Composite
resin
color change
after
vital
tooth
bleaching
Peter Monaghan, DDS,a Thomas Trowbridge, DDS,b and Eugene Lautenschlager, PhDC Northwestern University Dental School, Chicago, Ill., and Long Island Jewish Medical Center,
New Hyde Park, N.Y. Color change of composite resin was determined with the Minolta Chroma meter (CR-loo) after four sessions of vital bleaching. Specimens of selected composite resin materials were subjected to vital bleaching (37% H3PO4/1 minute, then 30% HxOz/infrared light/30 minutes.) Specimens were stored in water between bleaching. Control specimens were used to determine the effects of water storage alone. Initial L*a*b* color readings were made on 24-hour hydrated specimens. Final L*a*b* readings were made on 24-hour hydrated specimens. Calculations were made for the A E values for each specimen. Mean A E values and standard deviations were obtained for each material. Two-way ANOVA and Newman-Keuls analyses showed significant (a = 0.06) color change for most bleached materials. Additionally, some materials had A E values greater than 3. These were visibly lighter compared to their controls. Vital bleaching produced color change in most composites as measured with the Chroma meter. This technique may be used to lighten dark-colored or stained composite resin restorations. (J PROSTHET DENT 1992;67:778-81.)
V ltal bleaching of teeth has been used to improve the esthetics of the natural dentiti0n.l If the patients perceive a positive change in esthetics, vital bleaching can lead to improved attitudes of patients about themselves.2 This technique can be applied to both intrinsically and extrinsically stained teeth.3 The method involves isolation of the teeth, etching the enamel with phosphoric acid, placing an oxidizing agent (Superoxyl, Union Broach, Inc., New York, N.Y.), and applying heat.4 The procedure is repeated until the desired esthetic improvement is obtained. Much information exists concerning the effects of the bleaching protocol on natural tooth structure.5-8 However, no significant information is available about the effects vital bleaching techniques have on composite resins that are routinely used to restore teeth. The purpose of this study was to determine the color change, if any, of selected composite resins when subjected to a vital bleaching protocol. MATERIALS
AND
Product
Shade
Batch No.
L.D. Caulk, Inc. Milford, Del.
Prisma-Fil
3M, Inc. Minneapolis,
Silux Plus
L LY LG LYG L Y G DY 22 24 30 32 A B C I
0620863 069872 070681 1201862 Pa80128 P880128 P880128 P880128 1278 1278 1278 1278 30-6-89 30-6-89 30-6-89 30-6-89
Manufacturer
Minn.
Vivadent, Inc. Liechtenstein
Heliomolar
Kulzer, Inc. Germany
Multifil
VS
METHODS
Commercially available composite resin restorative materials were used as experimental substrates. These materials are listed with the manufacturers’ shade codes and batch numbers in Table I. Teflon tubing was made into rings by slicing with a scal-
Supported in part by the Graduate Training Grant NIDR 5T32 DE07042. %linical Assistant Professor, Division of Operative Dentistry and Graduate Trainee, Division of Biologic Materials, Northwestern University. bResident, General Dental Practice. cProfessor and Director, Division of Biologic Materials. 10/l/38185
778
Table I. Composite resin materials used as experimental substrates
pel blade. Each ring was 3 mm in height; the inside diameter of the tubing was 9 mm. The rings were filled with composite resin and covered with mylar film. The resin was cured through the film with a Prisma light (Caulk, Inc., Milford, Del.). Each side was exposed for 60 seconds, giving a total exposure time of 120 seconds. The rings were not removed in this study because they facilitated handling and identification of the specimens and did not interfere with bleaching or color measurement. The specimens were finished on one side only through 600 grit emery paper to provide a test surface that would be similar to that of a standard dental restoration. The
JUNE
1992
VOLUME
67
NUMBER
6
COMPOSITE
RESIN
COLOR
CHANGE
AFTER
VITAL
CAULK
22~
24b
3M SlLUX
HELlOMOLAR
24~
b - NLEACNED
I
BLEACHING
PRISMA-FIL
VIVADENT
22b
TOOTH
SOb
300
KULZER
326
OF PROSTHETIC
VS
320
MEAN
1. a E values of composite resins.
