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| Year : 2014 | Volume
: 17
| Issue : 6 | Page : 550-554 |
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| The comparison of the effects of different whitening toothpastes on the micro hardness of a nano hybrid composite resin
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Mohan Thomas Nainan1, Ashok Kalappurakkal Balan1, Roshni Sharma1, Sabeena Susan Thomas1, Santhosh B Deveerappa2
1 Department of Conservative Dentistry and Endodontics, Vydehi Institute of Dental Sciences and Research Centre, Bangalore, Karnataka, India
2 Department of Mechanical Engineering, Reva Institute of Technology and Management, Bangalore, Karnataka, India
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| Date of Submission | 15-May-2014 |
| Date of Decision | 09-Aug-2014 |
| Date of Acceptance | 23-Aug-2014 |
| Date of Web Publication | 13-Nov-2014 |
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 Abstract | | |
Aim: The aim of this study was to compare the micro hardness of a nanohybrid composite resin after brushing with two herbal and one non-herbal whitening toothpastes.
Materials and Methods: We divided Eighty disk-shaped specimens of a nanohybrid composite (Tetric N Ceram, Ivoclar Vivadent, Asia) into 4 groups of 20 specimens each: Groups A, B, C, and D. Group A was control, Group B was brushed with Colgate total advanced whitening (Colgate-Palmolive (India) Limited), Group C with Salt and Lemon, Dabur (Dabur International Limited, Dubai, UAE), and Group D with HiOra Shine, Himalaya (The Himalaya Drug Company, India). The specimens were polished using medium, fine, and superfine discs (Sof-lex, 3M, ESPE, USA) and subsequently placed at 37°C in distilled water. They were brushed for 2 minutes twice daily with a soft motorized toothbrush (Colgate 360 sonic power battery-operated tooth brush, Colgate Palmolive, India) for 30 days. The samples were rinsed under running water to remove the toothpaste and stored in distilled water at 37°C until the readout was taken on the Vickers's hardness tester for microhardness.
Results: The results revealed that the difference among the groups was statistically significant (P < 0.001). Tukey's test showed that reduction in microhardness for Group B was significantly higher than that for Group C and Group D (P < 0.001).
Conclusion: Within the limitations of this study, non-herbal whitening toothpaste had a greater impact on the microhardness of nanohybrid resin composite than herbal whitening toothpastes.
Keywords: Abrasives in toothpaste; herbal toothpaste; microhardness; resin composites; tooth whitening; Vickers hardness test
How to cite this article:
Nainan MT, Balan AK, Sharma R, Thomas SS, Deveerappa SB. The comparison of the effects of different whitening toothpastes on the micro hardness of a nano hybrid composite resin
. J Conserv Dent 2014;17:550-4 |
How to cite this URL:
Nainan MT, Balan AK, Sharma R, Thomas SS, Deveerappa SB. The comparison of the effects of different whitening toothpastes on the micro hardness of a nano hybrid composite resin
. J Conserv Dent [serial online] 2014 [cited 2023 Jun 9];17:550-4. Available from: https://www.jcd.org.in/text.asp?2014/17/6/550/144593 |
| Introduction | |  |
Tooth discoloration can be treated professionally with in office or home bleaching. [1] Whitening toothpastes have gained in popularity for treating extrinsic stains. Whitening toothpastes contain abrasive particles such as natural calcium carbonate, silica micro granules, and small percentages of H 2 O 2 and carbamide peroxide. Baking soda has also been introduced in some toothpastes to combat halitosis and as an antibacterial agent. Most of these components are strong abrasives that remove pellicle along with dental stains. [2] Most of the commercially available whitening toothpastes are meant to be used with an aid of a toothbrush. Studies have shown that movements of abrasive agents with the aid of toothbrush bristles will alter the roughness and mechanical properties of restorative materials. [3],[4],[5]
Patients who desire teeth whitening may have existing composite restorations. Ingredients in the whitening toothpaste can alter the surface characteristics of composites. [4] Nanofill composites were introduced to reduce polymerization shrinkage and higher resistance to traction, compression and fracture as well as improving optical properties, reducing attrition, and greater retention of gloss. Composite resin materials undergo a series of physical changes because of the polymerization reaction and subsequent interaction with reagents exposed to them. This process may cause the softening of the resin matrix and reduction of stain resistance. [6],[7],[8]
Hardness is commonly correlated to physical properties of composite resins such as mechanical strength, rigidity, and resistance to intraoral softening. [9] Microhardness is an important property of the restorative material that correlates with strength, proportionality limit, wear resistance, and hence, surface roughness and color stability.
Several studies have noted significant changes in the hardness of composite resins exposed to bleaching agents. [10],[11] According to Khamverdi et al. the use of whitening toothpaste reduces the surface hardness of microhybrid composite resins. [12] In our study, very little research was done to evaluate the effects of herbal whitening toothpastes on the microhardness of composite.
