educ 1988;52:309.
Reprint requests to: DR. EDWARD J. SWIFT, JR. COLLEGE OF DENTISTRY THE UNIVERSITYOF IOWA IOWA CITY, IA 52242
Shade selection by color v i s i o n - d e f e c t i v e dental personnel S. P. D a v i s o n , B.D.S.,* a n d N. R. M y s l i n s k i , Ph.D.**
University of Maryland, Baltimore College of Dental Surgery, Baltimore, Md. This investigation studied the impairment of Hue, Value, and Chroma matching by color v i s i o n - d e f e c t i v e dental personnel. Color,defective dental personnel w e r e found to m a k e significantly g r e a t e r errors in Hue and Chroma selection than normal-vision dental personnel. Value, the component of shade selection considered the m o s t important, w a s uneffected. Color-normal dental a s s i s t a n t s w e r e significantly m o r e accurate in Hue and Chroma selection than color-defective dental personnel and could a s s i s t affected dentists in clinical situations. (J PROSTHET DENT
1990;63:97-101.)
C o r r e c t shade selection is an important component of prosthetic dentistry. To ensure a successful esthetic prosthesis, development of acceptable morphology of the restoration must be achieved first, followed by careful consideration to correct shade reproduction.1 The shade match
Presented at the Capital Section of the American College of Prosthodontists, Baltimore, Md. Winner of the Victoria Gunning Dental Research Prize, University of Edinburgh, Edinburgh, Scotland. *Resident, Combined Prosthodontics. **Director of Physiology Graduate Studies. 10/1/12547 97
of a restoration or prosthesis to surrounding teeth may be the only parameter of treatment with which the patient is concerned. As early as 1931 Clark 2 realized the inherent problems associated with shade selection and attempted to establish and record the definitive specification of tooth color for further application and research in dentistry. Sproull 3 described color-matching in dentistry by using the Munsell color system as the standard. He elaborated on the shade guide 4 and color-matching problems in dentistry. 5 Factors such as lighting, 6, 7 color-vision deficiencies, 5-8 and experience may modify shade selection. Conflicting results on the influence of experience on correct shade selection have been reported. 7, s JANUARY 1990 VOLUME 83 NUMBER 1
DAV1SON AND MYSLINSKI
Table I. Frequency of shade selection errors in color-defective group (N = 20) Group
Hue Chroma Value
Mean
SD
2.50 0.85 0.05
1.7 0.81 0.22
F Ratio
25.976
F Prob
0.00001
It is conceivable that a discrepancy in the color vision of the dentist may constitute a problem in correct shade selection. Color-defective individuals in small groups have been compared with normal individuals in shade-selection studies. 6s Barna et al.7 found that color-defective dentists make significantly more errors in Hue selection studies than individuals with normal color perception, yet Jacobs et al.9 found them more sensitive in Value selection. Neither study detected differences in Chroma selection. Color-defective vision is a real problem because the prevalence among male dentists of this X-linked recessive trait ac: cording to McMaugh 8 is 8.2 %, to Moser et al. 1° 9.9 %, and to Barna et al. 7 14 %, all of which are at least as great as the 8% prevalence reported for men. It has been suggested that dentists be made aware of their color-vision deficiencies and consult assistants with normal color vision during shade selection. 5, 7, lo However, thus far, no studies in the field of color in dentistry have looked primarily at the color-defective group. This study investigated whether (1) color-defective vision reduces the ability to match shades; (2) color:vision deficiency has an unequal effect on Hue, Value, and Chroma selection, (3) dental assistants are more accurate at shade selection than color-defective dental students and dentists, and (4) experience improves shade selection in Color-normal individuals. METHODS
AND MATERIAL
The sample population for this study consisted of dental students and faculty and staff members at the University of Maryland Dental SchoOl. F o u r experimental groups (N = 20) were selected. They were: (1) color-defective dental students and dentists, (2) color-normal assistants, (3) Color-normal prosthodontic residents and prosthod0ntists, and (4) a control group randomly selected from the sample population. To differentiate color:defective from color-normal subjects, dental students, dental faculty members, and dental assistants were initially screened by using the American College of Prosthodontists Divorine Pseudoisochromatic slide test.* Those who failed were definitively tested by using the corresPonding plate test (Fig. 1). It was necessary to include most of the available assistants and prosthodon-
• 1777 N. E. Loop 410, Suite 904, San Antonio, Texas 78217.
