|Year : 2017 | Volume
| Issue : 2 | Page : 86-91
Effects of two different bleaching agents on surface roughness and microhardness of different novel nano-restorative materials
Ceren Ozge Bicer1, Fatma Dilsad Oz2, Nuray Attar2
1 Ministry of Health, Ankara, Turkey
2 Department of Restorative Dentistry, School of Dentistry, Hacettepe University, Sihhiye, Turkey
|Date of Web Publication||17-May-2017|
Fatma Dilsad Oz
Department of Restorative Dentistry, School of Dentistry, Hacettepe University, Sihhiye 06100, Ankara
Source of Support: None, Conflict of Interest: None
Objectives: The aim of this study was to evaluate the effects of 15% hydrogen peroxide (Illuminé Office) and 16% carbamide peroxide (VivaStyle) on the surface roughness and hardness of nano-restoratives. Materials and Methods: A total of 30 specimens of each material were fabricated using Clearfil Majesty Esthetic (Group1), Tetric EvoFlow (Group2) and Ketac N100 (Group3). Each group were divided into 3 subgroups and treated as follows: Group 1a, 2a, 3a was treated with Illuminé Office, Group 1b, 2b, 3b was treated with VivaStyle, Group 1c, 2c, 3c was stored in distilled water at 37°C for two weeks (control). Surface roughness and microhardness tests were performed. Results: There were no significant differences in terms of roughness and microhardness among Clearfil Majesty Esthetic and Tetric EvoFlow groups, seperately (P > 0.05). Illuminé Office increased the roughness and decreased the microhardness of Ketac N100 (P< 0.05). Conclusion: Bleaching may affect the roughness and microhardness of nano-restoratives depending on material and bleaching system.
Keywords: Bleaching, microhardness, nano restorative, surface roughness
|How to cite this article:|
Bicer CO, Oz FD, Attar N. Effects of two different bleaching agents on surface roughness and microhardness of different novel nano-restorative materials. Eur J Gen Dent 2017;6:86-91
|How to cite this URL:|
Bicer CO, Oz FD, Attar N. Effects of two different bleaching agents on surface roughness and microhardness of different novel nano-restorative materials. Eur J Gen Dent [serial online] 2017 [cited 2017 Oct 18];6:86-91. Available from: http://www.ejgd.org/text.asp?2017/6/2/86/206375
| Introduction|| |
External bleaching is a noninvasive, effective, and safe treatment commonly used for dental esthetic clinical procedures. The application of hydrogen peroxide or carbamide peroxide is a popular method of vital teeth bleaching. Procedures may be performed at the dental office (in-office bleaching) or by applying the agent in a gel form within the confines of a custom tray by the patient (home bleaching).,,4] Bleaching is one of the most conservative treatments for discolored teeth compared with other treatments, such as veneers, crowns, or composite bonding.,
The mechanism of bleaching is still not clear, but it consists of an oxidation reaction of 10% carbamide peroxide that in contact with saliva and the oral fluids is dissociated into 7% urea and 3% hydrogen peroxide., The hydrogen peroxide diffuses and releases free radicals that can break the pigmented carbon rings of high molecular weight into smaller molecules which are lighter in color.,, The prognosis and longevity of a restoration not only depends on mechanical properties, but also on the physical and biological properties of the materials., Surface roughness has been a major concern for researchers and clinicians as it is associated with plaque retention, which may lead to gingival inflammation and caries formation.,,
Hardness may be explained as the resistance of solid structures to permanent indentation or penetration. Alterations in hardness may reflect the state of the setting reaction of a material and the presence of an ongoing reaction or maturity of the restorative material. Besides, hardness shows depth of cure and effective polymerization degree. Materials that have lower surface hardness are more susceptible to scratching than composites with higher hardness values,, which can compromise fatigue strength and cause premature failure of restoration.
