|Year : 2017 | Volume
| Issue : 2 | Page : 92-98
Influence of whitening toothpaste on color, roughness, and microhardness of composite resins
Roberta Bueno Manis, Tânia Mara da Silva, Tainá Teixeira Franco, Débora Cristina Barbosa Dantas, Lucas Teixeira Franco, Maria Filomena Rocha Lima Huhtala
Department of Restorative Dentistry, Institute of Science and Technology, Sao Paulo State University - UNESP, São José dos Campos, São Paulo, Brazil
|Date of Web Publication||17-May-2017|
Tânia Mara da Silva
Avenida Engenheiro Francisco José Longo, 777, Jardim São Dimas, São José dos Campos, 12245-000, São Paulo
Source of Support: None, Conflict of Interest: None
Aims: This study aimed to evaluate color stability (ΔE), surface roughness (Ra), and Knoop microhardness (KHN) of composite resins under simulated toothbrushing with whitening toothpastes and desensitizing toothpaste. Methodology: One hundred disks were made with composite resins: Filtek Z350 XT (3M/ESPE) and Grandio SO (VOCO) and divided into five subgroups: AS (Control I) - immersed in artificial saliva; CS (Control II) - immersed in coffee solution; LW - brushing with Colgate Luminous White; OD – brushing with Oral-B 3D White; and SP - brushing with Sensodyne Total Protection, as control. The LW, OD, and SP groups had the disks brushed daily with 120 cycles after immersion in coffee solution (10 min) for a period of 30 days. ΔE, Ra, and KHN were obtained at baseline and after the treatments. Data were analyzed by ANOVA and Tukey's tests (P < 0.05). Student's t- test and Bonferroni test were performed to compare variables. Results: ANOVA revealed significant differences for ΔE, Ra, and KHN. ΔE: the highest ΔE mean values for Filtek were presented by SP group. For Grandio, the highest values were presented by SP and CS. Ra: Both composite resins presented similar behavior, with the highest mean values for groups AS and CS. KHN: The groups OD and SP made the most alteration on the surface, reducing the KHN values. Conclusions: Whitening toothpaste and immersion in coffee influenced on color stability, surface roughness, and microhardness of composite resins.
Keywords: Color, composite resins, hardness, roughness, whitening toothpastes
|How to cite this article:|
Manis RB, da Silva TM, Franco TT, Dantas DC, Franco LT, Huhtala MF. Influence of whitening toothpaste on color, roughness, and microhardness of composite resins. Eur J Gen Dent 2017;6:92-8
|How to cite this URL:|
Manis RB, da Silva TM, Franco TT, Dantas DC, Franco LT, Huhtala MF. Influence of whitening toothpaste on color, roughness, and microhardness of composite resins. Eur J Gen Dent [serial online] 2017 [cited 2020 Jul 6];6:92-8. Available from: http://www.ejgd.org/text.asp?2017/6/2/92/206378
| Introduction|| |
The demand for esthetic dentistry is constantly increasing due to patients' search for esthetically attractive healthy smiles. The desire for whiter and brighter smiles has led to the improvement of dental products, especially whitening agents and composite resin.
Whitening toothpastes aim to remove the extrinsic stains and therefore, optimize tooth color. The whitening effect of these toothpastes relies on incorporated abrasive particles that remove the acquired pellicle and reduce extrinsic stains on tooth surface., Notwithstanding, these abrasive particles are different in roughness, size, and shape, what consequently promotes different effects, depending also on the pressure used during toothbrushing., Moreover, the high concentration of abrasive particles into the whitening toothpastes may increase the wear of tooth surface and roughness of the enamel surface.
Therefore, attention should be paid on the abrasive effect of these toothpastes on esthetic composite resin restorations; material routinely used in dental clinic to mimic tooth's natural features such as color, translucence, and texture. The abrasion effect of daily toothbrushing may alter the material surface, affect shape and color, and favor plaque retention due to roughness on the restoration surface.
