|Year : 2016 | Volume
| Issue : 4 | Page : 179-186
Changes in surface roughness of bleached enamel by using different remineralizing agents
Reham M Attia PhD , Mohammed M Kamel
Department of Operative Dentistry, Faculty of Dentistry, Tanta University, Tanta, Egypt
|Date of Submission||26-May-2016|
|Date of Acceptance||11-Aug-2016|
|Date of Web Publication||14-Dec-2016|
Reham M Attia
Department of Operative Dentistry, Faculty of Dentistry, Tanta University, Tanta
Source of Support: None, Conflict of Interest: None
The purpose of this study was to determine the effect of fluoride gel, Remin Pro, and GC tooth mousse plus in changing surface roughness of enamel after bleaching procedures.
Materials and methods
Dental enamel blocks measuring 2 × 3 × 4 mm were prepared from nonerupted human third molars. The 38% hydrogen peroxide in-office bleaching protocols were performed. The specimens were randomly divided into three groups (n = 10 samples per group) according to the remineralizing agent used: group 1: using fluoride gel, group 2: using Remin Pro, and group 3: using GC tooth mousse plus. Measurements of surface roughness were carried out using a contact stylus profilometer before bleaching, after bleaching, and after remineralization.
Data were analyzed using analysis of variance and Tukey's test. There was a highly significant difference of enamel surface roughness measurements among initial, after bleaching, and final regarding the three tested groups (P < 0.001). There was no significant difference among the three tested groups in relation to enamel surface roughness before and after bleaching (P = 0.739 and 0.341, respectively). There was a highly significant difference in relation to final measurements (P < 0.001) among the three tested groups. The difference in Ra value of enamel between the group used fluoride gel and that used Remin Pro and GC tooth mousse plus was highly significant and that between groups 2 and 3 was not significant.
GC tooth mousse plus and Remin Pro are more effective in reducing enamel surface roughness after bleaching than fluoride product.
Keywords: bleached enamel, remineralizing agents, surface roughness
|How to cite this article:|
Attia RM, Kamel MM. Changes in surface roughness of bleached enamel by using different remineralizing agents. Tanta Dent J 2016;13:179-86
|How to cite this URL:|
Attia RM, Kamel MM. Changes in surface roughness of bleached enamel by using different remineralizing agents. Tanta Dent J [serial online] 2016 [cited 2017 Oct 22];13:179-86. Available from: http://www.tmj.eg.net/text.asp?2016/13/4/179/195707
| Introduction|| |
Cosmetic dentistry is an important part of today's restorative dental practice . Bleaching of vital teeth has obtained a specific benefit [2,3]. It has been admitted as one of the most effective methods of managing discolored teeth. It is considered to be a conservative approach towards gaining esthetic and cosmetic effects rather than other treatment methods such as using veneer or crown which need a specific teeth preparation . The growing demand for bleaching as an esthetic improvement has led to a considerable development in bleaching products and techniques . Procedures that utilize carbamide peroxide or hydrogen peroxide with different concentrations have been regularly used as dentists as 'in office' or as 'home bleaching' applications bleaching agents by . In addition, over the counter products of bleaching have been vastly used by patients . One of the most common products for bleaching procedures are those based on hydrogen peroxide at 35 or 38%, which should be applied in dental offices under the supervision of dental professionals . The breakdown of hydrogen peroxide leads to formation of oxygen and per-hydroxyl free radicals which oxidize the stained macromolecules and break them down into smaller lighter colored fragments . Then, the fragments disperse across the tooth surface resulting in the bleaching effect . Bleaching agents have generated microstructural changes on the bleached enamel surface . Studies demonstrated demineralization, degradation, and changes on surface microhardness and roughness of sound enamel surface . Roughness is often described as closely spaced irregularities or with terms such as 'uneven', 'irregular', 'coarse in texture', 'broken by prominences', and other similar ones. The significance of surface roughness depends on the scale of measurement . Surface roughness is an important matter when the main interest is to understand the nature. There are different methods used for surface roughness measurement. One of these methods is the contact tracing method where the probe slightly 'taps' on the sample surface during scanning, contacting the surface at the bottom of its swing. This method is considered one of the most precise methods and is used currently in many studies to estimate surface roughness [13-15].