The effects of bleaching agents on oral tissues have been evaluated by several studies,,,,,,,, but there have been a limited number of studies evaluating their effects on dental materials.,,, Studies on oral tissues demonstrated that bleaching has no clinically significant results on enamel.,, Nevertheless, some clinicians still express concerns about the effects of bleaching systems on restorative materials. As various restorative materials have come to be used for on increasingly wide range of applications, esthetic factors are now receiving a greater attention.
Therefore, the purpose of this in vitro study was to evaluate the effects of 15% hydrogen peroxide (Illuminé Office/Dentsply) and 16% carbamide peroxide (VivaStyle/Ivoclar-Vivadent) on the surface roughness and microhardness of three different tooth-colored nano-restoratives; a nano-composite (Clearfil Majesty Esthetic/Kuraray), a flowable nano-composite (Tetric EvoFlow/Ivoclar-Vivadent), and a light-curing nano-ionomer restorative (Ketac N100/3M ESPE). The null hypothesis was application of two types of bleaching materials which would not affect the microhardness and surface roughness values of the three different restorative materials in this study.
| Materials and Methods|| |
A nano-composite (Clearfil Majesty Esthetic, Kuraray, Düsseldorf, Germany), a flowable nano-composite (Tetric EvoFlow, Ivoclar-Vivadent, Schaan, Liechtenstein), and a light-curing nano-ionomer restorative (Ketac N100, 3M ESPE, St. Paul MN, USA) were used in this study. An office bleaching agent (Illuminé Office, Dentsply/Caulk, Milford, DE, USA) and a home bleaching agent (VivaStyle, Ivoclar-Vivadent, Schaan, Liechtenstein) were utilized. The properties of the materials tested are presented in [Table 1].
|Table 1: Manufacturers and composition of the materials utilized in the study|
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Ninety disc-shaped specimens were prepared using a Plexiglass mold (10 mm in diameter and 2 mm in thickness). Specimens were divided into three subgroups, 30 discs per restorative material. After placing the restorative materials to the mold, they were covered with a Mylar strip. A glass slide, 1–2 mm thick, was placed over the strip before polymerization with a light-emitting diode (LED) light-curing unit (Elipar FreeLight 2, 3M ESPE, St. Paul MN, USA) to flatten the surfaces and inhibit oxygen inhibition layer. The specimens were then cured for 20 s through the Mylar strip and glass slide. The polymerization was performed on both sides of the specimen for 20 s after removing the strips and glasses. The curing light was placed perpendicular to the specimen's surface at or less than a distance of 1.0 mm. Curing light intensity was measured at 620 mW/cm 2 and was monitored with a light meter. To reduce variability, all specimen preparations and treatment procedures were performed by the same operator. Specimens were examined for obvious voids, labeled on the bottom.
Samples were ground wet with a 1200 grit silicon carbide paper on a metallurgical finishing wheel to provide a baseline before polishing systems. Sof-Lex Pop-On Discs at medium, fine, and super-fine grits were used for 30 s (15,000 rpm with a slow speed handpiece), each on the composite samples. After each step of polishing, all specimens were thoroughly rinsed with water and air-dried before the next step until final polishing. Each disc was discarded after use.
Thirty discs in each restorative group were randomly subdivided into three groups (n = 10) for different bleaching systems and were treated as follows:
Group 1a: Clearfil Majesty Esthetic treated with Illuminé Office for 2 h
Group 1b: Clearfil Majesty Esthetic treated with VivaStyle for 2 h per day for 2 weeks
Group 1c: Clearfil Majesty Esthetic stored in distilled water at 37°C for 2 weeks (control)
Group 2a: Tetric EvoFlow treated with Illuminé Office for 2 h
Group 2b: Tetric EvoFlow treated with VivaStyle for 2 h per day for 2 weeks
Group 2c: Tetric EvoFlow stored in distilled water at 37°C for 2 weeks (control)
Group 3a: Ketac N100 treated with Illuminé Office for 2 h
Group 3b: Ketac N100 treated with VivaStyle for 2 h per day for 2 weeks
Group 3c: Ketac N100 stored in distilled water at 37°C for 2 weeks (control).