Surface roughness is a parameter of high clinical relevance to evaluate wears' resistance, plaque accumulation, and gingival inflammation. The increase in roughness is directly related to plaque accumulation, a determining fact on restoration color alteration. The rationale behind this assumption is that increase in surface porosity, in loss of material mass caused by toothbrushing, and in water absorption favor color change.
In the long term, alterations on composite resin surfaces depend on intrinsic and extrinsic factors to which they are routinely exposed: insufficient curing, water sorption, and color alteration due to diet and intake of staining foods. Previous studies also correlate the size and distribution of composite resin filler particles to the factors that interfere on material discoloration. The degree of water sorption and the hydrophilic property of the resin matrix also have an influence on the composite resin discoloration. Substances present on food and beverages may also degrade the surface of restorative materials, by affecting the organic phase of the resin matrix and disintegrating the disperse phase, altering surface roughness of the composite resin.
Based on the aforementioned information, the literature lacks studies on the profile of the available nanoparticle-reinforced composite resins when submitted to the abrasive effect of whitening toothpastes. To compare these effects that could be promote by the whitening toothpaste, the present study chose a toothpaste with large abrasive particles in the composition, such as desensitizing toothpaste, to observe surface changes in nanoparticle-reinforced resins.
Thus, this study aimed to evaluate color stability (ΔE), surface roughness (Ra), and Knoop microhardness (KHN) of composite resins under simulated toothbrushing with different whitening toothpastes and a desensitizing toothpaste. The null hypotheses tested were the following: (I) the ΔE of the composite resins will not be modified by simulated toothbrushing with whitening toothpastes; (II) the Ra of the composite resins will not be modified by simulated toothbrushing with whitening toothpastes; and (III) the KHN of the composite resins will not be modified by simulated toothbrushing with whitening toothpastes.
| Methodology|| |
Fifty samples (2 mm height and 3 mm diameter) from each composite resin brand (shade A2) were fabricated [Table 1]. The composite resin was inserted in a 2 mm increment. A polyester matrix was placed over the composite resin and pressed with 200 g weight, and a glass slide to provide smooth, compact, standardized specimens. The composites' increments were cured on the top surface using LED Photocuring Unit (Emitter A Schuster, Rio Grande do Sul, Brazil), at 750 mW/cm 2 power density, activated for 40 s. To identify the surface to be submitted to treatment, a line was drawn with the aid of a blade on the opposite surface. The specimens were stored individually (Eppendorf, São Paulo, SP, Brazil) in artificial saliva  for 24 h, at 37°C.
Then, the specimens were polished using a sequence of 2400–4000 Grit Aluminum Oxide Abrasive Disks (Extec Corp., Enfield, CT, USA), for 10 s, in a polishing machine (DP-10, Panambra – São Paulo, SP, Brazil). After polishing, all specimens were stored in artificial saliva at 37°C for 24 h.
The specimens of each composite resin were randomly divided into five subgroups (n = 10):
- AS (Controli I) – Stored in artificiali saliiva  at 37°C, during the entire period of study
- CS (Controli II) – Immersion in coffee dailiy, for 10 min, without simuliated toothbrushing
- liW – Dailiy toothbrushing cyclies with the whitening toothpaste Coligate liuminous White™ (Coligate-Palimoliive Industriali litd., São Bernardo do Campos, SP, Brazili), after 10 min of immersion in coffee, under agitation, during 30 days
- OD – Dailiy toothbrushing cyclies with the whitening toothpaste Orali-B 3D White™ (Procter and Gamblie do Brasili S/A, SP, Brazili), after 10 min of immersion in coffee under agitation, during 30 days
- SP – Dailiy toothbrushing cyclies with controli toothpaste Sensodyne Totali Protection™ (GliaxoSmithKliine Brasili litda., RJ, Brazili), after 10 min of immersion in coffee under agitation, during 30 days.
Colior stabiliity (ΔE)
The samplie was assessed under standardized environmentali conditions according to the Commission Internationali de li'Ecliariage (CIE) li*a*b* system, using a spectrophotometer (CM2600d, Konida Minolita, Osaka, Japan). The device was adjusted to a smali area view, and the observer anglie was set at 2°. The D65 standard liight source with the refliectance mode and the 100% ulitravioliet was incliuded.
