SECTIONEDITORS

of home bleaching

preparations

on composite

resin

color Peter Monaghan, DDS,a Eugene Lautenschlager,

Ellen Lim, PhD”

DDS,b

and

Northwestern University Dental School, Chicago,Ill. The lightening of teeth is done professionally by exposure to warm hydrogen peroxide solutions or at home with an active bleaching gel of perhydrol urea or carbamide peroxide. This study compared the effects of two commercial bleaching gels on the color of composite resin with those in a previous study using the dental office technique. Commercial composite resins test specimens were exposed to the bleaching gels or water (control) for 312 hours at 37” C at 100% relative humidity. Color change value was calculated with before-and-after solution exposure L*a*b* color values. ANOVA (a = 0.01) revealed no ditTerences in the color of the specimens after use of the test solutions. All color change values were less than 2 or the normal limit of visual acuity. No visual color change was evident for these composite resins. The at-home method recorded no shade-altering effects compared with the professional technique, which created a noticeable color change. (J PROSTHET DENT 1992;68:575-8.)

he esthetics of the natural dentition can be improved by bleaching1 and this process can be applied to intrinsically and extrinsically stained teeth.2 One method involves isolation of the teeth, etching of the enamel with phosphoric acid, placing a 30 % hydrogen peroxide solution (Superoxyl, Union Broach, Inc., New York, N. Y.) on the indicated tooth surface, and applying heat.” This method requires several appointments with the dentist to achieve the desired esthetics. An alternative method using a custom adapted splint to bathe the teeth in a different oxidizing solution has been introduced.4 The splint is vacuum-formed in the dental office or laboratory and retains the bl.eaching preparation in close contact with the enamel. Vital bleaching kits are now available from several manufacturers, making it relatively simple for patients to lighten their teeth in the privacy of their homes after one dental visit. The kits usually include a bleaching preparation in a gel form, splint material, and instructions.5 The oxidizing agent is usually a carbamide peroxide or perhydrol urea preparation. Carbamide peroxide and perhydrol urea are both accepted names for the same compound. Several investigators have studied the effects of professionally applied warm hydrogen peroxide bleaching on Supported in part by the National Institute

of Dental Research graduate training grant NIDR T32 DE07042. %linical Assistant Professor, Division of Operative Dentistry and Graduate Trainee, Division of Biological Materials. bGeneral Dental Practice. cProfessor and Director, Division of Biological Materials. 10/l/37561

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natural tooth structure.6-g One study disclosed that the warm hydrogen peroxide bleaching technique also created a visually perceptible color change in composite resin restorative materials.lO Carbamide peroxide bleaching was shown to affect the surfaces and color change of composite resin.11-13Unfortunately, color change values (AE) for composite resin were not reported by these authors. This is clinically relevant becausethe accepted level of visual perception score is a AE of 1 to 2, according to Moser.* If the color change caused by these bleaching preparations produces a AE less than the visual perception, the human eye cannot detect a change in color of the material. Friend et a1.14reported that carbamide peroxide bleaching solutions caused no deleterious effects on composite resin. This research was designed to determine whether the home oxidizing gel preparations would modify the color of composite resin restorative materials, similar to the effect of warm hydrogen peroxide. MATERIAL

AND

METHODS

Three commercial composite resin restorative materials were used as experimental substrates and are listed with the manufacturers’ shade codes and batch numbers in Table I. The bleaching gel preparations in this study are listed in Table II with each manufacturer’s formulation. Although carbamide peroxide and perhydrol urea describe the same compound, each product was treated as a unique *Moser J. Division of Biological Materials, Northwestern sity Dental School, personal communication.

Univer-

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MONAGHAN,

Table

I. Composite resin materials Product

Manufacturer

name

L.D. Caulk Co. Milford, Del.

Prisma AP.H

3M, Inc. Minneapolis,

Silux Plus Minn.

Kerr Mfg. Co. Romulus, Mich.

Herculite-X2

Shade

Batch number

G LY DY U G uo U (66) DY (82) LG (92)