specimens were soaked in 25” C tap water for 24 hours before any testing. Six specimens were made for each shade of each material. Baseline tristimulus L*a*b* color readings (CIE, 1976) were made with a Minolta Chroma meter CR-100 (Minolta, Inc., Ramsey, N.J.) for all specimens. The specimens were positioned on a white lucite square as a standard background. The meter was standardized according to the manufacturer’s instructions before any measurements. The Chroma meter read a specimen diameter of 8 mm. For each shade of each material, three specimens were bleached (experimental specimens) and three were not labelled (control specimens.) Phosphoric acid etchant (37 % HsP04) was applied to the finished surface of the experimental specimens for 1 minute. The specimens were rinsed with tap water for 1 minute and dried with compressed air for 1 minute. Superoxyl bleaching solution (30% HsOs) was applied to the fin4 ished surface of the specimens. In compliance with manufacturer’s directions, a single layer of cotton gauze, saturated with the Superoxyl solution, covered the specimens during the heating phase. The specimens were heated for 30 minutes with infrared radiation using a New Image light
JOURNAL
MULTIFIL
D - CDNTNOL
Fig.
TEE
PLUS
DENTISTRY
(Union Broach, Inc., New York, N.Y.). The distance from the light to the specimens was approximately 12 inches, the recommended clinical treatment distance. The Superoxyl solution was reapplied to the gauze to maintain a moist surface when needed. After the 30-minute heating time, all experimental specimens were rinsed with tap water for 1 minute to remove any remaining Superoxyl solution. During the bleaching phase, the control specimens were dried for 1 minute with compressed air and exposed to room temperature air. All specimens (experimental and control) were returned to fresh tap water for 24 hours between bleaching treatments. This procedure simulates the time required for rehydration and color equilibrium to occur. The process of bleaching and rehydration was repeated a total of four times. Color readings of both the control and experimental specimens were made after the fourth treatment plus an additional 24-hour rehydration time. During the study, the composite resin specimens were also assessedsubjectively by visual examination to evaluate whether a clinically observable color change occurred. 779
MONAGHAN,
TROWBRIDGE,
AND
LAUTENSCHLAGER
WHITE
YELLOW
BLACK Fig. 2. L*a*b* color space.
RESULTS The color change of the specimens was determined by calculating the A E from the L*a*b* values obtained with the Chroma meter. The following formula was used: AE = \/(L*F - L*#
+ (a*F - a*r)2 + (b*r - b*i)2
The subscript I stands for the initial value and the subscript F stands for the final value. The mean A E values and standard deviations were calculated for each shade. The results are graphically illustrated in Fig. 1, with each bar representing one group of three specimens. A two-way analysis of variance (ANOVA) (brand and bleaching factors) was performed to indicate significant differences at an (Y= 0.05 level. When significant differences were found by ANOVA, the Newman-Keuls multifactorial difference analysis was applied. All experimental groups except Heliomolar 24 and 32, Multifil VS C, and Silux Plus DY materials had A E values that were significantly different than their corresponding control groups. The A E values for the experimental groups for all Prisma-fil shades; Silux Plus L and Y; Heliomolar 22; and Multifil VS I materials were greater than 3. The only control group that had a change in A E of this magnitude was the one with Multifil VS I material. Visual observations comparing the experimental groups to their corresponding control groups confirmed that the bleaching protocol lightened most materials. To the observers’ eyes, the only groups that did not appear lighter were the groups that statistically had no differences. Experimental groups that had larger A E values compared to their control groups were relatively easy to distinguish by eye. DISCUSSION As shown in Fig. 2, the L*a*b* color space defines color in three parameters. L* :represents the degree of gray and
780