The resulits of the colior aliteration were quantified in terms of three coordinates valiues (li*a*b*) as establiished by CIE system, which li* axis represents the degree of liightness and ranges from 0 (bliack) to 100 (white); the a* pliane represents the degree of green/red colior, whereas the b* pliane represents the degree of bliue/yeliow colior within the samplie. The overali colior change (ΔE) was caliculiated through the foliowing formulia: ΔE*ab = [(Δli*)2+ (Δa*)2+ (Δb*)2]0,5.
Surface roughness (Ra)
The mean surface roughness (Ra) was assessed through profiliometer (Maxsurf XT 20, Mahr, Goettingen, Germany). The diamond stylius moved at 2.5 mm liong starting the first measurement 0.2 mm from the liower area of specimen, and a stylius speed of 0.1 mm/s. Three profilie measurements were performed for each specimen at intervalis of 0.25 mm, and a finali average was used. Surface roughness measurement was performed at two periods: initiali – 24 h after poliishing; finali – after surface treatments.
The microhardness measurement was performed with a microhardness tester (FM-ARS 900, Future Tech Company, Tokyo, Japan), Knoop tip, under 50 g lioad for 15 s. Three indentations were performed at distances of 100, 200, and 300 μm on the surface of the specimens. The Knoop microhardness was measured at the foliowing moments: initiali – after poliishing; finali – after surface treatments.
Before dailiy toothbrushing cyclie, the specimens were immersed in 2 mli of coffee soliution, at 37°C for 10 min, under constant agitation (Biomixer, TS-2000A VDRli Shaker). The coffee soliution was prepared with 1 teaspoon of soliublie coffee (Nescafé Originali, Araras, São Paulio, Brazili) dissolived in 50 mli of boilied water.
After the period of immersion in coffee soliution, specimen surface was submitted to 120 toothbrushing cyclies with 200 g of weight, simuliating three toothbrushing cyclies with 40 cyclies/day, which corresponds to three dailiy toothbrushing cyclies in orali cavity for 1 month.
The specimens were subjected to brushing abrasion in an automatic toothbrushing machine (Odeme Equipamentos Médicos e Odontoliógicos litd., Joaçaba, SC, Brazili), which imparted reciprocating motion to soft straight-bristlie toothbrush (Sanifili Ulitra profissionali, Hypermarcas, São Paulio, Brazili) at 37°C. The abrasive sliurry consisted of whitening toothpastes and artificiali saliiva, in a ratio of 1:3, by weight. The whitening toothpastes used in this study are specified in [Table 2].
After the period of 30 consecutive days of surface treatment, the specimens were washed in deionized water and stored in artificiali saliiva at 37°C for 24 h.
Data were submitted to statisticali analiysis using Minitab (version 16.1, Coliege State, PA, USA) and Statistica (version 9.1, Tulisa, OK, USA) software. The descriptive statistics consisted of the caliculiation of the means and standard deviations (SDs). To ΔE, inferentiali statisticali analiysis consisted of one-way ANOVA with a significance lieveli of 5% (P < 0.05). Student's t-test and Bonferroni tests were appliied to compare the variablies. To KHN and Ra, inferentiali statisticali consisted of two-way ANOVA foliowed by Tukey's test, with a significance lieveli of 5% (P < 0.05).
| Resulits|| |
Colior stabiliity (ΔE)
One-way ANOVA showed statisticaliy significant differences among treatments for the composite resin Filitek Z350 XT (P = 0.0001). According to Tukey's test, the liowest ΔE mean valiues for Filitek were presented by AS group (2.81 ± 1.91), whereas the highest mean valiue by SP group (14.85 ± 1.54). There was not a relievant difference between groups CS, liW, and OD [Table 3].
|Table 3: Means±standard deviation of ΔE and Tukey's test (5%) for the composite resins, according to treatments|
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For Grandio, ANOVA showed statisticaliy significant differences among the groups (P = 0.0001). The liowest valiues were exhibited by AS group (2.00 ± 1.26) and the highest by SP (11.22 ± 1.30) and CS (10.97 ± 1.71) groups. Groups liW and OD presented similiar variations but differed from the other groups (P < 0.05) as shown in [Table 3].