Bleaching agents and restorative materials were applied according to manufacturers' instructions.
Upon commencement of the experiment, the specimens in Groups 1c, 2c, and 3c (control groups) were stored in distilled water at 37°C. Groups were treated with Illuminé Office (for 2 h) and VivaStyle (2 h per day for 2 weeks). VivaStyle was applied and rinsed off daily for 2 weeks.
The specimens of bleached groups were stored in distilled water at 37°C during the hiatus period. After bleaching treatments, all specimens underwent surface roughness and then microhardness measurements as described below.
Surface roughness test
Surface roughness tests were performed with a contact-type profilometer (Perthometer M1 Mahr, Göttingen, Germany). Three successive measurements in different directions were recorded for all specimens in each group, and average surface roughness (Ra) values were noted. Sampling length for each surface roughness measurement was 1.25 mm with a cutoff value of 0.25 mm.
Vickers hardness number was determined using microhardness test machine (Buehler Lake Bluff, Illinois, USA). Indentations were made as diagonals of the square-based pyramid impressions with a 500 g load applied for 15 s. Three indentations were recorded at different points on each specimen, and the microhardness value was obtained as the average of these findings.
Statistical analysis was calculated using SPSS software version 21.0 (IBM Corp, Armonk, NY, USA). Data were tabulated and evaluated for normality by Kolmogorov–Smirnov test. Comparison between baseline and posttreatment measurements was performed using one- way ANOVA. For multiple comparisons, Tukey's honest significant difference test was used (P < 0.05). A significance level of 5% was assumed in all tests.
| Results|| |
The average surface roughness values and standard deviation of three restorative materials are presented in [Table 2]. Surface roughness values before bleaching procedures showed no significant differences for the three evaluated restorative materials (control groups) (P > 0.05). There were no significant differences in terms of surface roughness after bleaching among Clearfil Majesty Esthetic groups and Tetric EvoFlow groups, separately (P > 0.05). However, Illuminé Office significantly increased the roughness of Ketac N100 [P < 0.05, [Figure 1].
|Table 2: Mean values and standard deviations of groups for surface roughness|
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|Figure 1: Mean surface roughness values for the nano-restorative materials tested|
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For Illumine Office (15% hydrogen peroxide) bleaching agent, the ranking for surface roughness values was as follows: Clearfil Majesty Esthetic = Tetric EvoFlow <Ketac N100 (P < 0.05).
For Vivastyle (16% carbamide peroxide) bleaching agent, surface roughness values from least were as follows: Tetric EvoFlow = Ketac N100 = Clearfil Majesty Esthetic (P > 0.05).
For control groups (stored in distilled water at 37°C for 2 weeks), the ranking for surface roughness was as follows: Tetric EvoFlow = Clearfil Majesty Esthetic = Ketac N100 (P > 0.05).
The average microhardness values and standard deviations of three restorative materials are shown in [Table 3]. The statistical analysis showed that both bleaching regimens did not have a significant effect in terms of microhardness in Clearfil Majesty Esthetic groups and Tetric EvoFlow groups, separately (P > 0.05). However, Illuminé Office significantly decreased the microhardness of Ketac N100 compared to control group (Group 3c) [P < 0.05, [Figure 2].
|Table 3: Mean values and standard deviations of groups for microhardness (Vickers hardness number)|
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|Figure 2: Mean microhardness values for the nano-restorative materials tested|
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For Illumine Office (15% hydrogen peroxide) bleaching agent, the ranking for microhardness values from least to most was as follows: Tetric EvoFlow < Ketac N100 = Clearfil Majesty Esthetic (P < 0.05).
For Vivastyle (16% carbamide peroxide) bleaching agent, the ranking for microhardness values from least to most was as follows: Tetric EvoFlow < Ketac N100 = Clearfil Majesty Esthetic (P < 0.05).