corresponds to value or brightness. The a* is a HueChroma parameter in the red-green direction, whereas b* is a Hue-Chroma parameter in the blue-yellow axis. High L* values are obtained from bright or white specimens. Positive a* values are red, negative values are green. Positive b* values are yellow, negative values are blue.g Lightening of the specimens would be shown as an increase in L*, whereas actual Hue-Chroma change is demonstrated in changes in a* and/orb*. To some extent, all specimens exhibited an increase in L* and most showed a change in a* and b*. However, a change in the a* or b* direction can also produce a shift in the L* direction. The amount of gray or L* can be thought of as “simple” or “complex.” Simple gray comes from the amount of black and/or white present in the area of observation. Complex gray is made by the subtractive combination of a color with its complement (e.g., red with green, yellow with violet, or blue with orange).lO* l1 This situation results in an increase in gray, thus decreasing L* by shifting a* and/or b*. The combination of chemical agents used for bleaching teeth produced color change in most composite resin materials. Although determination of the mechanism of color change in composite resin when exposed to the vital bleaching regime was not part of this investigation, hypotheses for this include: 1. Oxidation of readily accessible surface pigments leads to less color-intense species. 2. Oxidation of amine compounds, which have been indicated as responsible for color instability over time, leads to color change. 3. The degree of conversion or the resin matrix to polymer may allow some resins to be attacked by the bleaching solutions and not others. 4. The formulation of each shade of composite resin is unique and, as such, is affected uniquely by the bleaching process. More work can be done to test these hypotheses. JUNE
1992
VOLUME
67
NUMBER
6
COMPOSITE
RESIN
COLOR
CHANGE
AFTER
VITAL
TOOTH
BLEACHING
Several of the resins tested exhibited A E values greater than 3. The accepted level of visual perception is a A E of 1 to 2.* This explains that these specimens visually appeared lighter than their corresponding control counterparts. It is possible that this information may be useful in some clinical situations. Slightly stained or dark color restorations that are otherwise clinically acceptable may be lightened using this technique. It is also possible that in some situations composite resin restorations may lighten along with teeth that are bleached to improve esthetic appearance for patients. CONCLUSIONS The vital bleaching protocol produced color change in some composite resin restorative materials, as measured with a Minolta Chroma meter. Statistical analysis showed these changes to be significant. Subjective observation by investigators confirmed a lightening in shade of the composite resins. This study showed that most composite resin restorative materials respond to the vital bleaching regimen, which may be a viable technique to lighten the shade of some darkened or stained tooth-colored restorations. *Moser Dental
THE
J., personal communication, School, Division of Biological
JOURNAL
OF PROSTHETIC
Northwestern Materials,
DENTISTRY
REFERENCES 1. Caldwell C. Bleaching of vital or nonvital teeth. J Cal Dent Assoc 1966;42:234-5. stained vital teeth. Oral Surg 2. Cohen S, Parkins F. Bleaching tetracycline 1970;29:465-71. 3. Goldstein R. Change your smile. 2nd ed. Chicago: Quintessence Publishing, 1984:20-64. 4. Feinman R, Goldstein R, Garber D. Bleaching teeth. 1st ed. Chicago: Quintessence Publishing, 1987:53-76. 5. Christensen G. Bleaching vital tetracycline-stained teeth. Quint Intl 1978;9:13-9. 6. Robertson W, Meifi R. Pulpal response to vital bleaching procedures. J Endod 1980;6:645-9. 7. Baumgartner J, Reid D, Pickett A. Human pulpal reaction to the modified McInnes bleaching technique. J Endod 1983;9:527-9. a. Jordan R, Boksman L. Conservative vital bleaching treatment of discolored dentition. Compend Cont Educ Dent 1964;5:603-8. 9. Operating Instructions for the Minolta Chroma Meter CR-100, Minolta Corporation, Ramsey, N.J. 10. Lemire P, Burke B. Color in dentistry. Hartford: FA Bassette, 1975:60. 11. Wood R, Garlapo D. Manual of preclinical fixed prosthodontics. SUNY/Buffalo, School of Dentistry, 1982:64. Reprint
requests
to:
PETER MONAGHAN, DDS OPERATIVE DENTISTRY NORTHWESTERN UNIVERXTY 240 EAST HURON ST. CHICAGO, IL 60611
DENTAL
SCHOOL
University Chicago, Ill.