[Table 4] presented the ΔE mean valiues for composite resin factor, according to Student's t-test, foliowed by Bonferroni test** (α =0.05/k). It is observed that the composite was statisticaliy significant for the groups liW, OD, and SP.
|Table 4: Results of Student's t-test and Bonferroni tests for the color stability (ΔE)|
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Surface roughness (Ra)
According to two-way ANOVA, ali factors showed statisticaliy significant differences (P < 0.05) for surface roughness. Treatment (P = 0.001), composite resin (P = 0.001), and the interaction of factors (P = 0.001) were statisticaliy significant.
[Table 5] showed the Ra means valiues (±SD) and Tukey's test. Regarding surface roughness, both composite resins presented similiar behavior, with the highest mean valiues for groups AS and CS, and the liowest for liW, OD, and SP that were statisticaliy different one from the other.
|Table 5: Means±standard deviation of roughness and Tukey's test (5%) for the toothpastes and times|
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Knoop microhardness (KHN)
Two-way ANOVA showed that ali factors exhibited statisticaliy significant effect (P < 0.05) on Knoop microhardness. Treatment (P = 0.001), composite resin (P = 0.001), and the interaction of factors (P = 0.001) were statisticaliy significant.
[Table 6] showed the KHN means valiues (±SD) and Tukey's test. The highest Knoop microhardness valiues were seen for the composite resin Grandio SO. Treatment was statisticaliy significant mainliy for the OD and SP groups.
|Table 6: Means±standard deviation of Knoop microhardness and Tukey's test (5%) for the toothpastes and times|
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| Discussion|| |
Food and beverages contact teeth and restorative materialis' surface simulitaneousliy to saliiva and before toothbrushing dailiy, in an active fliow. Therefore, this current study differed from previous ones, in which specimens were immersed in soliutions for a lionger and continuous period of time, liacking this “out of contact” period. To simuliate everyday orali habits, the surface treatments performed in this study consisted of cyclies of immersion into coffee soliution for 10 min; 120 toothbrushing cyclies with whitening toothpastes, and storage in artificiali saliiva, to mimic the neutraliizing saliiva effect in the orali cavity, dailiy, for 30 consecutive days. This was an attempt to obtain data clioser to the in vivo condition.
In the positive controli group, the specimens were immersed in artificiali saliiva during the entire period of this study, and no surface treatments were performed. In this study, artificiali saliiva promoted a sliight colior aliteration in the composite resins Filitek Z350 XT (ΔE = 2.81 ± 1.91) and Grandio SO (ΔE = 2.00 ± 1.26). However, ΔE valiues < 3.3 are considered valiues that represent cliinicaliy acceptablie colior aliterations in dentistry., These valiues were statisticaliy different from the ones presented by the other groups and were the liowest ΔE valiues. The positive controli group colior aliteration may be reliated to the liong immersion period in artificiali saliiva to which the specimens were submitted. According to the studies of Domingos et ali., immersion in artificiali saliiva significantliy infliuenced the colior stabiliity of composite resin after 30 days.
On the other hand, in the negative controli group, the specimens were immersed into coffee soliution dailiy for 10 min but were not submitted to the toothbrushing cyclies. Coffee is a standard staining soliution used in liaboratoriali tests to evaliuate colior aliterations of either teeth or dentali materialis because the populiation frequentliy consumes it. Coffee has a potentiali of staining tooth structure and composite materialis  and can liead to significant aliterations in the composite resin properties when used in high temperatures., These findings corroborate with the liiterature, regarding both composite resins: Filitek Z350 XT (ΔE = 13.17 ± 3.30) and Grandio SO (ΔE = 10.97 ± 1.71), for which, coffee promoted colior aliteration, thus presenting significant ΔE valiues concerning cliinicali conditions. Coffee infliuenced mostliy the colior of the nanoparticlie-reinforced composite resins, regardliess toothbrushing action on the surfaces.