98
tists from the sample population to make up group sizes of 20 individuals. To compare shade-selection ability, the correct matching of standard shade tabs was used. This study used three Munsell color tab grids similar to that described by Bergen and McCasland 6 and Barna et al.7 Clark's study 2 of 6000 natural teeth provided a guide for Hue, Value, and Chroma ranges. Each of the grid s was constant for a single parameter: (1) Hue, 2.5Y; (2) Value, 7/; and (3) Chroma,/4. The other parameters were variable. The Hue range was 7.5 yellow/red to 7.5 yellow in increments Of 2.5 Hue units. The Value range was 4 / t o 8 / i n increments of 1/Value units. The Chroma selections were from a range of/1 to / 12 with increments of/2 Chroma units. A larger range was used because the Munsell color system does not provide lower Chroma choices at higher Value levels. Some shades outside the range of Clark's study had to be used to give a full spectrum of selection, but these were kept to a minimum. Each axis of the grid had five variables for each of the parameters. Five Shade tabs from each of the grids were selected to represent the availability of shades and to avoid a predominance of shade examples from the extremes of the variables. These selected shade tabs were duplicated to be used for shade-matching against the grid from which they were selected (Fig. 2). The 25 tabs in the grid were mixed and i~resented to each individual to match identically the five duplicated tabs. The five duplicated tabs were supplied loose on the bottom line of the grid so that the testing individual could remove them and visually compare tabs side by side (Fig. 3). The grids were presented to every subject in the same order: Hue constant grid, Value constant grid, and finally Chroma constant grid. Because the time required to make a dental shade selection is an individual matter, no time limit was imposed. Incorrect matchings Were recorded for errors in Hue, Value, and Chromas, or a combination thereof (Table !). All definitive color-deficiency screening and shade-selection testing was done in an office fitted with a full-spectrum light source (Durolite Bulb, Durotest, North Bergen, N.J.) as recommended by Bergen and McCasland 6 and Saleski 11 (Fig. 4). RESULTS Color-blind screening of 343 students and faculty members showed a 5.54% incidence of color-defective vision. Since none of the 101 women tested showed color-defective vision, the color-defective group was 7.8% of the men. This compares favorably with the findings of Preston and Bergen 12(8%) and McMaugh s (8.2 % ). It was, however, less than that of Barna et al. 7 (14%) and Moser et al. 1° (9.9%). Statistical analysis was done by using a one-way analysis of variance followed by Duncan's multiple range test. The probability level was set at p < 0.01. The color-defective group was independently analyzed for differences in Hue, Value, and Chroma errors. Two different groups were
JANUARY 1 9 9 0
VOLUME 63 NUMBER 1
COLOR-DEFECTIVE DENTAL PERSONNEL
i:
!):
2
!
3 Fig. 1° Definitive color-defective testing by using Divorine Pseudoisochromatic plate test determined color perception in selecting subjects. Fig. 2. Color tab grids containing 25 tabs were kept cons.tant for one shade parameter. This grid was constant for Value 7/. Fig. 3. Shade tabs in grids were mixed and presented in this manner. Subjects were requested to match five duplicated shade tabs in bottom line. Fig. 4. Office equipped with full-spectrum light source is essential to shade-selection testing.
THE JOURNAL OF PROSTHETIC DENTISTRY
99
DAVISON AND MYSLINSKI
~ tb
T a b l e II. Results of the color-defective group (N = 20) Errors
Age
Experience
Hue
Value
Chroma
Total
23 23 32 25 33 28 24 35 23 34 38 26 37 49 33 38 31 28 46 24 Mean 31.5 +_ 7.5
1 1 1 1 2 2 2 10 1 10 18 2 1 27 6 16 7 2 24 2 6.8 +- 8.19
0 2 2 2 1 1 4 0 5 0 2 6 3 4 3 2 3 3 2 5 2.5 _+ 1.7
0 0 0 0 0 0 ,0 0 0 0 0 1 0 0 0 0 0 0 0 0 0.05 + 0.22
0 2 1 2 0 0 2 0 2 0 1 1 1 0 0 2 0 1 1 1 0.85 + 0.81
0 4 3 4 1 1 6 0 7 0 3 8 4 4 3 4 3 4 3 6 3.4 + 2.25
Table III. Type of shade selectionerror made by color-defectiveand color-normal groups G r o u p (N = 2 0 )
Mean
SD
F Ratio
Color-defective Control Assistant Value Color-defective Control Assistant Chroma Color-defective Assistant Control
2.50 0.10 0.05
1.70 0.30"] 0.22A
38.707
0.05 0.00 0.05
0.22-] J O.OO/ 0.31A
1.036
0.85 0.35 2
0.81 0.58~] 0.4 J
5.922
~-*
~.~ ~~t
4
44~
,~-
¢~
t, ~
T a b l e IV. Total shade-selection errors made by normal
color-vision groups
F Prob
Group (N = 20)
Mean
0.00001
Control Assistants Prosthodontists
0.3 0.5 0.4
Hue
SD
0.65-] / 0.83| 0.753
F Ratio
F Prob
0.356
0.702
~e--,t
t~
0.3613
0.0046
compared in the following order: (1) the color-defective individuals, the control group, and the dental assistants, and (2) the control group, the assistant group, and the prosthodontists group. A comparison was made of age and experience as well as errors in Hue, Value, Chroma, and total shade-selection errors (Table II). Isolated analysis of the color-defective group showed a statistically significant difference in the type of error made (p = 0.00001, Hue > Chroma > Value) (Table I). Compared with the control group and the assistants group, the color-defective group showed significantly more errors in
100
~"
Hue (p = 0.00001) and in Chroma (p = 0.0046) (Table III). The Value-matching was unaffected by color-defective vision. A comparison of the control group, assistants group, and prosthodontists showed a difference in age and n u m ber of years of experience for the prosthodontists, yet no statistically different errors in shade selection were found (Table IV). The mean n u m b e r of years of experience was 4.35 years for the control group, 7.55 years for the assistant group, and 19.2 years (10.75 specialty practice) for the prosthodontists (p = 0.0035). In errors made, the assistant group was statistically identical to the control group.