Ideally, a restoration must provide a smooth and regular surface, but this is not always possible as the composite restoration are frequently subjected to certain deleterious actions in the oral cavity through abrasion (brushing), attrition, and erosion (citrus drinks, citrus fruits, soft drinks, etc.). The brushing with toothpaste is the main method of oral hygiene, bringing many benefits in addition to a reduction in the incidence of caries.
Studies have shown that the movement of agents associated with tooth brushing can cause damage to the brushed substrate and are capable of altering the surface and properties of the restorative material.
Thus, the aim of this study was to compare the microhardness of a nanohybrid composite resin after brushing with two herbal and one non-herbal whitening toothpaste.
| Materials and methods | | |
Cylindrical-shaped rubber moulds with disk-shaped specimen wells (2-mm thickness and 15-mm diameter) were used to prepare 80 composite specimens. The material used in this study was a nanohybrid composite resin (Tetric N Ceram, Ivoclar Vivadent, Asia). Initially, the moulds were slightly overfilled with the restorative material, which were covered with a plastic matrix strip (mylar strip, Sammit products, India), and a glass slab was used to apply pressure to extrude excess material. The composite resin specimens were light cured (Spectrum 800, DENTSPLY,) for 60 seconds. Prior to photo curing of each composite specimen, a light intensity meter was used to make sure the intensity of the light source was 450 mw/cm 2 .
The specimens were polished using medium fine and superfine polishing discs in a sequential manner (Sof-lex, 3M, ESPE, USA). The polished specimens were cleaned in distilled water for 2 minutes to remove any surface contaminants. All discs were stored in 37°C distilled water for 24 hours.
The 80 specimens were randomly divided into 4 groups (A,B,C, and D) of 20 specimens each and subjected to tooth brushing for 2 minutes twice daily with a motorized tooth brush (Colgate 360 sonic power battery operated tooth brush, Colgate Palmolive, India) for 30 days. Group A was the controlled group where no paste was used with the toothbrush. For Groups B, C, and D Colgate total advanced whitening toothpaste (Colgate-Palmolive (India) Limited), salt and lemon toothpaste (Dabur International Limited, Dubai, UAE), and HiOra Shine toothpaste (The Himalaya Drug Company, India) were used, respectively.
Vickers hardness test was performed for all the specimens using a 10-N load and a 15-second dwell time at room temperature (Fuel instruments and engineering Pvt. Ltd, India).
Vickers hardness test method
Microhardness value of each composite specimen was calculated in the following way. A 136° pyramidal diamond indenter was used on each specimen to form a square indent. The indenter was pressed into the sample with an accurately controlled test force. The force was maintained for a specific dwell time of 15 seconds. The size of the indent was determined optically by measuring the two diagonals of the square indent. The Vickers hardness number is a function of the test force divided by the surface area of the indent. The average of the two diagonals is used in the following formula to calculate the Vickers hardness.
Hardness value = constant × test force/indent diagonal squared
Where the constant is a function of the indenter geometry and the units of force and diagonal. [13]
Data were analyzed by one way ANOVA and Tukey's tests. Mean and standard deviations were calculated. Statistical software namely SAS 9.2, SPSS 15.0, Stata 10.1, MedCalc 9.0.1, Systat 12.0, and R environment ver.2.11.1 were used for the analysis of the data, and Microsoft Word and Excel have been used to generate graphs, Tables etc.
| Results | | |
95% CI implies that the expected mean values will always be in the interval of 95% Confidence Interval Or Population values will be within this interval of 95% CI [Table 1] and [Table 2] and [Figure 1]. | Table 1: Comparison of micro hardness of experimental groups (Dabur, Colgate, and Himalaya) with control group (One-way ANOVA test)
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 | Table 2: Pair wise comparison of microhardness using Post-hoc Tukey's test
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 | Figure 1: Microhardness values of test and control groups F = 159.650; P < 0.001**
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Interpretation of results
- One-way Anova test showed statistically significant difference in reduction of microhardness among the groups (P < 0.001**) Control > Himalaya > Dabur > Colgate.
- Post-hoc Tukey's test showed that:
- All the experimental groups showed significant reduction in micro hardness compared with the control group. (P < 0.001 for all intergroup comparison).
- Maximum reduction in micro hardness was seen in Group B when compared with Group C and Group D (P < 0.001 and P < 0.001, respectively).
- Group C showed more reduction in microhardness than Group D (P < 0.001).
| Discussion | | |
Patients with composite restorations may opt for tooth whitening regimens. The use of over-the-counter whitening toothpastes is one such option. Such patients may have aesthetic restorations in their mouth. The effects of such products on the properties of the existing restorations need to be investigated thoroughly before their use can be advocated.