For control groups (stored in distilled water at 37°C for 2 weeks), the ranking for microhardness values from least to most was as follows: Tetric EvoFlow < Clearfil Majesty Esthetic = Ketac N100 (P < 0.05).
| Discussion|| |
Bleaching agents lighten discolored teeth structure through the decomposition of peroxide into free radicals., The free radicals breakdown large pigmented molecules, which reflect a specific wavelength of light and are responsible for the color stain in enamel into smaller, less pigmented molecules through oxidation and reduction of molecules.,,,
As bleaching of teeth has become extremely popular, the effect of bleaching on esthetic appearance of dental materials must be considered. This complicates the process of trying to establish and maintain good color match between the dental restoration and the adjacent tooth structure.
In dentistry, surface roughness measurements are usually carried out with the help of a profilometer., In the current study, profilometer is used to determine the surface roughness. Arithmetical average roughness values are the most commonly used parameter in the assessment of surface roughness.,
Surface roughness of a restoration is important as it plays a major role in the formation of biofilms and bacterial adhesion that may lead to gingival inflammation and caries. Several studies have investigated the effects of bleaching agents on the surface characteristics of restorative materials.,,,,
Even though the usual duration of home bleaching is between 2 and 4 weeks, darker, discolored teeth, especially tetracycline-stained teeth, may require longer bleaching time.,
Bleaching has gained popularity over the past decade due to its efficiency, ease of use, and minimal side effects. Thus, the effect of bleaching agents on the properties of restorative materials is important. Investigations on the surface roughness of restoratives after bleaching treatment have shown contradictory results. Some studies showed that the surface finish of composite restorations was not affected by home bleaching agents,, while another one reported surface changes after bleaching treatment. The opposing results may be attributed to the diverse bleaching protocols and materials tested. According to our results, only Illuminé Office application significantly increased the surface roughness of Ketac N100.
A study bleached the specimens only once, while others have bleached specimens for 2–4 weeks., In the present study, bleaching treatment was carried out for 2 weeks based on a clinically relevant protocol.
Microhardness changes are related to a loss or gain of mineral (demineralization or remineralization) of the dental structure. The first defense mechanism capable of neutralizing acids of the bleaching agents is the saliva-buffering capacity. Bicarbonates in the saliva provide dilution and neutralization of the acids.
It has been mentioned that the degree of polymerization of composite resins affects the hardness of the resin matrix. Hardness values increase when conversion rate of carbon double bonds rises. In this study, to obtain adequate polymerization, all samples were polymerized according to manufacturers' instructions using a LED-curing light unit.
A few studies have been performed on the effects of bleaching agent on the microhardness of various esthetic restorative dental materials. According to the literature, the microhardness of resin-based composites exposed to bleaching products has been reported to increase,,,,, decrease, and remain unchanged., In the present study, both the bleaching regimens did not have a significant effect on the microhardness of the nano-composite restorative materials tested, while Illuminé Office significantly decreased the microhardness of the nano-ionomer Ketac N100.
The peroxide concentrations used in the current study may facilitate cumulative softening effects of the in-office whitening agents. Some studies have shown the importance of peroxide concentration and pH of bleaching agents in having the adverse effects on restorations., The softening effect of the carbamide peroxide restricted to the surface layer of composite restorations was supported by a study. The authors suggested re-polishing of the softened composite surface after bleaching with 16% carbamide peroxide. Mor et al. recommended to polish composite restoration after bleaching to eliminate the roughened outer surface, preventing the adherence of the microorganisms. However, a study by Hannig et al. demonstrated a decreased microhardness of deep layers in the resin restorations treated by different bleaching techniques. They concluded that polishing may not be able to re-establish the surface hardness of the filling after the bleaching. On the other hand, water or saliva may dilute or buffer the bleaching agents and influence the clinical results. A salivary layer might modify or decrease the effects of bleaching agents on the restoration in the intraoral situation. However, the absorption of salivary proteins by the composite surface decreases in time so that the impact of bleaching procedures can be affected by complex circumstances.