Roughness is considered a predisposing factor for bacterial adhesion and extrinsic stain. It has been reported to play a distinguished function in biofilm development of oral bacteria . The special effects of surface roughness on biofilm development can be demonstrated by the reality that a rough surface can act as a buffer against shear forces and can increase the area available for biofilm formation . So, rough enamel surface encourages adhesion of Streptococcus mutans which is the major causative microorganism in the pathogenesis of dental caries as the subsistence of S. mutans in the oral environment be based on their ability to adhere to a tooth surface [18,19]. After bleaching procedures, coloring pigments may adhere to the rough bleached enamel surface with the micropores or superficial defects and lead to more discoloration than the original tooth color . To overcome the adverse effects of bleaching procedures, enamel surface defects could be managed by saliva, artificial saliva, or remineralizing agents .
Remineralization is the process of restoring mineral ions into the hydroxylapatite lattice work structure or is the natural repair process for noncavitated lesions. It depends upon calcium and phosphate ions assisted by fluoride to rebuild a new surface on already existing crystal remnants in subsurface lesions left behind after demineralization. These remineralized crystals are less soluble than the original mineral [22-24]. Enamel polishing has also been recommended to re-establish enamel smoothness and its glossy surface. However, polishing procedures can lead to removal of a few micrometers of the enamel, reducing its thickness with loss of the outer superficial layer . Currently, a wide range of remineralizing agents has been introduced to prevent these side effects and subsequent outcomes of bleaching procedures. During remineralization, calcium and phosphate ions from an external source reach the external tooth surface, resulting in an increase in deposition of ions in the crystal voids in demineralized enamel, which leads to increased net mineral gain . Fluoride is essential in the remineralization of tooth enamel and it could decrease the damaging effects of bleaching agents [21,27]. Casein phosphopeptide amorphous calcium phosphate (CPP-ACP) is another option for remineralization. The calcium and phosphate ions are released from the CPP complex and penetrate into the enamel rods, resulting in an increase in the density of hydroxylapatite crystals [28,29]. Remin Pro (VOCO GmbH, Cuxhaven, Germany) is a relatively new remineralizing water-based cream which contains hydroxylapatite, fluoride, and xylitol . Hydroxyapatite fills eroded enamel, fluoride seals dentinal tubules, and xylitol acts as an antibacterial agent. So, it offers triple protection of fluoride, hydroxylapatite (calcium and phosphate), and xylitol with no risk of milk protein allergies as with other brands . It has been recommended for the management of dentine hypersensitivity, to prevent enamel demineralization and to promote remineralization of enamel subsurface lesions .
Researchers believe tooth bleaching has shown to increase enamel surface roughness during or after treatment, which leads to an increase in susceptibility to bacterial adhesion and subsequent carious lesion with subsequent staining of the damaged enamel surface . Therefore, the current study was performed to determine the effect of fluoride gel, Remin Pro, and GC tooth mousse plus in changing surface roughness of enamel after bleaching procedures.
| Materials and methods|| |
Thirty freshly extracted, nonerupted human third molars were selected for the study. All patients were informed and signed written consent regarding using their extracted teeth according to committee of Ethics of Faculty of Dentistry, Tanta University. The enamel surfaces were devoid of any stains, enamel cracks, fractures, or other defects. The teeth were meticulously cleaned of any debris and soft tissues attached to tooth surfaces, and then stored in 0.5% thymol to prevent fungal and bacterial growth until used for the purpose of the study. All of the teeth were collected within 15 days and stored for no longer than 4 weeks [34,35].
The roots were discarded and 2 × 3 × 4 mm dental blocks were prepared from each tooth using a diamond disk (Imicryl, Konya, Turkey) under water cooling. The dental blocks were embedded individually in self-curing acrylic resin (Imicryl), with enamel surfaces exposed for application of bleaching agents. The enamel surfaces were flattened with wet 600, 1000, and 1200 grit aluminum oxide abrasive papers (3 mol/l aluminum oxide abrasive paper sheet, USA) and polished with (6, 3, 1, and 1/2 µm) grit diamond pastes (Ultradent Diamond Polishing Paste, MPN 5540; Ultradent Products Inc., South Jordan, Utah, USA). Specimens were examined under a stereomicroscope (SZ-CTY; Olympus, Tokyo, Japan) with ×10 magnification to verify the absence of dentine .