r.-
~4
DISCUSSION Color-defective dental students and dentists made significantly more errors in shade selection than normalvision controls. These errors are specifically in Hue a n d Chroma. This is important because Clark, la Hayashi, 14 and SproulP considered Value the most important parameter of shade selection. W h e n Clark TM designed a custom shade
JANUARY 1990
VOLUME 63
NUMBER 1
4-
COLOR-DEFECTIVEDENTAL PERSONNEL
guide, it contained 19 Value variations, compared with 10 Chroma and three Hue variations. As advised by previous authors, routine color-vision testing in dental schools is advocated to make students aware of their shade-selection deficiencies.5,10,15 Dental assistants are significantly more accurate than color-defective personnel in shade selection. This gives credence to the opinions of Barna et al., 7 Bentley, 16 Sproull, 5 and Schillingburg 15 that the shade-matching ability of an assistant should be used. The assistant group was all women; yet when compared with the control group of mixed gender and the prosthodontist group, which was 90% men, there was no statistically significant improvement in shade selection. The important factor was their normal color-vision. Even though the prosthodontists had a significantly greater number of years of experience with a mean of 19.2 years, with 10.75 years in specialty practice, they showed no significant improvement in shade selection. McMaugh s compared first-year dental students with prosthodontists and found that experience improves shade selection. However, Barna et al. 7 found no difference between individuals with more or less than 10 years in dental practice. These results agree with Barna et al., 7 that experience does not improve shade selection in color-normal individuals. CONCLUSIONS 1. Color-defective vision reduces the ability to match shades. 2. Color-vision deficiency has an unequal effect on shade selection for Hue, Chroma, and Value. 3. Value selection was not affected by color-defective vision in this study. 4. Dental assistants are more accurate at shade selection than color-defective dental students and dentists.
THE JOURNAL OF PROSTHETIC DENTISTRY
5. In this study, experience did not improve shade selection in individuals with normal color-vision. REFERENCES 1. Preston JD. Current status of shade selecting and color matching. Quintessence Int 1985;16:47-58. 2. Clark EB. An analysis of tooth color. J Am Dent Assoc 1931;18:20932103. 3. Sproull RC. Color matching in dentistry. Part I. The three-dimensional nature of color. J PROSTHETDENT 1973;29:416-24. 4. Sproull RC. Color matching in dentistry. Part If. Practical applications of the organization of color. J PROSTHETDENT 1973;29:556-66. 5. Sproull RC. Color matching in dentistry. Part II1. Color control. J PROSTHET DENT 1974;31:146-54. 6. Bergen SF, McCasland J. Dental operatory lighting and tooth color discrimination. J Am Dent Assoc 1977;94:130-4. 7. Barna GJ, Taylor JW, King GE, Pelleu GB Jr. The influence of selected light intensities on color perception within the color range of natural teeth. J PROSTHET DENT 1981;46:450-3. 8. McMaugh DR. A comparative analysis of the colour matching ability of dentists, dental students, and ceramic technicians. Aust Dent J 1977;22:165-7. 9. Jacobs SH, Goodacre CJ, Moore BK, Dykema RW. Effect of porcelain thickness and type of metal-ceramic alloy on color. J PROSTHETDENT 1987;57:138-45. 10. Moser JB, Wozniak WT, Naleway CA, et al. Color vision in dentistry: a survey. J Am Dent Assoc 1985;110:509-10. 11. Saleski CG. Color, light, and shade matching. J PROSTHET DENT 1972;27:263-8. 12. Preston JD, Bergen SF. Color science and dental art. 1st ed. St Louis: CV Mosby Co, 1980. 13. Clark EB. Tooth color selection. J Am Dent Assoc 1933;20:1065-73. 14. Hayashi T. Medical color standard V tooth crown. Tokyo: Japan Color Research Institute, 1967. 15. Shillingburg HT, Hobo S, Whitsett LD. Fundamentals of fixed prosthodontics. 2nd ed. Chicago: Quintessence Publ Co, lnc, 1979. 16. Bentley AN. The color and light problems in dentistry. J Ky Dent Assoc 1967;19:13-6.
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