781
resin
color change
after
vital
tooth
bleaching
Peter Monaghan, DDS,a Thomas Trowbridge, DDS,b and Eugene Lautenschlager, PhDC Northwestern University Dental School, Chicago, Ill., and Long Island Jewish Medical Center,
New Hyde Park, N.Y. Color change of composite resin was determined with the Minolta Chroma meter (CR-loo) after four sessions of vital bleaching. Specimens of selected composite resin materials were subjected to vital bleaching (37% H3PO4/1 minute, then 30% HxOz/infrared light/30 minutes.) Specimens were stored in water between bleaching. Control specimens were used to determine the effects of water storage alone. Initial L*a*b* color readings were made on 24-hour hydrated specimens. Final L*a*b* readings were made on 24-hour hydrated specimens. Calculations were made for the A E values for each specimen. Mean A E values and standard deviations were obtained for each material. Two-way ANOVA and Newman-Keuls analyses showed significant (a = 0.06) color change for most bleached materials. Additionally, some materials had A E values greater than 3. These were visibly lighter compared to their controls. Vital bleaching produced color change in most composites as measured with the Chroma meter. This technique may be used to lighten dark-colored or stained composite resin restorations. (J PROSTHET DENT 1992;67:778-81.)
V ltal bleaching of teeth has been used to improve the esthetics of the natural dentiti0n.l If the patients perceive a positive change in esthetics, vital bleaching can lead to improved attitudes of patients about themselves.2 This technique can be applied to both intrinsically and extrinsically stained teeth.3 The method involves isolation of the teeth, etching the enamel with phosphoric acid, placing an oxidizing agent (Superoxyl, Union Broach, Inc., New York, N.Y.), and applying heat.4 The procedure is repeated until the desired esthetic improvement is obtained. Much information exists concerning the effects of the bleaching protocol on natural tooth structure.5-8 However, no significant information is available about the effects vital bleaching techniques have on composite resins that are routinely used to restore teeth. The purpose of this study was to determine the color change, if any, of selected composite resins when subjected to a vital bleaching protocol. MATERIALS
AND
Product
Shade
Batch No.
L.D. Caulk, Inc. Milford, Del.
Prisma-Fil
3M, Inc. Minneapolis,
Silux Plus
L LY LG LYG L Y G DY 22 24 30 32 A B C I
0620863 069872 070681 1201862 Pa80128 P880128 P880128 P880128 1278 1278 1278 1278 30-6-89 30-6-89 30-6-89 30-6-89
Manufacturer
Minn.
Vivadent, Inc. Liechtenstein
Heliomolar
Kulzer, Inc. Germany
Multifil
VS
METHODS
Commercially available composite resin restorative materials were used as experimental substrates. These materials are listed with the manufacturers’ shade codes and batch numbers in Table I. Teflon tubing was made into rings by slicing with a scal-
Supported in part by the Graduate Training Grant NIDR 5T32 DE07042. %linical Assistant Professor, Division of Operative Dentistry and Graduate Trainee, Division of Biologic Materials, Northwestern University. bResident, General Dental Practice. cProfessor and Director, Division of Biologic Materials. 10/l/38185
778
Table I. Composite resin materials used as experimental substrates
pel blade. Each ring was 3 mm in height; the inside diameter of the tubing was 9 mm. The rings were filled with composite resin and covered with mylar film. The resin was cured through the film with a Prisma light (Caulk, Inc., Milford, Del.). Each side was exposed for 60 seconds, giving a total exposure time of 120 seconds. The rings were not removed in this study because they facilitated handling and identification of the specimens and did not interfere with bleaching or color measurement. The specimens were finished on one side only through 600 grit emery paper to provide a test surface that would be similar to that of a standard dental restoration. The
JUNE
1992
VOLUME
67
NUMBER
6
COMPOSITE
RESIN
COLOR
CHANGE
AFTER
VITAL
CAULK
22~
24b
3M SlLUX
HELlOMOLAR
24~
b - NLEACNED
I
BLEACHING
PRISMA-FIL
VIVADENT
22b
TOOTH
SOb
300
KULZER
326
OF PROSTHETIC
VS
320
MEAN
1. a E values of composite resins.