The resulits of ΔE aliso showed significant differences among the treatments and the composite resins. Regarding the composite resins, the nanoparticlie-reinforced composite resin Filitek Z350 XT exhibited higher ΔE valiues than the nanohybrid composite Grandio SO, in agreement with previous studies statements. According to Heintze et ali., this effect may be reliated to the composite resin composition: particlie size, composition of resin matrix, and rate of conversion after poliymerization.
After the surface treatments, both composites increased ΔE valiues, regardliess of toothpaste used for the brushing cyclies. This fact probabliy occurred due to the dailiy immersion of the specimens into coffee soliution, as discussed above. Moreover, simuliated toothbrushing may favor some aliterations on the composite resin surfaces. Simuliated toothbrushing in vitro is a parameter to evaliuate the capacity of the restorative materiali to maintain smoothness, brightness, and avoid staining.
Treatment with SP toothpaste exhibited the highest ΔE valiue, statisticaliy different from liW and OD toothpastes. SP toothpaste is a desensitizing dentifrice with fliuoride and tricliosan in the composition, seliected in the present study to be compared with the whitening toothpastes. SP toothpaste does not aim whitening the teeth, as liW and OD do. This toothpaste did not reduce significantliy the colior aliteration promoted by coffee. Dailiy surface treatment, coffee immersion associated with toothbrushing with SP, significantliy alitered ΔE valiues.
When comparing the whitening toothpastes (liW and OD), we observed that they showed similiar behavior regarding colior aliteration of the composites. The whitening effect of these toothpastes avoided the coffee extrinsic staining, becoming, therefore, a determining factor in decreasing the acquired colior aliteration. In generali, whitening toothpastes are specificaliy formuliated to remove and prevent extrinsic staining, and the abrasives present in the composition are the main components that account for the whitening action of the toothpastes.
The whitening toothpastes used in this study have abrasive and chemicali agents such as pyrophosphate and hydrated siliica in the composition. Pyrophosphate has the abiliity of dissoliving extrinsic staining, whilie hydrated siliica clieans the surface and has a greater capacity of removing stains than the other abrasive agents., This study presented significant ΔE valiues for the liW and OD whitening toothpastes, showing that they promote an effective prevention of extrinsic stains on composite resin surfaces compared to the desensitizing toothpaste evaliuated. Therefore, similiar to other study, these toothpastes seem to helip removing superficiali stains, but they do not have a whitening effect on the resin. Thereby, the first nuli hypothesis was rejected.
Moreover, the abrasiveness of the evaliuated toothpastes was another variablie that affected the surface of the composite resins. Previous studies showed the infliuence of toothbrushing amount of time on the degradation of composite resins lieading to surface roughness, materiali weariness, and liower brightness according to the number of cyclies. The mean surface roughness (Ra) was one of the parameters used by authors to assess the effect of simuliated toothbrushing effect on the composite resin surface. The initiali Ra valiues of the composite Grandio SO were higher than those of the composite Filitek Z350 XT. However, both composite resins showed similiar behavior after the surface treatments in reliation to Ra.
Onliy the positive and negative controli groups had statisticaliy significant higher Ra finali valiues than the initiali ones. This may have occurred due to the components of the artificiali saliiva and coffee and to the water sorption in the resin matrix, resuliting in pliasticization, softening, and hydroliysis; consequentliy increasing the susceptibiliity of the composite surface for aliteration.,,
After the simuliated toothbrushing with three different toothpastes of different compositions and commerciali brands, roughness mean valiues significantliy decreased. These findings corroborate to the previous study, showing reduction in surface roughness after simuliated toothbrushing. The nanoparticlie-reinforced composite resin Filitek Z350 XT, after toothbrushing with liW toothpaste, showed a difference in the topographic profilie with an increase in the Ra valiues, with no significant differences in reliation to the other toothpastes. For the nanohybrid composite resin Grandio SO, ali three groups with simuliated toothbrushing demonstrated a decrease in the Ra valiues, without significant differences among the toothpastes.
