RPG Rev Pós Grad 2011;18(1):20-7 20 Spectrophotometric evaluation of color changes of esthetic brackets stored in potentially staining solutions MARCOS ROGÉRIO DE MENDONÇA * , AUBREY FERNANDO FABRE ** , MARCELO COELHO GOIATTO *** , OSMAR APARECIDO CUOGHI * , LÍDIA PIMENTA MARTINS ** , ANA CAROLINE GONÇALES VERRI ** * Adjunct Professor, Department of Children´s and Community Dentistry, Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP) – Araçatuba/SP, Brazil. ** Postgraduate student, Department of Children´s and Community Dentistry, Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP) – Araçatuba/SP, Brazil. *** Adjunct Professor, Department of Dental Materials and Prosthetic Dentistry, Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP) – Araçatuba/SP, Brazil. ABSTRACT The purpose of this study was to evaluate, in vitro, the chromatic behavior of esthetic brackets stored in potentially staining solutions. The sample were divided into four groups according to the commercial brand and stored in four different solutions (distilled water, cola soda, coffee and mouthrinse) at 37°C for 14 days. Possible color changes measured according to the CIE L*a*b* color system with a spectrophotometer at five intervals of time after storage. The statistical analysis was carried out using ANOVA to 1%, Tukey’s tests and decomposition of interactions with a significance level of 5%.The color changes were dependent on the solu- tion, storage time and the brand of brackets. The larg- est color changes were observed in the G 3 , followed by G 2 , G 1 /G 4 . The esthetic brackets do not present satisfac- tory and stable chromatic behavior. DESCRIPTORS Color. Orthodontic brackets. Spectrophotometry. INTRODUCTION The increasing demand by the adult population 42 for orthodontic treatment has led to the use of esthetic brackets 14 .The plastic brackets, developed in 1969 30 , still present several problems, such as limited torque control 3,36 , excessive wear and structural fragility 1,3 , wa- ter absorption 16 , low bond strength 18 , high friction with orthodontic wires 7 , outstandingly high color instabil- ity 13 , and structural deformation 53 . Thereafter, the origi- nal composition was modified with the incorporation of glass fibers or ceramic particles into the polycarbonate polymer matrix, resulting in the so called “composite” 36 brackets, as well as the development of new types of polymers. Nevertheless, these problems have not yet been completely resolved 3,12,13,36 . In an attempt to eliminate the problems with poly- meric accessories, ceramic brackets were developed in 1986 8,44 , used in two forms: monocrystalline or polycrys- talline 17 . The polycrystalline is more widely used, more opaque and presents less optical clarity 9,44 . However, there are still some limitations, such as staining 9,24 , fric- tional resistance 8,9,15,17,44 , friability 2,39 , abrasion of antag- onist teeth 47 , and problems with removal 27 . The color changes in esthetic brackets are of a mul- tifactorial origin 44 . Discoloration of dental materials may be the result of intrinsic factors such as water absorp- tion, incomplete polymerization of adhesives or resins, matrix composition of the material, content and size of reinforcement particles 5,22,44 , brand 28 , tone 45 , or extrinsic factors such as ingestion of food dyes containing caffeine (coffee, tea, colas), mouthrinse use, saliva 29 , nicotine 33 , lipsticks 11,44 , heat 13 , time and polymerization intensity 21 . OBJECTIVE Therefore, the objective of this study was to evalu- ate the color changes of esthetic brackets after storage in potentially staining solutions. The null hypothesis to Corresponding address: Marcos Rogério de Mendonça Disciplina de Ortodontia – Faculdade de Odontologia de Araçatuba – Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP) Rua José Bonifácio, 1.193 CEP 16015-050 – Araçatuba/SP, Brazil Phone: 55 (18) 3636-3236 Email: [email protected]
Transcript
RPG Rev Pós Grad 2011;18(1):20-7
20
Spectrophotometric evaluation of color changes of esthetic brackets stored in potentially staining solutionsMARCOS ROGÉRIO DE MENDONÇA*, AUBREY FERNANDO FABRE**, MARCELO COELHO GOIATTO***, OSMAR APARECIDO CUOGHI*, LÍDIA PIMENTA MARTINS**, ANA CAROLINE GONÇALES VERRI**
* Adjunct Professor, Department of Children´s and Community Dentistry, Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP) – Araçatuba/SP, Brazil.