Measurements indicating initial surface roughness were carried out using a contact stylus profilometer (Mitutoyo surf test, Godl78-821; Mitutoyo, Kawasaki, Japan). The Ra parameter (µm) which is defined as the arithmetical average height of surface component irregularities (the absolute distance of the roughness profile) from the mean line within the measuring length was adopted. Five sequential readings were performed, with a length of 1.25 mm, a cut-off of 0.25 mm and a speed of 0.1 mm/s. The Ra of each sample was obtained from the arithmetic mean of its five Ra readings .
The 38% hydrogen peroxide in-office bleaching protocols (Opalescence Xtra Boost; Ultardent Products Inc.) was performed for 2 weeks, with one session each week. Each session consisted of three 15 min-period with a 5 min interval between them. After bleaching, surface roughness was remeasured. All specimens were stored in artificial saliva and renewed daily at 37°C during the entire experiment. The composition of the artificial saliva was 0.058 ppm fluoride, 1.55 mmol calcium, and 0.92 mmol phosphate . The specimens were randomly divided into three groups (n = 10 samples per group) according to the remineralizing agent used. Group 1: samples were brushed two times a day for 14 days with a commercial fluoride gel [Colgate PreviDent Brush-on Gel (Rx only); UK]. The interval between brushing sessions was 8 h. Every brushing session was performed for 30 s using an electric toothbrush with a constant pressure using a small size (bean sized) toothpaste aliquot wetted with deionized distilled water, closely resembling the in-vivo usual tooth brushing procedure. After every treatment session, each enamel sample was gently washed with deionized distilled water using a cleaned toothbrush in order to remove residual toothpaste.
Group 2: a water-based cream with fluoride and hydroxylapatite (Remin Pro) (Remin Pro Fluoride Cream; Voco Dental Materials, Toronto, Ontario, Canada) was applied for 5 min, two times a day for 14 days. Group 3: Casein phosphopeptide amorphous calcium phosphate with fluoride (CPP-ACPF) (GC tooth mousse plus; GC Corporation, Tokyo, Japan) was applied to specimens according to manufacturer's instructions for a period of 2 weeks for the recommended time period, 3 min daily. Then the teeth were cleaned and washed with deionized distilled water. The final surface roughness measurements were carried out after application of remineralizing agent in all groups.
| Results|| |
The data obtained were subjected to statistical analysis using statistical package for the social sciences (SPSS Inc., Chicago, Illinois, USA), version 19.
They were presented as range, mean and SD. Analysis of variance and Tukey's tests were used to analyze. The changes in surface roughness values (µm) at different times of assessment were recorded as initial (before bleaching), after bleaching, and final (after remineralization). In addition, they were used to compare the means of surface roughness among the three tested groups. P value of 0.05 was considered for statistical significance and 0.01 for high statistical significance.
The comparison of surface roughness measurements among different times of assessment (initial, after bleaching, and the final) in group 1 (fluoride gel application) is shown in [Table 1]. The comparison revealed that the difference was highly significant.
|Table 1 Statistical analysis of the mean surface roughness values (μm) of enamel in group 1 and comparison before bleaching (initial), after bleaching (bleach), and after remineralization (final) |
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There was an increase in surface roughness after bleaching. When compared to the initial value, this difference was highly significant (P < 0.001). When Ra value after bleaching was compared to that after remineralization; the difference was highly significant (P < 0.001). The surface roughness value after remineralization was less than that obtained at initial measurement with highly significant difference between the two assessed values (P < 0.001).
In group 2, where Remine Pro was applied after bleaching; there was a highly significant difference when the changes in Ra values were compared among the three different times of surface roughness measurements [Table 2].
|Table 2 Statistical analysis of the mean surface roughness values (μm) of enamel in group 2 and comparison before bleaching (initial), after bleaching (bleach), and after remineralization (final) |
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The comparison between initial and after bleaching revealed that there was a highly significant increase in Ra value after bleaching (P < 0.001). The Ra value after application of Remin Pro decreased when compared to the Ra value after bleaching with significant difference (P < 0.001). Comparison between final Ra value and initial one revealed that there was no significant difference.