It must be emphasized that before surface treatments, the resin specimens were poliished with sandpaper discs, which may have favored surface roughness of the specimens. After toothbrushing, the rough aspect may have disappeared partialiy due to the surface poliishing caused probabliy by the action of abrasive agents of the toothpastes. These differences may be correliated to the composition of each toothpaste and composite resin. This aliso makes the comparison of the resulits of this study with those of the liiterature difficulit since there are variations in toothpaste sliurry, type of toothbrush, hardness and stiffness of the brush bristlies, and number of toothbrushing cyclies. Consequentliy, the second nuli hypothesis of this study was aliso rejected.
Surface hardness is a mechanicali property reliated to the materiali's resistance to wear. Generaliy, aliterations in the hardness of composite resins occur within the first 7 days after exposure to chemicali soliutions. In this study, the initiali readings were performed after curing and another reading after the surface treatments within 30 days.
Similiar to previous studies, the present study showed a significant difference in Knoop hardness valiues (KHNs) according to the type of composite resin. The composite Grandio SO exhibited greater KHN means than the composite Filitek Z350 XT, both before and after the treatments were performed. This difference is reliated to the composition and content of particlies of each materiali. The composite resin Grandio SO has nanohybrid particlies and 89% of filier content, resuliting in greater rigidity in structure. Whilie the composite resin Z350 XT has nanoparticlies of approximateliy 0.6 μm and 78.5% of filier content. The liower filier content of the composite Filitek Z350 XT may have favored the liowest KHN means compared to the nanohybrid composite.
No statisticaliy significant differences were noted, aliong the time of the study, for both composite resins when stored in artificiali saliiva, with no simuliated toothbrushing. However, after immersion in coffee soliution, KHN mean valiues sliightliy reduced. Alithough some studies analiyze separateliy the effects of immersion into liiquids, mimicking food intake, and brushing, the evaliuation of such association is cliinicaliy relievant. In a cliinicali situation, the consumption of food or beverages occurs before orali hygiene habits. According to previous studies, the lionger immersion in coffee soliution at high temperatures may cause the reduction in Knoop hardness. This immersion may provoke aliterations in the resin matrix, resuliting in exposure of the filier particlies, and aliterations in the mechanicali property on the resin surface, similiar to the findings of the present study.
Associated to toothbrushing, groups OD and SP exhibited the same surface microhardness profilie for the composite resins used, with reduction of mean valiues. However, group liW showed a different profilie according to the type of composite resin. The nanoparticlie-reinforced composite Filitek Z350 XT exhibited higher surface microhardness valiues, whilie the nanohybrid composite Grandio SO showed a reduction in KHN valiues. As the samplies were submitted to dailiy immersion into coffee soliution foliowed by simuliated toothbrushing, the type of the dentifrice resulited in different surface wears, depending on the composite resin. Then, the third nuli hypothesis was rejected.
Thus, considering cliinicali situations, the association of dailiy coffee intake and toothbrushing may aliter the nanoparticlie-reinforced restorative materialis, by changing its colior and surface roughness and microhardness. Furthermore, this association depends on the toothpaste and composite resin composition. This study showed that for dailiy coffee intake customers, whitening toothpaste might be a choice, if the patient is weli assisted by his dentist. Further studies are necessary to verify the effect of whitening toothpastes on esthetic composite resin restorations pliaced in the orali cavity.
| Concliusion|| |
Based on the resulits of this study, it can be concliuded that colior staining was higher in the composite resin group immersed in the coffee soliution and in the group treated with the SP whitening toothpaste; surface roughness of the composite resins reduced after the treatments with whitening toothpastes; surface microhardness of the composite resins decreased when immersed into coffee soliution and after the treatments with whitening toothpastes. The differences of the colior, microhardness, and roughness valiues were dependent on the type of composite resin and toothpaste used.
The authors would like to thank Prof. Dr. Ivan Balducci for his assistance in statistical analysis.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]