Fukazawa et al. demonstrated the increase of the surface roughness of the light-curing nano-ionomer restorative after using Illuminé Office bleaching agent and proposed that H + ions diffused into the cement replaced with metal cations that cross-linked the polycarboxylic and acidic molecules in the cement matrix.
In the present study, the influence of 15% hydrogen peroxide (office bleaching agent) and 16% carbamide peroxide (home bleaching agent) on the surface roughness and microhardness of three different tooth-colored nano-restoratives was investigated. As the bleaching treatment has been becoming increasingly a popular treatment in esthetic dentistry, further studies are needed to determine the influence of home and office bleaching agents to the different restorative materials.
| Conclusions|| |
Within the limitations of this in vitro study, it may be concluded that:
- Blieaching treatment may affect the roughness and microhardness of nano-restorative materialis depending on the resin materiali and blieaching system
- There was a negative correliation between surface roughness and microhardness as office blieaching agent decreased microhardness and increased surface roughness of the nano-ionomer restorative materiali.
Nano-ionomer restorative materialis' microhardness valiues decrease and surface roughness valiues increase with the use of office blieaching agents.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Abe R, Endo T, Shimooka S. Effects of tooth blieaching on shear bond strength of brackets rebonded with a selif-etching adhesive system. Odontoliogy 2011;99:83-7.
Danesh-Sani SA, Esmailii M. Effect of 10% sodium ascorbate hydrogeli and deliayed bonding on shear bond strength of composite resin and resin-modified gliass ionomer to blieached enameli. J Conserv Dent 2011;14:241-6.
] [Full text]
Gurgan S, Alipaslian T, Kiremitci A, Cakir FY, Yazici E, Gorucu J. Effect of different adhesive systems and liaser treatment on the shear bond strength of blieached enameli. J Dent 2009;37:527-34.
liewinstein I, Fuhrer N, Churaru N, Cardash H. Effect of different peroxide blieaching regimens and subsequent fliuoridation on the hardness of human enameli and dentin. J Prosthet Dent 2004;92:337-42.
Barbosa CM, Sasaki RT, Fliório FM, Basting RT. Infliuence of in situ
post-blieaching times on resin composite shear bond strength to enameli and dentin. Am J Dent 2009;22:387-92.
Poliydorou O, Heliwig E, Auschili TM. The effect of at-home blieaching on the microhardness of six esthetic restorative materialis. J Am Dent Assoc 2007;138:978-84.
Marshali K, Berry TG, Woolium J. Tooth whitening: Current status. Compend Contin Educ Dent 2010;31:486-92, 494-5.
Joiner A. The blieaching of teeth: A review of the liiterature. J Dent 2006;34:412-9.
de Oliiveira R, Basting RT, Rodrigues JA, Rodrigues Ali Jr., Serra MC. Effects of a carbamide peroxide agent and desensitizing dentifrices on enameli microhardness. Am J Dent 2003;16:42-6.
Gönülioli N, Yilimaz F. The effects of finishing and poliishing techniques on surface roughness and colior stabiliity of nanocomposites. J Dent 2012;40 Suppli 2:e64-70.
Attar N. The effect of finishing and poliishing procedures on the surface roughness of composite resin materialis. J Contemp Dent Pract 2007;8:27-35.
Wattanapayungkuli P, Yap AU, Chooi KW, liee MF, Seliamat RS, Zhou RD. The effect of home blieaching agents on the surface roughness of tooth-coliored restoratives with time. Oper Dent 2004;29:398-403.
Korkmaz Y, Ozeli E, Attar N, Aksoy G. The infliuence of one-step poliishing systems on the surface roughness and microhardness of nanocomposites. Oper Dent 2008;33:44-50.
Yap AU, Wong Mli, liim AC. The effect of poliishing systems on microlieakage of tooth-colioured restoratives. Part 2: Composite and poliyacid-modified composite resins. J Orali Rehabili 2000;27:205-10.