[Table 3] represents group 3 where CPP-ACPF (GC tooth mousse plus) was used. The difference in Ra values among initial, after bleaching and after remineralization (final) was highly significant.
|Table 3 Statistical analysis of the mean surface roughness values (μm) of enamel in group 3 and comparison before bleaching (initial), after bleaching (bleach), and after remineralization (final) |
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When initial and after bleaching means of surface roughness measurements were compared, there was an increase in surface roughness. This increase was highly significant (P < 0.001). The roughness markedly decreased after application of CPP-ACPF (GC tooth mousse plus), the difference between after bleaching and final measurements were highly significant (P < 0.001). When final and initial measurements were compared, the difference was not significant.
Comparison among the three tested groups regarding initial, after bleaching and final surface roughness measurements revealed that there was no significant difference with regards to initial and after bleaching. However, the difference of final measurements was highly significant where P was less than 0.001 among the three groups as shown in [Table 4] [Table 5] [Table 6].
|Table 4 Comparison of enamel surface roughness among tested groups before bleaching (initial) |
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|Table 5 Comparison of enamel surface roughness among tested groups after bleaching (bleach) |
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|Table 6 Comparison of enamel surface roughness among tested groups after remineralization (final) |
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[Table 7] illustrates Tukey's test that was used to demonstrate the comparison of the surface roughness means of every group to the means of every other one. The comparison between group 1 and both of groups 2 and 3 revealed that the difference was highly significant. On the contrary, the difference between groups 2 and 3 was not significant. [Figure 1] [Figure 2] [Figure 3] [Figure 4] represent Ra value measurements of representative samples regarding each group.
|Figure 1: Ra measurements of representative samples of group 1 (control group). Each line of measurement represents one reading only. (a) Before bleaching, (b) after bleaching, and (c) final|
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|Figure 2: Ra measurements of representative samples of group 2. Each line of measurement represents one reading only. (a) Before bleaching, (b) after bleaching, and (c) final|
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|Figure 3: Ra measurements of representative samples of group 3. Each line of measurement represents one reading only. (a) Before bleaching, (b) after bleaching, and (c) final|
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|Figure 4: Ra measurements of representative samples of group 4. Each line of measurement represents one reading only. (a) Before bleaching, (b) after bleaching, and (c) final|
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|Table 7 Tukey's test compares the means of every group to the means of every other one |
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| Discussion|| |
Bleaching agents are considered as chemically active ingredients potentially able to induce substantial structural changes in enamel surfaces . Many previous studies reported the effects of bleaching on enamel surface texture and morphological changes of the enamel [39,40]. Some studies have demonstrated that bleaching did not extensively affect the enamel surface [41-43]. On the other hand, many other studies reported that bleaching procedures led to increased porosity of the enamel superficial structure, demineralization with decreased protein concentration, organic matrix degradation, modifications in the calcium: phosphate ratio with calcium loss and modifications in enamel crystal distribution [25, 44, 45]. The composition of products, the acidic pH of bleaching agents and the time of its application are some of the factors responsible for these superficial changes. Higher concentrations would lead to more morphological alterations than lower concentration products . In the current study, one of the in-office bleaching agents was tested with relatively higher concentration, 38% hydrogen peroxide. It is one of the commercially available bleaching products which has the highest concentration of hydrogen peroxide. It has a powerful oxidizing effect, making it potentially destructive to enamel, as this calcified tissue is susceptible to hydrogen peroxide. The surface alteration of enamel was demonstrated indirectly by studies demonstrating decreased enamel physical properties, among which surface roughness changes and enamel surface microhardness were reported [47,48]. The present study analyzed the surface roughness because it is possible to quantitatively assess the alteration of the dental structure that points to loss or gain of mineral of the dental tissues following bleaching therapy . In the present study, roughness measurements were performed using profilometry, which has an advantage of accurate and precise measurement of the surface roughness without the need for additional measurements. The profilometric method was considered by many studies as an effective quantitative evaluation [16,50]. The present study showed that there was a significant increase in the enamel surface roughness after application of bleaching agent. On the contrary, many previous studies found that there were no significant changes in enamel roughness after hydrogen peroxide and carbamide peroxide application even after using a high concentration of hydrogen peroxide. Previous studies [44,51-53] found that there were no changes on enamel after exposure to bleaching procedure.