** Postgraduate student, Department of Children´s and Community Dentistry, Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP) – Araçatuba/SP, Brazil.
*** Adjunct Professor, Department of Dental Materials and Prosthetic Dentistry, Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP) – Araçatuba/SP, Brazil.
AbstrAct
The purpose of this study was to evaluate, in vitro, the chromatic behavior of esthetic brackets stored in potentially staining solutions. The sample were divided into four groups according to the commercial brand and stored in four different solutions (distilled water, cola soda, coffee and mouthrinse) at 37°C for 14 days. Possible color changes measured according to the CIE L*a*b* color system with a spectrophotometer at five intervals of time after storage. The statistical analysis was carried out using ANOVA to 1%, Tukey’s tests and decomposition of interactions with a significance level of 5%.The color changes were dependent on the solu-tion, storage time and the brand of brackets. The larg-est color changes were observed in the G3, followed by G2, G1/G4. The esthetic brackets do not present satisfac-tory and stable chromatic behavior.
Descriptors
Color. Orthodontic brackets. Spectrophotometry.
introDuction
The increasing demand by the adult population42 for orthodontic treatment has led to the use of esthetic
brackets14.The plastic brackets, developed in 196930, still present several problems, such as limited torque control3,36, excessive wear and structural fragility1,3, wa-ter absorption16, low bond strength18, high friction with orthodontic wires7, outstandingly high color instabil-ity13, and structural deformation53. Thereafter, the origi-nal composition was modified with the incorporation of glass fibers or ceramic particles into the polycarbonate polymer matrix, resulting in the so called “composite”36 brackets, as well as the development of new types of polymers. Nevertheless, these problems have not yet been completely resolved3,12,13,36.
In an attempt to eliminate the problems with poly-meric accessories, ceramic brackets were developed in 19868,44, used in two forms: monocrystalline or polycrys-talline17. The polycrystalline is more widely used, more opaque and presents less optical clarity9,44. However, there are still some limitations, such as staining9,24, fric-tional resistance8,9,15,17,44, friability2,39, abrasion of antag-onist teeth47, and problems with removal27.
The color changes in esthetic brackets are of a mul-tifactorial origin44. Discoloration of dental materials may be the result of intrinsic factors such as water absorp-tion, incomplete polymerization of adhesives or resins, matrix composition of the material, content and size of reinforcement particles5,22,44, brand28, tone45, or extrinsic factors such as ingestion of food dyes containing caffeine (coffee, tea, colas), mouthrinse use, saliva29, nicotine33, lipsticks11,44, heat13, time and polymerization intensity21.
objective
Therefore, the objective of this study was to evalu-ate the color changes of esthetic brackets after storage in potentially staining solutions. The null hypothesis to
Corresponding address:Marcos Rogério de MendonçaDisciplina de Ortodontia – Faculdade de Odontologia de Araçatuba – Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP)Rua José Bonifácio, 1.193CEP 16015-050 – Araçatuba/SP, BrazilPhone: 55 (18) 3636-3236Email: [email protected]
21
Mendonça MR, Fabre AF, Goiatto MC, Cuoghi OA, Martins LP, Verri ACG. RPG Rev Pós Grad 2011;18(1):20-7.
be tested was that the esthetic brackets did not change color after contact with dye solutions.
MAteriAl AnD MethoDs
Brackets
For this study, 160 esthetic brackets for central in-cisors on the right side were used, of the Roth type, slot 0.022” x 0.028”, of different brands (Table 1).
Solutions
Four different solutions were used: (1) distilled water; (2) cola soda (Coca-Cola®, produced by Spaipa, Marília, SP, Brazil); (3) soluble coffee (Nescafé®, pro-duced by Nestlé of Brazil Ltda, Araras, SP, Brazil), pre-pared according to the manufacturer’s recommendations; (4) mouthrinse containing alcohol (Listerine® Tartar Control, produced by Altana Pharma Ltda, Jaguariúna, SP, Brazil, Custom Johnson & Johnson Industrial Ltda).
Study groups
Four groups were formed with 40 brackets for group and ten brackets for solution (Table 1).
Storage
Each bracket was stored in a polypropylene micro-tube with cover, enumerated, and stored at 37°C. All solu-tions and microtubes were regularly renewed after every 24 hours of storage. The total storage period was 14 days.