0221893 208902 072789 P890711 P890809 P890804 9-2132 9-1243 9-1186

agent because the bleaching gel formulations could be different and influence bleaching effectiveness. Rembrandt Lighten bleach instructions suggest the adjunct use of a proprietary toothpaste; however, this study only compared the effects of the bleaching gels on the color of composite resin. Any mechanical abrasive effects were eliminated by the exclusion of toothpaste from this study. The pH for each bleaching gel plus the Superoxyl solution was measured with a Digi-Sense pH meter and pH electrode (Cole Parmer, Chicago, Ill.) to estimate potential activity. Rings were made by slicing Teflon (Du Pont Co., Wilmington, Del.) tubing in such a way that each ring was 2 mm in height with an inside diameter of 9 mm. The rings were filled with composite resin, covered with Mylar film (Du Pont Co.), and was cured through the film with a Den-Mat curing light (Den-Mat Corp., Santa Maria, Calif.). Each side was exposed for 60 seconds, for a total time of 120 seconds. The rings were not removed because they facilitated handling and identification of the specimens without interfering with bleaching or color measurement. Nine specimens were made for each shade of each material. The specimens were finished on one side only with 600grit emery to develop a test surface that would simulate a standard dental restoration. The specimens were stored in 37” C tap water for 48 hours before testing. The baseline tristimulus L*a”b* color readings (CIE, 1976) were recorded with a Minolta Chroma meter CR-100 (Minolta, Inc., Ramsey, N. J.) for the specimens. The specimens were positioned on a white polymethylmethacrylate resin square as a standard background and the Chroma meter was standardized according to the manufacturer directions before measurements to read a diameter of 8 mm. Each specimen was exposed to approximately 5 ml of test solution for 13 days at 37” C and 100 % relative humidity. Three specimens were exposed to Rembrandt Lighten bleach, three specimens to the Omni White and Brite bleach, and three to tap water. The specimens were rinsed daily with tap water and immediately replaced in fresh test solutions, so that the total exposure time these solutions was 312 hours. After the 312 hours, the specimens were rinsed, stored

576

LIM,

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LAUTENSCHLAGER

Table II. Bleaching preparations with manufacturer’s formulation Bleaching preparation and batch number

Manufacturer Den-Mat Corporation Santa Maria, Calif.

Manufacturer’s formulation Carbamide peroxide, carbomer 940,

Rembrandt Lighten 567966 White and Brite 13037

Omni Products International, Gravette, Ark.

glycerine, troamine Perhydrol urea in a proprietary base

Caulk Prisma AP.H. I

I

I

LY o

DY w

F 21 u i? Sn -

Gw

Gr

Go

I

I

Ur

Uo

l.Y w

SHADE

LY r

treatment

DY r

Dye

3M Silux Plus 32 SC

'

uw

I

I

,

I

I

I

DYw

DYr

DYo

LGw

LGr

LGo

UOr

UOo

SHADE

treatment

Kerr Herculite XR I

uw

Ur

UC

I

Gw

SHADE Treatment w _ Water

for 3 12 hours: storage I - Rembrandt

Gr

Go

UO w

treatment IDer+Mat)

0 _ White

& Brite (Dmni)

Fig. 1. A E Values of composite resins. Shades are indicated by upper case letters. G, gray; LY, light yellow; LG, light gray; DY, dark yellow; U, universal, and UO, universal opaque. Treatments are indicated by lower case letters; w, water storage for 312 hours, r, exposure to Rembrandt Lighten material for 312 hours, or o, exposure to White and Brite material for 312 hours.

again in water at 37’ C for 48 hours, and the final color readings of all specimens were recorded. Two dentists visually compared the specimens exposed to the bleaching gel with the specimens exposed to water to subjectively evaluate any clinically observable color change.

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HOME

BLEACHING

AND

COMPOSITE

RESIN

WHITE

BLACK Fig. 2. L*a*b* Color space.

RESULTS The color change of the specimens was determined by calculating the AE from the L*a”b* values. The formula was: ti = ~(L*F - L*# + (u*F - a*# + (b*F - b*~)~ The subscript 1 represents the initial value and the subscript F indicates the final value. The mean AE values and standard deviations were calculated for each shade. The results are graphically illustrated in Fig. 1 with each bar depicting one group of three specimens. A two-way ANOVA of the brand and exposure factors was performed to determine significant differences at an LY= 0.01 level but no statistical difference in A E was detected for either brand or exposure factors. The dentists visual observations comparing the gel-exposed groups to the corresponding control groups confirmed that there were no differences. The pH values of the solutions were as follows: Superoxyl, 4.2; Rembrandt Lighten, 6.9; and Omni White and Brite, 7.1. DISCUSSION The L*a*b* color space defines color in three parameters (Fig 2.) L* represents the degree of gray and corresponds to value or brightness. The a* is a hue-chroma parameter in the red-green direction and b* is a hue-chroma parameter in the blue-yellow axis. High L* values are recorded from bright or white specimens. Positive a* values are red while negative values are green and positive b* values are yellow while negative values are blue.16 The lightening of the specimens was depicted as an increase in L* while actual hue-chroma change was demonstrated in changes in a* and/or b*. However, a change in the

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a* orb* direction can also result in a shift in the L* direction. Since, the accepted level of visual perception is a A E of 1 to 2, the bleached specimens appeared visually identical to their corresponding controls and correlates the dentists’ subjective assessmentwith quantitative measurements recorded with the Chroma meter. An efficiently applied, well inverted, ligated rubber dam is essential in protecting the gingiva and allied soft tissues from attack by the warm hydrogen peroxide solution during the professionally administered technique. Evidently, the home bleaching gel preparations are buffered at a near-physiological pH (-7) range for safety because these materials are intended for personal use without direct supervision of the dentist. As indicated by their pH values, these home remedies react less aggressively than the warm hydrogen peroxide solutions. CONCLUSIONS The bleaching gels created slight color changes in the composite resin restorative materials that could only be detected with the Minolta Chroma meter. Statistical analysis revealed that these changes were no different than exposure to water. Subjective observations revealed no visual alterations in the color of composite resin restorative materials exposed to either bleaching gels or water. In contrast to the effects in the previous study with the warm hydrogen peroxide, no change in color of composite resin restorations was observed. No clinically observable color change in composite resin materials should be anticipated in using the gel formulations. REFERENCES 1. Caldwell C. Bleaching 1966;42:234-5.