The results of the present study were in contrast to preceding research . Despite that the present study used the same method of surface roughness measurement, there was a difference in the results which may be attributed to the difference in the duration of the bleaching procedure. On the other hand, the results of the current study were supported by the results of previous studies [55,56]; where they demonstrated that there was alteration on enamel surface and increase in surface roughness after 10 h of 35% hydrogen peroxide bleaching. The authors attributed that fact to the relatively higher concentration of peroxide and low pH on eroded enamel.
In addition, the results of the present study were compatible with other studies , where the two bleaching systems used in this study increased the surface roughness and one of the tested bleaching agents was hydrogen peroxide bleaching agent. Although a different surface roughness measurement method was used, the results were in coincidence.
In an attempt to decrease the loss of mineral of the dental tissues which results in increased surface roughness, different remineralizing agents were used before, at the time of bleaching procedure and after the bleaching phase . The investigations demonstrated that their use could be a participating factor in preventing damage induced by bleaching agent . Regarding the present study, three different types of remineralizing agents were used. These were fluoride gel, Remin Pro, and CPP-ACPF (GC tooth mousse plus). The enamel surface roughness showed a significant reduction after using the three remineralizing agents. These results coincide with other studies [11,59-61].
Remineralization potential of fluoride gel indicated by the reduction in surface roughness was lower than that obtained by using Remin Pro and CPP-ACPF (GC tooth mousse plus). The results of the current study coincide with other studies which showed that fluoride is away from a complete remineralization substance of enamel . It was revealed that only the application of high concentrations of fluoride had the capability to increase the remineralizing effect [37,62]. Commercial fluoride gels used in the current study contain more than 1000 ppm fluoride.
In our study, reduction in surface roughness measured after using Remin Pro was significantly different from that produced by fluoride gel. Using fluoride and hydroxylapatite in the case of Remin Pro can increase enamel remineralization due to the creation of surface apatite coating the enamel, thus imitating the morphology, structure, composition and surface reactivity of the biological enamel hydroxylapatite. It combines the effect of fluoride and hydroxylapatite. On the other hand, previous studies showed that synthetic hydroxylapatite biomimetic coat is less crystalline than natural apatite in enamel, but it represents a repair process related to deposition of apatite inside the enamel demineralized areas [37,63]. In addition, the CPP-ACPF (GC tooth mousse plus) led to significant reduction in surface roughness which revealed that its remineralizing effect is greater than the fluoride gel. This may be due to the small size of the CPP-ACP nanocomplex. It can enter the porosities of an enamel subsurface lesion and diffuse along its concentration gradient into the body of the lesion . The CPP-ACP can then release its weakly bound calcium and phosphate ions, which would deposit into crystal voids. The crystal growth during remineralization has the same pattern as crystal growth during amelogenesis [26,65]. Microradiography has shown that CPP-ACPF tends to remineralize throughout the lesion even in the presence of fluoride. In addition, there is a complex localization of free calcium phosphate and fluoride ion activities in CPP-ACPF, which aid in maintaining a state of super saturation by suppressing demineralization [29, 66, 67]. The results are in agreement with other studies [67,68].
The effect of CPP-ACPF (GC tooth mousse plus) and Remin Pro on the reduction of enamel surface roughness was nearly comparable. There was no significant difference in their remineralizing effect. This appeared as a decrease in enamel surface roughness despite that each one of them has its own manner in remineralization. These results may be due to the fact that both (GC tooth mousse plus) and Remin Pro consist of more than one ingredient that plays a role in remineralization. These results are in agreement with the results of other studies .
| Conclusion|| |
Under limitations of this study it can be concluded that:
Financial support and sponsorship
- Bleaching procedures lead to increased enamel surface roughness.
- Remineralizing agents like fluoride gel, Remin Pro and GC tooth mousse plus can decrease the surface roughness of bleached enamel.
- GC tooth mousse plus and Remin Pro are more effective in reducing enamel surface roughness after bleaching than fluoride product.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]