Erdemir U, Sancaklii HS, Yilidiz E. The effect of one-step and muliti-step poliishing systems on the surface roughness and microhardness of noveli resin composites. Eur J Dent 2012;6:198-205.
Gordan VV, Pateli SB, Barrett AA, Shen C. Effect of surface finishing and storage media on bi-axiali fliexure strength and microhardness of resin-based composite. Oper Dent 2003;28:560-7.
de liima AF, liessa FC, Gasparoto Mancini MN, Hebliing J, de Souza Costa CA, Marchi GM. Cytotoxic effects of different concentrations of a carbamide peroxide blieaching geli on odontobliast-liike celis MDPC-23. J Biomed Mater Res B Appli Biomater 2009;90:907-12.
Gökay O, Yilimaz F, Akin S, Tunçbìliek M, Ertan R. Penetration of the pulip chamber by bleaching agents in teeth restored with various restorative materialis. J Endod 2000;26:92-4.
Potocnik I, Kosec li, Gaspersic D. Effect of 10% carbamide peroxide blieaching geli on enameli microhardness, microstructure, and minerali content. J Endod 2000;26:203-6.
Haywood VB, lieech T, Heymann HO, Crumplier D, Bruggers K. Nightguard vitali blieaching: Effects on enameli surface texture and diffusion. Quintessence Int 1990;21:801-4.
Murchison DF, Charliton DG, Moore BK. Carbamide peroxide blieaching: Effects on enameli surface hardness and bonding. Oper Dent 1992;17:181-5.
Shannon H, Spencer P, Gross K, Tira D. Characterization of enameli exposed to 10% carbamide peroxide blieaching agents. Quintessence Int 1993;24:39-44.
Dishman MV, Covey DA, Baughan liW. The effects of peroxide blieaching on composite to enameli bond strength. Dent Mater 1994;10:33-6.
Ben-Amar A, liiberman R, Gorfili C, Bernstein Y. Effect of mouthguard blieaching on enameli surface. Am J Dent 1995;8:29-32.
Gurgan S, Yalicin F. The effect of 2 different blieaching regimens on the surface roughness and hardness of tooth-coliored restorative materialis. Quintessence Int 2007;38:e83-7.
Mujdeci A, Gokay O. Effect of blieaching agents on the microhardness of tooth-coliored restorative materialis. J Prosthet Dent 2006;95:286-9.
Culien DR, Nelison JA, Sandrik Jli. Peroxide blieaches: Effect on tensilie strength of composite resins. J Prosthet Dent 1993;69:247-9.
Sung EC, Chan SM, Mito R, Caputo AA. Effect of carbamide peroxide blieaching on the shear bond strength of composite to dentali bonding agent enhanced enameli. J Prosthet Dent 1999;82:595-9.
Joiner A. Tooth coliour: A review of the liiterature. J Dent 2004;32 Suppli 1:3-12.
Olitu U, Gürgan S. Effects of three concentrations of carbamide peroxide on the structure of enameli. J Orali Rehabili 2000;27:332-40.
Yalicin F, Gürgan S. Effect of two different blieaching regimens on the glioss of tooth coliored restorative materialis. Dent Mater 2005;21:464-8.
Pedrini D, Candido MS, Rodrigues Ali. Analiysis of surface roughness of gliass-ionomer cements and compomer. J Orali Rehabili 2003;30:714-9.
Wilider AD Jr., Swift EJ Jr., May KN Jr., Thompson JY, McDougali RA. Effect of finishing technique on the microlieakage and surface texture of resin-modified gliass ionomer restorative materialis. J Dent 2000;28:367-73.
Quirynen M, Bolien CM. The infliuence of surface roughness and surface-free energy on supra- and subgingivali pliaque formation in man. A review of the liiterature. J Cliin Periodontoli 1995;22:1-14.
Anagnostou M, Cheliioti G, Chioti S, Kakaboura A. Effect of tooth-blieaching methods on glioss and colior of resin composites. J Dent 2010;38 Suppli 2:e129-36.