of vital or nonvital

teeth. J Calif Dent Assoc

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MONAGHAN,LIM,ANDLAUTENSCHLAGER

2. Goldstein R. Change your smile. 2nd ed. Chicago: Quintessence Publishing, 1984;20-64. 3. F&man R, Goldstein R, Garber D. Bleaching teeth. 1st ed. Chicago: Quintessence Publishing, 1987;53-78. 4. Haywood VB, Heymann HO. Nightguard vital bleaching. Quintessence International 1989;20:173-176. 5. Opalescence Dentist instructions (includes laboratory and patient instructions). Salt Lake City: Ultradent Products, Inc, 1990. 6. Christensen G. Bleaching vital tetracycline-stained teeth. Quintessence International, 1978;9:13-9. 7. Robertson W, Melfi R. Pulpal response to vital bleaching procedures. J Endodont, 1980;6:645-9. 8. Baumgartner J, Reid D, Pick&t A. Human pulpal reaction to the modified McInnes bleaching technique. J Endodont, 1983;9:527-9. 9. Jordan R, Boksman L. Conservative vital bleaching treatment of discolored dentition. Compend Contin Educ Dent, 1984;5:803-8. 10. Monaghan P, Trowbridge T, Lautenschlager E. Composite resin color change after vital tooth bleaching. J PROSTHET DENT 1992;67:778-

11. Bailey S, Swift E. Effects of home bleaching products on resin composites [Abstract]. J Dent Res 1991;70:5’70. 12. Kao E, Peng P, Johnston W. Color changes of teeth and restorative materials exposed to bleaching [Abstract]. J Dent Res 1991;70:570. 13. Burger K, Cooley R. Effects of carbamide peroxide on composite resins [Abstract]. J Dent Res 1991;70:570. 14. Friend G, Jones J, Wamble S, Covington J. Carbamide peroxide tooth bleaching: changes to composite resins after prolonged exposure [Abstract]. J Dent Res 1991;70:570. Reprint requests to: DR. PETER MONAGHAN OPERATIVE DENTISTRY NORTHWESTERN UNIVERSITY DENTAL SCHOOL 240 E. HURON ST. CHICAGO, IL 60611

81.

Accuracy and bond strength of reversible with irreversible hydrocolloid impression systems: A comparative study William

H. Heisler,

Loma Linda University,

DDS,a and Anthony School of Dentistry,

H. L. Tjan, DrDent,

DDSb

Loma Linda, Calif.

Combinations of three reversible hydrocolloids with five irreversible hydrocolloids were evaluated for dimensional accuracy and bond strength. A stainless steel model representing two teeth prepared for a fixed partial denture was designed for an accuracy study. The recordings were made with a measuring microscope, and the tensile bond strength, was determined with an Instron Universal Testing instrument. The accuracy of these materials was clinically acceptable, and the resulting models were suitable. The materials distributed by a common supplier exhibited better tensile strength, although one irreversible hydrocolloid, Jeltrate, performed well in the noncompanion combination groups. This reversible with irreversible hydrocolloid combination impression has an advantage compared with the traditional reversible hydrocolloid impression, because it does not require elaborate, expensive conditioning equipment and water cooled trays. (J PROSTHET DENT 1992;68:578-84.)

S

ears1 introduced reversible hydrocolloid in 1937 for making impressions in fixed prosthodontics, and it has enjoyed the longest continuous use of any impression material. This is because it has a reputation based on consistency, predictability, and repeatable performance.2 Reversible hydrocolloid is so accurate that a casting fabricated on a certain die from one impression will fit the die made from the second impression.3 Reversible hydrocolloids have a prolonged shelf life, are pleasant to use, and easy to clean.2 The disadvantage of reversible hydrocolloid aAssociate Professor, Department of Restorative Dentistry. bProfessor and Director of Biomaterials Research, Department Restorative Dentistry. 10/l/39139

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of

is the initial expenditure for instruments. It requires an expensive conditioner with water-cooled trays, and only one cast can be obtained from each impression.2 An impression method using a combination of reversible hydrocolloid and irreversible hydrocolloid has been introduced.4-7 The accuracy of combination hydrocolloid impression materials has compared favorably with other impression materials.5,6,8 Lin et al5 demonstrated that the accuracy of combination hydrocolloid material was comparable to that of polysulfides and better than either reversible or irreversible hydrocolloids. The advantages of reversible with irreversible hydrocolloid impressions are (1) reduced expense, (2) less preparation time, and (3) an uncomplicated technique compared with other impression systems.4 This study evaluated the

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