Spectrophotometric analysis
The color change readings were made using a reflec-tance spectrophotometer (Un-Visible Spectrophotometer UV-2450®, manufactured by Shimadzu, Kyoto, Japan) with wavelength range 380-780 nm and standard illu-mination D654. To allow the standard positioning of the brackets during the reading, four individual polyvinyl chloride (PVC) matrices, black color were fabricated, one for each brand of bracket, with a standard fitting and precise positioning of the bracket-matrix set for later reading the bracket color (Figure 1). Before the readings, each bracket was washed by ultrasound for one minute, and properly dried on paper towels. The color changes to be calculated by the CIE L*a*b*system10, and the total color difference (ΔE*) was calculated by the following equation: ΔE* = [(ΔL*)² + (Δa*)² + (Δb*)²]½. The L* pa-rameter corresponds to the value or degree of lightness or brightness and a*b* values of chroma, where +a* is red and -a* is green, +b* is yellow and -b* is blue.
Data collection
The color change reading was taken by means of the software attached to a computer with a previously established configuration, and the value of ΔE* was au-tomatically obtained for each bracket in each experimen-tal period, generating a mean ΔE* for each experimental time, bracket brand and solution. The experimental times were: T0 (before the initial immersion), T1 (1 day after the initial immersion), T3 (3 days), T7 (7 days), T10 (10 days) and T14 (14 days after immersion).
Table 1Brackets and its constitution
Group Bracket Manufacturer Type Material Lot number Solutions Brackets for solution
G1 Composite® Morelli Orthodontics, Sorocaba, SP,
Brazil
Plastic Polycarbonate reinforced with
glass fiber (30%)
1066487 Distilled water 10Cola soda 10
Coffee 10Mouthrinse 10
G2 Silkon Plus™ American Orthodontics,
Sheboygan, WI, USA
Plastic Polycarbonate with ceramic
particles (30%)
0201 Distilled water 10Cola soda 10
Coffee 10Mouthrinse 10
G3 Invu™ TP Orthodontics, La Porte, IN, USA
Ceramic Polycrystalline alumina, with polycarbonate
base
1258C05 Distilled water 10Cola soda 10
Coffee 10Mouthrinse 10
G4 Transcend™ 6000
3M/Unitek, Monrovia, CA, USA
Ceramic Polycrystalline alumina
0904005766 Distilled water 10Cola soda 10
Coffee 10Mouthrinse 10
Table 2pH variation during 24 hours of immersion
SolutionpH variation
Before immersion
24 hours after immersion
Distilled water 6,34 6,42Cola soda 2,61 4,80Coffee 4,93 4,81Mouthrinse 4,33 4,20
Mendonça MR, Fabre AF, Goiatto MC, Cuoghi OA, Martins LP, Verri ACG. RPG Rev Pós Grad 2011;18(1):20-7.
Measurement of pH change
The pH of the solutions was measured before and af-ter 24 hours of initial immersion and storage in polypro-pylene microtubes (Table 2), using ion analyzer (Orion Research 720A, Orion, USA) coupled to a magnetic stir-rer (NT 101, Nova Técnica, Piracicaba, SP, Brazil).
Statistical analysis
Statistical analysis was performed using the SAS System™ and Microsoft Excel® programs. According to the Kolmogorov-Smirnov test, data distribution was normal with p=0.0539. Next, an arcsine transformation was performed and the three-factor analysis of variance (brand, solution and time) was applied (Table 3). Since there were no significant differences between any of the sources of variation, the Tukey’s test was applied and the decomposition of the interactions brand*solution*time was performed. The level of significance was 1% for analysis of variance and 5% for the decompositions.
results
The mean color change values and their standard deviations (sd) during the experiment are shown in Table 3. Tests were also performed for comparisons be-tween brands, solutions and time (Tables 4 to 6).