specimens were soaked in 25” C tap water for 24 hours before any testing. Six specimens were made for each shade of each material. Baseline tristimulus L*a*b* color readings (CIE, 1976) were made with a Minolta Chroma meter CR-100 (Minolta, Inc., Ramsey, N.J.) for all specimens. The specimens were positioned on a white lucite square as a standard background. The meter was standardized according to the manufacturer’s instructions before any measurements. The Chroma meter read a specimen diameter of 8 mm. For each shade of each material, three specimens were bleached (experimental specimens) and three were not labelled (control specimens.) Phosphoric acid etchant (37 % HsP04) was applied to the finished surface of the experimental specimens for 1 minute. The specimens were rinsed with tap water for 1 minute and dried with compressed air for 1 minute. Superoxyl bleaching solution (30% HsOs) was applied to the fin4 ished surface of the specimens. In compliance with manufacturer’s directions, a single layer of cotton gauze, saturated with the Superoxyl solution, covered the specimens during the heating phase. The specimens were heated for 30 minutes with infrared radiation using a New Image light
JOURNAL
MULTIFIL
D - CDNTNOL
Fig.
TEE
PLUS
DENTISTRY
(Union Broach, Inc., New York, N.Y.). The distance from the light to the specimens was approximately 12 inches, the recommended clinical treatment distance. The Superoxyl solution was reapplied to the gauze to maintain a moist surface when needed. After the 30-minute heating time, all experimental specimens were rinsed with tap water for 1 minute to remove any remaining Superoxyl solution. During the bleaching phase, the control specimens were dried for 1 minute with compressed air and exposed to room temperature air. All specimens (experimental and control) were returned to fresh tap water for 24 hours between bleaching treatments. This procedure simulates the time required for rehydration and color equilibrium to occur. The process of bleaching and rehydration was repeated a total of four times. Color readings of both the control and experimental specimens were made after the fourth treatment plus an additional 24-hour rehydration time. During the study, the composite resin specimens were also assessedsubjectively by visual examination to evaluate whether a clinically observable color change occurred. 779
MONAGHAN,
TROWBRIDGE,
AND
LAUTENSCHLAGER
WHITE
YELLOW
BLACK Fig. 2. L*a*b* color space.
RESULTS The color change of the specimens was determined by calculating the A E from the L*a*b* values obtained with the Chroma meter. The following formula was used: AE = \/(L*F - L*#
+ (a*F - a*r)2 + (b*r - b*i)2
The subscript I stands for the initial value and the subscript F stands for the final value. The mean A E values and standard deviations were calculated for each shade. The results are graphically illustrated in Fig. 1, with each bar representing one group of three specimens. A two-way analysis of variance (ANOVA) (brand and bleaching factors) was performed to indicate significant differences at an (Y= 0.05 level. When significant differences were found by ANOVA, the Newman-Keuls multifactorial difference analysis was applied. All experimental groups except Heliomolar 24 and 32, Multifil VS C, and Silux Plus DY materials had A E values that were significantly different than their corresponding control groups. The A E values for the experimental groups for all Prisma-fil shades; Silux Plus L and Y; Heliomolar 22; and Multifil VS I materials were greater than 3. The only control group that had a change in A E of this magnitude was the one with Multifil VS I material. Visual observations comparing the experimental groups to their corresponding control groups confirmed that the bleaching protocol lightened most materials. To the observers’ eyes, the only groups that did not appear lighter were the groups that statistically had no differences. Experimental groups that had larger A E values compared to their control groups were relatively easy to distinguish by eye. DISCUSSION As shown in Fig. 2, the L*a*b* color space defines color in three parameters. L* :represents the degree of gray and
780