Nanocomposites are commonly used for restorations as they provide good aesthetics and longevity. A recent study has recommended nanocomposite as the restorative material of choice when bleaching has to be done after restoration. Hence, nanocomposite material was used in this study. [14]
The testing procedure was standardized using a motorized toothbrush to deliver uniform brushing strokes. Hardness of the toothbrush has a positive effect on the alteration of surface hardness of the resin composite on which it is used. [12] Considering this, a soft toothbrush was used in this study. However, a toothbrush simulator machine would have been a better option in delivering standardized strokes with uniform pressure. [15] A single operator performed the polishing procedures to minimize variation. The prepared specimens were stored in water as storing in artificial saliva is known to form a surface protective salivary layer on the restorative material and may influence the results. [16]
Hardness is a surface property of a restorative material to resist deformation. Vickers hardness test is one of the micro hardness tests that are commonly used to test the surface hardness of restorative materials. [12]
For a predetermined load, the Vickers indentations are twice the depth when compared to knoop indentations. The diagonal of the Vickers indentation is almost one-third the length of the longest diagonal of the knoop indentation. The Vickers hardness test is less sensitive to surface effects and textures (surface conditions) and more sensitive to measurement errors when equal loads are applied due to its shorter diagonals. Thus, Vickers hardness tester was chosen for this study. [17]
The results showed a significant reduction in microhardness of experimental groups compared to the control groups. The maximum reduction in microhardness was demonstrated by Colgate Total Advanced whitening and the least reduction in micro hardness was observed for Himalaya Group. Salt and lemon toothpaste showed intermediate values.
Whitening toothpastes have a mechanical abrasive action due to the abrasives included in it. The range of abrasives can be categorized into four groups, namely carbonates, phosphates, silica, and other agents such as alumina, clays, and oxides. Previous studies have revealed that silica is more abrasive than other agents are, such as sodium bicarbonate, calcium phosphate, and calcium carbonate with a Moh's hardness number of 2.5-5.0. [18]
Colgate Total Advanced whitening paste contains silica as the abrasive and can explain the reason why it has maximum effect on the microhardness. [19],[20] Salt and Lemon toothpaste contains sodium chloride (salt) whose Moh's hardness number 2.5, lesser than that of silica. This explains why it has shown lesser reduction microhardness than Colgate total advanced whitening paste. [21] According to the manufactures, HiOra-Shine toothpaste is an herbal teeth-whitening agent containing natural enzymes that gently dissolve the stains on the surface of the teeth, and it does not contain harsh abrasives [Table 3]. [22]
Salt and lemon toothpaste contains lemon extract and citric acid while HiOra shine toothpaste contains malic acid, tartaric acid, and racemic acid. [23],[24] Previous studies have shown that dentifrices, which have neutral or acidic pH, produced more abrasion than those with a basic pH. [25] However, in this study, Colgate Total Advanced toothpaste with a basic pH of 9.68 showed more abrasive properties (alteration in microhardness of composite) than the other two pastes with acidic pH. [26] Therefore, it can be suggested that the abrasive properties of whitening toothpastes can cause more alteration in the microhardness of the substrate to which it is exposed rather than the acidic content of the herbal toothpaste.
The results also conflict with the results of the studies showing no difference or improvement in microhardness. [27] However, the result supports earlier findings of reduction in microhardness of composites with whitening toothpastes. [12]
Previous studies have indicated that soft toothbrushes cause more abrasion as they retain more toothpaste in their fine bristles. [28] This factor needs to be considered in analyzing the results of this study.
The effect of herbal toothpastes on color stability, surface roughness, and other properties in comparison to regular whitening toothpastes are being investigated further using a toothbrush simulator machine.
| Conclusion | | |
According to the result of this study, the use of whitening toothpastes causes reduction in the microhardness of resin composite. Both abrasives and acids included in the whitening toothpaste can affect the microhardness of the composite. Herbal toothpastes cause lesser reduction in microhardness compared to the non-herbal whitening toothpastes. However, the whitening or bleaching effect has to be weighed against the abrasiveness of whitening toothpaste in future studies.
Patients need to be educated about opting for professional tooth whitening under the guidance of a dental professional, where the parameters can be controlled, rather than relying on over-the-counter products.
| Acknowledgement | | |
The authors would like to thank Dr. K. P. Suresh (Ph.D (Biostatistics) Scientist (SS), Project Directorate on Animal Disease Monitoring and Surveillance (PDADMAS) Hebbal, Bangalore 560024) for statistical analysis.
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Correspondence Address:
Mohan Thomas Nainan
Epip Area, Whitefield, Bangalore - 560 066, Karnataka
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0972-0707.144593
[Figure 1]
[Table 1], [Table 2], [Table 3] |
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