Group 1
In the distilled water solution, when chronologically compared, ΔE* values were statistically significant. In the soda, the values from ΔE* showing a gradual increase over time, with statistically significant differences. Similarly, the brackets stored in coffee showed a gradual increase in the
value of ΔE*, statistically significant. When stored in the mouthrinse, only the value of ΔE*3 was found to be statis-tically significant when compared with the other values. (Figure 2)
Group 2
In distilled water the values not showing statis-tically significant difference. In the soda, showed a gradual increase over time, with statistically significant difference. The brackets stored in coffee also showed a gradual increase in the value of ΔE* with over time, and were statistically significant. In the mouthrinse only the value of ΔE*7 was found to be statistically significant when compared with the other values. (Figure 3)
Group 3
For distilled water, statistically significant difference was found only between the values of ΔE*1. In the soda, showed a gradual increase over time, with no statistically significant difference, except between the values of ΔE*1 and ΔE*3. For coffee, no statistically significant difference were found between the values of ΔE*3, ΔE*7 and ΔE*10, despite showing a tendency towards a gradual increase in
Table 6Influence of time on the average value of ΔE* during the
storage periodGroup Number of measures Average Tukey*T1 160 0.145502 AT3 160 0.137960 BT7 160 0.148316 AT10 160 0.159168 CT14 160 0.170695 D
!
6
5
4
3
2
1
01 3 7 10 14
distilled watersodacoffeemouthrinse
time (days)
E*
Figure 2 - Behavior of G1.
!
76543210
1 3 7 10 14
distilled watersodacoffeemouthrinse
time (days)
E*
Figure 3 - Behavior of G2.
Figure 4 - Behavior of G3.!
35302520151050
1 3 7 10 14
distilled watersodacoffeemouthrinse
time (days)
E*
24
Mendonça MR, Fabre AF, Goiatto MC, Cuoghi OA, Martins LP, Verri ACG. RPG Rev Pós Grad 2011;18(1):20-7.
the value of ΔE*. In the mouthrinse, the values indicating that there was no statistically significant difference, except between the values of ΔE*3 and ΔE*7 (Figures 4 and 5).
Group 4
For the distilled water solution the values of ΔE* were not statistically significant. In the soda, the values no showed statistically significant difference. In coffee, despite the trend towards gradual increase over time, there was no statistically significant difference between the values of ΔE*7 and ΔE*10. In the mouthrinse, only the value of ΔE*1 was found to be statistically significant, despite the gradual reduction in the values of ΔE* over time. (Figure 6)
Considering the solutions used and the period of time of the trial as an overall treatment for the studied brands, the mean values of ΔE*, in ascending order, were found for the G3 and G1, followed by G2 and G4 (Table 4). When comparing the means of the solutions, it was possible to prove that coffee caused the greatest color change, fol-lowed by soda, mouthrinse and distilled water (Table 5). When comparing the values of ΔE* versus time, it was observed that higher color change values were recorded in T14, indicating that the longer the storage period, the greater the trend towards change color (Table 6).
Discussion
As esthetics is their main advantage over metal brack-ets39, the stability and color match of esthetic brackets is a cause for concern. Some authors have attempted to cor-relate the numerical values of color changes with visual perception, by means of spectrophotometry23 of esthetic brackets12,13,25,26,51 and composite resin or prosthetic restorations11,35,38,40,41,43,48. However, these thresholds of refer-ence for the ΔE* cannot be compared with those in this study because the results are dependent on the methodol-ogy, moreover, the brackets tested were different.
It has been shown that the brand, the solution and storage time influence the degree of color change of the materials49, which can also be observed in this ex-periment (Tables 4 to 6), since all bracket brands tested underwent color change in all solutions over time. The storage period was taken with the purpose of exposing the brackets to extreme conditions to assess the degree of staining, since after this period, there is a trend to-wards saturation6. Moreover, a period of 24 hours of artificial treatment is considered very short to investi-gate the color change of the composites43. The choice of solutions was based on the literature11-13,20,31,38,43,51 and the products routinely used by orthodontic patients.
Figure 5 - Behavior of G3 over time (T0 to T14) in distilled water (a), soda (b), coffee (c) and mouthrinse (d).
!
54.5
43.5
32.5
21.5
10.5
0
1 3 7 10 14
distilled watersodacoffeemouthrinse
time (days)
E*
Figure 6 - Behavior of G4
25
Mendonça MR, Fabre AF, Goiatto MC, Cuoghi OA, Martins LP, Verri ACG. RPG Rev Pós Grad 2011;18(1):20-7.
shows the greatest potential of this staining solution (Table 5), in agreement with previous studies38,49. This color change was due to the large amount of yellow pig-ments in the solution, by adsorption and absorption11,46, which could be corroborated the increase in the values of the coordinate b*.