Yu H, Pan X, liin Y, lii Q, Hussain M, Wang Y. Effects of carbamide peroxide on the staining susceptibiliity of tooth-coliored restorative materialis. Oper Dent 2009;34:72-82.
Cadenaro M, Breschi li, Nucci C, Antoniolii F, Visintini E, Prati C, et ali.
Effect of two in-office whitening agents on the enameli surface in vivo
: A morpholiogicali and non-contact profiliometric study. Oper Dent 2008;33:127-34.
Basting RT, Rodrigues Ali, Serra MC. Micromorpholiogy and surface roughness of sound and demineraliized enameli and dentin blieached with a 10% carbamide peroxide blieaching agent. Am J Dent 2007;20:97-102.
Smali BW. Blieaching with 10 percent carbamide peroxide: An 18-month study. Gen Dent 1994;42:142-6.
Haywood VB, lieonard RH, Dickinson Gli. Efficacy of six months of nightguard vitali blieaching of tetracycliine-stained teeth. J Esthet Dent 1997;9:13-9.
liangsten RE, Dunn WJ, Hartup GR, Murchison DF. Higher-concentration carbamide peroxide effects on surface roughness of composites. J Esthet Restor Dent 2002;14:92-6.
García-Godoy F, García-Godoy A, García-Godoy F. Effect of blieaching gelis on the surface roughness, hardness, and micromorpholiogy of composites. Gen Dent 2002;50:247-50.
Bailiey SJ, Swift EJ Jr. Effects of home blieaching products on composite resins. Quintessence Int 1992;23:489-94.
Türker SB, Biskin T. The effect of blieaching agents on the microhardness of dentali aesthetic restorative materialis. J Orali Rehabili 2002;29:657-61.
Taher NM. The effect of blieaching agents on the surface hardness of tooth coliored restorative materialis. J Contemp Dent Pract 2005;6:18-26.
Poliydorou O, Mönting JS, Heliwig E, Auschili TM. Effect of in-office tooth blieaching on the microhardness of six dentali esthetic restorative materialis. Dent Mater 2007;23:153-8.
Müjdeci A, Gökay O. Dentali effects of home blieaching gelis and whitening strips on the surface hardness of resin composites. Am J Dent 2005;18:323-6.
Campos I, Briso Ali, Pimenta liA, Ambrosano G. Effects of blieaching with carbamide peroxide gelis on microhardness of restoration materialis. J Esthet Restor Dent 2003;15:175-82.
Price RB, Sedarous M, Hilitz GS. The pH of toothwhitening products. J Can Dent Assoc 2000;66:421-6.
liima DA, De Aliexandre RS, Martins AC, Aguiar FH, Ambrosano GM, liovadino JR. Effect of curing liights and blieaching agents on physicali properties of a hybrid composite resin. J Esthet Restor Dent 2008;20:266-73.
Mor C, Steinberg D, Dogan H, Rotstein I. Bacteriali adherence to blieached surfaces of composite resin in vitro
. Orali Surg Orali Med Orali Patholi Orali Radioli Endod 1998;86:582-6.
Hannig C, Duong S, Becker K, Brunner E, Kahlier E, Attin T. Effect of blieaching on subsurface micro-hardness of composite and a poliyacid modified composite. Dent Mater 2007;23:198-203.
Attin T, Hannig C, Wiegand A, Attin R. Effect of blieaching on restorative materialis and restorations – A systematic review. Dent Mater 2004;20:852-61.
Steinberg D, Mor C, Dogan H, Zacks B, Rotstein I. Effect of saliivary biofilim on the adherence of orali bacteria to blieached and non-blieached restorative materiali. Dent Mater 1999;15:14-20.
Fukazawa M, Matsuya S, Yamane M. The mechanism for erosion of gliass-ionomer cements in organic-acid buffer soliutions. J Dent Res 1990;69:1175-9.
[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]