corresponds to value or brightness. The a* is a HueChroma parameter in the red-green direction, whereas b* is a Hue-Chroma parameter in the blue-yellow axis. High L* values are obtained from bright or white specimens. Positive a* values are red, negative values are green. Positive b* values are yellow, negative values are blue.g Lightening of the specimens would be shown as an increase in L*, whereas actual Hue-Chroma change is demonstrated in changes in a* and/orb*. To some extent, all specimens exhibited an increase in L* and most showed a change in a* and b*. However, a change in the a* or b* direction can also produce a shift in the L* direction. The amount of gray or L* can be thought of as “simple” or “complex.” Simple gray comes from the amount of black and/or white present in the area of observation. Complex gray is made by the subtractive combination of a color with its complement (e.g., red with green, yellow with violet, or blue with orange).lO* l1 This situation results in an increase in gray, thus decreasing L* by shifting a* and/or b*. The combination of chemical agents used for bleaching teeth produced color change in most composite resin materials. Although determination of the mechanism of color change in composite resin when exposed to the vital bleaching regime was not part of this investigation, hypotheses for this include: 1. Oxidation of readily accessible surface pigments leads to less color-intense species. 2. Oxidation of amine compounds, which have been indicated as responsible for color instability over time, leads to color change. 3. The degree of conversion or the resin matrix to polymer may allow some resins to be attacked by the bleaching solutions and not others. 4. The formulation of each shade of composite resin is unique and, as such, is affected uniquely by the bleaching process. More work can be done to test these hypotheses. JUNE
1992
VOLUME
67
NUMBER
6
COMPOSITE
RESIN
COLOR
CHANGE
AFTER
VITAL
TOOTH
BLEACHING
Several of the resins tested exhibited A E values greater than 3. The accepted level of visual perception is a A E of 1 to 2.* This explains that these specimens visually appeared lighter than their corresponding control counterparts. It is possible that this information may be useful in some clinical situations. Slightly stained or dark color restorations that are otherwise clinically acceptable may be lightened using this technique. It is also possible that in some situations composite resin restorations may lighten along with teeth that are bleached to improve esthetic appearance for patients. CONCLUSIONS The vital bleaching protocol produced color change in some composite resin restorative materials, as measured with a Minolta Chroma meter. Statistical analysis showed these changes to be significant. Subjective observation by investigators confirmed a lightening in shade of the composite resins. This study showed that most composite resin restorative materials respond to the vital bleaching regimen, which may be a viable technique to lighten the shade of some darkened or stained tooth-colored restorations. *Moser Dental
THE
J., personal communication, School, Division of Biological
JOURNAL
OF PROSTHETIC
Northwestern Materials,
DENTISTRY
REFERENCES 1. Caldwell C. Bleaching of vital or nonvital teeth. J Cal Dent Assoc 1966;42:234-5. stained vital teeth. Oral Surg 2. Cohen S, Parkins F. Bleaching tetracycline 1970;29:465-71. 3. Goldstein R. Change your smile. 2nd ed. Chicago: Quintessence Publishing, 1984:20-64. 4. Feinman R, Goldstein R, Garber D. Bleaching teeth. 1st ed. Chicago: Quintessence Publishing, 1987:53-76. 5. Christensen G. Bleaching vital tetracycline-stained teeth. Quint Intl 1978;9:13-9. 6. Robertson W, Meifi R. Pulpal response to vital bleaching procedures. J Endod 1980;6:645-9. 7. Baumgartner J, Reid D, Pickett A. Human pulpal reaction to the modified McInnes bleaching technique. J Endod 1983;9:527-9. a. Jordan R, Boksman L. Conservative vital bleaching treatment of discolored dentition. Compend Cont Educ Dent 1964;5:603-8. 9. Operating Instructions for the Minolta Chroma Meter CR-100, Minolta Corporation, Ramsey, N.J. 10. Lemire P, Burke B. Color in dentistry. Hartford: FA Bassette, 1975:60. 11. Wood R, Garlapo D. Manual of preclinical fixed prosthodontics. SUNY/Buffalo, School of Dentistry, 1982:64. Reprint
requests
to:
PETER MONAGHAN, DDS OPERATIVE DENTISTRY NORTHWESTERN UNIVERXTY 240 EAST HURON ST. CHICAGO, IL 60611
DENTAL
SCHOOL
University Chicago, Ill.
781