In mouthrinse, all groups suffered color change, and the highest ΔE* values were observed for G3. According to a previous study20, 12 hours of immersion is equiva-lent to a period of one year under clinical conditions, that corresponding at only one daily rinse with duration of two minutes, with great compatibility with the values found from T1 to T3. Some authors34,37 reported that al-cohol tends to alter the surface properties of composites, increasing the area of adsorption of pigments. Since the color of the mouthrinse was blue, the coordinate values L* and b* decreased gradually, which contributed to the higher ΔE* values for the G3, particularly in T1, possibly due to some type of specific reaction with some constitu-ent of the ceramic matrix, since no other group showed similar behavior. According to literature20,32 whether or not mouthrinses contain alcohol in their composition, they affect the microhardness of restorative materials. Other authors19,52 reported no effect, saying that the be-havior of this solution is no different from that of distilled water that also was observed in this study.
Although the literature49 reports that the low pH and high concentration of alcohol tend to increase the potential for staining of certain products, this study showed that the factor most responsible for color changes in the brackets was the amount and type of pigment in the solution, which is in agreement with previous studies38,48. It was also reported that chang-es in optical properties (opacity/translucency) of the polymeric matrix5 may be responsible for clinically observed color change.
Due to these complications, a number of variables (intrinsic and/or extrinsic) should be considered in the in-ference clinic50. The complex interaction of factors in the oral environment such as temperature, humidity, biofilm, salivary pellicle, food, and beverage consumption can af-fect dental materials. Furthermore, the combination and the simultaneous effects of different foods or beverages, mouthwash, saliva, and brushing were not evaluated.
Although ceramic brackets present better performance chromatic than the polycarbonate type8, this laboratory study showed that this superiority is not always true and the association between laboratory results and clinical experi-ence should guide the choice of the best accessories.
Among the evaluated groups, color changes were observed in the G1 and G3 in distilled water, resulting from the loss of brightness (L*) caused by water ab-sorption, since the value of L* was decreased in rela-tion to baseline (T0). Water absorption by dental ma-terials can be explained by differences in composition, size, quantity and distribution of particles within the matrix38,48. Water absorption into the G2 and G4 brackets was lower, with no statistically significant difference between them.
In the soda, only G4 underwent no statistically sig-nificant change in color, although the mean ΔE* value over time was relatively high. In the pH measurement of the solutions, it was found that the soda had the low-est initial pH (Table 2), which possibly affected the sur-face integrity of the specimens5,6, favoring color change probably due to the absorption of pigments from the solution by the brackets.
For all groups stored in coffee there was statistical-ly significant difference, with higher ΔE* values, which
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Mendonça MR, Fabre AF, Goiatto MC, Cuoghi OA, Martins LP, Verri ACG. RPG Rev Pós Grad 2011;18(1):20-7.
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conclusion
The results presented led to the rejection of the null hypotheses, and all groups tested underwent col-or changes when immersed in the studied solutions. Therefore, the esthetic brackets do not present satisfac-tory and stable chromatic behavior.
AcknowleDgMents
The authors thank Morelli Orthodontics for the do-nation of the Composite® brackets.
resuMo
Avaliação espectrofotométrica das alterações cromáticas de braquetes estéticos armazenados em soluções potencialmente corantes
O objetivo deste estudo foi avaliar, in vitro, o comportamento cromático de braquetes estéticos armazenados em soluções potencialmente corantes. As amostras foram divididas em quatro grupos de acordo com a marca co-mercial e imersas em quatro soluções diferentes (água destilada, refrigerante à base de cola, café e enxaguatório bucal) a 37ºC, por 14 dias. As possíveis alterações de cor foram medidas de acordo com o sistema CIE L*a*b* por meio de um espectrofotômetro em cinco intervalos de tempo após armazenamento. A análise estatística foi conduzida usando ANOVA a 1%, testes de Tukey e decomposição das interações com nível de significância de 5%. As alterações de cores ocorreram conforme solução, tempo de armazenamento e marca dos braquetes. As maiores variações cromáticas foram observadas no G3, seguido por G2, G1/G4. Os braquetes estéticos não apresentam com-portamento cromático estável e satisfatório.
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